The 36th annual State of the Climate report, published by the American Meteorological Society, is based on contributions from 625 scientists in 60 countries. It provides the most comprehensive update on Earth’s climate indicators, notable weather events and other data collected by environmental monitoring stations and instruments located on land, water, ice and in space.
Greenhouse gas
The report found that carbon dioxide (CO2), methane, and nitrous oxide — Earth’s major atmospheric greenhouse gases — once again reached record high concentrations in 2025.
The globally averaged CO2 level reached 425.6±0.1 parts per million, a 53% increase from the preindustrial level of ~278 parts per million.
Fossil fuel emissions last year were also a record high, estimated to be 10.3±0.5 petagrams of carbon per year, more than three times the 3.0±0.2 petagrams of carbon per year in the 1960s.
Temperatures
Last year’s global mean temperature across land and ocean was among the three highest years on record, with records dating back as far as the mid-1800s.
Near-neutral and La Niña-like conditions occurred in the eastern Pacific Ocean throughout the year, making last year the warmest year on record in which no El Niño conditions were present.
Europe reported its warmest year on record, and Russia, China, the Republic of Korea and Argentina each reported their second warmest.
All five major global temperature datasets used for analysis in the report agree that the last 11 years (2015–25) were the 11 warmest on record.
Despite the cooler conditions in the equatorial Pacific Ocean throughout much of last year, the mean annual global sea surface temperature was the third highest in the 172-year record, and 0.38°C above the 1991–2020 average.
About 87% of the ocean surface experienced at least one marine heat wave last year. Only 26% of the ocean surface experienced at least one marine cold spell.
Ocean heat and global sea levels
Over the past half-century, the oceans have stored almost 90% of the excess energy trapped in Earth’s system by greenhouse gases and other factors. The global ocean heat content, measured from the ocean’s surface to a depth of 2000 metres, continued to rise, and reached new record highs last year.
Global mean sea level was a record high for the 14th consecutive year, reaching about 111.2 millimetres above the average for 1993, when satellite altimetry measurements began.
Warming oceans have contributed an average of 1.6±0.3 millimetres per year to rising sea levels since 2005, while melt from ice sheets and glaciers has contributed an average of 2.0±0.4 millimetres during that same period.
Arctic
The Arctic had its second-warmest year in the 126-year record. Surface air temperatures in the Arctic are rising at roughly three times the global average rate.
Rainfall is also rising across the region. In response to the rainfall and temperature rises, tundra plants have been increasing; last year marked the third-highest value in the record with respect to greenness, a measure of the increase in plants and productivity.
In Arctic waters, maximum sea ice extent in 2025 was the lowest in the 47-year record, while minimum extent was the 11th lowest. The thickness of the sea ice, which is related to its age, has also been decreasing over time. Ice older than four years old is nearly absent, with only 95,000 square kilometres of older ice in September 2025 as compared to 1.5 million square kilometres in the 1980s.
Antarctica
Antarctica had its warmest year since the start of the record in 1979. Surface melt on the continent was above average on most ice shelves, and melt on the Antarctic Peninsula approached record levels in early January.
Surrounding the continent, sea ice remained below average last year, following a nearly decade-long trend. Annual daily maxima and minima of sea ice extent were the third and fourth lowest on record, respectively.
Glaciers
Land-based glaciers continued to lose ice for the 38th consecutive year, losing the equivalent of more than 1 metre of water on average for the fourth straight year. About 41% of the loss experienced by glaciers since 1976 has occurred in the past decade.
Hurricanes and cyclones
Ninety-seven named tropical cyclones were observed during the Northern and Southern Hemispheres’ storm seasons, above the 1991–2020 average of 87.
Five storms reached Category 5 intensity. Three of these occurred in the North Atlantic, tying for the second most on record for that basin.
Hurricane Melissa became one of the strongest Atlantic hurricanes on record, with a maximum intensity of 306km/hr and a minimum central pressure of 892 hPa on October 28. Melissa made landfall in Jamaica as a Category 5 storm, causing 95 fatalities and resulting in at least US$12.2 billion in damage.
There were 12 named storms in the Australian basin during the 2024/25 season, which was the most in a season since 2005/06. In February, Tropical Cyclone Zelia reached Category 5 intensity at sea and made landfall as a Category 4 storm in Western Australia. Flood heights at the town of Marble Bar due to heavy rainbands were nearly 2 metres above previous records.
[Abridged and lightly edited for style from Climate and Capitalism.]