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What to expect from the latest IPCC impacts report

Senior scientists and government officials are meeting in Japan to finalise a new report on the impacts of climate change. It will be the first Intergovernmental Panel on Climate Change (IPCC) report in…

We’ll need a lot more than sandbags in years to come. EPA/Facundo Arrizabalaga

Senior scientists and government officials are meeting in Japan to finalise a new report on the impacts of climate change. It will be the first Intergovernmental Panel on Climate Change (IPCC) report in seven years and will outline the impact that rising temperatures will have on humans, animals and ecosystems over the next century.

The meeting in Japan marks the end of a very long process that’s involved in producing an IPCC report. As a lead author in the chapter which deals with freshwater resources, I’ve attended meetings over the last seven years with other experts to pour over the research papers published on the topic. We’ve spent many hours discussing how best to summarise all these results – drafting and re-drafting as well as dealing with many review comments from academics the world over.

Over the next few days, government representatives are gathered together in Yokohama to agree every single word of the report summary. The hall has the look of a UN summit. All the delegates with their headphones on and banks of hard working translators sitting behind glass panels, making sure that whatever language you speak you can contribute to the process.

You might suspect that this rather formal IPCC governmental approval process would make the report a highly political document and of course there are some countries that argue to make the conclusions stronger and some that argue for them to be weaker. But the report has to remain true to the scientific evidence. Many of the scientists who have helped write the report are there at every step of the meeting, keeping the statements spot on with what the scientific evidence can tell us.

So, how has our understanding of the impacts of climate change developed over the last seven years? There are no really big game changers; just a growing body of evidence that climate change, if left unchecked, could have very serious impacts on the food we eat, the water we drink and the places we live. A lot of details are still uncertain, but the risks are very clear.

Many regions of the world will face multiple impacts. For example, populous parts of south and southeast Asia are likely to be exposed to increasing flood risk (along coasts and rivers), increasing risks of drought, decreases in crop productivity and more frequent heat waves.

Water resources and flooding

In my area of research, we know with high confidence that many parts of the world will see changes in the amount of rainfall they receive. Local details and magnitudes vary, but dry areas tend to get drier, and wet areas tend to get wetter – models consistently show this.

Water is already a scarce resource for more than a billion people in the world and with an increasing population it will get scarcer. Climate change will make the challenge of getting enough water even harder. For example, by 2050, one to three billion people in currently dry regions could have less water as a result of climate change, if greenhouse gases continue to rise rapidly.

On the other hand, 300 million to almost 3 billion people could have more water. But this water might not necessarily be available for people to use unless it is stored in some way (such as in reservoirs) and the risk of flooding for these people could increase.

There has been less work done on how flood risk along rivers might change in the future. Clearly some regions will see increasing rainfall and there is also a clear signal that heavy rainfall will increase across many areas – all this points to increasing flood risk. One study suggests that the current once in a century flood could occur twice as frequently across up to 40% of the world’s floodplains.

Reducing impacts

There’s also been a lot more research looking at how impacts might be reduced if we can keep the rise in global temperatures to below 2°C and to look at how quickly the severity of impacts increases with increasing temperature. This research helps to inform international climate policy, which is trying to agree reductions in greenhouse gas emissions to keep the impact of climate change from getting too bad.

If global temperature rise can be limited to 2°C (which is looking increasingly challenging), this could reduce impacts in 2050 on water scarcity by 22-24% and on river flooding by around 16%. So, even with stringent emission reductions and limited warming, the world will still need to adapt to the significant impacts that climate change is bringing. And this is perhaps where the new IPCC report will show the greatest advances in our understanding.

Over the past few years, many organisations have begun to think about how to adapt to climate change. We now have many more examples in many parts of the world. They show that adaptation can substantially reduce the impacts of climate change – but they also show that there are many barriers to successful adaptation. A key one is the uncertainty in exactly how climate may change, and a clear lesson from the recent literature is that we need to think flexibly and innovatively in order to cope with our changing climate.

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11 Comments sorted by

  1. Max Beran

    Retired hydrologist

    The "come on" for Prof Arnell's article says, "The evidence is clear that climate change, if left unchecked, could have very serious impacts on the food we eat, the water we drink and the places we live" and the "evidence" word appears within the article albeit in a more measured and conditional way,

    The global warming issue has spawned many linguistic abuses but I think labeling hypothetical future impacts as "evidence" figures large as one of the most blatant misdirections. The atmosphere's…

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    1. David Jordan

      Earth scientist

      In reply to Max Beran

      I have evidence, in the form of subjectively recorded analogues, that if I kick a basketball it will move forward. I have never actually kicked a basketball but because I have kicked other sorts of ball, all of which then moved (in doing which they conformed to the predictions made by my models of energy transfer) "the evidence is clear that" if I do so it will so move.

      The Prof's contention - and his use of the word "evidence" - seems reasonable.

