A largest-of-its-kind study, using data from 732 locations across 43 countries worldwide, shows the actual contribution of human-made climate change in increasing heat-related mortality risks. This is the first time that research uncovers detailed information on the matter.
The London School of Hygiene & Tropical Medicine and the University of Bern led the Multi-Country Multi-City (MCC) Collaborative Research Network study. The scientists found that over a third (37%) of all heat-related deaths (in the locations analyzed) between 1991 and 2018 were owing to human-induced global heating.
This percentage was highest in South and Central America (up to 76% in Colombia and Ecuador) and second highest in South-East Asia (between 48% to 61%), suggesting that those are the most affected regions.
Estimates also show the number of deaths per city:
- 82 additional deaths per year in London (33.6% of total heat-related deaths in the city),
- 136 in Santiago de Chile (44.3%),
- 137 in Ho Chi Minh City (48.5%),
- 141 in New York (44.2%),
- 146 in Bangkok (53.4%),
- 156 in Tokyo (35.6%),
- 172 in Rome (32%),
- 177 in Madrid (31.9%),
- 189 in Athens (26.1%).
Dr. Clare Goodess, a senior research fellow at the University of East Anglia, said:
The study’s conclusions are both scientifically robust and alarming. They tell us that people are already dying on every continent due to increased heat stress caused by human-induced climate change. This highlights the imperative for global action to cut greenhouse gas emissions. Therefore, it is more important than ever that meaningful agreements emerge from [UN climate conference] Cop26 in November.
The authors stress that their findings are further evidence of the need to reduce future warming by adopting strong mitigation policies and implementing interventions to protect citizens from the adverse consequences of heat exposure.
The study first author, Dr. Ana M. Vicedo-Cabrera of the University of Bern, said:
We expect the proportion of heat-related deaths to continue to grow if we don’t do something about climate change or adapt. 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.
Global warming affects our health in several ways, from changes in the spread of vector-borne diseases to direct impacts linked to extreme weather and wildfires, among others. Elderly and people with underlying chronic conditions such as asthma are disproportionately affected as the temperatures rise because they are more vulnerable to disease and premature death.
Dr. Vicedo-Cabrera continued:
Aside from death, other health problems are associated with high temperatures, such as hospital admissions sparked by cardiovascular or respiratory complications. These problems are generally more frequent and add to mounting healthcare costs. Mortality … is just the tip of the iceberg.
This new study focused on human-made global heating through a ‘detection & attribution’ analysis. The team examined prior weather conditions simulated under event sequences with and without anthropogenic emissions. Like this, they were able to separate the warming-related health impacts from human activities versus natural trends.
The senior study author, Professor Antonio Gasparrini of the London School of Hygiene & Tropical Medicine and coordinator of the MCC Network, said:
This data suggests the health effects of rapid warming are already being felt even at these relatively early stages of potential catastrophic changes in climate. So it’s a kind of call to action to prevent or try to attenuate potential effects, which, of course, will be much higher in the future as long as global warming goes on. So the main message is: you don’t have to wait until 2050 to see increases in heat-related deaths.
This is the largest detection & attribution study on current health risks of climate change. The message is clear: climate change will not just have devastating impacts in the future, but every continent is already experiencing the dire consequences of human activities on our planet. We must act now.
The authors admit there are limitations to the study, such as not including locations in all world regions due to a lack of empirical data; for instance, they did not include large parts of South Asia and Africa.
Last year, global temperatures were 1.2°C above pre-industrial levels despite a 7% fall in fossil fuel burning due to coronavirus lockdowns. This is uncomfortably close to the 1.5°C Paris Acord target set by the world’s nations – beyond which could significantly worsen the risks of extreme heat, drought, floods, and poverty for hundreds of millions of people. Moreover, meteorologists from the World Meteorological Organization recently published a report in which they forecasted a 40% chance of 1.5°C temperatures for at least one, if not more, of the next five years.
