tag:theconversation.com,2011:/fr/topics/climate-consensus-11888/articlesClimate consensus – The Conversation2021-10-28T19:15:32Ztag:theconversation.com,2011:article/1703702021-10-28T19:15:32Z2021-10-28T19:15:32ZThe ‘97% climate consensus’ is over. Now it’s well above 99% (and the evidence is even stronger than that)<figure><img src="https://images.theconversation.com/files/428997/original/file-20211028-17-1z114vn.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C6233%2C3648&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Martin Meissner/AP</span></span></figcaption></figure><p>Despite the <a href="https://theconversation.com/99-999-certainty-humans-are-driving-global-warming-new-study-29911">overwhelming evidence</a>, it’s still common to see <a href="https://theconversation.com/australias-stumbling-last-minute-dash-for-climate-respectability-doesnt-negate-a-decade-of-abject-failure-169891">politicians</a>, media commentators or social media users cast doubt on the role of humans in driving climate change.</p>
<p>But this denialism is now almost nonexistent among climate scientists, as a <a href="https://iopscience.iop.org/article/10.1088/1748-9326/ac2966">study released this month</a> confirms. US researchers examined the peer-reviewed literature and found more than 99% of climate scientists now endorse the evidence for human-induced climate change. </p>
<p>That’s even higher than the 97% reported by an influential <a href="https://iopscience.iop.org/article/10.1088/1748-9326/8/2/024024/meta">2013 study</a>, which has become a widely cited statistic by both climate change deniers and those who accept the evidence. </p>
<p>Why has the needle evidently shifted even more firmly in favour of the evidence-based consensus? Or, to put it another way, what happened to the 3% of researchers who rejected the consensus of human caused climate change? Is this change purely because of the growing weight of evidence published over the past few years?</p>
<h2>Unpicking the polls</h2>
<p>We must first ask whether the two studies are directly comparable. The answer is yes. The <a href="https://iopscience.iop.org/article/10.1088/1748-9326/ac2966">latest study</a> has reexamined the literature published since 2012, and is based on the same methods as the <a href="https://theconversation.com/consensus-confirmed-over-90-of-climate-scientists-believe-were-causing-global-warming-57654">2013 study</a>, albeit with some important refinements.</p>
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Read more:
<a href="https://theconversation.com/consensus-confirmed-over-90-of-climate-scientists-believe-were-causing-global-warming-57654">Consensus confirmed: over 90% of climate scientists believe we're causing global warming</a>
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<p>Both studies searched the <a href="https://clarivate.com/webofsciencegroup/solutions/web-of-science/">Web of Science</a> database – an independent worldwide repository of scientific paper citations – using the keywords “global climate change” and “global warming”. However, the recent study added “climate change” to the other two keyword searches, because the <a href="https://iopscience.iop.org/article/10.1088/1748-9326/ac2966">authors found</a> that most climate-contrarian papers would not have been returned with only the two original terms.</p>
<p>The <a href="https://iopscience.iop.org/article/10.1088/1748-9326/8/2/024024/meta">2013 study</a> examined 11,944 climate research papers and found almost one-third of them expressed a position on the cause of global warming. Of these 4,014 papers, 97% endorsed the consensus position that humans are the cause, 1% were uncertain, and 2% explicitly rejected it.</p>
<p>A <a href="https://link.springer.com/article/10.1007/s00704-015-1597-5">2015 review</a> examined 38 climate-contrarian papers published over the preceding decade, and identified a range of methodological flaws and sources of bias.</p>
<p>One of the <a href="https://qz.com/1069298/the-3-of-scientific-papers-that-deny-climate-change-are-all-flawed/">reviewers commented</a> that “every single one of those analyses had an error – in their assumptions, methodology, or analysis – that, when corrected, brought their results into line with the scientific consensus”.</p>
<p>For example, many of the contrarian papers had “<a href="https://dictionary.cambridge.org/dictionary/english/cherry-pick">cherrypicked</a>” results that supported their conclusion, while ignoring important context and other data sources that contradicted it. Some of them simply ignored fundamental physics.</p>
<p>The 2015 reviewers also made the important point that “science is never settled and that both mainstream and contrarian papers must be subjected to sustained scrutiny”. This is the cornerstone of the <a href="https://www.britannica.com/science/scientific-method">scientific method</a>, and few if any climate scientists would disagree with this statement. </p>
<h2>Separating the human influence from the natural</h2>
<p>The recently published Intergovernmental Panel for Climate Change (IPCC) <a href="https://www.ipcc.ch/assessment-report/ar6/">Synthesis Report</a>, says “it is unequivocal that human influence has warmed the atmosphere, ocean and land”, and warns that the Paris Agreement goals of 1.5°C and 2°C above pre-industrial levels will be <a href="https://theconversation.com/if-all-2030-climate-targets-are-met-the-planet-will-heat-by-2-7-this-century-thats-not-ok-170458">exceeded during this century</a> without dramatic emissions reductions.</p>
<p>In reaching this conclusion, it is important to distinguish between changes caused by <a href="https://www.science.org.au/curious/earth-environment/enhanced-greenhouse-effect">human activities</a> altering the atmosphere’s chemistry, and <a href="https://www.pacificclimatefutures.net/en/help/climate-projections/understanding-climate-variability-and-change/">climate variability</a> caused by natural factors. </p>
<p>These natural variations include small changes in the <a href="https://climate.nasa.gov/blog/2910/what-is-the-suns-role-in-climate-change/">Sun’s energy output</a> due to sunspots and solar flares, infrequent <a href="https://www.usgs.gov/natural-hazards/volcano-hazards/volcanoes-can-affect-climate">volcanic eruptions</a>, and the effects of <a href="https://www.carbonbrief.org/interactive-much-el-nino-affect-global-temperature">El Niño</a> weather patterns in the Pacific Ocean. </p>
