tag:theconversation.com,2011:/us/topics/australian-temperature-records-14272/articlesAustralian temperature records – The Conversation2016-07-10T20:38:53Ztag:theconversation.com,2011:article/621742016-07-10T20:38:53Z2016-07-10T20:38:53ZHow a single word sparked a four-year saga of climate fact-checking and blog backlash<p>In May 2012, my colleagues and I had a paper accepted for publication in the <a href="https://www.ametsoc.org/ams/index.cfm/publications/journals/journal-of-climate/">Journal of Climate</a>, showing that temperatures recorded in Australasia since 1950 were warmer than at <a href="https://theconversation.com/post-1950s-warming-in-region-unmatched-in-1-000-years-7081">any time in the past 1,000 years</a>.</p>
<p>Following the early online release of the paper, as the manuscript was being prepared for the journal’s print edition, one of our team spotted a typo in the methods section of the manuscript.</p>
<p>While the paper said the study had used “detrended” data – temperature data from which the longer-term trends had been removed – the study had in fact used raw data. When we checked the computer code, the DETREND command said “FALSE” when it should have said “TRUE”.</p>
<p>Both raw and detrended data have been used in similar studies, and both are scientifically justifiable approaches. The issue for our team was the fact that what was written in the paper did not match what was actually done in the analysis – an innocent mistake, but a mistake nonetheless.</p>
<p>Instead of taking the easy way out and just correcting the single word in the page proof, we asked the publisher to put our paper on hold and remove the online version while we assessed the influence that the different method had on the results.</p>
<h2>Enter the bloggers</h2>
<p>It turned out that someone else had spotted the typo too. Two days after we identified the issue, a commenter on the Climate Audit blog also pointed it out. </p>
<p>The website’s author, Stephen McIntyre, <a href="https://climateaudit.org/2012/06/06/gergis-significance/">proceeded to claim</a> (incorrectly) that there were “fundamental issues” with the study. It was the start of a concerted smear campaign aimed at discrediting our science.</p>
<p>As well as being discussed by bloggers (sometimes with a <a href="http://www.c3headlines.com/2012/06/smackdown-of-bimbo-climate-scientist-joelle-gergis-her-ballyhooed-southern-hemisphere-hockey-stick-s.html">deeply offensive and sexist tone</a>), the “flaw” was <a href="http://www.theaustralian.com.au/higher-education/climate-paper-flawed/story-e6frgcjx-1226393519781">seized upon by sections of the mainstream media</a>. </p>
<p>Meanwhile, our team received a flurry of hate mail and an onslaught of time-consuming Freedom of Information requests for access to our raw data and years of our emails, in search of ammunition to undermine and discredit our team and results. This is part of a <a href="https://www.theguardian.com/environment/climate-consensus-97-per-cent/2016/jul/07/climate-scientists-are-under-attack-from-frivolous-lawsuits">range of tactics</a> used in Australia and overseas in an attempt to intimidate scientists and derail our efforts to do our job.</p>
<p>Bloggers began to accuse us of conspiring to reverse-engineer our results to dramatise the warming in our region. Former geologist and prominent climate change sceptic Bob Carter published an <a href="http://www.theaustralian.com.au/national-affairs/opinion/settled-science-no-such-thing/story-e6frgd0x-1226409521856">opinion piece in The Australian</a> claiming that the peer-review process is faulty and climate science cannot be trusted.</p>
<h2>Checking the facts</h2>
<p>Meanwhile, we set about rigorously checking and rechecking every step of our study in a bid to dispel any doubts about its accuracy. This included extensive reprocessing of the data using independently generated computer code, three additional statistical methods, detrended and non-detrended approaches, and climate model data to further verify the results.</p>
<p>The mammoth process involved three extra rounds of peer-review and four new peer-reviewers. From the original submission on 3 November, 2011, to the paper’s re-acceptance on 26 April, 2016, the manuscript was reviewed by seven reviewers and two editors, underwent nine rounds of revisions, and was assessed a total of 21 times – not to mention the countless rounds of internal revisions made by our research team and data contributors. One reviewer even commented that we had done “a commendable, perhaps bordering on an insane, amount of work”.</p>
<p>Finally, today, we <a href="http://journals.ametsoc.org/doi/10.1175/JCLI-D-13-00781.1">publish our study again</a> with virtually the same conclusion: the recent temperatures experienced over the past three decades in Australia, New Zealand and surrounding oceans are warmer than any other 30-year period over the past 1,000 years.</p>
<p>Our updated analysis also gives extra confidence in our results. For example, as the graph below shows, there were some 30-year periods in our palaeoclimate reconstructions during the 12th century that may have been fractionally (0.03–0.04°C) warmer than the 1961–1990 average. But these results are more uncertain as they are based on sparse network of only two records – and in any event, they are still about 0.3°C cooler than the most recent 1985–2014 average recorded by our most accurate instrumental climate network available for the region.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/129665/original/image-20160707-30718-1djptnf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/129665/original/image-20160707-30718-1djptnf.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=282&fit=crop&dpr=1 600w, https://images.theconversation.com/files/129665/original/image-20160707-30718-1djptnf.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=282&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/129665/original/image-20160707-30718-1djptnf.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=282&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/129665/original/image-20160707-30718-1djptnf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=355&fit=crop&dpr=1 754w, https://images.theconversation.com/files/129665/original/image-20160707-30718-1djptnf.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=355&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/129665/original/image-20160707-30718-1djptnf.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=355&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Comparison of Australasian temperature reconstructions. Red: original temperature reconstruction published in the May 2012 version of the study; green: more recent reconstruction published in Nature Geoscience in April 2013; black: newly published reconstruction; orange: observed instrumental temperatures. Grey shading shows 90% uncertainty estimates of the original 2012 reconstruction; purple shading shows considerably expanded uncertainty estimates of the revised 2016 version based on four statistical methods. The recent 30-year warming (orange line) lies outside the range of temperature variability reconstruction (black line) over the past 1,000 years.</span>
</figcaption>
</figure>
<p>Overall, we are confident that observed temperatures in Australasia have been warmer in the past 30 years than every other 30-year period over the entire millennium (90% confidence based on 12,000 reconstructions, developed using four independent statistical methods and three different data subsets). Importantly, the climate modelling component of our study also shows that only human-caused greenhouse emissions can explain the recent warming recorded in our region.</p>
<p>Our study now joins the vast body of evidence showing that our region, in line with the rest of the planet, has warmed rapidly since 1950, with all the impacts that climate change brings. So far in 2016 we have seen <a href="https://theconversation.com/fires-in-tasmanias-ancient-forests-are-a-warning-for-all-of-us-53806">bushfires ravage Tasmania’s ancient World Heritage rainforests</a>, while <a href="https://www.theguardian.com/environment/2016/jun/07/the-great-barrier-reef-a-catastrophe-laid-bare">93% of the Great Barrier Reef</a> has suffered bleaching amid Australia’s <a href="https://theconversation.com/this-summers-sea-temperatures-were-the-hottest-on-record-for-australia-heres-why-56906">hottest ever sea temperatures</a> – an event made <a href="https://theconversation.com/great-barrier-reef-bleaching-would-be-almost-impossible-without-climate-change-58408">175 times more likely by climate change</a>. Worldwide, it has <a href="https://theconversation.com/its-official-2015-was-the-hottest-year-ever-recorded-53283">never been hotter in our recorded history</a>.</p>
<h2>Speed vs accuracy</h2>
<p>There are a couple of lessons we can take away from this ordeal. The first is that it takes far more time and effort to do rigorous science than it does to attack it.</p>
<p>In contrast to the instant gratification of publishing a blog post, the scientific process often takes years of meticulous evaluation and independent expert assessment.</p>
<p>Yes, we made a mistake – a single word in a 74-page document. We used the word “detrended” instead of “non-detrended”. Atoning for this error involved spending four extra years on the study, while withstanding a withering barrage of brutal criticism.</p>
<p>This brings us to the second take-home message. Viciously attacking a researcher at one of Australia’s leading universities as a “bimbo” and a “brain-dead retard” doesn’t do much to encourage professional climate scientists to engage with the scores of online amateur enthusiasts. Worse still, <a href="http://www.c3headlines.com/2012/06/smackdown-of-bimbo-climate-scientist-joelle-gergis-her-ballyhooed-southern-hemisphere-hockey-stick-s.html">gender-based attacks</a> may discourage women from engaging in public debate or pursuing careers in male-dominated careers like science at all.</p>
<p>Although climate change deniers are desperate to be taken seriously by the scientific community, it’s extremely difficult to engage with people who do not display the basic principles of common courtesy, let alone comply with the standard scientific practice of submitting your work to be scrutinised by the world’s leading experts in the field.</p>
<p>Despite the smears, a rummage through hundreds of our emails revealed nothing but a group of colleagues doing their best to resolve an honest mistake under duress. It wasn’t the guilty retreat from a flawed study produced by radical climate activists that the bloggers would have people believe. Instead, it showed the self-correcting nature of science and the steadfast dedication of researchers to work painstakingly around the clock to produce the best science humanly possible. </p>
<p>Rather than take the easy way out, we chose to withdraw our paper and spent years triple-checking every step of our work. After the exhaustive checking, the paper has been published with essentially the same conclusions as before, but now with more confidence in our results. </p>
<p>Like it or not, our story simply highlights the slow and unglamorous process of real science in action. In the end, this saga will be remembered as a footnote in climate science, a storm in a teacup, all played out against the backdrop of a planet that has never been hotter in human history.</p><img src="https://counter.theconversation.com/content/62174/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Joelle Gergis receives funding from the Australian Research Council. </span></em></p>Australasia’s warming in recent decades is unprecedented in the past millennium. But a mistake in the paper reporting this finding took four years to fix, and was viciously attacked by bloggers.Joelle Gergis, ARC DECRA Climate Research Fellow, School of Earth Sciences, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/603292016-06-01T08:33:52Z2016-06-01T08:33:52ZAustralia simmers through hottest autumn on record<figure><img src="https://images.theconversation.com/files/124756/original/image-20160601-26863-7f0usa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Summer stayed into autumn in many parts of Australia.</span> <span class="attribution"><span class="source">Bondi image from www.shutterstock.com</span></span></figcaption></figure><p>It’s the same old story: with 2016 on track to become the <a href="https://theconversation.com/2016-is-likely-to-be-the-worlds-hottest-year-heres-why-59378">hottest year on record globally</a>, and <a href="https://theconversation.com/what-is-going-on-with-indias-weather-59883">record-breaking heat already evident around the world</a>, Australia has just experienced its hottest autumn on record.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/124755/original/image-20160601-1951-1kya857.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/124755/original/image-20160601-1951-1kya857.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/124755/original/image-20160601-1951-1kya857.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/124755/original/image-20160601-1951-1kya857.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/124755/original/image-20160601-1951-1kya857.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/124755/original/image-20160601-1951-1kya857.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/124755/original/image-20160601-1951-1kya857.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Figures from the Bureau of Meteorology indicate Australia has experienced its hottest autumn on record.</span>
