Climate change made US and Mexico heatwave 35 times more likely

A billboard shows the temperature on 5 June in Phoenix, Arizona

Human-induced climate change made recent extreme heat in the US south-west, Mexico and Central America around 35 times more likely, scientists say.

The World Weather Attribution (WWA) group studied excess heat between May and early June, when the US heatwave was concentrated in south-west states including California, Nevada and Arizona.

Extreme temperatures in Mexico also claimed lives during the period.

Such attribution studies take some time to complete, so it is too soon for scientists to say how much of a role climate change is playing in the current heatwave stretching from the centre of the US through to the north-east and into Canada.

In their new report, the scientists said such a heatwave was now four times more likely than it was in the year 2000, driven by planet-warming emissions.

Many extreme weather events including heatwaves are becoming more frequent and intense as a result of climate change, experts say.

“The results of our study should be taken as another warning that our climate is heating to dangerous levels," said Izidine Pinto, Researcher at the Royal Netherlands Meteorological Institute.

“Potentially deadly and record-breaking temperatures are occurring more and more frequently in the US, Mexico and Central America due to climate change.

“As long as humans fill the atmosphere with fossil fuel emissions, the heat will only get worse – vulnerable people will continue to die and the cost of living will continue to increase.”

The WWA study focused on a region including the US south-west and Mexico, as well as Guatemala, Belize, El Salvador and Honduras which also saw dangerously high temperatures.

The scientists said that the hottest five-day stretch across the region in June was made about 1.4C warmer by climate change.

“Every fraction of a degree of warming exposes more people to dangerous heat," said Karina Izquierdo, Urban Advisor for the Latin American and Caribbean region at Red Cross Climate Centre.

“The additional 1.4C of heat caused by climate change would have been the difference between life and death for many people during May and June."

Mexican officials have linked the heatwave to the deaths of scores of people. It has also been blamed for the deaths of howler monkeys in the southern state of Tabasco.

The scientists underlined the danger from high night-time temperatures - a severe threat to health as the body does not have time to rest and recover.

The WWA group conducts rapid-attribution studies on weather events around the world to look at the role climate change has played in their severity.

The scientists examine the events, comparing them against models of what would have likely occurred in a world not subjected to human-induced global warming.