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<a href="https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Graphs of global temperatures" src="https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=314&fit=crop&dpr=1 600w, https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=314&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=314&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=394&fit=crop&dpr=1 754w, https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=394&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/428996/original/file-20211028-17-1y4ntru.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=394&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">History of global temperature change and causes of recent warming.</span>
<span class="attribution"><span class="source">IPCC</span></span>
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<p>Excluding these natural variations, Earth’s surface temperature was generally stable from about 2,000 to 1,000 years ago. After that, the planet cooled by about 0.3°C over <a href="https://www.ipcc.ch/assessment-report/ar6/">several centuries</a>, before the advent of fossil fuel-based industrialisation in the 1800s.</p>
<p>One <a href="https://www.researchgate.net/publication/344709426_Prominent_role_of_volcanism_in_Common_Era_climate_variability_and_human_history">study</a> identified 12 major volcanic eruptions from 100 to 1200 CE, compared with 17 eruptions from 1200 to 1900 CE. Hence, heightened volcanic activity over roughly the past 800 years was associated with a general global cooling before the industrial revolution. </p>
<p>Current rates of global warming are <a href="https://www.ipcc.ch/assessment-report/ar6/">unprecedented</a> in more than 2,000 years and temperatures now exceed the warmest (multi-century) period in <a href="https://www.ipcc.ch/assessment-report/ar6/">more than 100,000 years</a>. Global average <a href="https://www.ipcc.ch/assessment-report/ar6/">surface temperature</a> for the decade from 2011-20 was about 1.1°C higher than in 1850-1900. Each of the past four decades has been warmer than any preceding decade since 1850, when reliable weather observations began.</p>
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<a href="https://theconversation.com/99-999-certainty-humans-are-driving-global-warming-new-study-29911">99.999% certainty humans are driving global warming: new study</a>
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<p>Researchers can separate human and natural factors in the modern global temperature record. This involves a process called <a href="https://www.climate.gov/maps-data/climate-data-primer/predicting-climate/climate-models">hindcasting</a>, in which a climate model is run backwards in time to simulate human and natural factors, and then compared with the observed data to see which combination of factors most accurately recreates the real world. </p>
<p>If human factors are removed from the data set and only volcanic and solar factors are included, then global average surface temperatures since 1950 should have remained similar to those over the preceding 100 years. But of course they haven’t.</p>
<p>The evidence, and the scientific consensus on it, are both clearer than ever.</p><img src="https://counter.theconversation.com/content/170370/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Steve Turton has previously received funding from the Australian Government. Steve is the independent chair of the Wet Tropics Healthy Waterways Partnership, an initiative of the Reef 2050 Long Term Sustainability Plan.</span></em></p>One of the most famous stats in the climate debate is the 97% of scientists who endorse the consensus on human-induced global heating. Ahead of the Glasgow summit, that figure has climbed even higher.Steve Turton, Adjunct Professor of Environmental Geography, CQUniversity AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1185012019-09-05T11:27:01Z2019-09-05T11:27:01ZHow many Americans believe in climate change? Probably more than you think, research in Indiana suggests<figure><img src="https://images.theconversation.com/files/289294/original/file-20190823-170931-1xqzxjh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Concern about climate change is broader than many Hoosiers think. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/welcome-sign-indiana-state-line-20250787?src=3nqmMMNCOUW-KBcNK1aiWw-1-0">Katherine Welles/Shutterstock</a></span></figcaption></figure><p>Indiana certainly doesn’t look like a state that’s ready to confront climate change. Its former governor, Vice President Mike Pence, has questioned <a href="https://www.factcheck.org/2016/11/pences-stance-on-climate-change/">whether human actions affect the climate</a>. In 2016 the majority of Indiana residents <a href="https://uselectionatlas.org/RESULTS/state.php?f=0&fips=18&year=2016">voted for Donald Trump</a>, who <a href="https://www.cnn.com/2019/03/12/us/trump-climate-change-tweet-patrick-moore/index.html">rejects mainstream climate science</a>. And the state <a href="https://news.gallup.com/poll/125066/State-States.aspx">ranks first</a> in the proportion of its population that identifies as conservative – a position that generally means <a href="https://www.nationalaffairs.com/publications/detail/conservatives-and-climate-change">resisting calls</a> to address climate change.</p>
<p>Given these realities, it would be easy to assume that all Hoosiers largely doubt climate change and humans’ contribution to it. The truth is surprising. </p>
<p><a href="https://scholar.google.com/citations?user=LktEWJgAAAAJ&hl=en">My research</a> focuses on the human dimensions of climate change, including public opinion. In a recent statewide survey, I found that the majority of Indiana residents supported taking action on climate change. However, most Hoosiers underestimate just how widespread this view is in their state.</p>
<h2>Evolving perspectives</h2>