<span class="attribution"><span class="source">Bureau of Meteorology</span></span>
</figcaption>
</figure>
<p>The Bureau of Meteorology has <a href="http://www.bom.gov.au/climate/current/statements/scs56.pdf">reported</a> that for average temperatures across Australia, this has been the hottest March-May period ever recorded – beating the previous record, set in 2005, by more than 0.2°C. </p>
<p>Within this period, March was also the hottest on record, while April and May were each the second-warmest in a series extending back to 1910.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/124754/original/image-20160601-2812-fyiluh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/124754/original/image-20160601-2812-fyiluh.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=412&fit=crop&dpr=1 600w, https://images.theconversation.com/files/124754/original/image-20160601-2812-fyiluh.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=412&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/124754/original/image-20160601-2812-fyiluh.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=412&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/124754/original/image-20160601-2812-fyiluh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=518&fit=crop&dpr=1 754w, https://images.theconversation.com/files/124754/original/image-20160601-2812-fyiluh.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=518&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/124754/original/image-20160601-2812-fyiluh.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=518&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Temperatures were well above average across much of the country, especially in the east.</span>
<span class="attribution"><span class="source">Bureau of Meteorology</span></span>
</figcaption>
</figure>
<h2>Why so hot?</h2>
<p>El Niño events tend to cause warmer weather across the east and north of Australia and the major El Niño of 2015-16 undoubtedly contributed to the extreme temperatures experienced across these areas.</p>
<p>However, climate change also played a significant role in our warmest autumn. <a href="http://www.bom.gov.au/amm/docs/2014/lewis2_hres.pdf">Previous work</a>, led by ANU climatologist <a href="https://theconversation.com/profiles/sophie-lewis-22297">Sophie Lewis</a>, indicates that the human influence on the climate has made a record-breakingly hot autumn roughly 20 times more likely. </p>
<p>In other words, without climate change we would be much less likely to experience autumns as warm as this one has been in Australia.</p>
<h2>How we’ll remember autumn 2016</h2>
<p>In the past few months, Australia has seen many extreme hot weather events. Melbourne experienced its <a href="http://www.theage.com.au/victoria/melbourne-weather-melburnians-swelter-as-temperatures-march-into-record-books-20160308-gne1ek.html">warmest March night on record</a>, while Sydney had a run of <a href="https://theconversation.com/sydney-so-hot-right-now-whats-behind-the-citys-record-run-of-warm-weather-55756">39 days with daytime highs above 26°C</a>, as the summer heat continued long into March.</p>
<p>But it’s the <a href="https://theconversation.com/au/topics/2016-coral-bleaching-event">coral bleaching event</a> on the Great Barrier Reef that will likely linger in our memories the longest. Some <a href="https://theconversation.com/great-barrier-reef-bleaching-stats-are-bad-enough-without-media-misreporting-58283">93% of the reef was found to be affected by bleaching</a> and recent surveys have revealed that <a href="https://theconversation.com/how-will-the-barrier-reef-recover-from-the-death-of-one-third-of-its-northern-corals-60186">more than one-third of coral</a> in the northern and central parts of the reef have died. </p>
<p>Without climate change, a bleaching event like this would be <a href="https://theconversation.com/great-barrier-reef-bleaching-would-be-almost-impossible-without-climate-change-58408">virtually impossible</a>.</p>
<p>The extreme heat over Australia this autumn and the associated damage to the reef are also having an effect on the election campaign. As public concern over the future of the reef grows, the parties are being asked to defend their climate change policies. </p>
<p>Both major parties have made election commitments to the reef, with the Coalition announcing an extra A$6 million to tackle crown-of-thorns starfish (adding to a further A$171 million committed under the 2016 budget), and Labor an extra A$377 million over five years (A$500 million in total). While both Labor and the Coalition aim to improve water quality in the reef through their policies, the coral bleaching and death this year is linked with warm seas.</p>
<p>Whether we’ll be able to save parts of the reef largely depends on whether we reduce our greenhouse gas emissions and manage to prevent the rising trend in temperatures from continuing.</p><img src="https://counter.theconversation.com/content/60329/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew King receives funding from the ARC Centre of Excellence for Climate System Science.</span></em></p>Autumn 2016 was Australia’s hottest, beating the previous record set in 2005.Andrew King, Climate Extremes Research Fellow, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/569062016-04-04T20:07:21Z2016-04-04T20:07:21ZThis summer’s sea temperatures were the hottest on record for Australia: here’s why<figure><img src="https://images.theconversation.com/files/116575/original/image-20160329-17857-fkhdta.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Spencer Gulf at sunset in South Australia.</span> <span class="attribution"><span class="source">Australian Bureau of Meteorology</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The summer of 2015-2016 was <a href="http://www.bom.gov.au/climate/current/season/aus/summary.shtml">one of the hottest on record in Australia</a>. But it has also been hot in the waters surrounding the nation: the hottest summer on record, in fact.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/116577/original/image-20160329-13683-1r3b0g7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/116577/original/image-20160329-13683-1r3b0g7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/116577/original/image-20160329-13683-1r3b0g7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/116577/original/image-20160329-13683-1r3b0g7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/116577/original/image-20160329-13683-1r3b0g7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/116577/original/image-20160329-13683-1r3b0g7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/116577/original/image-20160329-13683-1r3b0g7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Difference in summer sea surface temperatures for the Australian region relative to the average period 1961-1990.</span>
<span class="attribution"><span class="source">Australian Bureau of Meteorology</span></span>
</figcaption>
</figure>
<p>While summer on land has been <a href="https://theconversation.com/sydney-so-hot-right-now-whats-behind-the-citys-record-run-of-warm-weather-55756">dominated by significant warm spells</a>, bushfires, and <a href="https://theconversation.com/hasta-la-vista-el-nino-but-dont-hold-out-for-normal-weather-just-yet-53565">dryness</a>, there is a bigger problem looming in the oceans around Australia. </p>
<p>This summer has outstripped long-term sea surface temperature records that extend back to the 1950s. We have seen warm surface temperatures all around Australia and across most of the Pacific and Indian oceans, with particularly warm temperatures in the southeast and northern Australian regions. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/116585/original/image-20160329-13698-wpsqi0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/116585/original/image-20160329-13698-wpsqi0.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=250&fit=crop&dpr=1 600w, https://images.theconversation.com/files/116585/original/image-20160329-13698-wpsqi0.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=250&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/116585/original/image-20160329-13698-wpsqi0.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=250&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/116585/original/image-20160329-13698-wpsqi0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=314&fit=crop&dpr=1 754w, https://images.theconversation.com/files/116585/original/image-20160329-13698-wpsqi0.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=314&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/116585/original/image-20160329-13698-wpsqi0.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=314&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Last summer’s sea surface temperature rankings for Australia.</span>
<span class="attribution"><span class="source">Australian Bureau of Meteorology</span></span>
</figcaption>
</figure>
<p>In recent months, this warming has been boosted – just like land temperatures – by natural and human-caused climate factors. </p>
<h2>Why so warm?</h2>
<p>These record-breaking ocean temperatures around Australia are somewhat surprising. <a href="https://theconversation.com/bom-were-calling-it-the-2015-el-nino-is-here-41598">El Niño events</a>, such as the one we’re currently experiencing, typically result in cooler than normal Australian waters during the second half of the year. So what is the cause? </p>
<p>The most likely culprit is a combination of local ocean and weather events, with a substantial contributor being human-caused climate change. </p>
<p>In the north, the recent weak monsoon season played a role in warming surface waters. Reduced cloud cover means more sunshine is able to pass through the atmosphere and heat the surface of the ocean. Trade winds that normally stir up the water and disperse the heat deeper into the ocean have also remained weak, leaving the warm water sitting at the surface.</p>
<p>In the south, the <a href="https://theconversation.com/can-you-surf-the-east-australian-current-finding-nemo-style-27392">East Australian Current</a> has extended further south over the summer. This warm current flows north to south down Australia’s east coast. Normally it takes a left turn and heads towards New Zealand, but this year it extended down to Tasmania, bringing warm waters to the south east. </p>
<p>This current is also getting stronger, transporting larger volumes of water southward over time. This is due to the southward movement of high pressure systems towards the pole. </p>
<p>High pressure systems are often associated with clear weather in Australia, and when they move south they prevent rain. This southward movement over time has also been linked to climate changes in our region, meaning that changes in both rainfall and ocean temperatures are responses to the same global factors.</p>
<p>We’ve also seen high ocean temperatures in the Indian Ocean. Around 2010, temperatures in the region suddenly jumped, likely because of the La Niña event in the Pacific Ocean. The strong events during this period transferred massive amounts of warmth from the Pacific Ocean into the Indian Ocean through the Indonesian region.</p>
