The exposed feet of a corpse lying on a coroner’s table, with a blank identification tag around the big toe.
Image credit: KatarzynaBialasiewicz on

Buried in a landslide, drowned in a flood, or left without food in a drought; in 2023, 12,000 people30 percent more than in 2022—are estimated to have been killed as a result of extreme weather events. That number is only expected to rise. 

A report released at the World Economic Forum in January estimates that by 2050, climate change may be responsible for an additional 14.5 million deaths. Those deaths could be directly due to extreme weather events like floods or wildfires, or indirectly responsible: higher temperatures and air pollution are linked to heart attacks, malnutrition, diarrheal disease, and lung cancer and can worsen issues such as asthma.

Yet its unlikely that any paperwork will reflect the role global warming played in these deaths. Instead, “stroke” or “chronic obstructive pulmonary disease” will be listed. This discrepancy is an urgent issue for those working to improve the environment. If climate change-related deaths aren’t adequately recorded, that lack of information trickles down, resulting in an underestimation of the impact of extreme weather.

The Call to Modernize

Quantifying the impacts of climate change, particularly on death rates, is of enormous importance, said Andrew Dessler, a professor of atmospheric sciences and director at the Texas Center for Climate Studies at Texas A&M University. “It grounds the debate in empirical evidence rather than speculation. Most people don’t understand how bad climate change is, and [data] is one way to help them understand.”

Useful climate data can be used at higher levels to inform policy. “If we know people die from heat, it can be used to come up with an extreme heat plan,” Dessler explained. 

In 2020, a cohort of researchers in Australia called for modernizing death certification and data on climate deaths to allow for better reporting and recognition of weather events on mortality. Their plea, published in the Lancet, followed a series of devastating heatwaves and bushfires in the country.

As it stands, a death certificate in most parts of the world allows for a medical professional to detail a primary cause of death. While a secondary cause such as an environmental variable can be listed, it doesn’t happen often, explained Dr. Arnagretta Hunter, a physician, cardiologist, and lecturer at the Australian National University and one of the letter’s authors. In Australia, for example, excessive natural heat was referenced in less than 0.1 percent of 1.7 million deaths between 2006 and 2017. Research suggested it should have been 50 times more than that.

In the United States, many cases of heat-related deaths also go unreported, according to the US Environmental Protection Agency (EPA), because a medical examiner does not indicate them or they are not correctly coded on a death certificate. For example, the Centers for Disease Control and Prevention (CDC) uses the International Classification of Diseases to document underlying causes of death—but none of the ICD-10 codes include climate change, Remmington Belford, an EPA spokesperson, noted in an email. 

We’re not necessarily [wanting to put] climate change on death certificates, but recognizing that environmental variables…have a significant impact on our health and wellbeing, so mortality can be directly and indirectly attributable to [them],” Hunter explained.

She’s not alone in her thinking. On social media, a concerned citizen from the United Kingdom wrote that highlighting climate change-related deaths on death certificates would “help track and understand the different types of climate change deaths.” In a 2020 landmark ruling, a coroner in London listed air pollution as the primary cause of death for a young person who had died of asthma in 2013.

Barriers to Improving Data

“It’s really hard to determine who died from heat and who would have had a heart attack anyway.”

This kind of tracking isn’t happening on a larger scale in part because of a scarcity of resources and a lack of physician training in death certificate completion, according to the Lancet. 

According to Hunter, there’s also been a historical focus on the biology of disease rather than social determinants of health, such as where people live and work, socioeconomic circumstances, or climate factors. As NPQ has written, social determinants of health is a “concept that points out that true health has less to do with doctor’s visits, medicine, and health insurance than it does with factors outside the healthcare system, such as poverty, environmental hazards, lack of access to healthy food, and a built environment that makes walking and exercise difficult.”