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<span class="caption">Vice President Mike Pence opposed federal action to address climate change as governor of Indiana.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Pence-Governor/a95e1399582349068a4bd0af5a75ba24/2/0">Michael Conroy/AP</a></span>
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<p>To explore climate change views, my colleagues and I commissioned an online survey of 1,002 Indiana residents statewide in April 2019. The most reported political affiliation was Republican (28%), though there was a wide diversity of affiliations across the sample. A slight majority were men (52%) and the largest age category was 25-34 (20%). </p>
<p>I found that, overall, Hoosiers believed that climate change was real and was happening. Around 80% of respondents reported believing that climate change was occurring “somewhat” or “to a great extent.” </p>
<p>Similarly, a majority felt that climate change will harm Indiana’s economy “somewhat” or to a “great extent” (77%) and that climate change was “already” causing harm in the United States or would by 2030 (72%). Over 65% “somewhat” or “strongly agreed” that climate change effects are greater now than five years ago, and 75% supported initiatives to address these impacts in Indiana. </p>
<p>In the United States, the public’s view of climate change often <a href="https://doi.org/10.1016/j.erss.2016.08.003">divides along party lines</a>, and respondents in my survey were no exception. Those identifying with more conservative parties reported lower levels of belief in and support for action on climate change across the board. </p>
<p>Still, a majority of Republicans – 66% – believed climate change is real, compared to 91% of Democrats, and supported initiatives to address it. A slight majority of Republicans reported that their acceptance of the reality of climate change had strengthened over the last five years. The fact that these attitudes were held by a majority of respondents of all political affiliations was our most surprising finding.</p>
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<h2>Underestimating climate change consensus</h2>
<p>If citizens keep their support for acting on climate change to themselves, society struggles to build consensus. But relatives and friends <a href="https://doi.org/10.1177/0013916519853302">can influence individuals’ attitudes</a> on climate. </p>
<p>Research shows that people’s willingness to change their beliefs or attitudes depends to a great extent on what they already <a href="http://dx.doi.org/10.1038/nclimate1743">perceive as normal</a>. Therefore, I next examined whether Hoosiers correctly perceived the existence of widespread support for climate change in their state. My survey asked, “What percentage of other Indiana residents do you think believe climate change is happening (whether caused by human activity or not)?”</p>
<p>On average, respondents underestimated by about 24% how many Hoosiers accept climate change. Doubters thought that most others shared their skepticism, estimating that only around 43% in Indiana held the opposite opinion. </p>
<p>Surveyed Hoosiers who believed climate change is happening perceived that a higher percentage of Hoosiers felt like them. However, they too underestimated the percentage who accepted the reality of climate change’s occurrence, by around 20 points on average. </p>
<p><iframe id="EtbYH" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/EtbYH/2/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>Such misperceptions <a href="http://dx.doi.org/0.31219/osf.io/vg74q">hinder action</a> on climate change. Previous research has shown skeptics can fall prey to a “<a href="https://doi.org/10.1016/0022-1031(77)90049-X">false consensus effect</a>” – the tendency to assume one’s own opinion is held by a majority of others. For example, climate skeptics who falsely assume that most others share their opinion are less likely to <a href="http://dx.doi.org/10.1038/nclimate1743">change their minds</a>. But if they recognize that a consensus exists on the issue and is different from their own initial belief, that could encourage more conservatives to <a href="http://dx.doi.org/10.31219/osf.io/vg74q">believe in climate change</a>. </p>
<p>In the same way, believers who underestimate just how many actually agree with them are <a href="https://doi.org/10.1016/j.jenvp.2016.05.002">more likely to self-silence</a> for fear of being stigmatized. They may avoid calling their political representatives to urge support of climate change policies. Researchers have identified such “<a href="http://dx.doi.org/10.1037/0022-3514.64.2.243">pluralistic ignorance</a>” in studies of college students and social norms around alcohol use.</p>
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<h2>Capitalizing on consensus, fighting misperceptions</h2>
<p>Even in a state as conservative as Indiana, belief that climate change is occurring and support for action to curb it are now mainstream.</p>
<p>Our survey did not ask more controversial questions, such as whether humans had a role in causing climate change or how to reduce emissions. While I expect that many in the state <a href="https://theconversation.com/many-midwesterners-will-likely-never-believe-in-climate-change-heres-how-to-encourage-them-to-act-anyway-105199">remain divided on these issues</a>, I still find my results encouraging. </p>
<p>Perhaps one sign of quietly changing attitudes in Indiana is South Bend Mayor and presidential candidate Pete Buttigieg’s <a href="https://grist.org/article/where-is-pete-buttigiegs-climate-plan/">rise in national polls</a>, due in part to his climate change agenda, which Buttigieg has linked to broader action to <a href="https://www.desmoinesregister.com/story/opinion/columnists/caucus/2019/08/13/pete-buttigieg-my-plan-re-imagines-opportunity-rural-america-iowa-caucus/1997170001/">revive rural America</a>.</p>
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<span class="caption">South Bend Mayor Pete Buttigieg has made climate change part of his agenda in campaigning for the 2020 Democratic presidential nomination.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Election-2020-Pete-Buttigieg/e67cdf13af17434bbf81985a8c4e0d77/5/0">Mary Schwalm/AP</a></span>
