2024 was warmest year on record, 1.55°C above pre-industrial level

As California continues to suffer through some of the worst wildfires it has ever seen — in the middle of an abnormally dry winter, no less — the World Meteorological Organization (WMO) has confirmed that 2024 was the warmest year on record, based on six international datasets. Indeed, each year in the last decade is one of the 10 warmest on record, in what the WMO describes as an extraordinary streak of record-breaking temperatures.

The WMO provides a temperature assessment based on multiple sources of data to support international climate monitoring and to provide authoritative information for the UN Climate Change negotiating process. The datasets are from the European Center for Medium Range Weather Forecasts (ECMWF), the Japan Meteorological Agency, NASA, the US National Oceanic and Atmospheric Administration (NOAA), the UK’s Met Office in collaboration with the Climatic Research Unit at the University of East Anglia (HadCRUT), and Berkeley Earth.

The global average surface temperature for the past year was 1.55°C (with a margin of uncertainty of ±0.13°C) above the 1850–1900 average, according to WMO’s consolidated analysis of the six datasets (not all the datasets show the temperature anomaly above 1.5°C, due to differing methodologies, but they all place 2024 as the warmest year on record). This means that we have likely just experienced the first calendar year with a global mean temperature of more than 1.5°C above the 1850–1900 average.

“It is important to emphasise that a single year of more than 1.5°C for a year does NOT mean that we have failed to meet Paris Agreement long-term temperature goals, which are measured over decades rather than an individual year,” said WMO Secretary-General Celeste Saulo. “However, it is essential to recognise that every fraction of a degree of warming matters. Whether it is at a level below or above 1.5°C of warming, every additional increment of global warming increases the impacts on our lives, economies and our planet.”

A separate study published in Advances in Atmospheric Sciences found that ocean warming in 2024 played a key role in the record high temperatures. The ocean is the warmest it has ever been as recorded by humans, not only at the surface but also for the upper 2000 metres, according to the study led by Professor Lijing Cheng from the Institute of Atmospheric Physics at the Chinese Academy of Sciences. It involved a team of 54 scientists from seven countries and 31 institutes.

About 90% of the excess heat from global warming is stored in the ocean, making ocean heat content a critical indicator of climate change. From 2023 to 2024, the global upper 2000 m ocean heat content increase is 16 zettajoules (1021 joules) — about 140 times the world’s total electricity generation in 2023, according to the study.

Other key data, revealed by the Copernicus Climate Change Service (C3S) on behalf of the ECMWF, includes the following:

• 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.
• The total amount of water vapour in the atmosphere reached a record high in 2024, at about 5% above the 1991–2020 average — significantly higher than in 2023. This abundant supply of moisture amplified the potential for extreme rainfall events and contributed to the development of major storms, including tropical cyclones.
• Much of the Northern Hemisphere experienced more days than average with at least strong heat stress, and some areas saw more days than average with extreme heat stress. On 10 July, around 44% of the globe was affected by strong-to-extreme heat stress — a new record annual maximum.
• Prolonged dry periods in several regions created conditions conducive to wildfires. Large-scale and persistent wildfires were recorded across the Americas, while Bolivia and Venezuela recorded their highest wildfire carbon emissions levels on record and Canada saw its second highest.
• 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.
• 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 2.9 ppm higher than in 2023, whereas methane concentrations were 3 ppb higher.
   

“Global heating is a cold, hard fact,” said UN Secretary-General Antóno Guterres.

“Blazing temperatures in 2024 require trailblazing climate action in 2025,” he added. “There’s still time to avoid the worst of climate catastrophe, but leaders must act — now.”

Image caption: Surface air temperature anomalies for 2024 relative to the average for the 1991–2020 reference period. Data: ERA5. Credit: C3S/ECMWF.