While understanding of how social determinants impact health is growing, it hasn’t yet reached the point of being adequately reflected on death certificates, according to Hunter. “Making those links is really important in how we plan for the changing climate and I think that’s the most compelling reason,” she said.

But for Dessler, the issue is that so few deaths are clearly caused by climate change. In an extreme weather event, it’s hard to determine whether those who died would have perished otherwise had there not been a storm or extreme temperatures. In the summer of 2022, for example, estimates put the number of deaths due to extreme heat at over 61,000 in Europe. Still, many had preexisting health issues, making it hard to determine how much of a role the soaring temperatures played.

“Very few people die during heat waves from hyperthermia,” Dessler said. “Rather, the heat causes other problems [such as] heart attacks. If you look at individual cases, it’s really hard to determine who died from heat and who would have had a heart attack anyway.”

According to Dessler, the best way to reach a figure is via a large-scale statistical analysis of a large population. Attribution science, an expanding area of study important for climate justice, uses observational data, statistics, and climate models to better determine the impact of extreme weather events. But only seeing the deaths statistically makes them an estimate.

“We had a heat dome here in the Pacific Northwest, and it took a year to get all the death certificates in and to do the retrospective analysis. The analysis suggests over 440 people in the state died because of climate change,” said Dr. Kristie L. Ebi, professor at the Center for Health and the Global Environment at the University of Washington. 

Sometimes, the lack of resources kills people during a disaster rather than the event itself.

This is a challenge that Lauren Moran, director of the Mortality Data Center at the Australian Bureau of Statistics, also faces in her work. The Center compiles information on every death in Australia and generates statistics and commentary around what that could mean for public policy.

The Center has tried to analyze whether there has been a change in mortality patterns pertaining to extreme weather events. “What we tend to see more of is people with preexisting chronic conditions, and it could be the weather that’s exacerbating that existing condition,” explained Moran. Determining whether they’d have survived without the event is reliant on the opinion of medical practitioners and coroners.

How to Move Forward

To ask practitioners to record deaths in a way that pertains to the potential impact of weather places an additional responsibility on often overburdened healthcare professionals, notes Ebi. It would also likely require additional training in detection and attribution studies.

Extreme weather often occurs in low-income areas. An average of 189 million people per year have been affected by extreme weather-related events in lower-income countries since 1991, according to Oxfam. These countries may lack the resources to thoroughly report deaths, with many still relying on paper records.

Data are often missing on smaller weather events, from countries with lesser insurance coverage, and on undocumented workers and other marginalized groups.

Sometimes, the lack of resources kills people during a disaster rather than the event itself, explained Dr. Sébastien Gasana, a social sciences lecturer and researcher in Rwanda. “People or countries which are well-prepared, and have means for that, are not facing the same consequences as others that are less prepared or not able to anticipate and mitigate the consequences,” he said. 

A lack of warning systems, poor forecasting, or sparse protection could endanger people, while people in places with early warning mechanisms may have stayed safe. It would be hard to detail this on a death certificate. “In order to really understand the various effects of climate change, we need deep analyses…[and] to take into consideration different and specific aspects: political, demographic, geographic, developmental,” Gasana said.

Ebi called for better resourcing of low- and middle-income countries so that “data can be captured accurately at a scale that will tell you about how different kinds of weather patterns are affecting our health.” 

The United Nations Office for Disaster Risk Reduction also calls for similar measures. In 2023, it highlighted in an explainer on data gaps in disasters how data are often missing on smaller weather events, from countries with lesser insurance coverage, and on undocumented workers and other marginalized groups. This makes impact hard to measure. And without such data, action is harder to galvanize and finance.

Knowing the precise number of climate-related casualties does not change what is happening, said Belford, but provides an additional tool for strengthening strategies to best protect human health. “Emergency managers, communicators in local government, and first responders already use well-honed strategies to help protect people facing risks from climate-intensified weather events,” he said. Ebi adds that finding better ways to make sure that people are protected has to be a priority.”