The 10 deadliest weather disasters since 2004, including three tropical cyclones, four heatwaves, two floods and a drought, killed at least 570,000 people, and a new study shows how all of them were intensified by global warming, “caused by the burning of oil, gas and coal and deforestation.”

In a press briefing on the new study, by World Weather Attribution, an international research group, the authors emphasized that the total death toll is a major underestimate. Many heat-related deaths, possibly running into the millions, are not reported officially and don’t show up in the International Disaster Database, especially in poorer countries that are most vulnerable to high temperatures.

The deadliest single climate event in the official global record was a 2011 drought in Somalia that killed at least 258,000 people, and the report found that human-caused warming intensified the drought with disrupted rainfall patterns and warmer temperatures that evaporate more moisture from the soil. 

In 2008, Cyclone Nargis killed more than 138,000 people in southern Myanmar. The new study found that global warming intensified the storm’s wind speed by 18 percent, and that the warm ocean temperatures that boosted Nargis’s rainfall were made 47 percent more likely by warming.

In the case of the 2023 European heatwave that killed more than 37,000 people, the research showed that some of the regional peak temperatures in the western Mediterranean region would have been impossible without global warming, and were made 1,000 times more likely across Southern Europe.

The new study did not try to attribute any share of the deaths to human-caused warming. But related recent research, combining climate attribution with epidemiological models, attributed about half the mortality burden of the even deadlier 2022 European heatwave to human-caused warming. 

The new study, the 90th by World Weather Attribution, “underscores the simple fact that burning fossil fuels causes climate change and climate change causes death and destruction,” said author Friederike Otto, co-founder of the organization and a senior lecturer at the Centre for Environmental Policy, Imperial College London.

The growing body of attribution science has helped shift conversations around global warming and its impacts over the last 10 years, she said. Before 2004, many scientists were cautious about linking climate extremes with human-caused warming, but the studies have helped “many people understand that climate change is already making life more dangerous,” she said. “What did not work yet is turning knowledge into action on a large enough scale.”

Finding the Global Warming Fingerprint

Report co-author Sjoukje Philip, a researcher at the Royal Netherlands Meteorological Institute working with World Weather Attribution, explained the peer-reviewed process for identifying global warming fingerprints when climate extremes emerge from the observational records.

“When we detect a trend in observations, we cannot say straight away if it’s due to climate change or not,” she said. “We need to use models to investigate the role of climate change.” 

World Weather Attribution, which pioneered attribution research over the past decade, has increased the number of models used for each study to add confidence to its findings, she said. By comparing models that include the effects of greenhouse gas warming with others that don’t, and combining that with decades of observational data from weather stations, balloons, satellites and other sources, the studies can conclude how global warming affects the probability and magnitude of the weather events, and, in some cases, even provide clues on future expected changes.

“Our early attribution studies did not always include observations,” she said. “We, however, found it important to include them.”

Without including the observations, especially those from recent record heatwaves, the models don’t produce temperatures as high as those recorded during Europe’s 2023 heatwave. That’s what enables the scientists to say confidently that some of the heat extremes that are blistering parts of the globe today—including the 2021 Pacific Northwest heatwave—would not be possible without human-caused warming.

The new study not only shows how warming intensifies precipitation from tropical cyclones and hurricanes, but also measures the effect of the sea surface temperature on wind speeds and the potential intensity of storms.

And while some of the increases of extreme weather phenomenons attributed to warming may sound small, like 7 percent more precipitation during the September 2024 floods in Europe, those numbers don’t reflect the impacts, Otto added. 

“Seven percent more intense rainfall can make the difference between a dam breaking and a dam not breaking,” she said. And estimates for levels of wind damage from hurricanes suggest that just a 10 percent increase in wind speed “leads to about a 50 percent increase in the economic damages.”

There is, she added, a powerful nonlinear connection between small changes and damages.

She cited the human body, with a normal temperature of 98.6 degrees Fahrenheit (37 degrees Celsius), as a useful analogy. 

Earth’s average surface temperature has been hovering at about 1.5 degrees Celsius above average for the past several months, and if a human body stays overheated by that much, “It makes a huge difference to your body and your well-being,” she said. “You will feel very ill and have brain fog. And that’s how these seemingly small changes in the climate system affect humans and social systems and our communities.”

Limits to Adaptation

From the beginning, World Weather Attribution’s work has included researchers from the Red Cross and Red Crescent, and local experts in countries affected by extremes, to combine the attribution science with analyses of vulnerability and exposure.

“We observe that many of the countries in which these events are happening are not well adapted to the extreme weather of today, with 1.3 degrees of warming, let alone 1.5, 2 degrees or 3 degrees,” said co-author Roop Singh, head of urban and attribution at the Red Cross Red Crescent Climate Centre.

After analyzing the 10 deadliest extreme climate events, she added, it’s clear there is a need to center policies and plans around the most vulnerable people.

“Time and again, in our studies we see that it’s the elderly who tend to die disproportionately during heat waves,” she said. “It’s marginalized communities affected by conflict and displacement, and people with disabilities who lack access to information, who are disproportionately affected by floods and storms.”

She said the overview also reinforces the importance of “maintaining and updating critical infrastructure for the new climate of today rather than the climate of the past.”

In the 2023 flooding caused by Storm Daniel in Libya, most of the more than 12,000 deaths were the result of extreme rainfall driving the collapse of two dams, and this year, there have been more deaths in Sudan and Nigeria after dam failures. 

“There’s this global risk associated with aging infrastructure worldwide that’s starting to emerge,” Singh said. “Therefore, it’s really important for us to invest in climate-resilient infrastructure going forward, and to maintain that infrastructure.”

Much more work is also needed to ensure that people get adequate warnings if they are at risk, she said.

“We know that effective early warning systems to evacuate people from the path of a cyclone into safe shelters have been shown to save thousands of lives, especially from dangerous storm surges,” she said. “When people don’t perceive the risk and don’t receive warnings, and when they don’t have a means to evacuate, or they’re not comfortable in the temporary shelters that are put up, we tend to see higher impacts.”

Their close look at the climate carnage of the past two decades also spurred the scientists to wrestle with what they called “existential questions” related to adaptation. Some of the disasters they studied were so unusual or so extreme that they questioned if any adaptation measures currently under consideration would have saved lives.

“There’s this global risk associated with aging infrastructure worldwide that’s starting to emerge.”

— Roop Singh, the Red Cross Red Crescent Climate Centre

“Can the global pace of adaptation catch up to today’s new climate, let alone the climate of the future?” they wrote. “When an entire town is wiped away, including the ‘safe’ areas, what could have reasonably been done differently?”

Limits are showing up already, including for funding available for adaptation, the technological feasibility of adaptive measures and “in the political will of leaders and constituents to proactively adapt infrastructure to the much more common and extreme events of today.”

Singh said the study raises questions about “the reasonable ability of any government to prepare and design for those very, very extreme events.” That, she added, “underscores the urgent need to mitigate, to reduce the pace and the number of these extremely rare events going forward in order to ensure a safe future.”