New research is quantifying the rate at which intense summer heat brought on by human-induced climate change is killing humans around the world.
More than one-third of all heat-related deaths from 1991 to 2018 are attributable to human-caused climate change, according to alarming new research published in Nature Climate Change. It’s a sobering reminder of the mess we’re in, and yet another wake up call to do something about it.
“We expect the proportion of heat-related deaths to continue to grow if we don’t do something about climate change or adapt,” said Ana Vicedo-Cabrera, the first of 30 co-authors on the study and a climate change and health scientist at the University of Bern, in a statement. “So far, the average global temperature has only increased by about 1°C, which is a fraction of what we could face if emissions continue to grow unchecked.”
The effects of climate change are not felt equally around the globe, with certain regions more prone to experiencing extreme weather events, such as heat waves and droughts. The new investigation, led by researchers from the London School of Hygiene & Tropical Medicine and the University of Bern, was an effort to determine the impact of human-caused climate change on human mortality due to heat, and how these mortality rates vary across countries.
Studies such as this are very tough to pull off, as not all countries can record the needed health-related metrics. Sadly, this tends to happen in poorer countries with underdeveloped infrastructures, which also tends to involve the countries most at risk from the calamitous effects of climate change. The new study, while rough around the edges, succeeded in presenting the largest collection of heat mortality figures to date. The researchers sourced data from 732 locations in 43 countries around the world to “estimate the mortality burdens associated with the additional heat exposure that has resulted from recent human-induced warming, during the period 1991–2018,” as the scientists wrote in the study.
Equipped with this data, the scientists ran simulated scenarios to tease out the anthropogenic climate change-related heat impacts from natural trends. Results showed that, on average, 37% of global heat-related deaths could be blamed on global warming. These deaths were found on every continent, but warmer countries in general experienced a higher proportion of deaths; notable examples included Ecuador, Colombia, and parts of southeast Asia.
The scientists also estimated mortality rates in specific cities, with 136 additional deaths in Santiago de Chile, 189 in Athens, 172 in Rome, 156 in Tokyo, and 141 in New York City, among others.
“Our findings support the urgent need for more ambitious mitigation and adaptation strategies to minimise the public health impacts of climate change,” scientists wrote in the paper.
Heat waves, which are happening with greater frequency and severity since the start of the industrial revolution, are a major driver of these deaths. Vulnerable populations include the elderly, and people with chronic respiratory and cardiovascular conditions. The deleterious health effects of heat waves are compounded in regions with bad air pollution.
Writing in an associated News and Views article, Dann Mitchell, a climate change researcher from the University of Bristol, said there’s more to this problem than just heat:
It varies dramatically from country to country, and even city to city within a country, with the interplay between meteorological and socioeconomic factors making the problem far from trivial to dissect. For instance, inadequate infrastructure for psychiatric patients and prisoners in Egypt mean they are often disproportionately affected by heat, or using loft conversions (the hottest part of the house) for bedrooms in the UK’s ageing houses hinders people’s ability to cool during the night-time. Each country has its own combination of factors that feed into its heat–health burden, and modelling this requires details specific to each city.
Mitchell said the authors of the new study undertook a “momentous task,” but understanding how climate change makes the “heat–health problem worse is critical.”
The new paper, while important and revealing, remains incomplete. The team was unable to gather data from key areas, including parts of Africa and South Asia. Moving forward, it will be important for researchers to fill these gaps in order to acquire a clearer understanding of mortality rates, the regions at risk, and other factors at play. The new work “highlights how important these issues are on a country-by-country level, and it is only by expanding the network of countries involved that we can start to understand the true global burden of heat-related mortality from our changing climate,” wrote Mitchell.
Limitations aside, the new paper is as frightening as it is discouraging. We’re firmly situated within a climate crisis, and the associated mortality numbers are now reflecting this very sad reality.