2024 confirmed to be the warmest year on record

According to the report, human-induced climate change remains the primary driver of extreme air and sea surface temperatures. Other factors, such as the El Niño Southern Oscillation (ENSO), also contributed to the unusual temperatures observed during the year.

Ten of the hottest years on record have occurred within the last decade but this is the first time a calendar year has exceeded the 1.5°C target set by the 2015 Paris Agreement to help limit global warming.

In the ocean during 2024, the annual average sea surface temperature for non-polar regions reached a record high of 20.87°C, 0.51°C above the 1991–2020 average.

The average non-polar sea surface temperature was at record high levels for the time of year from January to June 2024, continuing the streak of record months seen in the second half of 2023. A study of the 2023 marine heatwave, including contributions from PML scientists, concluded while high-pressure weather conditions were the main driver behind the elevated temperatures, warming due to climate change made it reach category II (strong) instead of I (moderate).

Dr Lee de Mora, Marine Ecosystem Modeller at Plymouth Marine Laboratory and composer of ‘Marine Heat Waves – a sonification of ocean model data’, commented on the report:

“The warming described in the C3S report is unprecedented. 2024 was the warmest year on record, 0.12 degrees warmer than the previous record in 2023. The rise largely due to the continuing rise in atmospheric CO2, which increased by 2.9 parts per million (ppm) up to 422ppm.”

“Sustained high temperatures are likely to cause all sorts of problems to the UK and our marine environment, including sea level rise, increased number and size of storms, higher precipitation and flood risk. Marine ecosystems are equally vulnerable, and sea life is likely to be exposed to heat stress, increasingly acidic water, and habitat loss”.

Prof. Tim Smyth, Head of Science for Marine Biogeochemistry and Observations at PML, highlighted the importance of sustained long-term monitoring:

“It is only with regular, high-frequency and high-quality data that we can begin to contextualise marine heatwaves (MHW). What is clear from our sea temperature monitoring is that the MHW conditions have increased in their frequency over the past 50 years, and extreme cold conditions have been relatively rarer in that same period. This is not just at the surface but is a feature of the entire water column.”

Key messages from the report:

Global surface air temperatures

• 2024 was the warmest year in global temperature records going back to 1850. According to ERA5 (1), the global average temperature of 15.10°C was 0.72°C above the 1991-2020 average, and 0.12°C above 2023, the previous warmest year on record. This is equivalent to 1.60°C above an estimate of the 1850-1900 temperature designated to be the pre-industrial level.
• 2024 is the first calendar year that has reached more than 1.5°C above the pre-industrial level.
• Each of the past 10 years (2015–2024) was one of the 10 warmest years on record.
• The monthly global average temperature exceeded 1.5°C above pre-industrial levels for 11 months of the year. Going back further, all months since July 2023, except for July 2024, have exceeded the 1.5°C level.
• A new record high for daily global average temperature was reached on 22 July 2024, at 17.16°C.
• 2024 was the warmest year for all continental regions, except Antarctica and Australasia, as well as for sizeable parts of the ocean, particularly the North Atlantic Ocean, the Indian Ocean, and the western Pacific Ocean.
• 2024 saw three record-warm seasons for the corresponding time of the year: boreal winter (December 2023-February 2024), boreal spring (March-May) and boreal summer (June-August) at 0.78°C, 0.68°C and 0.69°C respectively above the 1991-2020 average.
• Each month from January to June 2024 was warmer than the corresponding month in any previous year on record. Each month from July to December, except August, was each the second warmest, after 2023, for the time of year. August 2024 was tied with August 2023 as the warmest on record.

Ocean surface temperatures

• In 2024, the annual average sea surface temperature (SST) over the extra-polar ocean reached a record high of 20.87°C, 0.51°C above the 1991–2020 average.
• The average extra-polar SST was at record high levels for the time of year from January to June 2024, continuing the streak of record months seen in the second half of 2023. From July to December 2024, the SST was the second warmest on record for the time of year, after 2023.
• 2024 saw the end of the El Niño event that started in 2023 and the transition towards more neutral or La Niña conditions.

European temperatures

• 2024 was the warmest year on record for Europe, with an average temperature of 10.69°C, 1.47°C above the average for the 1991-2020 reference period, and 0.28°C warmer than the previous record set in 2020.
• Spring and summer were the warmest on record for Europe, with the average temperature for spring (March-May) 1.50°C higher than the 1991-2020 seasonal average and the average temperature for summer (June–August) 1.54°C above the 1991-2020 seasonal average.

Global impacts

• The total amount of water vapour in the atmosphere reached a record value in 2024, at about 5% above the 1991–2020 average, more than 1% higher than in 2016 and 2023, the years with the previous highest and second highest values, respectively.
• Extreme temperatures and high humidity contribute to increased levels of heat stress. Much of the Northern Hemisphere experienced more days than average with at least ‘strong heat stress’ during 2024, and some areas saw more days than average with ‘extreme heat stress’.
• In 2024, the area of the globe affected by at least ‘strong heat stress’ reached a new record annual maximum on 10 July, when around 44% of the globe was affected by ‘strong’ to ‘extreme heat stress’. This is 5% more of the globe compared to the average annual maximum.
• Around Antarctica, after reaching record-low values for the time of year during eight months of 2023, the sea ice extent reached record or near-record low values again during a large part of 2024. From June to October, the monthly extent ranked second lowest, behind 2023, and lowest in November. At its annual minimum in February, the monthly extent ranked third lowest in the satellite record.
• In the Arctic, the sea ice extent was relatively close to its 1991–2020 average until July but fell well below average in the following months. At its annual minimum in September, the monthly extent ranked fifth lowest in the satellite record.
• The atmospheric concentrations of carbon dioxide and methane continued to increase and reached record annual levels in 2024, at 422 parts per million (ppm) and 1897 parts per billion (ppb) respectively. Carbon dioxide concentrations in 2024 were 2.9ppm higher than in 2023, whereas methane concentrations were 3ppb higher.

C3S is implemented on behalf of the European Commission by the European Centre for Medium-Range Weather Forecasts (ECMWF), whose scientists have been monitoring key climate indicators, and documenting unprecedented daily, monthly, and annual temperature records over 2024. This year organisations involved in global climate monitoring (ECMWF, NASA, NOAA, UK Met Office, Berkeley Earth and the World Meteorological Organization) have aggregated their data for a more comprehensive view of the current state of Earth’s climate and to help highlighting the exceptional conditions experienced during 2024.