A third of all deaths linked to heat in the past 30 years are linked to global warming

Over the past 30 years, a third of all deaths where heat played a part, have been blamed on human-induced global warming, according to a new study.

Data from 737 locations in 42 countries was used by researchers from the London School of Hygiene and Tropical Medicine (LSHTM) to estimate the impact of global warming on deaths caused by heat in some form between 1991 and 2018.

Researchers found that 37 per cent of all heat-related deaths in recent summer periods could be linked directly to human-caused warming of the planet. 

They found this figure varied significantly depending on the economic power of the city and how vulnerable the population were to disease and the heat.

Percentage of heat-related deaths attributed to human-induced climate change was highest in Central and South America, going up to 76 per cent in Ecuador or Colombia, and second highest in South-East Asia ranging from 48 to 61 per cent 

Study authors say countries responsible for a minor part of emissions originating from humans in the past, were most affected in terms of heat-related deaths.

Over the past 30 years, a third of all deaths where heat played a part, have been blamed on human-induced global warming, according to a new study. Stock image

Data from 737 locations in 42 countries was used by researchers from the London School of Hygiene and Tropical Medicine (LSHTM) to estimate the impact of global warming on deaths caused by heat in some form between 1991 and 2018. Stock image

As well as taking a global average, the team, including experts from the University of Bern, estimated deaths from climate change in specific cities.

They found that in London 35 per cent of heat-related deaths in the city in that period were directly linked to climate change, rising to 44.2 per cent for New York. 

In the UK an average of 35 per cent of heat-related deaths could be attributed to human-induced climate change every summer. 

This corresponds to approximately 82 deaths in London, 16 deaths in Manchester, 20 in West Midlands or four in Bristol and Liverpool every season.

Study authors say their findings show for the first time the ‘actual contribution of man-made climate change in increasing mortality risks due to heat.’

Three of the worst affected cities were Santiago in Chile at 44.3 per cent, Ho Chi Minh City in Vietnam at 48.5 per cent and Bangkok in Thailand at 53.4 per cent. 

The findings are based on simulations of climate, with and without human-induced emissions, allowing the team to estimate the total impact.

The authors say the research is evidence of the need to adopt strong mitigation policies to reduce future warming, adding that it is also an argument for the implementation of interventions to protect from consequences of heat exposure. 

Dr Ana Vicedo-Cabrera, from the University of Bern and first author of the study, said they 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 (1.8F), which is a fraction of what we could face if emissions continue to grow unchecked.’

They focused on human-induced global warming through the detection and attribution of phenomena that can change climate and weather. 

Researchers examined past weather conditions simulated under scenarios with and without human activity caused emissions.

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

In the study, 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.

Researchers found that 37 per cent of all heat-related deaths in recent summer periods could be linked directly to human-caused warming of the planet. Stock image

The team found that while, on average, more than one third of heat-related deaths are due to human-induced climate change, the impact varied substantially.

Climate-related heat casualties ranged from a few dozen to several hundred deaths each year per city, depending on the local changes in climate in each area.

The other major factor was the vulnerability of the population within any single city.

The researchers found that people living in low and middle-income countries were those most affected by climate change.

Percentage of heat-related deaths attributed to human-induced climate change was highest in Central and South America, going up to 76 per cent in Ecuador or Colombia, and second highest in South-East Asia ranging from 48 to 61 per cent. Stock image

Professor Antonio Gasparrini from LSHTM, senior author of the study and coordinator of the MCC Network, said: ‘This is the largest detection & 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 authors note a number of limitations of the study including being unable to include locations in all world regions, for example, large parts of Africa and South Asia, due to a lack of empirical data.

The findings have been published in the journal Nature Climate Change.