Dangerous, record-breaking heat waves are set to increase as the climate crisis intensifies, and they will be particularly devastating in countries and regions that are least prepared for them, according to a new study.
Scientists analyzed temperature data sets spanning more than 60 years, as well as climate models, to calculate the likelihood of unprecedented heat extremes occurring -- and where these might happen.
They identified Afghanistan, Papua New Guinea and Central America -- including Guatemala, Honduras and Nicaragua -- as "hot spots" for high-risk heat waves.
These regions are particularly vulnerable due to their fast-growing populations and limited access to healthcare and energy supplies, which undermine their resilience to extreme temperatures, according to the report, published Tuesday in the journal Nature Communications.
"There's evidence there that those regions may well be in for a big heat wave and they wouldn't be prepared for it," said Dann Mitchell, a professor in atmospheric sciences at the University of Bristol in the UK and a study co-author.
The threat facing Afghanistan is particularly stark, Mitchell told CNN. Not only is there high potential for record-breaking extreme heat, but the impacts will be intensified by the huge difficulties the country already faces, he said.
Afghanistan is struggling with dire social and economic problems. It also has a growing population which is increasingly exposed to the problems of limited resources, according to the report.
"When a really extreme heat wave does finally come along, then there are instantly going to be a lot of problems," Mitchell said.
Heat waves have a wide-ranging negative impact. They reduce air quality, worsen drought, increase the risk of wildfires and can lead infrastructure to buckle.
They also take a heavy toll on human health, and extreme heat is one of the deadliest natural disasters. Heat stroke or heat exhaustion can trigger a wide range of dangerous symptoms, including headaches, dizziness, nausea and loss of consciousness, among others. Heat stroke is the most serious heat-related illness, according to the Centers for Disease Control and Prevention, causing body temperature to skyrocket in a matter of minutes, and can lead to permanent disability or death.
Several regions have already seen unprecedented temperatures this year. In March, parts of Argentina grappled with temperatures up to 10 degrees Celsius, or 18 degrees Fahrenheit, above normal, while high temperature records were smashed across large parts of Asia in April.
"Heat waves and other extreme weather events will only become more intense as the world continues to burn fossil fuels," said Friederike Otto, a climate scientist at the Grantham Institute for Climate Change at Imperial College London, who was not involved with the study.
Nowhere is safe, noted the report, which found that "statistically implausible" heat waves -- those that fell well outside the historical norm -- occurred between 1959 and 2021 in around 30% of the regions assessed. These include the 2021 Pacific Northwest heat wave, where high temperature records were not just broken but completely smashed, killing hundreds of people.
In Lytton, British Columbia, temperatures peaked at just under 50 degrees Celsius (121 degrees Fahrenheit) in June 2021, breaking the previous record by almost 5 degrees. The village was almost completely destroyed by a wildfire just days later.
Scientists determined that the event would have been almost impossible without climate change.
Parts of China, including Beijing, and European countries, such as Germany and Belgium, also face a high risk, according to the report.
The millions of people who live in these densely populated regions could be badly affected by heat waves, even if these countries are more likely to have resources to mitigate some of the worst impacts.
The report calls on governments around the world to prepare for heat events that go far beyond current record temperatures, such as setting up cooling centers and reducing hours for those working outside.
Many policies exist that governments can implement to save lives, Otto said, including "preparing heat wave management plans, ensuring and testing they are implemented, informing the public about imminent heat waves, and protecting people who are vulnerable to the impacts of heat waves."
Unprecedented heat events are becoming more likely as the world continues to burn fossil fuels, said Lucas Vargas Zeppetello, a research fellow at Harvard University, whose 2022 research found that dangerous levels of heat are set to at least triple across the world by the end of the century.
"By definition, we don't know what could happen if large populations are exposed to unprecedented heat and humidity stress," Vargas Zeppetello told CNN, "but heat waves in the past few decades have already been extremely deadly and there is serious cause for concern in the future."