<p>The warmer waters in the Indian Ocean have persisted since and have influenced land temperatures. The five years since the 2010 La Niña are the five hottest on record in southwest Western Australia (ranked 2011, 2015, 2014, 2013 and 2012). </p>
<h2>What are the impacts?</h2>
<p>The world’s oceans play a major role in global climate by absorbing surplus heat and energy. Oceans have absorbed 93% of the extra heat trapped by the Earth since 1970 as the greenhouse effect has increased. This has lowered the rate at which the atmosphere is warming – which is a good thing. </p>
<p>However, it also means the oceans are heating up, raising sea levels as well as leading to more indirect impacts, such as shifting rainfall patterns.</p>
<p>As a nation that likes to live by the coast as well as enjoy recreation activities and harvest produce from the sea, warmer-than-usual oceans can have significant impacts. </p>
<p>Australia derives a lot of its income from its oceans and while such impacts aren’t often seen immediately, they become apparent over time. </p>
<p>Warm sea temperatures this summer and in the past have seen declines in coral reef health, and strains on commercial fisheries and aquaculture. The <a href="https://theconversation.com/coral-bleaching-comes-to-the-great-barrier-reef-as-record-breaking-global-temperatures-continue-56570">Great Barrier Reef is currently experiencing coral bleaching</a> amid very warm water temperatures.</p>
<p>Our neighbouring Pacific islands have also seen the impacts of these very high sea surface temperatures, with recent mass fish kills and coral bleaching episodes in Fiji.</p>
<p>The impacts of warmer ocean temperatures are also felt on land, as ocean temperatures drive climate and weather. Abnormally <a href="https://theconversation.com/winston-strikes-fiji-your-guide-to-cyclone-science-55134">high sea surface temperatures may have contributed to the intensity of Cyclone Winston</a> as cyclone potential intensity increases with ocean temperature. </p>
<h2>What is the outlook?</h2>
<p>The seasonal outlook from the Bureau of Meteorology shows El Niño weakening over the next few months. This typically means cooler weather and can mean more rain on land.</p>
<p>However, closer inspection shows surface temperatures over the entire Indian Ocean and coastal Australian waters will very likely continue to remain well above average for the next few months. There are currently signs that surface currents are moving warm El Niño waters from the eastern Pacific over to the western Pacific, towards Australia. </p>
<p>There is potential for the East Australian Current to continue to transport this warmth to southern waters as far as Tasmania. Warm water could also be transported through Indonesia and travel south along the Western Australian coast via the warm Leeuwin Current, potentially causing further warming of already record warm waters.</p>
<p>So for the near future, the waters are going to continue to be warm. That’s good news if you’re heading to the beach, but not so good for the environment.</p><img src="https://counter.theconversation.com/content/56906/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Claire Spillman has received research funding in the past from CSIRO, Fisheries Research and Development Corporation (FRDC), eReefs/National Plan for Environmental Information (NPEI) and AusAID. </span></em></p><p class="fine-print"><em><span>David Jones, David Walland, and Elaine Miles do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The summer of 2015-2016 was the hottest on record for Australia’s oceans.Elaine Miles, Ocean Climatologist , Australian Bureau of MeteorologyClaire Spillman, Research Scientist, Australian Bureau of MeteorologyDavid Jones, Scientist, Australian Bureau of MeteorologyDavid Walland, Australian Bureau of MeteorologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/563412016-03-16T03:49:04Z2016-03-16T03:49:04ZFebruary’s global temperature spike is a wake-up call<p>Global temperatures for February showed a disturbing and unprecedented upward spike. It was 1.35°C warmer than the average February during the usual baseline period of 1951-1980, according to <a href="http://data.giss.nasa.gov/gistemp/">NASA data</a>. </p>
<p>This is the largest warm anomaly of any month since records began in 1880. It far exceeds the records set in 2014 and again in 2015 (the first year when the 1°C mark was breached). </p>
<p>In the same month, <a href="http://nsidc.org/arcticseaicenews/">Arctic sea ice cover reached its lowest February value ever recorded</a>. And last year carbon dioxide concentration in our atmosphere increased by more than 3 parts per million, another record. </p>
<p>What is going on? Are we facing a climate emergency?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/115226/original/image-20160316-8453-ayn212.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/115226/original/image-20160316-8453-ayn212.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/115226/original/image-20160316-8453-ayn212.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=341&fit=crop&dpr=1 600w, https://images.theconversation.com/files/115226/original/image-20160316-8453-ayn212.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=341&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/115226/original/image-20160316-8453-ayn212.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=341&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/115226/original/image-20160316-8453-ayn212.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=429&fit=crop&dpr=1 754w, https://images.theconversation.com/files/115226/original/image-20160316-8453-ayn212.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=429&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/115226/original/image-20160316-8453-ayn212.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=429&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">February temperatures from 1880 to 2016 from NASA GISS data. Values are deviations from the base period of 1951-1980.</span>
<span class="attribution"><span class="source">Stefan Rahmstorf</span></span>
</figcaption>
</figure>
<h2>El Niño plus climate change</h2>
<p>Two things are combining to produce the record warmth: the well-known global warming trend caused by our greenhouse gas emissions, and an El Niño in the tropical Pacific.</p>
<p>The record shows that global surface warming has always been overlaid by natural climate variability. The biggest single cause of this variability is the natural cycle between El Niño and La Niña conditions. The El Niño in 1998 was a record-breaker, but now we have one that looks even bigger by some measures.</p>
<p>The pattern of warmth in February shows typical signatures of both long-term global warming and El Niño. The latter is very evident in the tropics. </p>
<p>Further north, the pattern looks similar to other Februaries since the year 2000: particularly strong warming in the Arctic, Alaska, Canada and the northern Eurasian continent. Another notable feature is a cold blob in the northern Atlantic, which has been attributed to a <a href="http://www.realclimate.org/index.php/archives/2015/03/whats-going-on-in-the-north-atlantic/">slowdown in the Gulf Stream</a>.</p>
<p>The February warming spike brought us at least 1.6°C above pre-industrial global average temperatures. This means that, for the first time, we have passed the 1.5°C international aspirational goal <a href="https://theconversation.com/the-paris-climate-agreement-at-a-glance-50465">agreed in December in Paris</a>. We are coming uncomfortably close to 2°C. </p>
<p>Fortunately, this is temporary: the El Niño is beginning to subside. </p>
<h2>Emissions still increasing</h2>
<p>Unfortunately, we have done little about the underlying warming. If unchecked, this will cause these breaches to happen more and more often, with a greater than 2°C breach perhaps only a couple of decades away.</p>
<p>The greenhouse gases slowly heating the Earth are still increasing in concentration. The <a href="http://www.esrl.noaa.gov/gmd/ccgg/trends/">12-month average surpassed 400 parts per million roughly a year ago</a> – the highest level for at least a million years. The average rose even faster in 2015 than previous years (probably also due to the El Niño, as this tends to bring drought to many parts of the globe, meaning less carbon is stored in plant growth). </p>
<p>A glimmer of hope is that our <a href="https://theconversation.com/growth-in-fossil-fuel-emissions-slowed-in-2015-so-have-we-finally-reached-the-peak-51669">carbon dioxide emissions from fossil fuels</a> have, for the first time in decades, stopped increasing. This trend has been evident over the past couple of years, mainly due to a decline of coal use in China, which recently announced the closure of around 1,000 coal mines.</p>
<h2>Have we underestimated global warming?</h2>
<p>Does the “spike” change our understanding of global warming? In thinking about climate change, it is important to take the long view. A predominant La Niña-like situation over recent years did not mean global warming had “stopped” as a few public figures were (and probably still are) claiming. </p>
<p>Likewise, a hot spike due to a major El Niño event – even though it is surprisingly hot – doesn’t mean global warming was underestimated. In the longer run the <a href="https://twitter.com/rahmstorf/status/698380997222510592">global warming trend agrees very well</a> with longstanding predictions. But these predictions nevertheless paint a picture of a very warm future if emissions are not brought down soon.</p>
<p>The situation is similar to that of a serious illness like cancer: the patient usually does not get slightly worse each day, but has weeks when the family thinks he may be recovering, followed by terrible days of relapse. The doctors do not change their diagnosis each time this happens, because they know this is all a part of the disease.</p>
<p>Although the current El-Niño-driven spike is temporary, it will last long enough to have some severe consequences. For example, <a href="http://www.abc.net.au/news/2016-03-14/coral-bleaching-is-getting-worse-great-barrier-reef-gbrmpa/7244742">a massive coral bleaching event now appears likely on the Great Barrier Reef</a>.</p>
<p>Here in Australia we have been breaking heat records in the past few months, including 39 straight <a href="https://theconversation.com/sydney-so-hot-right-now-whats-behind-the-citys-record-run-of-warm-weather-55756">days in Sydney above 26°C (double the previous record)</a>. News reports seem to be focusing on the role of El Niño, but El Niño does not explain why oceans to the south of Australia, and in the Arctic, are at record high temperatures. </p>
<p>The other half of the story is global warming. This is boosting each successive El Niño, along with all its other effects on <a href="http://www.realclimate.org/index.php/archives/2016/02/millennia-of-sea-level-change/">ice sheets and sea level</a>, the global ecosystem and <a href="http://www.nap.edu/catalog/21852/attribution-of-extreme-weather-events-in-the-context-of-climate-change">extreme weather events</a>. </p>
<p>This is the true climate emergency: it is getting more difficult with each passing year for humanity to prevent temperatures from rising above 2°C. February should remind us how pressing the situation is.</p><img src="https://counter.theconversation.com/content/56341/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Steve Sherwood receives funding from the Australian Research Council, the New South Wales Government Office of Environment and Heritage, and the Federal Department of the Environment.</span></em></p><p class="fine-print"><em><span>Stefan Rahmstorf receives funding from the German science ministry for a research project on modelling Ice Age cycles.</span></em></p>February 2016 was the hottest month by the biggest margin ever. Does that mean global warming has gone into hyperdrive?Steven Sherwood, Director and ARC Laureate Fellow, Climate Change Research Centre, UNSW SydneyStefan Rahmstorf, Professor of Physics of the Oceans, Potsdam Institute for Climate Impact ResearchLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/554382016-03-07T18:58:04Z2016-03-07T18:58:04ZWe traced the human fingerprint on record-breaking temperatures back to the 1930s<figure><img src="https://images.theconversation.com/files/113009/original/image-20160226-18066-l3gr18.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Climate change has been implicated in record-breaking temperatures across the 20th century.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/kayveeinc/5418365624/in/photolist-9fNxjY-4yZrQ2-4z4GTS-9t7KM8-9eTavx-4yZsor-jgfDMf-5Zx7um-5XTkCj-7eRtnf-jgJbfp-6c5Dmj-5XkNzn-jHg9yt-jHiSBJ-je6XBW-je49xB-9t7KTB-7uZJaT-5W4jx8-5YemcW-5W6tDu-9f2Yav-jHfZvZ-5X7ZSd-dLHJPg-6uzGbR-7hskq1-jHg4Ji-jHggUv-4yZsEt-4z4HgJ-63iwCo-63iwCq-63iwCj-9taKrb-7Lo9Tf-7LbF3N-ptKWJC-qDJ1uF-dMv4LK-dMABCJ-dMv3P8-dMAE4U-dMAEUy-xcjRj-6c5wzW-6c1nkt-6c5wfh-6c5vwj">KayVee.INC/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>In recent years climate scientists have looked at the role climate change played in unusual extreme weather events such as <a href="https://theconversation.com/the-human-role-in-our-angry-hot-summer-15596">Australia’s hottest summer in 2012-13</a> and <a href="https://theconversation.com/a-year-of-records-the-human-role-in-2014s-wild-weather-50208">recent heatwaves</a>. </p>
