Evidence grows of climate change impact on emerging heatwave risks

Experts have warned the soaring temperatures across the globe could not have occurred without the impact of climate change on the world’s weather systems.

Following a record hot June, large areas of the US and Mexico, Southern Europe and China experienced extreme heat in July 2023, breaking many local high temperature records. A  new study from World Weather Attribution has examined the role of climate change in this extreme weather.

The study said: “July 2023 saw extreme heatwaves in several parts of the Northern Hemisphere, including the Southwest of the US and Mexico, Southern Europe and China. Temperatures exceeded 50°C on the 16 July in Death Valley in the US as well as in Northwest China. Records were also reached in many other weather stations in China and the all-China heat record was broken in Sanbao on the 16 July.

“In Europe, the hottest ever day in Catalunya was recorded and highest-ever records of daily minimum temperature were broken in other parts of Spain. In the US, parts of Nevada, Colorado and New Mexico tied their all time high, parts of Arizona, Cayman Islands, highest ever night time temperatures in Phoenix Arizona which also had its record for longest time without falling below 90°F/32.2°C.”

Professor Liz Stephens, professor in Climate Risks and Resilience at the University of Reading, explained: “The temperatures recorded during the recent heatwave across Southern Europe would have been impossible without climate change.

“This extreme weather in Southern Europe is not the ‘new normal’. Heatwaves will get over 1 degree hotter again within 30 years even if the goals of the Paris Agreement are met.

“Despite this increasing risk, there are relatively simple solutions that can reduce the impacts of heatwaves, provided that governments act now. This means more investment in adapting our homes and urban environments, ensuring critical infrastructure is resilient, and putting plans in place to support the members of our communities most vulnerable to the extreme heat.”

The report warned heatwaves are amongst the deadliest natural hazards with thousands of people dying from heat-related causes each year. However, the full impact of a heatwave is rarely known until weeks or months afterwards, once death certificates are collected, or scientists can analyse excess deaths. Many places lack good record-keeping of heat-related deaths, therefore currently available global mortality figures are likely an underestimate.

“Without human induced climate change these heat events would however have been extremely rare,” it added. “In China it would have been about a 1 in 250 year event while maximum heat like in July 2023 would have been virtually impossible to occur in the US/Mexico region and Southern Europe if humans had not warmed the planet by burning fossil fuels.

“In all the regions a heatwave of the same likelihood as the one observed today would have been significantly cooler in a world without climate change. Similar to previous studies we found that the heatwaves defined above are 2.5°C warmer in Southern Europe, 2°C warmer in North America and about 1°C in China in today’s climate than they would have been if it was not for human-induced climate change. “

The study warned unless the world rapidly stops burning fossil fuels, these events will become even more common and the world will experience heatwaves that are even hotter and longer-lasting. A heatwave like the recent ones would occur every 2-5 years in a world that is 2°C warmer than the preindustrial climate.

Leading scientists have warned the current wildfires are indicative of the impact of climate change.

Prof Guillermo Rein, professor of Fire Science, Imperial College London, said: “The combination of heat, wind and people in the Mediterranean is mortal.  There have always been wildfires in the South but climate change is making them larger, faster, and harder to stop.

“The intense heat of the summer dries vegetation and makes it very flammable, easier to catch fire.  A heat wave or an unusually hot summer leads to even more flammable forests.”

Dr Thomas Smith, associate professor in Environmental Geography, London School of Economics and Political Science (LSE), warned: “Human-driven climate change is increasing the likelihood and intensity of heatwaves.  This is the second major heatwave in the Mediterranean this year.  The first heatwave was found to have been made 100-times more likely due to the human impact on climate change, and at least 2°C hotter.  I expect there will be a similar finding for the current situation, which is ultimately responsible for the wildfires we’ve been seeing over the past week.”

“It is too early to say if climate change has caused these wildfires.  However, the fact there are now so many across the world, most recently in Greece and Canada, is a clear sign that climate change is causing an increase in the number of severe wildfires globally,” added Dr Douglas Kelley, a land surface modeller at the UK Centre for Ecology & Hydrology.

It comes as the UK Met Office warned that the 40°C temperatures seen last year will be a more regular event.

Oli Claydon, from the Met Office, said: “It is evident that the climate is possible to reach 40°C in the UK now, as we saw in a number of stations in July last year.

“The likelihood of exceeding it going forward somewhere in the UK in a given year is now increasing due to human-induced climate change.”

“So as well as the need to mitigate against future climate change by reducing emissions of greenhouse gases, we’re already experiencing the impacts of climate change now, so there’s already a need to adapt to the types of weather extremes that we can see in the UK,” he explained.

The study warned unless the world rapidly stops burning fossil fuels, these events will become even more common and the world will experience heatwaves that are even hotter and longer-lasting.