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 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 per cent of the world’s floodplains.
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 degrees 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 degrees (which is looking increasingly challenging), this could reduce impacts in 2050 on water scarcity by 22-24 per cent and on river flooding by around 16 per cent. 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.
Nigel Arnell is professor of Climate Change Science and director of the Walker Institute at the University of Reading, UK.
Nigel Arnell receives funding for the University of Reading from research councils and government departments.