<p>Before now no one had looked at how far back in time we could go and still link these weird weather events and record-breaking climate extremes to our influence on the climate.</p>
<p><a href="http://onlinelibrary.wiley.com/doi/10.1002/2015GL067448/abstract">Our study</a>, published in Geophysical Research Letters, addressed the question of when climate change started altering the influence of record hot years and summers in a way we can detect. We looked at five regions of the world, as well as the whole globe.</p>
<h2>We’ve been changing the weather for a long time</h2>
<p>Human-made climate change has been influencing heat extremes for decades, with many past records directly attributable to the effect we have had on the climate.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/113004/original/image-20160226-18089-pqr7j3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/113004/original/image-20160226-18089-pqr7j3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/113004/original/image-20160226-18089-pqr7j3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=706&fit=crop&dpr=1 600w, https://images.theconversation.com/files/113004/original/image-20160226-18089-pqr7j3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=706&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/113004/original/image-20160226-18089-pqr7j3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=706&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/113004/original/image-20160226-18089-pqr7j3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=887&fit=crop&dpr=1 754w, https://images.theconversation.com/files/113004/original/image-20160226-18089-pqr7j3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=887&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/113004/original/image-20160226-18089-pqr7j3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=887&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Number of record-breaking hot years and summers attributable to the human influence on the climate</span>
<span class="attribution"><span class="source">Author provided</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The map above shows how many record-breaking hot years and summers we can attribute to climate change in different parts of the world.</p>
<p>We found the last 16 record-breaking hot years globally up to 2014 were made more likely because of climate change (we didn’t include 2015 – the current holder of the hottest year record – because we performed our analysis before the end of last year). The earliest year we found that humans had contributed to temperature records was 1937. Since then every record-breaking year globally (all 15 following 1937 that were the hottest up to that time) can be attributed to climate change. </p>
<p>The record-breaking hot years the world has experienced in the last couple of decades would have been almost impossible in a world without climate change.</p>
<p>Even on a regional scale we see many record-breaking hot years and summers where the fingerprint of climate change is clear. The last six record hot years and three record hot summers in Australia were made more likely by the human influence on the climate.</p>
<h2>Hot and cold</h2>
<p>In other regions of the world, human activities have also had a cooling effect through increasing aerosols in the atmosphere (due to industrial activity and the emissions of particulates from cars and airplanes, for example). Here fewer record heat events show as clear a human influence. But even in areas such as eastern Asia the overall human influence on the climate has increased the likelihood of hot years and summers back to the 1980s.</p>
<p>Central England has had no record-breaking hot summers since the extreme heat of 1976. Any future hot summer that breaks that record will be associated with climate change.</p>
<p>In fact, for all the regions of the world we studied, the influence of climate change on record-breaking heat extremes has been increasing through time. For instance, we find that the Australian record hot year of 2013 was 22 times more likely due to climate change, whereas if we look back at the 1980 record we find only a three-fold increase in likelihood of that record from human influences (<a href="https://theconversation.com/hottest-12-month-period-confirmed-so-what-role-did-humans-play-17737">see here for an explanation of how these studies are done</a>). </p>
<p>As we have exerted a greater influence on the climate, by increasing the concentration of greenhouse gases in the atmosphere, the likelihood of record-breaking heat extremes has increased.</p>
<p>This study shows that the human influence on record-breaking hot extremes extends back many decades, especially when we look at the globe and Australia. While our aerosol emissions have delayed a clear human influence appearing in other areas of the world, the fingerprint of climate change has become clear over recent decades as the warming influence of greenhouse gases has overtaken the cooling influence of aerosols.</p>
<h2>Reduce emissions and we should get fewer records</h2>
<p>Other factors also influence the likelihood of record heat events occurring – for example, El Niño events. We looked at only the human influence in this study. Undoubtedly natural variability was important in many of these events occurring; by isolating the human influence we found that climate change played a major role in many record heat events as well.</p>
<p>Any hot years or summers in the near future in these regions will be strongly linked with climate change. This analysis was conducted before the end of last year, so although we didn’t include it we would expect a similar result for the <a href="https://theconversation.com/2015-to-be-hottest-year-ever-world-meteorological-organization-51310">2015 global heat record</a>. Already, <a href="http://www.theguardian.com/environment/2015/dec/17/2016-set-to-be-hottest-year-on-record-globally">2016 is expected to challenge that record</a>.</p>
<p>Whether we continue to experience such frequent record-breaking heat extremes will in part depend on whether we reduce the influence on the climate as the Paris agreement sets out to do. </p>
<p>If we reduce our emissions, we may not see as many future record hot summers and years. The impacts these events have on society and the environment may be reduced.</p><img src="https://counter.theconversation.com/content/55438/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew King receives funding from the ARC Centre of Excellence for Climate System Science.</span></em></p><p class="fine-print"><em><span>Mitchell Black receives funding from the ARC Centre of Excellence for Climate System Science. </span></em></p>Record-breaking years have been almost impossible without human-caused climate change.Andrew King, Climate Extremes Research Fellow, The University of MelbourneMitchell Black, PhD Candidate, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/557562016-03-06T19:04:47Z2016-03-06T19:04:47ZSydney, so hot right now: what’s behind the city’s record run of warm weather?<figure><img src="https://images.theconversation.com/files/113834/original/image-20160304-20126-1nz3fjo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Nice day for the beach. In fact there have been rather a lot of those in Sydney lately.</span> <span class="attribution"><span class="source">Natalia Montes de Oca/Wikimedia Commons</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Sydney is hot. Well technically, it’s persistently warm and lacking cool outbreaks, but this run of weather is no less remarkable for that.</p>
<p>The city has had a record 31 straight days above 26°C (and counting), smashing the previous record of 19 days in a row set in 2014. Nights have also been unusually warm, with only two nights in February dropping below 19°C (equalling the record set in 2003 and 1983).</p>
<p>Only one day last month dipped below the average February maximum temperature for Sydney (25.8°C). The previous record for February was five below-average days, which happened in 2000, 1983 and 1978. </p>
<p>March has continued this pattern, with every day so far (including the forecast period) expected to be above average.</p>
<p>So what’s going on here? Is it climate change? Is it the <a href="https://theconversation.com/the-rise-and-rise-of-the-2015-el-nino-41616">super El Niño</a>? Is it urban heating, or some other factor? Or is it just natural variation in the weather?</p>
<p>Like many things in life, the answer is that it’s complicated. </p>
<h2>Weather report</h2>
<p>Over recent weeks, there have been extended periods with a high-pressure ridge over eastern New South Wales and weak low-pressure troughs inland. That is creating mostly stable atmospheric conditions for Sydney (that is, no rain) and funnelling warm air from central Australia over the metropolitan region.</p>
<p>In addition, the <a href="http://www.bom.gov.au/climate/enso/history/ln-2010-12/SAM-what.shtml">Southern Annular Mode (SAM)</a>, the oscillating latitude of prevailing westerly winds, has been positive for most of February. This results in high-pressure systems sitting further to the south, blocking the passage of cold fronts across New South Wales. </p>
<p>But while it’s not the first time we’ve seen this combination of weather factors, it’s the first time it has resulted in such a persistently warm February.</p>
<p>Of course, February is warm anyway: Sydney’s second-warmest month of the year, only 0.1°C behind January on average. And, with apologies for stating the obvious, summer is our warmest season and therefore the one when high temperature records are most likely to fall.</p>
<p>A key question to ask is: if the February average is 25.8°C and we’re talking about a run of days above 26°C, is this really that exceptional? </p>
<p>Well, perhaps not in terms of news headlines, although we’ve all noticed the summer warmth <a href="http://www.smh.com.au/environment/weather/sydney-weather-no-end-in-sight-for-unusual-early-autumn-heat-20160303-gna5ft">spilling into autumn</a>. But what is most notable is the total lack of intervening cool conditions. </p>
<p>It’s not just a case of picking one number that works either. Sydney has set a record for the longest run of days above 24°C, 25°C, 26°C and 27°C for any month. <a href="http://www.bom.gov.au/climate/current/month/nsw/sydney.shtml">Sydney’s February 2016</a> average maximum temperature was 28.2°C, its equal-fifth-warmest February on record.</p>
<h2>The oceans around us</h2>
<p>Beyond the regional weather conditions, the strong El Niño conditions have also influenced the persistent warmth. A “strong” El Niño – a description that refers to the distribution of heat in the tropical Pacific – doesn’t necessarily equate to a correspondingly strong impact on our weather.</p>
<p>That said, El Niños tend to result in <a href="https://theconversation.com/this-summers-el-nino-looks-set-to-bring-more-heatwaves-to-australias-north-and-east-47704">more hot days and heatwaves</a> for eastern Australian locations like Sydney. </p>
