The WMO, the UN's weather and climate agency, published its State of the Global Climate 2024 report on 19 March 2025. It confirms that 2024 was the warmest year in the 175-year observational record, with a global mean near-surface temperature about 1.55°C above the 1850 to 1900 average, with a margin of uncertainty of plus or minus 0.13°C. The WMO says 2024 was likely the first calendar year more than 1.5°C above the pre-industrial level.
The figure is a consolidated estimate from six international datasets. The European Union's Copernicus Climate Change Service, which published its own Global Climate Highlights in January, put 2024 at 1.60°C above pre-industrial using its ERA5 reanalysis, with a global average temperature of 15.10°C. That was 0.12°C above 2023, the previous record, and 0.72°C above the 1991 to 2020 average.
One year is not the Paris threshold
Both organisations stress that a single year above 1.5°C does not mean the Paris Agreement's temperature goal has been breached. The agreement's goals refer to long-term warming, typically assessed over periods of at least 20 years. Copernicus noted that the two-year average for 2023 and 2024 was also above 1.5°C, and that every month from July 2023 to December 2024, except July 2024, exceeded the 1.5°C level.
The difference between the WMO and Copernicus figures reflects methodology. ERA5 tends to produce slightly higher anomalies for recent years than the other datasets. The other datasets, from Berkeley Earth, NASA, the UK Met Office and Hadley Centre, and NOAA, placed 2024 at between 1.51°C and 1.55°C above pre-industrial, according to Copernicus. All agree that 2024 was the warmest year on record and that the past ten years, 2015 to 2024, were the ten warmest.
Regional detail
Copernicus reported that 2024 was the warmest year on record for every continental region except Antarctica and Australasia. Europe had its warmest year on record, with an average temperature of 10.69°C, 1.47°C above the 1991 to 2020 average and 0.28°C above the previous record set in 2020. A new record for daily global average temperature was set on 22 July 2024, at 17.16°C. Sea surface temperatures outside the polar regions also reached a record annual average of 20.87°C.
The WMO report adds indicators beyond temperature, including ocean heat content, sea level rise, glacier mass loss and sea ice extent, several of which also set records in 2024.
Why this matters for energy
Temperature is one of the main drivers of short-term electricity demand. In countries with high air conditioning penetration, peak demand rises sharply with temperature during heatwaves. In India, Pakistan, the Middle East, Southeast Asia, the southern United States and southern Europe, summer peaks are already set by cooling load, and each warmer summer pushes those peaks higher, all else being equal.
Warmer winters work in the opposite direction in heating-dominated systems, reducing gas and electricity demand for space heating. The net effect varies by country. In northern Europe, milder winters have contributed to lower gas demand in recent years, alongside high prices and efficiency gains. In southern Europe and much of Asia, the cooling effect dominates.
The International Energy Agency's Global Energy Review 2025, published in March, attributed a significant share of the growth in global electricity demand in 2024 to hot weather, particularly in China and India. The IEA's analysis found that weather effects added materially to both power demand and emissions during the year.
Stress on supply as well as demand
High temperatures also affect the supply side. Thermal power plants, including coal, gas and nuclear units, lose efficiency when air and cooling water are hotter. Plants that use river water for cooling may have to reduce output when water temperatures exceed environmental limits, as happened at several European nuclear plants in the summers of 2022 and 2023. Solar panels are less efficient at very high temperatures, although total solar output usually rises in hot, sunny weather.
Transmission lines can carry less power when ambient temperatures are high, because conductors heat up and sag. Grid operators in the United States, Europe and elsewhere are increasingly using dynamic line ratings, which adjust capacity limits to real-time weather, to manage this.
Drought, which often accompanies heat, reduces hydropower output. In 2024, southern Africa experienced severe drought linked partly to El Niño, which cut generation at the Kariba hydropower complex shared by Zambia and Zimbabwe and led to long daily power cuts.
El Niño and what comes next
The 2023 to 2024 El Niño event contributed to the record warmth, alongside the long-term warming trend. El Niño ended in the first half of 2024, and the WMO and national agencies have noted that La Niña-like conditions developed late in the year. Historically, years following an El Niño have often been slightly cooler than the El Niño peak.
For energy planners, the relevant question is less whether a particular year breaks the record and more how the distribution of extreme temperatures is shifting. Peak demand forecasts, reserve margins and hydro planning increasingly use climate-adjusted weather data rather than historical averages. The record in 2024 adds to the evidence that historical weather records may understate the probability of extreme heat events.
Reading the numbers for markets
Gas and power traders already price weather through forward curves and degree-day forecasts, and those forecasts are anchored in historical normals. Many forecasters in Europe and North America still use 30-year averages to define a normal season. When the climate is warming at about 0.2°C per decade, as Copernicus estimates for the period since the late 1970s, a 30-year average lags the current climate. That lag tends to understate cooling degree days in summer and overstate heating degree days in winter.
Utilities and system operators are adjusting. Several now use shorter averaging windows, trend-adjusted normals or climate model outputs when they set demand forecasts. The choice matters for resource adequacy, because a peak demand forecast set too low can leave a system short of capacity in an extreme week.
What to watch
Summer 2025 in the northern hemisphere will be the next test. Grid operators in North America, Europe and South Asia will publish summer reliability assessments in the coming months. Those assessments will set out expected peak demand under normal and extreme weather and the resources available to meet it. The gap between the two scenarios is a useful indicator of how exposed each system is to heat.