Heat hell: 2 billion people suffer over 30 days of extreme temperatures fuelled by climate change

The summer of 2024 shattered records as Earth’s hottest ever in the Northern Hemisphere. According to a report by Climate Central, climate change exposed over 2 billion people to more than 30 days of "risky heat", soaring above 90% of what’s typical for their local climates.

Additional June-August 2024 days with temperatures above the 90th percentile, added by the burning of fossil fuels. Presented as per-capita averages for countries and states. Analysis based on ECMWF ERA5 data and the Climate Shift Index (CSI) system. Produced September 6, 2024.
Additional June-August 2024 days with temperatures above the 90th percentile, added by the burning of fossil fuels. Presented as per-capita averages for countries and states. Analysis based on ECMWF ERA5 data and the Climate Shift Index (CSI) system. Produced September 6, 2024.

In this three-month period, climate change influenced temperatures globally with 4.1 billion people (half the global population) facing extreme heat on 13th August. This heat was made at least three times more likely due to human activities, such as burning fossil fuels. The average person experienced 17 extra days of risky heat compared to what would have occurred in a world without climate change. For people in regions like northern Africa, southern Europe and the Caribbean, 30 or more days of these elevated temperatures were the norm.

Daily global population exposed to Climate Shift Index (CSI) level 3 or higher. Analysis based on ECMWF ERA5 data. Produced September 6, 2024.
Daily global population exposed to Climate Shift Index (CSI) level 3 or higher. Analysis based on ECMWF ERA5 data. Produced September 6, 2024.

The Climate Shift Index (CSI) tool, developed by Climate Central, quantifies how much climate change is responsible for these temperature spikes. The CSI showed that in many regions the likelihood of experiencing such extreme heat was tripled due to the ongoing climate crisis.

Dangerous heatwaves hit major cities

Across the globe, 180 major cities in the Northern Hemisphere suffered dangerous heatwaves. A heatwave is defined as five or more consecutive days with temperatures hotter than 99% of what a city usually experiences. In cities like Longyearbyen in Norway and Athens, Greece, these heatwaves lasted for weeks. These temperatures, amplified by climate change, are 21 times more likely now than in a world without human impact.

Northern Hemisphere cities with extreme heat waves (at least five consecutive days with temperatures above the 99th percentile) during June-August 2024. Colors indicate the multi-day CSI of each city’s longest extreme heat wave. The multi-day CSI indicates the increase in likelihood of such an event occurring as a result of climate change. Analysis based on ECMWF ERA5 data and the CSI system. Produced September 6, 2024.
Northern Hemisphere cities with extreme heat waves (at least five consecutive days with temperatures above the 99th percentile) during June-August 2024. Colors indicate the multi-day CSI of each city’s longest extreme heat wave. The multi-day CSI indicates the increase in likelihood of such an event occurring as a result of climate change. Analysis based on ECMWF ERA5 data and the CSI system. Produced September 6, 2024.

Extreme heat exacerbates existing problems, stretching healthcare systems and critical infrastructure to their limits. In Saudi Arabia, heat levels exceeding 50°C during the Hajj pilgrimage led to hundreds of deaths, while emergency services in Iran were overwhelmed by heatstroke cases. These heatwaves also led to the melting of pavements and the suspension of basic services in numerous cities around the world.

Southern Europe's extreme heat: A closer look

Southern European countries experienced the most number of days strongly influenced by climate change in Europe, with the overall temperature being 1.54°C above the normal (30-year average). On average, a person in Southern Europe experienced 39 days with temperatures made at least three times more likely because of climate change.

Malta, Italy, and Greece saw the highest number of climate change-influenced heat days in Europe, ranging between 47 and 52 days. Additionally, populations in Austria, Poland, Spain, Germany, and Belgium faced temperatures considered risky to human health for at least 40 days during these summer months.

Global impacts of a warming world

Heat wasn’t the only consequence of climate change in 2024. Other weather extremes, including flooding, droughts, and wildfires, wreaked havoc globally. Countries like Ethiopia and Bangladesh saw deadly floods displace millions, while wildfires ravaged Brazil, Greece and the U.S.


The Pantanal region of Brazil, known for its biodiversity, experienced its most intense fires in decades, driven by rising temperatures and dry conditions. In total, 62 extreme weather events from wildfires to floods, were linked to climate change in these three months.

Part of Pantanal in Brazil hit by wildfires in summer 2024. Around 2,500 fires were identified in June. The highest number since 1998.
Part of Pantanal in Brazil hit by wildfires in summer 2024. Around 2,500 fires were identified in June. The highest number since 1998.

Hurricane activity was also influenced by the hottest ocean temperatures in 400 years. Hurricanes like Beryl and Debby were strengthened by these warm waters, causing extensive damage in the Caribbean and the U.S.

Conclusion: Climate change’s growing influence on daily life

The summer of 2024 has provided a vivid demonstration of the growing impact of climate change on our planet. As the Climate Central report shows, rising temperatures and extreme weather events are no longer a future concern, they are happening now and affecting billions of people.