<p>Offshore sea temperatures have also been uncharacteristically warm. The East Australian Current has <a href="https://theconversation.com/things-warm-up-as-the-east-australian-current-heads-south-31889">extended further south</a> (incidentally causing havoc with the oyster industry), bringing warm waters to the southeast coast and also contributing to Tasmania’s <a href="http://www.bom.gov.au/climate/current/season/tas/summary.shtml">hottest summer on record</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/113833/original/image-20160304-20108-1gcfac9.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/113833/original/image-20160304-20108-1gcfac9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/113833/original/image-20160304-20108-1gcfac9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=327&fit=crop&dpr=1 600w, https://images.theconversation.com/files/113833/original/image-20160304-20108-1gcfac9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=327&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/113833/original/image-20160304-20108-1gcfac9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=327&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/113833/original/image-20160304-20108-1gcfac9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=412&fit=crop&dpr=1 754w, https://images.theconversation.com/files/113833/original/image-20160304-20108-1gcfac9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=412&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/113833/original/image-20160304-20108-1gcfac9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=412&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sea surface temperatures off Australia, January 2016.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>If we don’t consider Sydney’s recent weather in isolation, then it is clear that climate change is playing its role here as well. Both land and ocean temperatures have warmed. And those warmer offshore sea surface temperatures keep our nights warmer, particularly in coastal cities. </p>
<p>Warm, hot conditions are becoming <a href="https://theconversation.com/climate-council-heatwaves-are-getting-hotter-and-more-frequent-23253">more likely</a>, while cool outbreaks are becoming less so. The whole of southeastern Australia has experienced fewer cold outbreaks in recent years (although they do still happen).</p>
<h2>Highs and lows</h2>
<p>Sydney in January had warm temperatures, with two heatwaves (defined as at least three 30°C days in a row), but interspersed with quite a few wet spells. One of them, caused by an East Coast Low, resulted in the coldest January day since 1978 – a maximum of just 18.6°C on January 6, 2016. </p>
<p>Sydneysiders probably remember this as that one weird day when we all wore jumpers and Ugg boots. </p>
<p>The persistent warmth has the effect of making these cool changes more noticeable and memorable. But the ongoing high temperatures are actually the more unusual aspect of our weather, which is why <a href="https://theconversation.com/sure-winter-felt-chilly-but-australia-is-setting-new-heat-records-at-12-times-the-rate-of-cold-ones-35607">hot records are being broken far more regularly than cold ones</a>. </p>
<p>It’s not just February and March. It may be but a distant memory now, but Sydney has already had four heatwaves (three straight days of at least 30°C) this warm season (October 4-6; November 18-20; January 11-14; and January 19-21) – another record.</p>
<p>According to our <a href="http://www.bom.gov.au/climate/outlooks/#/temperature/summary">climate outlook</a>, March is shaping up to be warm for both daily maximum and nightly minimum temperatures. The record warm run could extend to 37 days, with possibly another heatwave thrown into the mix. It’s lucky that Sydney has lots of beaches. </p>
<p><em>All statistics in this article are based on records from <a href="http://www.bom.gov.au/products/IDN60901/IDN60901.94768.shtml">Sydney Observatory Hill</a>, which run from 1858 to the present.</em></p><img src="https://counter.theconversation.com/content/55756/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Sydney is in the process of smashing the record for the longest run of days above 26°C. Weather, El Nino and climate change are all playing their part.Agata Imielska, Senior Climatologist, Australian Bureau of MeteorologyBlair Trewin, Climatologist, National Climate Centre, Australian Bureau of MeteorologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/539822016-02-02T05:37:30Z2016-02-02T05:37:30ZThe weather bureau might be underestimating Australian warming: here’s why<figure><img src="https://images.theconversation.com/files/109900/original/image-20160202-32257-19lvg1a.jpg?ixlib=rb-1.1.0&rect=943%2C97%2C3158%2C2649&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">It's all a matter of perspective. </span> <span class="attribution"><span class="source">Australia image from www.shutterstock.com</span></span></figcaption></figure><p>Former prime minister’s business advisor Maurice Newman fired <a href="http://www.theaustralian.com.au/opinion/australian-bureau-of-meteorology-needs-to-open-records-to-audit/news-story/64dee9b2edb78bd8477c620775ad3eb7">another attack</a> at the Australian Bureau of Meteorology on Monday, arguing in The Australian that the weather bureau needs to be investigated for fiddling with the climate data that show Australia is getting warmer. </p>
<p>Technically known as “homogenisation”, the practice of removing biases from historical climate data has been <a href="https://theconversation.com/no-the-bureau-of-meteorology-is-not-fiddling-its-weather-data-31009">well defended</a>. In fact, you can <a href="https://theconversation.com/why-scientists-adjust-temperature-records-and-how-you-can-too-36825">do it yourself</a>. </p>
<p>In his latest salvo, Newman claims that estimates of surface temperature trends by weather bureaus “diverge increasingly with satellite and radiosonde datasets”, and thus call into question the “integrity” of the surface data and the processing of those data.</p>
<p>This is a very easy claim to check, and interestingly it shows the weather bureau might actually be <em>underestimating</em> warming.</p>
<h2>Surface v satellite</h2>
<p>You can find <a href="http://www.bom.gov.au/climate/change/">yearly average Australian temperatures</a> at the Bureau of Meteorology. I have plotted the mean annual temperature for Australia, expressed as difference from the 1979-2015 average, in the graph below. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/109892/original/image-20160201-32222-1b5jxqp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/109892/original/image-20160201-32222-1b5jxqp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/109892/original/image-20160201-32222-1b5jxqp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/109892/original/image-20160201-32222-1b5jxqp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/109892/original/image-20160201-32222-1b5jxqp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/109892/original/image-20160201-32222-1b5jxqp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/109892/original/image-20160201-32222-1b5jxqp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/109892/original/image-20160201-32222-1b5jxqp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Satellite data show a stronger warming trend.</span>
<span class="attribution"><span class="source">Neville Nicholls</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>I have only plotted the data since 1979, since that is the first year for which satellite estimates of temperatures are available. The Bureau estimates of average annual Australian temperature for each year are shown as the thin blue line. The linear trend is shown as a thick blue line.</p>
<p>The satellite data for the temperature of the lower atmosphere, averaged across Australia, are available from the <a href="http://vortex.nsstc.uah.edu/data/msu/v6.0beta/tlt/uahncdc_lt_6.0beta4.txt">scientists at the University of Alabama</a> at Huntsville. I have also plotted these data in the graph below (as a thin red line).</p>
<p>These are the latest version of the satellite data (version 6.0). As with the surface data, I have plotted the satellite data as differences from their 1979-2015 average. The linear trend of the satellite estimates of temperature over Australia is shown as a thick red line.</p>
<p>You can see immediately that the two graphs vary up and down quite similarly, but that the two graphs are indeed diverging. This is because the satellite estimates of Australian temperature show much stronger warming than do the surface temperatures measured by thermometers by the Bureau. </p>
<p>The Bureau data show warming at a rate of about 1.3°C per century, over the period 1979 to 2015. The satellite data reveal a warming rate of about 2.4°C per century over the same period.</p>
<h2>Why the difference?</h2>
<p>It is not surprising that the Bureau’s surface data and the satellite data are not identical. They measure two different things, and use very different data to do it. </p>
<p>The Bureau’s data are from thermometers at the surface. These data are adjusted to take into account possible sources of bias, such as the urban heat island effect or changes in the location of the thermometers. </p>
<p>The satellite data are from remote observations of radiation from the lower layers of the atmosphere, observed by a small number of satellites. These data have been adjusted for changes between satellites, changes in instrumentation, and even changes in the time of observation. (You can read a discussion of these adjustments <a href="http://www.drroyspencer.com/2015/04/version-6-0-of-the-uah-temperature-dataset-released-new-lt-trend-0-11-cdecade">here</a>.)</p>
<p>But despite all these adjustments (to the satellite data and to the surface data), the two estimates of temperature averaged across Australia show quite similar variations between years, and both show substantial warming over the period for which we have satellite estimates. </p>
<p>But the stronger warming trend in the satellite data suggests that the Bureau, if anything, is underestimating the rate at which Australia is warming.</p>
<p>However, I suspect that the stronger warming shown by the satellite data in the graph above is incorrect.</p>
<p>In the graph below I’ve used a slightly <a href="http://vortex.nsstc.uah.edu/data/msu/t2lt/uahncdc_lt_5.6.txt">older version</a> of the satellite data still available from the University of Alabama. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/109893/original/image-20160201-32240-18qwlhr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/109893/original/image-20160201-32240-18qwlhr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/109893/original/image-20160201-32240-18qwlhr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=424&fit=crop&dpr=1 600w, https://images.theconversation.com/files/109893/original/image-20160201-32240-18qwlhr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=424&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/109893/original/image-20160201-32240-18qwlhr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=424&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/109893/original/image-20160201-32240-18qwlhr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/109893/original/image-20160201-32240-18qwlhr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/109893/original/image-20160201-32240-18qwlhr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Older satellite data are more similar to surface measurements.</span>
<span class="attribution"><span class="source">Neville Nicholls</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Using the older version of the satellite data (that has somewhat different adjustments made by the University of Alabama scientists), the similarity with the Bureau’s estimates of Australian average temperature is even more striking. </p>
<p>And the satellite data show a warming trend much closer to the Bureau’s estimate (although the satellite data still exhibit slightly more warming over Australia than do the Bureau’s surface measurements).</p>
