Weather disaster-related deaths are down—warming could undo that trend

The World Meteorological Organization (WMO) published a report in August containing some rare good news about extreme weather: Despite a sharp increase in the number of weather- and climate-related disasters reported worldwide over the past 50 years, the number of deaths tied to those disasters has dropped nearly threefold.

To disaster researchers, that’s no surprise. While natural hazards like extreme rainfall and heat waves are becoming more frequent and severe as the planet heats up, our scientific understanding of those hazards, and the early warning systems that safeguard communities, have improved significantly over recent decades. As a result, disasters related to weather and climate have become less deadly over time.

There’s no guarantee, however, that this positive trend will continue forever. While we are better equipped than ever before to save lives during disasters, it will be a challenge to deploy existing solutions at the pace and scale needed to protect growing populations in a warming climate.

“If we are not continually investing in warning systems, if we are not building differently at the same time that we have intensification or changes to these hazards, that could very easily lead to increased deaths,” says disaster researcher Samantha Montano, the author of the recent book Disasterology: Dispatches from the Frontlines of the Climate Crisis, who was not involved in the WMO study.

Defining a disaster death

Every time a disaster occurs, whether it’s due to a hurricane, wildfire, volcanic eruption, tornado, or earthquake, one of the first questions people ask is how many lives were lost. Death tolls help the public understand the scale of the disaster and help those in affected communities memorialize the tragedy. They provide situational awareness for emergency managers while disasters are unfolding, and they can help shape public policy long after the crisis has ended.

But despite their importance, disaster death tolls are incredibly fraught.

In the United States and globally, Montano says, there is a huge amount of variation in how disaster-related deaths are determined and how overall death tolls are calculated. Sometimes officials only count deaths that occurred as a direct result of a storm, wildfire, or flood, while in other cases, they include indirect deaths caused by the social disruption in their wakes. Death tolls can be the sum of individual deaths attributed to a disaster by coroners, or they can be a population-level estimate calculated using statistical methods.

Overall, researchers believe disasters are severely underreported in places lacking adequate emergency management infrastructure, where fatalities are likely to be highest. As a commentary published in Nature Climate Change last year noted, between 1900 and 2019 only two heat waves were recorded for all of sub-Saharan Africa on the emergency events database (EM-DAT)—a widely cited global database used to evaluate mortality from mass disasters. The true number is unknown, but heat researchers believe it is far higher.

Even with good reporting, disaster databases only capture a fraction of the lives lost from natural hazards. While heat is the deadliest meteorological hazard in the U.S., many heat deaths occur outside of a heat wave, a discrete meteorological event that officials are more likely to categorize as a disaster, says Liza Kurtz, a PhD candidate at Arizona State University who studies heat and human health.

The question of what constitutes a disaster “has never been fully settled,” Kurtz says.

More disasters, fewer fatalities

Caveats notwithstanding, when researchers take a bird’s- eye view of the human toll of mass disasters, they see some positive trends.

The recent WMO report drew on EM-DAT to assess the impact of storms, droughts, floods, heat and cold waves, wildfires, and landslides from 1970 to 2019. It found that mortality from these types of disasters has fallen decade after decade, from over 50,000 deaths per year in the 1970s to fewer than 20,000 in the 2010s. At the same time, the number of reported disaster events rose sharply, a trend the WMO believes is partly due to climate change but also due to better reporting, says Cyrille Honoré, director of the WMO’s disaster risk reduction department. 

Less reporting in the early part of the record—where several large droughts and storms in South Asia and Africa dominate the death toll—suggests that the actual drop in deaths over time from weather- and climate-related disasters might be even steeper.

A key reason for this trend, Honoré says, is the immense progress societies have made in developing early warning systems. Our ability to accurately forecast weather and climate hazards has “improved drastically,” he says, thanks to the proliferation of sophisticated satellite sensors and rapid advances in computer models.

Building codes and new engineering methods that allow structures to withstand high winds, floods, and ground shaking are also helping to reduce the number of deaths from disasters, says Sara McBride, a social scientist at the U.S. Geological Survey’s Earthquake Science Center. So is the internet and social media.

When a disaster happens today, “even in remote areas, we know about it,” McBride says. “New information is coming out almost instantaneously, and communities and countries can ask for aid and support.”

“The long-term story with disasters is an incredible story of scientific and technological success,” says Roger Pielke Jr., a professor of environmental studies at the University of Colorado, Boulder. “It’s a little like advancing lifespan: It’s something that happens little by little over a long time, but if you compare 2021 to 1921, there’s good news there.”

The future is in our hands

Disaster researchers emphasize that this positive trend is no reason to be complacent about the grave toll disasters take today, or the risks civilization faces going forward due to climate change. According to the recent WMO report, 91 percent of deaths from weather- and climate-related disasters over the past 50 years occurred in developing nations . As climate change tips the scales toward more extreme weather, those regions of the world are likely to bear the brunt of the toll in terms of lives lost.

“The risk for mortality from heat going forward is a daunting challenge,” says Cascade Tuholske, a postdoctoral researcher at the Center for International Earth Science Information Network at Columbia University. Recent research led by Tuholske found that between 1983 and 2016, exposure to potentially deadly extreme heat tripled worldwide due to population growth, climate change, and cities getting hotter as roads and other hard surfaces absorb heat from the sun. Most of the increased exposure to deadly heat is being felt in South Asia and sub-Saharan Africa—places that are already very hot and where urban populations are growing rapidly.

To prevent a grim uptick in disaster deaths in a world that could warm by 3 degrees Celsius (5 degrees Fahrenheit) and add over a billion people this century, putting policies in place that address the root causes of vulnerability are needed, experts say. In the case of heat, that could mean everything from building community centers where people can stay cool during heat waves, to planting trees to give city dwellers relief from the sun, to tackling underlying social problems like poverty.

“It’s not an inevitability that increased temperatures means increased deaths,” Kurtz says. “If we brought enough political will or social resources to bear on this problem, deaths could go down even as temperatures go up.”

McBride agrees that nothing about the future is inevitable and that making good choices about where and how we choose to build—avoiding high wildfire risk zones and active faults, for example—could greatly reduce disaster fatalities in the future. But she also stresses that the death toll shouldn’t be the only metric for evaluating how well or how poorly we are responding to disasters. The time it takes to restore power—after Hurricane Ida, for example, some Louisiana residents remained without power for more than a month—the capacity of local health care systems to respond, and the ability of communities to rebuild quickly are all important factors.

The number of lives lost during a disaster—even if accurately tallied—also can’t provide a complete picture of the impact of those lives.

“Each death is a person who was meaningful to their community and their family, and the loss of that person can mean structure in that community is gone, social capital is gone,” McBride says. “People are more than just numbers on pieces of paper.”