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<p>Addressing climate change will require <a href="https://www.nytimes.com/2018/10/07/climate/ipcc-climate-report-2040.html">major societal changes</a>, which in turn will require overcoming barriers that discourage or prevent collective action. Hoosiers’ underestimation of local consensus on climate change is likely one such barrier in Indiana. </p>
<p>Our respondents are not alone in misperceiving how many of their peers hold supportive attitudes. Many people nationwide <a href="https://scholar.harvard.edu/files/dtingley/files/mildenbergertingley_bjps.pdf">underestimate consensus on this issue</a>. One way to overcome this tendency may be to focus on <a href="https://climatecommunication.yale.edu/visualizations-data/ycom-us-2018/?est=happening&type=value&geo=county">communicating the commonness</a> or the <a href="https://climatecommunication.yale.edu/publications/a-growing-majority-of-americans-think-global-warming-is-happening-and-are-worried/">growing belief</a> in climate change. </p>
<p>I also see it as critical for individuals who believe climate change is occurring to <a href="http://dx.doi.org/10.31219/osf.io/vg74q">discuss the topic</a> with friends and relatives, especially if these loved ones are doubters. Helping people to recognize just how normal it is to believe in climate change could lead to broader calls for action in Indiana and beyond.</p>
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<p class="fine-print"><em><span>Matthew Houser is an assistant research scientist at Indiana University. </span></em></p>A recent survey in Indiana finds broad concern about climate change and support for addressing it in this red state, with one catch: Many Hoosiers don’t realize their neighbors agree with them.Matthew Houser, Assistant Research Scientist and Faculty Fellow, Indiana UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/801172017-08-18T02:18:53Z2017-08-18T02:18:53ZCurbing climate change: Why it’s so hard to act in time<figure><img src="https://images.theconversation.com/files/182223/original/file-20170816-32640-1a43s57.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">March for Science, Washington, D.C., April 29, 2017.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/washington-dc-april-29-2017-thousands-630429824?src=N_ANcSEM1VWrRYZfThhccQ-1-0">Shutterstock.com</a></span></figcaption></figure><p>This summer I worked on the Greenland ice sheet, part of a scientific experiment to study surface melting and its contribution to Greenland’s accelerating ice losses. By virtue of its size, elevation and currently frozen state, Greenland has the potential to cause large and rapid increases to sea level as it melts. </p>
<p>When I returned, a nonscientist friend asked me what the research showed about future sea level rise. He was disappointed that I couldn’t say anything definite, since it will take several years to analyze the data. This kind of time lag is common in science, but it can make communicating the issues difficult. That’s especially true for climate change, where decades of data collection may be required to see trends. </p>
<p>A recent draft <a href="https://www.nytimes.com/interactive/2017/08/07/climate/document-Draft-of-the-Climate-Science-Special-Report.html">report on climate change</a> by federal scientists exploits data captured over many decades to assess recent changes, and warns of a dire future if we don’t change our ways. Yet few countries are aggressively reducing their emissions in a way scientists say are needed to avoid the dangers of climate change. </p>
<p>While this lack of progress dismays people, it’s actually understandable. Human beings have evolved to focus on immediate threats. We have a tough time dealing with risks that have time lags of decades or even centuries. As a geoscientist, I’m used to thinking on much longer time scales, but I recognize that most people are not. I see several kinds of time lags associated with climate change debates. It’s important to understand these time lags and how they interact if we hope to make progress. </p>
<h2>Agreeing on the goal</h2>
<p>Changing the basic energy underpinnings of our industrial economy will not be easy or cheap, and will require broad public support. Today nearly half of Americans – presumably including President Trump, based on his <a href="http://www.newsweek.com/what-has-trump-said-about-global-warming-quotes-climate-change-paris-agreement-618898">public comments</a> – <a href="https://www.wilsoncenter.org/sites/default/files/wilson.report.mind_the_gap.2-2.pdf">do not believe</a> that humans are the primary cause of modern rapid climate change. Others admit that humans have contributed, but may not support strict regulations or big investments in response. </p>
<p>In part, these views reflect the <a href="http://www.penguinrandomhouse.com/books/215462/dark-money-by-jane-mayer/9780307947901/">influence of special interest groups</a> who benefit from our high-carbon “business as usual” economic system. But they also reflect the complexity of the problem, and the difficulty scientists have in explaining it. As I point out in my <a href="https://www.cambridge.org/core/books/curbing-catastrophe/02789220833AB1F54C51B9D0628E639C">recent book</a> on how we think about disasters, statements made by scientists in the 1980s, 1990s and early 2000s about global warming were often vague and full of caveats, which made it easy for climate change skeptics to forestall action by emphasizing how uncertain the picture was. </p>
<p>Fortunately, scientists are improving at communication. The <a href="https://www.nytimes.com/interactive/2017/08/07/climate/document-Draft-of-the-Climate-Science-Special-Report.html">increasing frequency of coastal flooding, summer heat waves and droughts</a> could also help to change minds, but it may take a few more decades before a solid majority of Americans supports high-level action.</p>
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<figcaption><span class="caption">Earth’s average temperature has risen over 1 degree Fahrenheit in the past century. It is projected to rise an additional 3°F to 10°F over the next 100 years.</span></figcaption>
</figure>
<h2>Designing cleaner technologies</h2>