<p>But whichever version of the satellite data we use, there is no evidence from the satellite data that the Bureau is overestimating the rate of warming, and there is some reason to believe, if we were to trust the satellite data, that Australia may even be warming (slightly) faster than the Bureau’s data indicate.</p><img src="https://counter.theconversation.com/content/53982/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Neville Nicholls has received funding, in the past, for climate research from various government research funding agencies. He researches the nature, causes, impacts and predictability of natural and human-caused climate variations and change. He was a research scientist at the Bureau of Meteorology 1971-2005, where he initiated and led efforts to develop high-quality historical climate data sets (which involved removing biases caused by changes in instrumentation, location and exposure) and to make these data freely available. </span></em></p>Former PM’s business advisor Maurice Newman recently claimed that satellite temperature data tell a different story to data collected on the ground. He’s right - but that’s how it’s meant to be.Neville Nicholls, Professor emeritus, School of Earth, Atmosphere and Environment, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/532832016-01-21T01:36:19Z2016-01-21T01:36:19ZIt’s official: 2015 was the hottest year ever recorded<p>It’s official: 2015 was the hottest year on record. The US-based National Oceanic and Atmospheric Administration has confirmed overnight that 2015 saw the global average temperature <a href="https://www.ncdc.noaa.gov/sotc/global/201513">climbing to 0.90°C</a> above the 20th-century average of 13.9°C. The record has been confirmed by the <a href="http://www.metoffice.gov.uk/news/releases/archive/2016/2015-global-temperature">UK Met Office</a>. </p>
<p>It’s been only a year since the record was previously broken, but 2015 stands out as an extraordinarily hot year. 2014, the previous hottest year, was 0.74°C above the global average. December 2015 marks the first time in the NOAA record a global monthly temperature anomaly has exceeded 1°C - it reached 1.11°C.</p>
<p>Every month since February 1985 has been warmer than average, and 2015 is the 39th consecutive year with above-average annual temperatures in an uninterrupted run that began in the mid 1970s. Ten months in 2015 beat previous records for those months. </p>
<p>The evidence that the so-called <a href="https://theconversation.com/improved-data-set-shows-no-global-warming-hiatus-42807">“global warming hiatus” is over</a> is compelling – <a href="http://www.nature.com/news/climate-change-hiatus-disappears-with-new-data-1.17700">if it ever existed</a>.</p>
<iframe src="https://charts.datawrapper.de/9RvfW/index.html" frameborder="0" allowtransparency="true" allowfullscreen="allowfullscreen" webkitallowfullscreen="webkitallowfullscreen" mozallowfullscreen="mozallowfullscreen" oallowfullscreen="oallowfullscreen" msallowfullscreen="msallowfullscreen" width="100%" height="400"></iframe>
<p>Air temperatures over the land rose markedly to a new record of 1.33°C above average, and ocean temperatures also reached a new record anomaly of 0.74°C in 2015. The global ocean has absorbed up to 90% of the excess heat retained or accumulated by human activities since the industrial revolution, and <a href="http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate2915.html">ocean temperatures</a> show clear warming trends both at the surface and deep down. </p>
<p>In 2015/2016 a strong El Niño event is bringing some of that heat buried in the ocean back to the surface.</p>
<h2>The “perfect storm”</h2>
<p>Global temperatures are influenced by both natural and human factors. </p>
<p>2015 saw the development of an El Niño event classed as one of the <a href="https://theconversation.com/2015-16-is-shaping-up-to-deliver-a-rollercoaster-from-strong-el-nino-to-la-nina-46135">three strongest on record</a>, comparable to those of <a href="http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensoyears.shtml">1982/83 and 1997/98</a>. </p>
<p>These events are linked to higher global air temperatures. Since 1850 <a href="http://www.giss.nasa.gov/research/news/20150116/">many of the warmest years have also been El Niño years</a>. El Niño events are driven by changes in the winds across the Pacific Ocean, which move warm water from the western Pacific to the east. </p>
<p>In 2015 central Pacific sea surface temperatures were more than 3°C above average over an area of approximately 5.5 million square kilometres, around 70% of the size of the Australian continent. Air temperatures increase during El Niño events as heat is transferred from the ocean to the atmosphere.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/108380/original/image-20160118-20933-ea932c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/108380/original/image-20160118-20933-ea932c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108380/original/image-20160118-20933-ea932c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=383&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108380/original/image-20160118-20933-ea932c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=383&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108380/original/image-20160118-20933-ea932c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=383&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108380/original/image-20160118-20933-ea932c.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=481&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108380/original/image-20160118-20933-ea932c.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=481&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108380/original/image-20160118-20933-ea932c.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=481&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sea surface temperature anomalies, Oct-Dec 2015 showing the characteristic El Niño pattern of increases across the central to eastern Pacific.</span>
<span class="attribution"><a class="source" href="http://www.esrl.noaa.gov/psd/map/clim/sst.shtml">NOAA</a></span>
</figcaption>
</figure>
<p>But a strong El Niño event alone is not sufficient to account for the 2015 record temperature anomaly. </p>
<p>In May 2015 carbon dioxide concentrations reached a monthly value of 403.9 parts per million (ppm) - the <a href="http://www.esrl.noaa.gov/gmd/ccgg/trends/">highest ever recorded</a>. The average concentration of CO₂ in 2015 may exceed 400 pppm for the first time in human history. CO₂ is the one of the principal greenhouse gases responsible for human-induced global warming. </p>
<p>Since 2008 the CO₂ concentration has increased by an average of 2.1 ppm per year, largely due to fossil fuel and land-use emissions, emphasising the <a href="http://www.globalcarbonproject.org/carbonbudget/15/hl-compact.htm">significant impact of human activity</a> on the atmosphere. </p>
<p>CO₂ concentrations now <a href="https://www.ipcc.ch/publications_and_data/ar4/wg1/en/tssts-2-1-1.html">exceed pre-industrial levels</a> by more than <a href="">40%</a>, and the likelihood of this increase and the associated warming being due only to natural factors is <a href="https://theconversation.com/99-999-certainty-humans-are-driving-global-warming-new-study-29911">vanishingly small</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/108382/original/image-20160118-20933-z9xr3m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/108382/original/image-20160118-20933-z9xr3m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108382/original/image-20160118-20933-z9xr3m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=465&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108382/original/image-20160118-20933-z9xr3m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=465&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108382/original/image-20160118-20933-z9xr3m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=465&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108382/original/image-20160118-20933-z9xr3m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=585&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108382/original/image-20160118-20933-z9xr3m.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=585&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108382/original/image-20160118-20933-z9xr3m.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=585&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Carbon dioxide exceeded 400 ppm in 8 months in 2015.</span>
<span class="attribution"><a class="source" href="http://www.esrl.noaa.gov/gmd/ccgg/trends/">NOAA</a></span>
</figcaption>
</figure>
<h2>Climate extremes everywhere</h2>
<p>Across the globe 2015 was characterised by <a href="https://www.wmo.int/media/content/wmo-2015-likely-be-warmest-record-2011-2015-warmest-five-year-period">weather and climate extremes</a> from floods and severe storms to droughts and heatwaves.</p>
<p>In Australia climate conditions are being pushed beyond our historical experience of natural climate variability and into new territory. Global warming has increased the <a href="https://theconversation.com/australias-hottest-year-was-no-freak-event-humans-caused-it-21734">likelihood of record-breaking temperatures</a> by up to 100 times. </p>
<p>In 2015 records were broken once again across Australia, in a series of high temperature events particularly in Western Australia (<a href="http://www.abc.net.au/news/2015-01-23/heatwave-conditions-in-pilbara-as-close-to-record-temps-tipped/6041834">January</a>), Queensland (<a href="http://www.abc.net.au/news/2015-03-02/heatwave-in-western-queensland-heading-towards-southeast/6271986">March</a>), and the south-eastern states (<a href="http://www.smh.com.au/environment/weather/southern-australias-heatwave-smashed-records-as-warmth-starts-to-build-again-20151008-gk4xa2.html">October</a>, <a href="http://www.abc.net.au/news/2015-11-16/heatwave-builds-across-australia-this-week/6944702">November</a> and <a href="http://www.abc.net.au/news/2015-12-19/fire-danger-in-vic-and-sa-as-temperature-soar/7042932">December</a>). </p>
<p>The <a href="http://media.bom.gov.au/releases/237/bureau-confirms-2015-was-australias-fifth-warmest-year-on-record/">Bureau of Meteorology 2015 Annual Climate Statement</a> highlights October as particularly noteworthy. October 2015 was 2.89°C warmer than the average October inn Australia. While this doesn’t make October the hottest month overall (that title still belongs to the summer months), it is the largest margin by which a monthly record has ever been broken. </p>
<p>High temperatures <a href="http://www.smh.com.au/digital-life/digital-life-news/perth-heat-melts-the-internet-20150105-12iee2.html">broke the internet</a> (literally); led to cancelled <a href="http://www.abc.net.au/news/2015-12-18/racing-victoria-cancels-meetings-statewide-due-to-heat/7041080">sporting events</a> in Victoria and South Australia; and added to <a href="http://www.theguardian.com/australia-news/bushfires">severe bushfire conditions</a> in several states.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/108383/original/image-20160118-20951-cxegio.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/108383/original/image-20160118-20951-cxegio.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/108383/original/image-20160118-20951-cxegio.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=412&fit=crop&dpr=1 600w, https://images.theconversation.com/files/108383/original/image-20160118-20951-cxegio.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=412&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/108383/original/image-20160118-20951-cxegio.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=412&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/108383/original/image-20160118-20951-cxegio.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=518&fit=crop&dpr=1 754w, https://images.theconversation.com/files/108383/original/image-20160118-20951-cxegio.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=518&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/108383/original/image-20160118-20951-cxegio.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=518&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">October 2015 warmest on record with largest temperature anomaly.</span>
<span class="attribution"><a class="source" href="http://www.bom.gov.au/climate/current/statements/scs52.pdf">Australia Bureau of Meteorology</a></span>
</figcaption>
</figure>
<p>In response to concerns about this ongoing warming and the associated heat extremes, the <a href="https://theconversation.com/developing-a-taste-for-sagrantino-climate-change-and-australias-wine-industry-4399">wine industry</a> is exploring adaptation options including changing grape varieties; <a href="http://www.abc.net.au/news/2014-01-16/nrn-heat-vegies/5203214">cereal crop, fruit, vegetable and milk producers</a> are trying to reduce the impact of heatwaves and droughts on yields; and we need to change our behaviour and infrastructure to deal with the <a href="https://theconversation.com/adapt-now-to-prevent-poor-health-from-climate-change-report-40958">health impacts</a> of more extreme temperatures and more frequent heatwaves. </p>
