Copernicus found 2024 was the first calendar year above 1.5°C, but says the Paris limit is judged over decades

On January 10, 2025, the Copernicus Climate Change Service (C3S), part of the European Union's Earth observation program and implemented by the European Centre for Medium-Range Weather Forecasts (ECMWF), reported that 2024 was the warmest year in a global temperature record going back to 1850. It was also the first calendar year more than 1.5°C above the pre-industrial level, at 1.60°C in ECMWF's ERA5 dataset. That threshold comes from the Paris Agreement, but C3S itself explained that a single year above it is not a breach. By the end of 2025, its estimate of long-term warming stood at about 1.4°C.

What Copernicus reported for 2024

The global average temperature in 2024 was 15.10°C, according to C3S: 0.12°C above 2023, the previous highest year, and 0.72°C above the 1991-2020 average. Eleven months of the year, and about three-quarters of its days, were more than 1.5°C above the 1850-1900 average that stands in for pre-industrial conditions. Each month from January to June was warmer than the same month in any earlier year. Taken together, 2023 and 2024 averaged 1.54°C above the pre-industrial level, and the ten most recent years were the ten warmest on record.

Europe also had its warmest year, at 10.69°C, 0.28°C above the previous record set in 2020. In 2023 and 2024, C3S noted, record warmth in the tropical Atlantic and Indian Oceans added to the boost that an El Niño event gave global temperatures. All of this sits on a warming trend that has averaged around 0.2°C per decade since the late 1970s.

Why one year above 1.5°C is not a breach

Under the Paris Agreement, countries aim to hold warming well below 2°C and to pursue efforts to limit it to 1.5°C. The agreement does not specify exactly how those levels are defined, C3S noted. It wrote in its 2024 report that temperatures averaged over two or three decades are generally agreed to be needed to confirm that either threshold has been passed, and that one or two years above 1.5°C do not imply a breach. Natural swings of up to about 0.3°C from one year to the next come on top of the trend, it said, and several strong El Niño events since the late 1970s produced pairs of consecutive record years, the latest being 2023 and 2024.

Its 2025 report adds that the Paris levels are understood to mean long-term change in global surface temperature, and that work is still under way in the scientific community to settle which methods should define the current level. C3S tracks three: the average of the last five years, its global trend monitor and a smoothed curve based on several datasets. At the end of 2025, all three put long-term warming at about 1.4°C above pre-industrial.

Different agencies, different numbers

Figures for the same year can differ. C3S noted in its 2024 report that the values published by individual data centers ranged from 1.46°C to 1.62°C above 1850-1900, mainly because each measured against its own estimate of the pre-industrial level. C3S puts the six datasets it monitors on a common footing, using an offset of 0.88°C between the 1991-2020 and 1850-1900 averages; on that basis, the Japanese JRA-3Q reanalysis gave 1.57°C for 2024. For the World Meteorological Organization's provisional figures for 2026, see our report from the COP31 climate conference.

What has happened since

C3S's report on 2025, published on January 14, 2026, put that year at 1.47°C, the third warmest, with 2024 still the warmest on record. The average for 2023 to 2025 reached 1.52°C in ERA5, the first three-year average above 1.5°C in the instrumental period, and 1.50°C in JRA-3Q. The service's trend monitor, which assumes warming continues at the rate of the past 30 years, points to the long-term level crossing 1.5°C in 2029. C3S says that date falls in the early part of the window given in the Intergovernmental Panel on Climate Change's 1.5°C report and roughly matches the IPCC's central estimate of the early 2030s.

C3S expects 2026 to become the second calendar year above the threshold. Its bulletin for October 2026 reported the warmest October on record, at 1.75°C above pre-industrial, and an average of 1.51°C for the 12 months from November 2025 to October 2026, while sea surface temperatures outside the polar regions set an October record as an exceptionally strong El Niño kept building in the tropical Pacific. Its statistical model predicts 1.56°C to 1.61°C for the full year, rates it virtually certain (more than 99% probability) that 2026 exceeds 1.5°C, and gives about a 20% chance that it ties or beats 2024. Another year above 1.5°C would also lift the four-year average for 2023 to 2026 past the mark, C3S notes, a sign of how fast temperatures are approaching the Paris Agreement's long-term limit.