A heat wave in Central America, southern U.S. was made 35 times more likely by climate change, a study says

Human-caused climate change made a devastating May heat wave in Central America and the southern U.S. 35 times more likely, a new study says. It also found that heat waves are set to happen way more often in the coming decades.

The extreme heat broke temperature records in the region. Shocking images of howler monkeys falling dead off trees from heat exposure in Mexico drove attention to the wave, which lasted for weeks. 

It also killed 125 people across Mexico — though that’s likely an undercount due to the challenge of accurately estimating heat-related deaths. 

“These are just the first impacts, in the short term. As this gets worse, the consequences as well will be worse,” said Ruth Cerezo-Mota, climate scientist at the Universidad Nacional Autónoma de México and part of the new study. 

“We will be risking the loss of biodiversity here in the region.”

A daunting climate future

The analysis is from World Weather Attribution, a research group that does “rapid attribution” studies — a way to quickly determine how much a severe weather event like a heat wave or flood was caused or worsened by climate change from human activities like burning fossil fuels for energy.

Such a heat wave is now expected to happen every 15 years in today’s climate, and more often if the planet continues to warm. That’s compared to once in about 60 years, if the world still had the climate of the year 2000, according to the analysis. 

That means the average person in Central America and the southern U.S. can expect to suffer a heat wave five to six times within their lifetime — or even more often, as climate change worsens. 

It’s a daunting prospect for young people across the Americas, as climate studies are increasingly showing that they may be destined to suffer climate extremes for the rest of their lives. 

“We’ll never know the world that we knew in our childhood, where access to the outdoors didn’t come with a fatal warning or a caution, which is going to become more and more of the norm,” said Bushra Asghar, a Montreal-based youth climate organizer.

Dangerously high temperatures this week in Ontario, Quebec and the Atlantic provinces are a warning of that here in Canada, which follow other extreme heat events in recent years, such as the B.C. heat wave in 2021 that killed over 600 people.

Temperature records broken 

In May, temperature records were broken in over 10 major Mexican cities, including the capital. Mexico City is at an elevation of 2,200 metres above sea level (about 800 metres higher than, for example, Banff), which usually moderates its summer weather — but on May 24, it reached a record high of 34.7 C.

Speaking to reporters in May, Mexico’s outgoing president Andres Manuel Lopez Obrador said, “The heat is very strong. Since I’ve been visiting these states, I’ve never felt it as much as I do now.”

Other cities also broke their own temperature records, and parts of Mexico rose into the 40s. Gallinas, in the northeastern state of Tamaulipas, recorded a scorching 51.1 C.

WATCH | More on May’s deadly heat in Mexico: 

Mexico gripped by deadly heat in May

Much of Mexico sweltered through temperatures above 45 C in May, with the extreme heat killing dozens of people. Dehydrated howler monkeys dropped dead from trees in the southern Mexican jungle as rescuers raced to give them water.

“The people here in Veracruz are suffering a lot from the heat,” Cinthia Zuniga, a resident of Veracruz in eastern Mexico working at the city’s pier, told the AFP news agency the same month. 

“Pets are also suffering — there are people who are working, too, for example, street vendors, construction workers — many people are suffering from the heat. In the stores there is no water to drink, there is no ice and the electricity is out.” 

Temperatures soared in the southwestern U.S., as well, with Las Vegas hitting 43.9 C and Phoenix 44.4 C.

That sounds warning bells for Asghar, who says governments need to acknowledge the outsized impact on the younger generation when moving on climate policy.

“I find that they are moving really slowly, they are practising incrementalism, which is, I think, a generational justice issue,” she said.

“Because if they did care about younger generations and what we will live to see and the world that we will inherit, they would be making different decisions.”

While the daytime highs captured much of the attention, the analysis also highlighted the nighttime temperatures, which have a significant impact on people’s health and ability to get a reprieve from the heat. The high nighttime temperatures in Central and North America were made a whopping 200 times more likely due to human-caused climate change, according to the researchers.

The researchers warned that this leaves Central America especially vulnerable, as it has fewer resources than the U.S. and other higher-income countries to deal with the heat.

“In Mexico and countries within Central America, there are currently no heat governance systems and there is lower capacity to adapt at the household level, with less access to air conditioning and high reliability and hybrid power,” said Karina Izquierdo of the Red Cross Red Crescent Climate Centre and part of the WWA study.

Izquierdo contrasted this to cities in the U.S., which have appointed climate chiefs and even officials devoted to tackling extreme heat. 

The study urges communities to prepare for when temperatures inevitably soar again, including having heat warning systems, laws to protect outdoor workers, reliable electricity and overhauling urban planning.