<p>We are <a href="https://theconversation.com/whos-been-affected-by-australias-extreme-heat-everyone-36116">all affected</a> by global warming.</p>
<h2>The necessity of mitigation</h2>
<p>The climate and weather impacts of 2015 in Australia are examples of what is happening around the globe, adding to the overwhelming body of evidence of the reality and impacts of global warming. </p>
<p>The combination of a strong El Niño event with ongoing human-induced warming of the ocean and atmosphere set up the conditions for 2015. It is unlikely to be the last such record. </p>
<p>El Niño events are part of natural climate variability and will continue to occur, and until greenhouse gas emissions are reduced at least in line with the <a href="https://theconversation.com/au/topics/paris-2015-climate-summit">Paris Climate Agreement</a> global temperatures will <a href="http://ipcc.ch/pdf/assessment-report/ar5/syr/AR5_SYR_FINAL_SPM.pdf">continue to rise for the foreseeable future</a>. </p>
<p>As agreed by the governments of the world at the <a href="https://unfccc.int/resource/docs/2015/cop21/eng/l09r01.pdf">Paris UNFCCC meeting</a>, the need for effective and urgent local, national and global action to <a href="https://theconversation.com/removing-co2-from-the-atmosphere-wont-save-us-we-have-to-cut-emissions-now-51684">reduce emissions</a> has never been more pointed.</p><img src="https://counter.theconversation.com/content/53283/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The author does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and holds only the academic appointment above.</span></em></p><p class="fine-print"><em><span>Mark Howden does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>2015 was the world’s hottest year ever by a long shot. But what drove the record temperatures, and what role did climate change play?Janette Lindesay, Professor of Climatology, Australian National UniversityMark Howden, Research Scientist, Agriculture Flagship, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/365922015-01-28T03:17:56Z2015-01-28T03:17:56ZBureau’s weather records to be reviewed again – sure, why not?<figure><img src="https://images.theconversation.com/files/70233/original/image-20150128-12455-1nm0i0o.jpg?ixlib=rb-1.1.0&rect=26%2C35%2C1940%2C1254&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Adjusted data from Australian weather stations has been peer-reviewed before. But the government's new technical panel could still offer useful advice.</span> <span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File%3ATuggeranong_(Isabella_Plains)_Automatic_Weather_Station.jpg">Bidgee/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>The federal government’s new “Technical Advisory Forum” on weather data, <a href="http://www.environment.gov.au/minister/baldwin/2015/mr20150119.html">announced by parliamentary environment secretary Bob Baldwin last week</a>, will “review and provide advice on Australia’s official temperature data set”. This data set, known as <a href="http://www.bom.gov.au/climate/change/acorn-sat/">ACORN-SAT</a> and maintained by the Bureau of Meteorology, is the primary record used for monitoring temperature trends around the country.</p>
<p>Although the advisory forum’s detailed terms of reference have not been released, it seems clear that when the panel meets in March it will not be tasked with delivering the comprehensive audit demanded by some of the Bureau’s prominent critics, such as the Prime Minister’s business adviser <a href="http://www.theaustralian.com.au/opinion/climate-is-right-for-a-probe-into-the-bureau-of-meteorology/story-e6frg6zo-1227075659378">Maurice Newman</a>.</p>
<p>That’s fair enough, considering that a comprehensive, independent and international peer review was <a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.222.9455&rep=rep1&type=pdf">carried out as recently as 2011</a> and concluded that the Bureau’s practices and data meet the world’s best standards.</p>
<p>Instead, the announcement seems to be acting on a recommendation from the 2011 review (see <a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.222.9455&rep=rep1&type=pdf">recommendation E4, page 14</a>), which suggests that a technical advisory group be established so that “respected external scientists, statisticians and stakeholders [can] provide an opportunity for external comment on the further development of the ACORN-SAT system”. </p>
<p>The new panel features eight scientists, with a variety of backgrounds but based mostly in statistics, chaired by University of New South Wales statistician Ron Sandland. What advice are they likely to offer?</p>
<h2>What will be reviewed?</h2>
<p>While we do not yet know in any detail, with all this statistical expertise we can perhaps assume that one of the main areas for review will be the statistical practices applied to the ACORN-SAT data. In particular, it is likely that the practices around <a href="https://theconversation.com/no-the-bureau-of-meteorology-is-not-fiddling-its-weather-data-31009">data homogenisation</a> will be covered. </p>
<p>This blending, merging and/or adjusting of weather data is a necessary step in the generation of uniform, continuous climate records of the highest quality. </p>
<p>As described in a <a href="https://theconversation.com/how-to-become-a-citizen-climate-sleuth-31100">previous Conversation article</a>, raw climate data can sometimes be patchy over time, and often contains artificial jumps and/or trends that are due to non-climate factors such as changes in observing practices, the <a href="http://www.theage.com.au/victoria/la-trobe-street-weather-station-closes-after-107-years-20150106-12irxc.html">movement of stations</a>, or changes to the surroundings at the instrument’s location (for instance because of urban development). </p>
<p>For changes to our climate to be effectively monitored, continuous records must be generated that show only those influences associated with the climate. To do this, climate scientists use statistical adjustments that are based on cross-comparisons with any information about what could have caused any artificial signals, or comparisons with other nearby instruments. </p>
<p>Given the expertise of those listed as members of the Technical Advisory Forum, we might speculate that it is these statistical adjustments that are likely to be examined in more detail by the advisory group.</p>
<h2>Fact-checking is a must in science</h2>
<p>The “fact-checking” of scientific data is a necessary part of the scientific process. Thorough, objective and critical evaluation of scientific methods and findings must be undertaken to ensure confidence in scientific findings. </p>
<p>Such tenets underpin the process of peer-review in scientific journals. Notionally, all studies are examined with a fine-toothed comb by a series of experts to ensure they are robust before they are published (although there is <a href="http://www.nature.com/news/publishers-withdraw-more-than-120-gibberish-papers-1.14763">recent evidence</a> that this comb is, unfortunately, not always as rigorous as we might expect).</p>
<p>The same standards must apply for any form of scientific inquiry, including those areas that have become highly politicised and polarised, such as climate science.</p>
<p>An objective external review might also provide information that can be highly constructive and encourage scientific advancement, as well as checking the existing work. For example, a panel of experts in statistical theory and application might be able to provide information on new statistical techniques that could be applied to the data. Any scientist would welcome such input, as it will help to advance scientific knowledge.</p>
<h2>Does Australia’s temperature record need another review?</h2>
<p>This will not be the first time that official temperature records, either in Australia or globally, have been reviewed and their statistical techniques critiqued.</p>
<p>One of the most comprehensive reviews of global surface temperature records was the <a href="http://berkeleyearth.org/">Berkley Earth project</a>, which also included a section on <a href="http://berkeleyearth.lbl.gov/regions/australia">Australia’s data</a>. The review concluded that the evidence of warming in surface temperature records is robust.</p>
<p>Given the previous reviews, it is worth asking whether yet another review is really necessary. There are philosophical arguments as to whether or not it is strictly necessary, but in my opinion it’s worth doing anyway.</p>
<p>On one hand, commissioning review after review does rather give an impression that time and resources are being wasted, especially if the answer is fundamentally the same every time. It is my opinion that any recommendations implemented from the advisory group will not change the key features of Australia’s official temperature record, which shows that the country has warmed by around <a href="http://www.bom.gov.au/state-of-the-climate/">0.9C since 1910</a>, and that <a href="https://www.youtube.com/watch?v=21tjidn6eDI&feature=youtu.be&t=2m44s">7 of the 10 hottest years</a> have happened since 2002.</p>
<p>But on the other hand, such reviews have the capacity to lead to more transparent and reproducible science. This is fundamental to the scientific method and so, in my opinion, should <a href="https://theconversation.com/an-independent-inquiry-into-the-bureau-of-meteorology-bring-it-on-32692">always be welcomed</a>.</p>
<hr>
<p><em>Editor’s note: Ailie will be answering questions between 3:30 and 4:30pm AEDT on Wednesday January 28. You can ask your questions about the article in the comments below.</em></p><img src="https://counter.theconversation.com/content/36592/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ailie Gallant receives funding from the Australian Research Council.</span></em></p>The federal government’s new “Technical Advisory Forum” on weather data, announced by parliamentary environment secretary Bob Baldwin last week, will “review and provide advice on Australia’s official…Ailie Gallant, ARC DECRA Fellow, School of Earth, Atmosphere and Environment, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/368252015-01-28T01:46:29Z2015-01-28T01:46:29ZWhy scientists adjust temperature records, and how you can too<figure><img src="https://images.theconversation.com/files/70224/original/image-20150128-12432-ypois7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What does Paraguay have to do with the global temperature record?</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/dany13/12833448084">dany13/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>An <a href="http://www.theaustralian.com.au/news/health-science/north-americas-weather-agencies-on-rack-over-hottest-year-claim/story-e6frg8y6-1227198838612">article</a> in The Australian today has once again raised the question of why scientists, in trying to estimate how the global and regional surface temperatures of Earth may have changed over the past century or so, “adjust” the raw temperature data. </p>
<p>It is important to note, first off, that no data have been “altered” or destroyed in this process – all the raw data remain available for investigation by anyone who has the inclination (as I’ll show below). </p>
<p>But this process can lead to large adjustments to the raw data, and in at least some instances the adjusted data can suggest long-term warming even when the raw data indicate cooling. </p>
<p>This appears to have happened at the Paraguay stations mentioned in the article – the raw temperature recordings suggest cooling over decades, whereas warming appears after the raw data have been adjusted by NASA and NOAA. </p>
<p>The figure below shows this at one station in Paraguay. I have obtained the data from this station (raw and adjusted) from <a href="http://berkeleyearth.lbl.gov/auto/Stations/TAVG/Text/157444-TAVG-Data.txt">Berkeley Earth</a>, an independent group who have, quite separately from NASA and NOAA, checked global temperature data for these so-called “inhomogeneities” and adjusted the raw data themselves. </p>
