Climate change is a threat facing humankind and all life on earth as we know it. Although the most catastrophic effects will occur in the future unless we drastically act now, human deaths caused by global warming are already a reality. Thanks to developments in attribution science and other modern methods of analysis, researchers have been able to determine the impact of anthropomorphic climate change on human death rates.

One such study was published on May 31, 2021, in the Nature Climate Change journal. Dozens of researchers looked at heat deaths in 732 cities between 1991-2018, using mortality data to show how the heat-related death rate has changed in accordance with temperature. The study found that 37% of heat deaths worldwide are caused by climate change; an alarming statistic that conveys the severity of the effects of global warming already upon us.

Extreme heat is dangerous for human health. As global temperatures rise, the frequency and intensity of heatwaves will increase, leading to more instances of heat exhaustion, heat stroke and death. Heatwaves can also stunt children’s growth and cause more stillbirths, and they are more dangerous for the elderly and people with chronic conditions. In addition, the Urban Heat Island Effect describes how cities are usually warmer than their surroundings because of the dense concentration of infrastructure and roads, which absorb and radiate heat. With over half of the world’s population now living in urban settings, the increase of heat-related illness and death is a major risk.

The World Health Organization (WHO) estimates that the number of people exposed to heatwaves between 2000-2016 increased by roughly 125 million. The paper’s lead author, epidemiologist Ana Vicedo-Cabrera, explains that mortality is just the “tip of the iceberg;” death is not the only negative outcome of extreme heat. Many other health problems can occur in higher temperatures, which leads to more sickness and hospitalizations.

In addition to the effects of heat on human health, there are also far-reaching environmental, economic and societal consequences. Intense heat can cause drought and wildfires, with the high temperatures also being harmful to livestock and agricultural systems. Due to rising global temperatures, diseases carried by mosquitos are expanding to more parts of the world. Although many people believe a warmer climate will reduce energy use and therefore save money, this is a grave misconception. Heat is expected to increase our energy use because high temperatures can lower the efficiency of hydropower production, reduce the effectiveness of transmission lines and create less reliable electricity.

While the study found that heat-related deaths increased worldwide, there were regional variations. Across all seven continents, the heat deaths caused by climate change ranged from 20-76%, showing that although the effect is still global, some regions have been much more impacted. South America had the highest percentage of heat deaths caused by climate change, while South Asia and some Middle Eastern countries were hot spots as well. North America, East Asia and most of Europe had relatively lower percentages of deaths caused by heat from global warming. São Paulo in Brazil, had the highest total number of climate-related heat deaths, with an average of 239 a year.

Although this study showed the substantial impact that increased temperatures from climate change have had on global heat-related deaths, there are some gaps to acknowledge. The calculated 37% increase in heat deaths due to climate change is likely an underestimation because many heat deaths go unreported, and the study did not include rural areas. Moreover, the study only looked at the four warmest months in each country, which also means the true death toll is likely larger, as heat extremes in tropical regions can occur outside these months. Due to multiple factors suggesting that this study underestimates the effects, the toll of climate change on heat deaths is likely worse than suggested by these already alarming statistics.

The researchers themselves point out the limitations they faced due to a lack of sufficient data for some countries and regions. Most of Africa, all of India and parts of South Asia were not included because of the lack of data needed to conduct a proper analysis. However, as these are also some of the most heat-affected places on Earth, they would likely have a measurable impact on the conclusions. The inability to properly study these areas shows that significant gaps exist in our knowledge about the impact of heatwaves, especially in poorer countries. Studying these regions is crucial, however, as they are both more susceptible to climate change, especially heat, and are expected to have the greatest population growths. Data gaps need to be filled in order to quantify the effects of climate change to help all countries adapt and take action.

The study’s findings directly show the massive effect humans have on climate change and how our impact is causing deaths. Lead author Vicedo-Cabrera explained that “these are deaths related to heat that actually can be prevented. It is something we directly cause.” Proving that these are preventable deaths hammers home the harmful impact that climate change is having and that it is humans who are causing it. Understanding that human action has led to climate change, and therefore more heat-related deaths, signals the imperative for immediate action on a global scale to cut greenhouse gas emissions and prevent further global warming.

One of the most important impacts of this study is it proves and further amplifies that climate change is already having an immediate effect on human health and directly causing deaths. Much of the narrative on climate change centers around the future impact it will have. To strengthen the calls for action now, it is also crucial to show that global warming already causes human deaths and this is not simply a problem for the future. One of the paper’s authors, Professor Antonio Gasparrini, says that “you don’t have to wait until 2050 to see increases in heat-related deaths;” they are already happening. Gasparrini called their findings a “call to action,” to prevent and lessen the effects of climate change. This study has shown we have the ability to actually quantify some impacts climate change is already having, as well as to predict how it will worsen in the future.

Vicedo-Cabrera reiterated these ideas in a New York Times interview. She said, “we are thinking about these problems of climate change as something the next generation will face,” as opposed to a current threat. “This burden will amplify,” Vicedo-Cabrera says, meaning there is no time to waste in both preventing future catastrophe and addressing present dangers. The findings of this study show that humans are dying on every continent from extreme heat caused by anthropomorphic climate change; nowhere is safe from its effects. Even now in our relatively early stage, compared to the level of damage to come if climate change continues, global warming is causing deaths.

Increased deaths and health problems from heat caused by global warming are only one aspect of the broad toll taken by climate change. Melting glaciers are one of the most common images associated with global warming but, although this is a major issue, it can appear distant to some people and make them feel safe from the impacts. However, the effects of human-induced climate change are already causing deaths around the world, and the consequences go beyond health to society as a whole. Climate change has drastic effects on our daily lives that will become more apparent as the crisis worsens. Just as heat deaths will exponentially grow with rising temperatures, so will extreme weather events, such as storms, floods and droughts. Climate change will significantly disrupt food supply chains, which can lead to food crises, a major cause of conflict as well as sickness and death. For example, more than 3 billion people globally depend on rice for food consumption, however the production of rice is expected to be reduced by climate change. This would have devastating effects on food supply as well as peace and economic stability.

Climate change will continue to worsen the health of our planet and decrease its ability to sustain human life as it functions now unless dramatic changes are made. Enough time has been wasted with inaction that could have been spent cutting emissions and working to prevent further global warming. Currently, at least 37% of heat deaths are caused by human-induced climate change; how much will that number grow after another decade with no change?