All of today’s heatwaves bear the unmistakable and measurable fingerprint of global warming, leading experts in quantifying climate change’s impact on extreme weather said Wednesday.
Burning fossil fuels and destroying forests have released enough greenhouse gases into the atmosphere to also increase the frequency and intensity of many floods, droughts, wildfires and tropical storms, they said in a scientific report.
“There is no doubt that climate change is a big change when it comes to extreme heat,” Friederike Otto, a researcher at Imperial College London’s Grantham Institute, told AFP.
Extreme heat spells like the heatwave that swept South Asia in March and April are already the deadliest extreme events, she added.
“Any heatwave around the world is now becoming stronger and more likely due to man-made climate change,” said Otto and co-author Ben Clarke of the University of Oxford in the report, which was presented as a briefing paper for the news media.
Evidence of the impact of global warming on extreme weather has been accumulating for decades, but only recently has it been possible to answer the most obvious questions: To what extent was a particular event caused by climate change?
Most scientists could predict that an unusually severe hurricane, flood, or heat wave would be consistent with general predictions about how global warming would ultimately affect the weather.
The news media, on the other hand, sometimes ignored climate change altogether or, at the other extreme, incorrectly attributed a weather catastrophe solely to rising temperatures.
However, with more data and better tools, Otto and other pioneers in the field of event attribution science were able to calculate—sometimes in near real time—how much more likely or intense a given storm or heatwave has become due to global warming.
evidence in the courtroom
For example, Otto and colleagues from the World Weather Attribution (WWA) consortium concluded that the heatwave that swept western North America last June, taking temperatures in Canada to a record 49.6 °C (121 °F). , without which human-caused climate change would have been “virtually impossible”.
A heatwave that scorched India and Pakistan last month is still under review, Otto told AFP, but the bigger picture is startlingly clear.
“What we’re seeing now in terms of extreme heat will be very normal, if not cool, in a world of 2 to 3 degrees Celsius,” she said, referring to average global temperatures above pre-industrial levels.
The world has warmed by almost 1.2 degrees so far.
That increase made record-breaking rains and floods in Germany and Belgium last July, which killed more than 200 people, up to nine times more likely, the WWA found.
But global warming is not always to blame.
A two-year drought in southern Madagascar that led to starvation, which the United Nations blames on climate change, was actually a product of natural weather variability, experts reported.
Quantifying the impact of global warming on extreme weather events using peer-reviewed methods has real-world policy implications.
For example, attribution studies have been used as evidence in landmark climate processes in the United States, Australia and Europe.
In a case set to reopen later this month, Saul Luciano Lliuya is suing RWE AG, a Peruvian farmer, the German energy giant over the costs of preventing harmful flooding from a glacial lake destabilized by climate change.
A scientific review concluded that man-made global warming is directly responsible for creating a “critical threat” of a devastating eruption putting a city of about 120,000 in the path of potential flooding.
© Agence France-Presse
https://www.sciencealert.com/heatwaves-are-stronger-thanks-to-climate-change-say-experts Climate change is a “game changer” when it comes to heat waves, experts say