<p>It will also take time for technological developments to support our transition to a low-carbon energy future. Here, at least, there is reason for optimism. A few decades ago renewable energy sources such as wind and solar seemed unlikely to replace a significant fraction of carbon-based energy. Similarly, electric vehicles seemed unlikely to meet a significant share of our transportation needs. Today both are realistic alternatives. </p>
<p>This year wind and solar power <a href="https://www.eia.gov/todayinenergy/detail.php?id=31632">hit 10 percent of U.S. electricity generation</a> for the first time. Electric vehicles and hybrids are also <a href="https://theconversation.com/how-electric-vehicles-could-take-a-bite-out-of-the-oil-market-81081">becoming more common</a>. The recent advent and rapid adoption of LED lighting could start to have an impact on our electrical consumption. </p>
<p>Thanks to these developments, humanity’s carbon footprint will look quite different in a few decades. Whether that’s quick enough to avoid 2 degree Celsius of warming is not yet clear.</p>
<h2>Funding the transition</h2>
<p>Once we finally decide to make a low-carbon transition and figure out how to do it, it will cost <a href="https://theconversation.com/how-electric-vehicles-could-take-a-bite-out-of-the-oil-market-81081">trillions of dollars</a>. Capital markets can’t provide that sort of funding instantaneously. </p>
<p>Consider the cost of upgrading just the U.S. housing market. The United States has approximately 125 million households, of which about 60 percent (75 million) own their own homes. The majority of these are <a href="https://www.kansascityfed.org/publicat/econrev/pdf/13q4Rappaport.pdf">single-family residences</a>. </p>
<p>If we assume that at least 60 million of these residences are single-family homes, duplexes or townhomes where it is feasible for residents to upgrade to solar photovoltaic power, then equipping just half (30 million homes) with a standard solar energy package and battery storage, at a cost of about US$25,000 per household, would cost nearly a trillion dollars. Our economy can support this level of capital investment over one or two decades, but for most of the world it’s going to take longer. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/182226/original/file-20170816-32614-1x77dnq.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/182226/original/file-20170816-32614-1x77dnq.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/182226/original/file-20170816-32614-1x77dnq.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=144&fit=crop&dpr=1 600w, https://images.theconversation.com/files/182226/original/file-20170816-32614-1x77dnq.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=144&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/182226/original/file-20170816-32614-1x77dnq.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=144&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/182226/original/file-20170816-32614-1x77dnq.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=181&fit=crop&dpr=1 754w, https://images.theconversation.com/files/182226/original/file-20170816-32614-1x77dnq.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=181&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/182226/original/file-20170816-32614-1x77dnq.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=181&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Solar Charging Station for Electric Vehicles at Phillips Chevrolet, Frankfort, Illinois. New energy technologies require infrastructure to support them.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/9/95/Phillips_Chevrolet%27s_Solar_Charging_Station_for_Electric_Vehicles.JPG">Phillipschevy</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>The natural carbon cycle</h2>
<p>Our ability to add carbon dioxide to the atmosphere greatly exceeds nature’s ability to remove it. There is a time lag between carbon emission and carbon removal. The process is complicated, with multiple pathways, some of which operate over centuries. </p>
<p>For example, some atmospheric carbon dioxide at the ocean’s surface dissolves into seawater, forming carbonate ions. Meanwhile, rainfall weathers rocks on land, slowly breaking them apart and washing calcium and magnesium ions into rivers and streams and on into the oceans. These materials combine into minerals such as aragonite, calcite or dolomite, which eventually sink and become entombed in sedimentary layers at the bottom of the ocean. </p>
<p>But since this process plays out over many centuries, most of the carbon dioxide that we put into the atmosphere today will continue to heat the world for <a href="https://doi.org/10.1146/annurev.earth.031208.100206">hundreds to thousands of years</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/182227/original/file-20170816-32614-pas3m9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/182227/original/file-20170816-32614-pas3m9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/182227/original/file-20170816-32614-pas3m9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/182227/original/file-20170816-32614-pas3m9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/182227/original/file-20170816-32614-pas3m9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/182227/original/file-20170816-32614-pas3m9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/182227/original/file-20170816-32614-pas3m9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/182227/original/file-20170816-32614-pas3m9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Earth’s carbon supply constantly cycles between land, atmosphere and oceans. Yellow numbers are natural fluxes, and red are human contributions in gigatons of carbon per year. White numbers indicate stored carbon.</span>
<span class="attribution"><a class="source" href="https://earthobservatory.nasa.gov/Features/CarbonCycle/">NASA Earth Observatory</a></span>
</figcaption>
</figure>
