Ten years of the Paris Agreement: The present and future of extreme heat
Ten years after the Paris Agreement was signed, a new global analysis shows that the agreement has helped to mitigate global warming. The expected warming this century is now 2.6 degrees, compared to 4 degrees as expected in 2015. But even though developments are moving in the right direction to some extent, scientists warn that global warming continues to increase, and with it the risk of extreme heat.
Since the Paris Agreement was adopted in 2015, the global average temperature has risen by 0.3 degrees. This means an average of 11 more hot days per year worldwide, according to a new study by Climate Central and World Weather Attribution (WWA).
If countries fulfill their current climate commitments and limit warming to 2.6 degrees, the world will experience an average of 57 more hot days each year compared to today. In a scenario where the temperature rises by 4 degrees, the corresponding figure is 114 more hot days. Countries such as Kenya, Mexico, and Brazil would avoid between 60 and 80 hot days each year with 2.6 degrees of global warming compared to 4 degrees of global warming.
– The report highlights the seriousness of the climate issue and the importance of the Paris Agreement's goal of keeping warming well below 2 degrees, as warming has more severe consequences for every fraction of a degree. We are already seeing extreme heat becoming more common, with consequences for both people and ecosystems, says Erik Kjellström, professor of climatology at SMHI.
Heat in cities affects people all over the world. Image from a heatwave in Italy. Photo by Richard Vanlerberghe via Unsplash.
Extreme heat is increasing in all regions
The report shows that extreme heat waves have already become more likely since 2015. Of the six events analyzed in the report, including in southern Europe, the Amazon, and West Africa, three of them would have been almost impossible without climate change. Two of them are now estimated to be ten times more likely than ten years ago.
With a 4 degrees rise in temperature, heat waves will be approximately 3 to 6 degrees warmer and 5 to 75 times more likely than today, the study shows. At 2.6 degrees, the changes are smaller – about 1.5 to 3 degrees warmer and 3 to 35 times more likely.
– The Paris Agreement acts as a global safety net, but it needs to be strengthened. To protect people, faster emissions reductions and a transition away from fossil fuels are needed, says Erik Kjellström.
Adaptation is progressing – but resources are limited
Since 2015, about half of the world's countries have some form of heat warning system, and at least 47 have heat wave action plans. To further improve global adaptation to heat, researchers say that many countries in Africa, Latin America, and parts of Asia still need to develop early warning systems, as well as heat and health plans. They also emphasize the importance of national weather services issuing heat warnings. At the same time, researchers point out that funding for adaptation measures is still insufficient.
Heat waves are the weather event that causes the most deaths globally, estimated at around half a million per year. Historically, the danger of heat has been underestimated because its effects are less visible than those of other extreme weather events. Measures such as increased greenery in cities, more shaded environments, and improved healthcare are highlighted as crucial to reducing the risks.
– We see that communities in many parts of the world are ill-equipped for the heat. This is also true in Europe, where high temperatures have had major consequences for health and energy systems. Adaptation must take place in parallel with emissions reductions, says Erik Kjellström.
The science behind the analysis
When conducting the study, the researchers identified local hot days by calculating the threshold temperature for the top 10% of temperatures from 1991 to 2020. These days, which exceed the 90th percentile of historical temperatures, are days that can be considered hot from a local perspective. They then compared the number of days that exceeded this threshold at different levels of global temperature increase.
To quantify the effect of human-induced warming on heat waves, WWA researchers analyzed weather data and climate models using methods that undergo peer review. They compared how these types of events have changed between a climate with human-induced warming and the cooler pre-industrial climate, as well as how they are expected to change by the end of the century under different degrees of continued global warming.
The study, conducted by 18 researchers from Climate Central and WWA, is one of the most comprehensive analyses to date of how extreme heat has changed since the Paris Agreement.
– The science is clear: the world has already become warmer, but the future will be determined by our decisions today. The Paris Agreement has made a difference—but it is not enough, concludes Erik Kjellström.
