Climate change behind one in three heat-related deaths globally: Study

Human-induced global warming is responsible for over a third of all deaths in which heat played a role in the last three decades, according to a study.

The research, published on Monday in the journal Nature Climate Change, used data from 732 locations in 43 countries, showing for the first time the actual contribution of human-made climate change in increasing mortality risks due to heat.

The researchers at the London School of Hygiene & Tropical Medicine (LSHTM), UK, and the University of Bern in Switzerland found that 37 per cent of all heat-related deaths in the recent summer periods were attributable to the warming of the planet due to human-caused activities.

This percentage of heat-related deaths attributed to human-induced climate change was highest in Central and South America -- up to 76 per cent in Ecuador or Colombia, for example -- and South-East Asia, between 48 per cent and 61 per cent.

The findings are further evidence of the need to adopt strong mitigation policies to reduce future warming, and to implement interventions to protect populations from the adverse consequences of heat exposure, the researchers said.

"We expect the proportion of heat-related deaths to continue to grow if we don't do something about climate change or adapt," said first author of the study, Ana M. Vicedo-Cabrera, from the University of Bern.

"So far, the average global temperature has only increased by about 1 degree Celsius, which is a fraction of what we could face if emissions continue to grow unchecked," Cabrera said.

The study examined past weather conditions simulated under scenarios with and without anthropogenic or human-caused emissions.

This enabled the researchers to separate the warming and related health impact linked with human activities from natural trends.

Heat-related mortality was defined as the number of deaths attributed to heat, occurring at exposures higher than the optimum temperature for human health, which varies across locations.

While on average over a third of heat-related deaths are due to human-induced climate change, impact varies substantially across regions, according to the researchers.

Climate-related heat casualties range from a few dozen to several hundred deaths each year per city, depending on the local changes in climate in each area and the vulnerability of its population, they said.

The researchers noted that populations living in low and middle-income countries, which were responsible for a minor part of anthropogenic emissions in the past, are those most affected.

"This is the largest detection & attribution study on current health risks of climate change," said senior author of the study, Antonio Gasparrini, Professor at LSHTM.

"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," Gasparrini added.

The researchers acknowledge some limitations of the study, such as their inability to include locations in all world regions, for example, large parts of Africa and South Asia, due to a lack of empirical data.