<p>Today the concentration of carbon dioxide in the atmosphere is just over 400 parts per million, rising by <a href="http://scrippsco2.ucsd.edu">about 3 ppm yearly</a>. Given the political, technological and economic time lags that we face, it’s likely that we will hit at least 450-500 ppm before we can seriously curtail our carbon emissions. The last time Earth’s atmosphere contained this much carbon dioxide was several million years ago, during the Pliocene era. Global temperatures were <a href="http://dx.doi.org/%2010.1126/science.1233137">much higher than 2°C above today’s average</a>, and global sea level was <a href="http://dx.doi.org/10.1126/science.aaa4019">at least 6 meters (nearly 20 feet) higher</a>. </p>
<p>We haven’t seen comparable temperature or sea level increases so far because of <a href="https://theconversation.com/if-we-stopped-emitting-greenhouse-gases-right-now-would-we-stop-climate-change-78882">time lags in Earth’s climate response</a>. It takes a while for our elevated carbon dioxide levels to trigger impacts on this scale. Given the various time lags that are in play, it is quite possible that we have already exceeded the 2°C rise over preindustrial temperatures – a threshold most scientists say we should avoid – but it hasn’t shown up on the thermometer yet. </p>
<p>We may not be able to predict exactly how much future temperatures or sea levels will rise, but we do know that unless we curb our carbon emissions, our planet will be a very uncomfortable place for our grandchildren and their grandchildren. Large-scale social changes take time: they are the sum of many individual changes, in both attitudes and behaviors. To minimize that time lag, we need to start acting now.</p><img src="https://counter.theconversation.com/content/80117/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Timothy H. Dixon has received funding from the US National Science Foundation, the National Aeronautics and Space Administration, the Department of Energy and the Office of Naval Research. </span></em></p>Why is it so hard to reach consensus about how to slow climate change? Multiple time lags get in the way: some make it hard to convey the risk, while others prolong the search for solutions.Timothy H. Dixon, Professor, Geology and Geophysics, Natural and human-caused hazards, sea level rise and climate change, University of South FloridaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/592432016-05-13T03:59:13Z2016-05-13T03:59:13ZThe things people ask about the scientific consensus on climate change<figure><img src="https://images.theconversation.com/files/122201/original/image-20160512-18128-11krp42.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">So many questions on climate change.</span> <span class="attribution"><span class="source">Shutterstock/Kuznetsov Dmitry </span></span></figcaption></figure><p>It’s been almost a month since the paper I co-authored on the <a href="http://iopscience.iop.org/article/10.1088/1748-9326/11/4/048002">synthesis of research</a> into the scientific consensus on climate change was published. Surveying the many studies into scientific agreement, we found that more than 90% of climate scientists agree <a href="https://theconversation.com/consensus-confirmed-over-90-of-climate-scientists-believe-were-causing-global-warming-57654">that humans are causing global warming</a>.</p>
<p>It’s a topic that has generated much interest and discussion, culminating in American Democrat Senator Sheldon Whitehouse <a href="http://www.c-span.org/video/?c4594408/senator-whitehouse-cook-et-al-2016">highlighting our study on the US Senate floor</a> this week. </p>
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<p>My co-authors and I even participated in an Ask Me Anything (AMA) session on the online forum <a href="https://www.reddit.com/r/science/comments/4f6f6g/science_ama_series_we_just_published_a_study/">Reddit</a>, answering questions about the scientific consensus. </p>
<p>While <a href="https://theconversation.com/the-science-for-climate-change-only-feeds-the-denial-how-do-you-beat-that-52813">my own research</a> indicates that explaining the scientific consensus isn’t that effective with those who reject climate science, it does have a positive effect for people who are open to scientific evidence. </p>
<p>Among this “undecided majority”, there was clearly much interest with the session generating 154,000 page views and our AMA briefly featuring on the Reddit homepage (where it was potentially viewed by 14 million people).</p>
<p>Here is an edited selection of some of the questions posed by Reddit readers and our answers.</p>
<p><strong>Q: Why is this idea of consensus so important in climate science? Science isn’t democracy or consensus, the standard of truth is experiment.</strong></p>
<p>If this were actually true, wouldn’t every experiment have to reestablish every single piece of knowledge from first principles before moving on to something new? That’s obviously not how science actually functions. </p>
<p>Consensus functions as a scaffolding allowing us to continue to build knowledge by addressing things that are actually unknown. </p>
<p><strong>Q: Does that 97% all agree to what degree humans are causing global warming?</strong></p>
<p>Different studies use different definitions. Some use the phrase “humans are causing global warming” which carries the implication that humans are a dominant contributor to global warming. Others are more explicit, specifying that humans are causing most global warming.</p>
<p>Within <a href="http://iopscience.iop.org/article/10.1088/1748-9326/8/2/024024/meta">some of our own research</a>, several definitions are used for the simple reason that different papers endorse the consensus in different ways. Some are specific about quantifying the percentage of human contribution, others just say “humans are causing climate change” without specific quantification. </p>
<p>We found that no matter which definition you used, you always found an overwhelming scientific consensus.</p>
<p><strong>Q: It’s very difficult to become/remain a well-respected climate scientist if you don’t believe in human-caused climate change. Your papers don’t get published, you don’t get funding, and you eventually move on to another career. The result being that experts either become part of the 97% consensus, or they cease to be experts.</strong></p>
<p>Ask for evidence for this claim and enjoy the silence (since they won’t have any). </p>
