Nearly 4.1 billion people, roughly half the planet’s population, experienced unusually hot temperatures between June and August, in what was Earth’s hottest season on record.

Climate change made these high temperatures three times more likely, according to the latest report by Climate Central, a US-based non-profit of scientists and science communicators that conducts research on climate change.  

The average person experienced 17 extra days of risky heat because of climate change during this period. Risky heat days are when temperatures are hotter than 90% of the temperatures recorded in a local area from 1991-2020. Heat-related health risks rise when temperatures climb above this local threshold.

The report looked at 22 regions across 218 countries and territories using the Climate Shift Index (CSI), a metric developed by Climate Central and launched in 2022, that quantifies the influence of climate change on daily temperatures.
The report is among the growing pieces of evidence on the deadly impact of heat. In July this year UN Secretary-General António Guterres called on countries to act on heat by protecting vulnerable populations and by investing in early warning systems. 

The health impacts of climate change have also been discussed at the ongoing climate week in New York as well as the United Nations General Assembly.

Hottest season on record

The effects of human-induced climate change, mainly from burning fossil fuels, were evident in all regions of the world in the form of extreme heat, climate scientists found.  

The heat was so bad that one in four people on the planet had no break from climate change-driven heat. On every day in June, July, and August, they experienced unusually warm temperatures made at least three times more likely by climate change. 

Over two billion people or 25% of the global population experienced 30 or more days of risky heat that were made at least three times more likely by climate change. 

This heat can worsen underlying illnesses including cardiovascular disease, diabetes, mental health, asthma, and can increase the risk of accidents and transmission of some infectious diseases, according to the World Health Organization (WHO).  
Heavy rainfall, deadly floods and storms, and raging wildfires were also exacerbated during this period. 

Global phenomenon

The areas affected by deadly heat were spread around the world. This included nearly the entire population of the Caribbean and at least three in every four people in Western Asia, Micronesia, Northern Africa, and Southern Europe. 

As many as 72 countries, home to more than 2.3 billion people, experienced their hottest June–August period since at 1970. The average person in these countries experienced a very strong influence of climate change on 34 of the 92 total days from June-August.

Around 180 cities in the Northern Hemisphere where June to August were the summer months had at least one dangerous extreme heatwave. Heatwaves were calculated as a place having at least five consecutive days with temperatures hotter than 99% of temperatures recorded in that city from 1991-2020.

Across these 180 cities, extreme heat waves of this intensity and duration are, on average, 21 times more likely today because of human-caused climate change, the report found. 

Influence of climate change 

The report did not just look at the heat extremes but also the influence of climate change.

Of the 22 regions analyzed, the highest regional average temperature anomalies were in Eastern Europe. The region experienced temperatures 1.9°C above normal, and 14 days with temperatures very strongly influenced by climate change.

Western Asia, Southern Europe, Northern Africa and Eastern Asia were other regions that saw temperatures significantly above normal for several days.

WHO and the World Meteorological Organization (WMO) are already working together to draw attention and respond to the health impacts of heat on human health. 

Guterres has reiterated the call for limiting temperature rise to 1.5°C by phasing out fossil fuels and scaling up investment in renewable energy to prevent further heat escalation. 

Image Credits: Dikaseva/ Unsplash.