<p>Their results provide an independent check for the NASA and NOAA groups doing this adjustment. The raw data (blue line) at this station suggest cooling, whereas the “adjusted” data (pink line) indicate warming. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/70212/original/image-20150128-17629-ihm1yb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/70212/original/image-20150128-17629-ihm1yb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=367&fit=crop&dpr=1 600w, https://images.theconversation.com/files/70212/original/image-20150128-17629-ihm1yb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=367&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/70212/original/image-20150128-17629-ihm1yb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=367&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/70212/original/image-20150128-17629-ihm1yb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=461&fit=crop&dpr=1 754w, https://images.theconversation.com/files/70212/original/image-20150128-17629-ihm1yb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=461&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/70212/original/image-20150128-17629-ihm1yb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=461&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="source" href="http://berkeleyearth.lbl.gov/auto/Stations/TAVG/Text/157444-TAVG-Data.txt">Berkeley Earth</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>The problem with thermometers</h2>
<p>So why do scientists “adjust” the raw data – why don’t they simply accept that the raw data are the best estimate of how the temperature has changed over decades? </p>
<p>The underlying problem is that whether or not a specific thermometer reading is a good estimate of the air temperature depends on how the thermometer is exposed. </p>
<p>Take a thermometer and attach it to a wall, and then compare the temperature you read from that thermometer with the reading from an identical thermometer in a modern Stevenson Screen located nearby. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/58063/original/s4hzm8pp-1409708905.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/58063/original/s4hzm8pp-1409708905.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/58063/original/s4hzm8pp-1409708905.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=406&fit=crop&dpr=1 600w, https://images.theconversation.com/files/58063/original/s4hzm8pp-1409708905.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=406&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/58063/original/s4hzm8pp-1409708905.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=406&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/58063/original/s4hzm8pp-1409708905.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=510&fit=crop&dpr=1 754w, https://images.theconversation.com/files/58063/original/s4hzm8pp-1409708905.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=510&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/58063/original/s4hzm8pp-1409708905.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=510&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This shows the thermometer screens at the Adelaide Observatory in 1888. Charles Todd established a very long experiment (it ran well into the 20th century) to compare temperature observations in the three different exposures illustrated here. His data show that the summer daytime temperatures measured in the typical 19th century thermometer exposure, the open stand shown on the right, were biased warm compared with the typical 20th century exposure in the Stevenson Screen shown on the left. So simply comparing the raw data from the 19th century with data from the 20th century would be misleading.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>On a warm summer day the thermometer on the wall will usually record higher temperatures than the one in the Stevenson Screen. As well, any trees around the observing site, or buildings or roads or car parks, as well as many other factors, can all affect the recorded temperature. </p>
<p>Because nearly all long-term records of temperature anywhere in the world have been affected by such factors, for instance as a rural station or airport gets surrounded by suburbs and roads, the scientific thing to do is to make sure you take these factors into account when trying to get a picture of how the world may have warmed. </p>
<h2>How to adjust data scientifically</h2>
<p>It would be nice if we had a compete record of all the changes to all the temperature recording sites around the world, listing in forensic detail when and where stations were moved (even a few metres can make a difference), when trees around the site were planted or removed, when car parks nearby were built, and all the buildings for tens of metres around the site. </p>
<p>And we would need all these details stretching back over many decades. </p>
<p>Unfortunately, no station exists with such comprehensive information for the last century or so. But even if these “metadata” did exist, we could not just use the raw data at a single station alone to work out how much to adjust the raw data for changes in exposure and location. </p>
<p>So scientists identify other “comparison” stations (as many as they can find) with which to compare the raw data at the “target” station (such as the station in the graph from Paraguay). These comparison stations are selected because their temperature variations from year-to-year generally track the changes at the “target” station.</p>
<p>If, however, the target station temperatures change suddenly and that change is not matched by similar changes in all the comparison stations, it is reasonable to conclude that something has happened to corrupt the raw data at the target station. The relationship between temperatures at the target and comparison stations is then used to adjust the raw data at the target station. </p>
<p>The details of the way this adjustment process is done varies between the groups who do this. The result of the adjustments made by Berkeley Earth for a station in Paraguay is shown in the figure above. </p>
<p>Both the raw and adjusted data show warming over the past forty or so years, but before the mid-1960s the data are quite different. Even looking at the raw data alone, a scientist would worry that some change in exposure has corrupted the data, because of the sudden large drop in temperature. </p>
<p>But the Berkeley Earth scientists have objectively adjusted for this drop, through their comparisons with other stations in the region. Their adjustments remove the sudden drop in the mid-1960s, and indicate that temperatures in the region have been warming for more than the 40 years shown by the raw data.</p>
<h2>Do it yourself</h2>
<p>I encourage anyone who worries about the sort of adjustments made by NASA or NOAA, or in Australia by the Bureau of Meteorology, to go to the Berkeley Earth website, look at their independent results, and perhaps even <a href="https://theconversation.com/how-to-become-a-citizen-climate-sleuth-31100">do some calculations themselves</a> to check what these other groups have done. </p>
<p>But don’t just think that the raw data will tell you much more than that the way the thermometer has been exposed has changed, or a car park has been built nearby, or a suburb now surrounds what once was a rural station. </p>
<p>You need to do the science and adjust for these corrupting factors, if you really want to work out how global and regional temperatures have changed. I’ve never been to Paraguay and I know almost nothing about the station whose data are in the graphs above. But scientists around the world have made these data available so we can do this work from our desktops. </p>
<p>I think this is great fun, but then I’m a nerdy meteorologist, so I would think that, wouldn’t I?</p><img src="https://counter.theconversation.com/content/36825/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Neville Nicholls in the 1990s initiated and led the efforts by the Bureau of Meteorology to adjust raw meteorological observations to reduce the effect of changes of exposure etc., to build a credible picture of how Australia's climate has been changing. He is a member of the National Council of the Australian Meteorological and Oceanographic Society.</span></em></p>An article in The Australian today has once again raised the question of why scientists, in trying to estimate how the global and regional surface temperatures of Earth may have changed over the past century…Neville Nicholls, Professor emeritus, School of Earth, Atmosphere and Environment, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/359042015-01-06T03:14:56Z2015-01-06T03:14:56Z2014 was Australia’s third-hottest year on record, says Bureau of Meteorology<p>2014 has been confirmed as Australia’s third-hottest year, capping off a record-breaking decade, according to the Bureau of Meteorology’s <a href="http://www.bom.gov.au/climate/current/annual/aus/">annual climate statement</a>, released today. </p>
<p>Seven of Australia’s ten hottest years have occurred in the past 13 years. During that period, only 2011 was cooler than the 1961-1990 average. Experts said this long-term trend and temperature extremes are a clear signal that climate change is happening in Australia now. </p>
<p>“If we want to look at the impact of climate change, what we’re really seeing is the climate of Australia has continued to warm,” said Karl Braganza, manager of Climate Modelling at the Bureau of Meteorology.</p>
<p>In the ten years to 2014, temperatures have been running 0.55C above the long-term average. The previous ten-year record was held by 2004-2013 at 0.5C above average. </p>
<figure>
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<p>The two-year period of 2012-2013 also smashed the previous 24-month record by 0.32C. </p>
<p>2014 on its own was the third-hottest year since Australia’s official records began in 1910, with temperatures 0.91C above average. This followed Australia’s <a href="https://theconversation.com/2013-was-australias-hottest-year-warm-for-much-of-the-world-21670">hottest ever year</a>, with temperatures 1.2C above average. </p>
<p>2014 also set a new record for the <a href="https://theconversation.com/sound-familiar-spring-2014-was-australias-hottest-on-record-again-34973">hottest spring</a>, breaking the previous record set the year before.</p>
<p>Sophie Lewis, a climate scientist at the Australian National University, said these extremes were “at least 30 times more likely because of human influences, such as greenhouse gases”. </p>
<p>Globally, 2014 is likely to have been the <a href="https://theconversation.com/hot-2014-closes-in-on-top-spot-in-world-temperature-rankings-35046">hottest on record</a>, driven by record-breaking sea surface temperatures. The UK Met Office also recorded 2014 as the <a href="http://www.metoffice.gov.uk/news/releases/archive/2015/Record-UK-temps-2014">UK’s hottest year</a>. </p>
<p>Sarah Perkins, a climate researcher at the University of New South Wales, said that while 2014 was not Australia’s hottest, the year included significant hot periods, including the “infamous” <a href="https://theconversation.com/athletes-can-beat-the-heat-even-during-an-australian-summer-22088">Australian Open heatwave</a>. The record-breaking spring contributed to another early start to the bushfire season, and recent heatwaves increased the bushfire risk and poor fire-fighting conditions currently in South Australia, she said. </p>
<p>Lower rainfall linked to El Niño conditions was driving warmer temperatures over the last six months, Braganza said. Models suggest El Niño could persist into 2015, potentially making 2015 as warm or warmer than 2014. </p>
<p>Braganza also said there has been a “notable absence” of cold weather. </p>
<p>“We’ve had heatwaves consistently every six weeks or over the past two or three years, even <a href="https://theconversation.com/winter-heatwaves-are-nice-as-extreme-weather-events-go-27172">throughout winter</a>. </p>
<p>"Since the mid-20th century, the spatial extent of these heat events has been growing. Heatwaves are becoming more frequent, they’re becoming hotter, lasting longer, and covering more of the continent.”</p>
<p><em>Comments compiled with the help of the <a href="http://www.smc.org.au/">Australian Science Media Centre</a>.</em></p><img src="https://counter.theconversation.com/content/35904/count.gif" alt="The Conversation" width="1" height="1" />
2014 has been confirmed as Australia’s third-hottest year, capping off a record-breaking decade, according to the Bureau of Meteorology’s annual climate statement, released today. Seven of Australia’s…James Whitmore, Deputy Editor: Arts + Culture, The ConversationLicensed as Creative Commons – attribution, no derivatives.