<p>As a scientist, the pressure actually is mostly reversed: you get rewarded if you prove an established idea wrong. </p>
<p>I’ve heard from contrarian scientists that they don’t have any trouble getting published and getting funded, but of course that also is only anecdotal evidence.</p>
<p>You can’t really disprove this thesis, since it has shades of conspiratorial thinking to it, but the bottom line is there’s no evidence for it and the regular scientific pressure is to be adversarial and critical towards other people’s ideas, not to just repeat what the others are saying.</p>
<p><strong>Q: What’s the general reasoning of the other 3%?</strong></p>
<p>Interesting question. It is important and diagnostic that there is no coherent theme among the reasoning of the other 3%. Some say “there is no warming”, others blame the sun, cosmic rays or the oceans. </p>
<p>Those opinions are typically mutually contradictory or incoherent: Stephan Lewandowsky <a href="https://www.opendemocracy.net/conspiracy/suspect-science/stephan-lewandowsky/alice-through-looking-glass-mechanics-rejection-of-climate-science">has written elsewhere about</a> a few of the contradictions. </p>
<p><strong>Q: Do we have any insight on what non-climate scientists have to say about climate change being caused by CO2?</strong></p>
<p>In a <a href="http://iopscience.iop.org/article/10.1088/1748-9326/10/9/094025/meta">paper published last year</a>, Stuart Carlton and colleagues surveyed biophysical scientists across many disciplines at major research universities in the US. </p>
<p>They found that about 92% of the scientists believed in anthropogenic climate change and about 89% of respondents disagreed with the statement: “Climate change is independent of CO2 levels”. In other words, about 89% of respondents felt that climate change is affected by CO2.</p>
<p><strong>Q: It could be argued that climate scientists may be predisposed to seeing climate change as more serious, because they want more funding. What’s your perspective on that?</strong></p>
<p>Any climate scientist who could convincingly argue that climate change is not a threat would:</p>
<ol>
<li>be famous</li>
<li>get a Nobel prize</li>
<li>plus a squintillion dollars in funding</li>
<li>a dinner date with the Queen</li>
<li>lifelong gratitude of billions of people.</li>
</ol>
<p>So if there is any incentive, it’s for a scientist to show that climate change is not a threat.</p>
<p><strong>Q: I was discussing politics with my boss the other day, and when I got to the topic of global warming he got angry, said it’s all bullshit, and that the climate of the planet has been changing for millennia. Where should I go to best understand all of the facts?</strong></p>
<p>Skeptical Science has a <a href="http://www.skepticalscience.com/argument.php?f=taxonomy">list of common myths</a> and what the science says.</p>
<p>But often facts are not enough, especially when people are angry and emotional. The Skeptical Science team has made a <a href="http://sks.to/denial101x">free online course</a> that addresses both the facts and the psychology of climate denial.</p>
<p>You can also access the <a href="http://www.skepticalscience.com/denial101x-videos-and-references.html">individual Denial101 videos</a>.</p>
<p>Also, remember that you may not convince him, but if you approach him rationally and respectfully you may influence other people who hear your discussion.</p><img src="https://counter.theconversation.com/content/59243/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Cook 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>Research showing that more than 90% of climate scientists agree that we’re causing global warming prompted plenty of questions. And the authors are only too happy to answer.John Cook, Climate Communication Research Fellow, Global Change Institute, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/303522014-08-12T20:30:48Z2014-08-12T20:30:48ZAppeals to the climate consensus can give the wrong impression<figure><img src="https://images.theconversation.com/files/56251/original/8gv8ty3h-1407818379.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">When it comes to arguing about climate science, it would be better to play the science, not the scientists. </span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/marsdd/2986989396">MaRS Discovery District/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span></figcaption></figure><p>You might have heard that 97% of climate scientists agree the world is warming and people are the cause. This level of agreement, known as “consensus”, is often put forward in the climate debate in support of human-caused global warming and action to mitigate it. It was recently popularised on US talk show Last Week Tonight with John Oliver: </p>
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<figcaption><span class="caption">John Oliver’s statistically representative climate debate.</span></figcaption>
</figure>
<p>The 97% figure comes from a paper by social scientist John Cook at the University of Queensland and colleagues, who quantified this consensus by analysing the abstracts of scientific papers on climate change. Cook estimated <a href="http://iopscience.iop.org/1748-9326/8/2/024024/article">97%</a> of the abstracts supported the idea that recent climate change is man-made. </p>
<p>Another social scientist, Richard Tol at the University of Sussex, has <a href="http://www.sciencedirect.com/science/article/pii/S0301421514002821">challenged the Cook study</a>. Cook and colleagues <a href="http://www.sciencedirect.com/science/article/pii/S0301421514003747">have replied</a>, and Tol <a href="http://www.sciencedirect.com/science/article/pii/S0301421514003759">has replied to the reply</a>. And so it goes…</p>
<p>This to-ing and fro-ing might give the impression that climate science is somehow still under debate, but the scientific evidence that people are causing climate change is overwhelming, and mounting. </p>
<p>But “consensus” means different things to different people — and herein lies the problem. </p>
<h2>What does consensus mean?</h2>
<p>“Consensus” is understood differently in science compared to politics or society. </p>
<p>Scientists use this word to refer to consilience of multiple lines of evidence that underlie widespread agreement or support a theory.</p>
