For many in Europe, the summer of 2003 underscored the dangers of extreme heat. Between June and August that year, there were over 70,000 excess deaths in Europe compared to previous years1 and the economic costs of the heat wave amounted to over $13 billion Euros.2

Twenty years later, during the spring and summer of 2023, China, India, Pakistan, and countries in the Persian Gulf experienced dangerously high temperatures. In Europe, heat led the Greek authorities to close access to the Acropolis, one of the country’s most visited monuments, during the middle of the day. In the United States, Phoenix had temperatures greater than 43.3° C (110° F) for 19 days in a row.3 The health impacts of extreme heat can also be seen in medical costs. By extrapolating insurance claims data from Virginia’s all payer claims database nationally, a study by the Center for American Progress estimated that heat is responsible for an additional $1 billion in U.S. healthcare costs each summer.4

From a health perspective, the secondary impacts of extreme heat may also be significant. Extreme heat can compound the health risks associated with other perils like wildfires, air pollution, and decreased precipitation. During a 44-day heat wave in 2010 in Moscow, Russia, there were over 10,000 excess deaths recorded compared to previous years. A nearby wildfire caused ambient concentrations of ozone and particulate matter across the city to rise during the heat wave; the combined effects of air pollution from the wildfire and heat may have been associated with as many as 2,200 of the excess deaths.5 Increases in mortality due to cardiopulmonary diseases have also been associated with wildfires and wildfire-generated air pollution in continental Europe.6

Over the next few decades, ICE’s analysis projects that extreme heat will increase in severity and duration in much of the world. The impacts will continue to affect the health of individuals, communities, and countries—and the global financial markets than tie us all together.

ICE Sustainable Finance combines ICE Global Heat Models with information about the exposed populations around the globe to model the excess in mortality due to temperature increases over the course of the 21st century under three different climate change scenarios: the International Panel on Climate Change’s Shared Socioeconomic Pathways 1-2.6 (the “Sustainability” pathway, with global emissions declining to net-zero by 2050), 3-7.0 (the “Regional Rivalry” pathway, with global emissions roughly doubling by 2100), and 5-8.5 (the “Fossil-fueled development” pathway, with global emissions roughly doubling by 2050). Excess mortality is estimated for the subset of the population that is most vulnerable—those over 65 years old and under 6 years old. Estimates also account for countries’ income levels (based on the World Bank’s classifications in 2022 ) and climate zone (based on latitude). For example, a country that has low per capita income and a cold climate might be expected to experience the higher levels of excess mortality at the same temperature than a high per capita income country with ample health care resources and a population accustomed to an already warm climate.

ICE Sustainable Finance projections of excess mortality per 100,000 among vulnerable population—those younger than 6 years old and older than 65—due to extreme heat under the SSP 5-8.5 emissions scenario from 2023 to 2100. Source: ICE Sustainable Finance as of 10/1/2023.