Heatwaves will become more deadly with climate change, new study shows

Reducing emissions and developing adaption plans can help though.

Beachgoers pack their belongings near the end of day at Sunset Beach in Huntington Beach, California on July 21, 2018.  (Credit: FREDERIC J. BROWN/AFP/Getty Images)
Beachgoers pack their belongings near the end of day at Sunset Beach in Huntington Beach, California on July 21, 2018. (Credit: FREDERIC J. BROWN/AFP/Getty Images)

There will be an increase in heatwave-related deaths due to climate change in the future under nearly every scenario, according to a new study released Tuesday.

Taking steps to adapt to and mitigate the impacts of rising greenhouse gas emissions could help curb the number of heatwave-related fatalities. But researchers found that even if countries are able to adapt, under the most extreme scenarios of high temperatures and population growth, deaths will still increase in virtually every region.

Analyzing data from more than 400 communities across 20 different countries and regions — from North, South, and Central America to Europe, Asia, and Oceania — researchers projected potential mortality rates from heatwaves in decades to come, between 2031 and 2080.

The report claims to be the largest international study on the potential health impacts of heatwaves as expected under different climate change scenarios.


Researchers found that with no adaptation to climate change and little effort to curb emissions, deaths from heatwaves will increase substantially. Tropical and subtropical countries will be most affected, with at least 650 percent more heatwave-related deaths expected between 2031 and 2080 compared to the average number of deaths linked to heatwaves for the period between 1971 and 2020.

European countries and the United States will in comparison see a smaller increase in heatwave-related deaths. The number of fatalities from heatwaves could increase by as much as 400 to 600 percent in the United States, for example, compared to the past five decades. Europe will see a roughly 275 percent increase.

Predicted percentage increase in deaths related to heatwaves across the world.
Predicted percentage increase in deaths related to heatwaves across the world.

“Future heatwaves in particular will be more frequent, more intense and will last much longer,” Yuming Guo, associate professor at Monash University in Australia, said in a statement. Guo was the lead author of the study, published in the journal PLOS Medicine.

“If we cannot find a way to mitigate the climate change, reduce the heatwave days, and help people adapt to heatwaves,” Guo said, “there will be a big increase of heatwave-related deaths in the future, particularly in the poor countries located around the equator.”

Heatwaves have a range of health impacts, from heat exhaustion, heat stroke, aggravated cardiac or pulmonary conditions, psychiatric illness, and death. Beyond this, heat can trigger other health risks, such as the spread of disease.


During Europe’s 2003 heatwave, tens of thousands of people died. In 2010, Russian heatwaves were linked to an estimated 55,000 deaths. And this summer has seen record-breaking temperatures around the world. In Quebec, Canada, the heat has claimed the lives of up to 70 people this month.

The PLOS study looked at a series of different emissions pathways laid out by the U.N. Intergovernmental Panel on Climate Change (IPCC) — from business as usual leading to extreme temperature increase to more significant reductions in emissions limiting global warming. Within this, they factored in adaptation scenarios and population growth.

Researchers found that as populations and greenhouse gas emissions increase, so do the number of deaths from heatwaves. As the study states, “Future changes in heatwave-related excess mortality are highly affected by greenhouse gas emissions and human adaptation to climate change.”

There is one scenario, however, in which deaths from extreme heat go down. Under a low-population scenario, Italy, Japan, Moldova, and Spain will see fewer heatwave-related deaths regardless of how much greenhouse gas emissions increase. This is mainly due to a drop in population numbers.

And while under the study’s adaptation scenarios, “most of the heatwave-related excess mortality would be offset in the future,” increases in population numbers will mean more deaths. It’s also not clear how different countries and communities will respond to climate change.


There is a range of ways societies can adapt to a warmer world. This can include more and better air conditioning or other cooling technologies, improvements in health care services and city planning, and better heatwave warning systems. More efficient cooling technology sourced from renewable energy is needed, however, otherwise increased use of air conditioning will inevitably have its own negative impact on climate change.

How individuals adapt can also vary, from physiological changes in our core body temperatures to behavioral changes such as how much time is spent outdoors, the type of clothing we wear, and level of physical activity.

As the study recommends, adaptation planning is needed in order to reduce the health impacts of heatwaves. While true for the whole world, it is most pressing in tropical and subtropical regions.

Ultimately, the study says, “stricter mitigation policy” is needed to reduce emissions, because lower greenhouse gas emissions mean fewer deaths due to heatwaves.

“The good news is that if we mitigate greenhouse gas emissions under scenarios that comply with the Paris Agreement, then the projected impact will be much reduced,” Antonio Gasparrini, associate professor at the London School of Hygiene and Tropical Medicine, said in a statement. 

But, according to the U.S. National Climate Assessment published last year, heatwaves in the U.S. are expected to be 12°F warmer by mid-century if emissions aren’t reduced as recommended by the Paris climate accord — a deal President Donald Trump chose to abandon.