<p>In the case of climate change, multiple lines of evidence underpin the prevailing view that the climate system is showing decade-on-decade warming over the past 50 years. </p>
<p>In particular, this warming bears temporal and spatial patterns, or “fingerprints”, that point to human causes. </p>
<p>For example, the stratosphere (that part of the atmosphere higher than about 11 km) <a href="http://dx.doi.org/10.1002/wcc.125">has been cooling</a>
as the lower atmosphere and the ocean warm. This is the pattern we expect from the addition of greenhouse gases and not from, say, changes in the sun’s output.</p>
<p>But in public and especially political discourse, “consensus” tends to imply majority opinion or concurrence. As consensus in this public context is often arrived at by negotiation, saying there’s a scientific “consensus” may imply to the community that prevailing scientific views represent a negotiated outcome. This is the antithesis of science.</p>
<p>Consensus of the non-scientific kind does have a role to play in the climate debate. This includes negotiating whether warming is a “good” or “bad” thing and what, if anything, we should do about it.</p>
<p>These are not scientific questions. These are issues of values, politics, ethics and economics. As a nation and as a global society we need to reach consensus to resolve those questions and to make and implement appropriate public policy.</p>
<h2>How science works</h2>
<p>Science is based on three main things: data, testability and contestability.</p>
<p>Scientists, for example, don’t “negotiate” with data. We may re-analyse, reject outliers, replicate, recalibrate, but we do not negotiate. If the thermometer reads 25C, we don’t say, “I’d like 30; how about we settle on 27.5?” </p>
<p>Testability is a particular challenge for climate science, because we can’t do a laboratory experiment to test the hypothesis that humans are causing climate change. Most of the impacts we are concerned about are in the future and we have no data for the future. Instead, we use models based on the best understanding we have of physics, chemistry and biology to anticipate possible climate futures. </p>
<p>We are of course currently conducting the experiment that will prove whether humans cause global warming, in the uncontrolled planet-wide release of greenhouse gas emissions. However, by the time we’re in a position to test the result of, say, doubling greenhouse gas concentrations, it may be too late to mitigate the impacts. </p>
<p>That last attribute – contestability — is the antithesis of “consensus”. Indeed, it is the adversarial nature of science that is its real strength. In science you’re right until you’re proven wrong, and theories survive only as long they stand up to challenge.</p>
<p>Alfred Wegener’s theory of <a href="https://theconversation.com/breaking-new-ground-the-rise-of-plate-tectonics-7514">continental drift</a> (which sought to explain how the continents are distributed across the earth) was rejected for decades. That was partly because there was no plausible mechanism to explain continents moving, and because most geologists at the time viewed vertical movements as the dominant earth-shaping forces. Wegener had been trained in astronomy and most of his work was in meteorology, so he was an “outsider” in geology.</p>
<p>Geological and geophysical observations in the 1960s and 1970s provided the evidence that the earth’s surface could and had shifted, moving continents in the way Wegener had suggested.</p>
<h2>Play the science, not the scientist</h2>
<p>The second problem with consensus is who to trust. On the website <a href="http://www.skepticalscience.com">Skeptical Science</a> Cook and his colleagues note they “decided that researchers who work and publish on climate science are the right group to ask.” Others have also tried to identify <a href="http://www.pnas.org/content/early/2010/06/04/1003187107.abstract">expert credibility</a> in climate science.</p>
<p>But the problem with asking “who to believe” is that it ignores the merits, or lack thereof, of the arguments.</p>
<p>Kevin Cowtan and Robert Way from <a href="http://dx.doi.org/10.1002/qj.2297">the UK and Canada</a> came up with an innovative application of data analysis to “fill in” temperature data where observations are sparse, especially in polar regions. Their paper suggests a greater rate of global warming over the past two decades than previously estimated; their conclusion is that global warming has slowed but not as much we thought. </p>
<p>But Cowtan is a crystallographer, not (previously) a “climate scientist”. There’s a whole world of scientists who may have novel techniques, new insights and compelling arguments for different estimates of warming, or new estimates of climate sensitivity, than adopted by the <a href="https://theconversation.com/topics/ipcc-fifth-assessment-report">IPCC</a> and other synthesis studies. Are they afraid to publish these arguments and the data supporting them because they are worried they may be dismissed as “non-climate scientists”?</p>
<p>We need all the contributions we can get from all the disciplines we can access to understand the crucial challenges posed by climate change. We need to open up scientific discourse on climate change — the very purpose of science is to broaden intellectual exploration.</p>
<p><em>UPDATE: This article was updated August 13 to add the source for the quote “Cook and his colleagues note they ‘decided that researchers who work and publish on climate science are the right group to ask.’”</em></p><img src="https://counter.theconversation.com/content/30352/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Will Howard has received funding from the Australian Research Council, the Australian Government Department of Climate Change, the Cooperative Research Centres Program, and the Australian Antarctic Science Program.</span></em></p>You might have heard that 97% of climate scientists agree the world is warming and people are the cause. This level of agreement, known as “consensus”, is often put forward in the climate debate in support…Will Howard, Research scientist, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.