Clear link between extreme weather and human activity, studies show

Researchers warn ‘our civilisation is increasingly out of sync with changing climate’

Civilisation is increasingly out of sync with the world's changing climate, as heatwaves, such as those in the Mediterranean and in China during 2017, were made more likely by human-caused climate change, according to new research.

A similar link was confirmed with droughts on US Northern Plains and in East Africa, and floods that occurred in South America and Bangladesh.

The findings were published on Monday in the Bulletin of the American Meteorological Society (BAMS). "These attribution studies are telling us that a warming Earth is continuing to send us new and more extreme weather events every year," said Jeff Rosenfeld, editor in chief of BAMS.

“The message of this science is that our civilisation is increasingly out of sync with our changing climate.”


The seventh edition of the report, Explaining Extreme Events from a Climate Perspective, also included analyses of ocean events, including intense heatwaves in the Tasman Sea off Australia in 2017 and 2018, all of which were "virtually impossible" without human-caused climate change.

What’s more, the scientists are now able to predict the increased chances of them happening.

Intimately connected

This is the second year they have identified extreme weather events that they concluded could not have happened without warming of the climate through human-induced climate change – their report is widely regarded as the definitive evaluation of extreme weather events globally.

Dr Martin Hoerling, a research meteorologist with the National Oceanic and Atmospheric Administration, said while the events studied spanned six continents and a calendar year, what became clear is they were intimately connected.

“These studies confirm predictions of the 1990 First [UN] Intergovernmental Panel on Climate Change report, which foresaw that radical departures from 20th century weather and climate would be happening now,” he said. “Scientific evidence supports increasing confidence that human activity is driving a variety of extreme events now. These are having large economic impacts across the US and around the world.”

ClientEarth climate lawyer and co-author of the report's introduction, Sophie Marjanac said: "Extreme weather events around the world, such as the recent catastrophic Californian wildfires, European heatwave and monsoon floods in Bangladesh, show that insurers need to be integrating academic climate science into their natural catastrophe models or face increasing losses.

“The strength of the findings in this report shows that it is only a matter of time before climate attribution science translates into legal liability for those that continue to ignore these risks,” he added.

Findings were made on three categories of extremes:


Climate change has made the chances of heatwaves in the Euro-Mediterranean region that are at least as hot as 2017's three times more likely than they were in 1950. The chance of such a heatwave recurring is now 10 per cent in any given year. Heatwaves like the record-breaking 2017 event in central and eastern China were once rare. They are now one-in-five-year events due to climate change.


Climate change made the 2017 Northern Great Plains drought 1.5 times more likely.


Extreme, pre-monsoon rainfall that inundated northeast Bangladesh was made up to 100 per cent more likely by climate change, which has made chances of the extreme rain that collapsed thousands of houses in southeastern China in June 2017 twice as likely.

Ocean-driven events

Scientists found record sea surface temperatures in the Tasman Sea in 2017 and 2018 were virtually impossible without global warming. Extremely warm sea surface temperatures off the coast of Africa doubled the probability of 2017's East Africa drought, which left more than 6 million people in Somalia facing food shortages. An analysis found the extreme ocean warmth could not have occurred in a pre-industrial climate.

Record-low Arctic sea ice due to climate change influenced record-breaking "precipitation deficits" across a large part of western Europe in December 2016.

Oceanic events, from unusual hot spots to sea-ice melt, are among the cases studied this year. The oceans participate in global warming, and “there’s ample reason to believe that the reservoir of heat in the ocean will be a significant driver of extreme events on land”, the authors note.

Kevin O'Sullivan

Kevin O'Sullivan

Kevin O'Sullivan is Environment and Science Editor and former editor of The Irish Times