Climate crisis ‘responsible for one in three heat-related deaths’

Counting the human cost of inaction should force authorities to rethink their priorities when it comes to reducing emissions, writes Harry Cockburn

‘We expect the proportion of heat-related deaths to continue to grow if we don’t do something about climate change' (Getty)

Higher temperatures due to the climate crisis – driven by human-made greenhouse gas emissions – are already responsible for one in three heat-related deaths, new research suggests.

Between 1991 and 2018 more than a third of all deaths in which heat played a role were attributable to human-induced global heating, according to an international study using data from 43 countries, which was led by the London School of Hygiene and Tropical Medicine (LSHTM) and the University of Bern in Germany.

Researchers used records from 732 locations around the world which they said revealed “the actual contribution of man-made climate change in increasing mortality risks due to heat”.

They found that overall, 37 per cent of all heat-related deaths in the recent summer periods were attributable to the warming of the planet due to human activities.

The percentage of heat-related deaths attributable to the climate crisis 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 to 61 per cent).

The research team’s estimates also revealed the number of deaths from the climate crisis that occurred in specific cities.

These included: 136 additional deaths per year in Santiago de Chile, which accounted for 44.3 per cent of total heat-related deaths in the city; 189 additional deaths per year in Athens, accounting for 26.1 per cent of the total of heat-related deaths; 172 in Rome (32 per cent); 156 in Tokyo (35.6 per cent); 177 in Madrid (31.9 per cent); 146 in Bangkok (53.4 per cent); 82 in London, (33.6 per cent); 141 in New York (44.2 per cent); and 137 in Ho Chi Minh City, (48.5 per cent).

The authors said the results highlight the need to adopt stronger policies to halt future warming, and also the need for authorities to protect people from the impacts of heat exposure.

Dr Ana Vicedo-Cabrera, from the University of Bern and first author of the study, 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 1C, which is a fraction of what we could face if emissions continue to grow unchecked.”

The authors noted that the climate crisis is affecting our health in many different ways, with direct impacts linked to wildfires and extreme weather, as well as less obvious impacts, such as changes in the spread of vector-borne diseases, among others.

“Perhaps most strikingly is the increase in mortality and morbidity associated with heat,” they said.

Scenarios of future climate conditions predict a substantial rise in average temperatures, with extreme events such as heatwaves leading to future increases in the related health burden.

However, until now, no research had been conducted into the extent of these impacts over recent decades.

The study focused on the human-induced climate crisis examined through “detection and attribution” research, which identified and attributed observed phenomena to changes in climate and weather.

Specifically, the team examined past weather conditions simulated under scenarios with and without anthropogenic emissions. This enabled the scientists to separate the warming and related health impacts 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, more than a third of heat-related deaths are due to human-induced climate change, impact varies substantially across regions.

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

Populations living in low and middle-income countries, which have only been responsible for a small part of anthropogenic emissions in the past, are those most affected.

In the UK, 35 per cent of heat-related deaths could be attributed to human-induced climate change, which corresponds to approximately 82 deaths in London, 16 deaths in Manchester, 20 in West Midlands or 4 in Bristol and Liverpool every summer season.

Professor Antonio Gasparrini from LSHTM, senior author of the study and coordinator of the Multi-City Multi-Country (MCC) Network, said: “This is the largest detection and attribution study on the 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 research is published in the journal Nature Climate Change.