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    2. Max Beran

      Retired hydrologist

      In reply to David Jordan

      That basketball case you mention as some sort of killer response would surely fall wihin the ambit of an acceptable use of the term "evidence". But it's a million miles from the gulf that exists between the first and last of my list of "begets" that underpins policy actions now to remedy putative impacts anticipated for the far future.

      Do you really think the evidence is strong enough to increase the design standards of flood protection works (so being able to fund a fraction of what could otherwise…

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    3. Dorothy L Robinson

      logged in via email @gmail.com

      In reply to Max Beran

      As a retired hydrologist, you will no doubt understand that water has a much greater capacity to store heat than air. The world has not, as you suggest, stopped warming over the past decade and a half. The amount of heat stored in the oceans continues to rise at an alarming rate, as shown in the graph at http://woodsmoke.3sc.net/amlet (sourced from the CSIRO/Australian Bureau of Meteorology ‘State of the Climate’ report - http://www.csiro.au/Outcomes/Climate/Understanding/State-of-the-Climate-2014.aspx

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    4. Max Beran

      Retired hydrologist

      In reply to Dorothy L Robinson

      You miss the point I'm afraid which was about the word "evidence" and its use (or abuse) when applied to something as numinous as impacts. The warming and the hiatus qualify as evidence (albeit of different things) because they actually happened; the experience of kicking a basketball mentioned by David Jordan likewise qualifies as "evidence" in the normal meaning of the word and can be exploited to make predictions. But calling something like a future impact that hasn't happened and sits at the…

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    5. Nick Goldie

      science writer

      In reply to Max Beran

      This seems to be a case of misdirection. Retired hydrologist Max Beran asserts that the consequences of climate change, as predicted by the IPCC team, are based on a series of "begets". It's a nice argument, and might win a debate, but flies in the face of reality. Researchers around the world are busy with their own areas of research, and come to conclusions, published in reputable peer-reviewed journals. It is not a cascade of "begets". The IPCC team collates and checks this diverse collection of evidence, and produces a meta-conclusion. This is far more substantial than the "mathematical models and thought experiments" beloved of denialists. Locally, for example, I accept the evidence for the high probability that climate change will increase the frequency of bush-fires in SE Australia. It isn't proof, produced after the event, but it is a high probability, based on observational evidence and sound theory.

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    6. Max Beran

      Retired hydrologist

      In reply to Nick Goldie

      I’ll try not to play the provoke and respond game beloved of the blogosphere but just remind Nick that this thread was not so much about global warming as such but about what could qualify for the word “evidence”. And of course evidence cuts both ways – there can be evidence for and evidence against as I tried to convey with those nuggets about recent temperature change in my initial post.

      The IPCC process is a lot more linear and sequential (and model-bound) than would normally be bundled into…

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    7. Nick Goldie

      science writer

      In reply to Max Beran

      Something that has not happened cannot, of course, be offered as "evidence". In my bushfire example, I did not suggest that increased bushfire risk (as enumerated by CSIRO, for example) is in itself evidence. It is the highly probable result of observed and measured events (evidence) together with a sound theoretical explanation for these events. So I repeat: this seems to be a case of misdirection, otherwise known as a straw man. Phrases like "a long chain of supposition" are clearly tendentious, and, it seems to me, not supported by, umm, the evidence.

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    8. Max Beran

      Retired hydrologist

      In reply to Nick Goldie

      I am delighted you agree. It took a few exchanges to say so and, as your "of course" suggests, it is almost trivially obvious - things which might or might not happen in the future do not merit the word "evidence". Nevertheless it is the reverse of the common attitude including the by-line for this article (which is why I raised the issue in the first place). After all none of us want to be thought tendentious especially in The Conversation fighting the causes of academic rigour and journalistic…

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    9. Nick Goldie

      science writer

      In reply to Max Beran

      Another straw man, or the same man recycled. So far as I can see, the original article nowhere suggests that the anticipated impacts are in themselves "evidence". Quote (from your original post): "The evidence is clear that climate change ... could have very serious impacts". Persisting with the straw man allows you to enjoy a reasonable sounding but quite specious attack on the science and scientists involved in climate research.

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    10. Max Beran

      Retired hydrologist

      In reply to Nick Goldie

      I've said above that I won't play the provoke and bite back game with you. About your substantial point, I agree and say as much in the first paragraph of the first post - the offending use is in the by-line rather than in the article (repeated below).

      "The "come on" for Prof Arnell's article says, "The evidence is clear that climate change, if left unchecked, could have very serious impacts on the food we eat, the water we drink and the places we live" and the "evidence" word appears within the article albeit in a more measured and conditional way,"

      It's a recurrent theme in many articles where a monolithic view of the the process of climate forecasting is presented whose particular nature is more accurately depicted with my list of "begets". I would also argue that this same view is implicit in the "97% of all scientists" thing. It builds to an impression of certainty in a field replete with unknowables.

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