Executive Summary
The 2025 global climate remained near record warmth without the amplifying influence of El Niño, according to the 36th annual State of the Climate assessment. All five datasets examined placed 2025 among the three warmest years since records began in 1850, and 2015 through 2025 contained the 11 warmest years on record. Carbon dioxide, methane, and nitrous oxide concentrations reached new highs, along with global ocean heat content and mean sea level. Compiled by 626 authors and editors from 60 countries, the 527-page report documents interconnected changes across the atmosphere, oceans, cryosphere, water cycle, and regional climates.
Record Heat Persisted Without El Niño
Four of the five global datasets ranked 2025 as the third-warmest year, behind 2024 and 2023, while NASA’s GISTEMP dataset ranked it second. Global surface temperature was 0.51°C-0.59°C above the 1991-2020 average and 1.33°C-1.41°C above the 1850-1900 preindustrial reference period. The report identifies 2025 as the warmest year on record without an El Niño episode, with weak La Niña conditions present for much of the year. Atmospheric carbon dioxide averaged 425.6±0.1 parts per million, 2.9 ppm higher than in 2024 and approximately 53% above the preindustrial level of about 278 ppm. Europe recorded its warmest year, the Arctic its second-warmest since 1900, and Antarctica its warmest since records began in 1979.
Oceans and Ice Set New Benchmarks
Global ocean heat content from the surface to a depth of 2,000 meters reached another record, and marine heatwaves affected approximately 87% of the ocean surface. Mean sea level rose to 111.2 millimeters above the 1993 satellite-era baseline, setting a record for the 14th consecutive year. The report’s new ocean dissolved-oxygen assessment estimates that oxygen inventories in the upper 1,800 meters have declined by approximately 0.45% per decade since 1965. Land-based glaciers lost ice for the 38th consecutive year, with approximately 41% of cumulative glacier loss since 1976 occurring during the past decade. Greenland lost an estimated 129±50 gigatons of ice, while the Arctic’s maximum sea-ice extent was the lowest in the 47-year satellite record. Arctic ice older than four years covered only 95,000 square kilometers in September 2025, compared with approximately 1.5 million square kilometers during the 1980s.
Extremes Raised Human and Economic Stakes
The report recorded 97 named tropical cyclones, 10 more than the 1991-2020 global average of 87, including five storms that reached Category 5 intensity. Hurricane Melissa caused 95 fatalities and at least US$12.2 billion in damage — one of the strongest Atlantic hurricanes on record and making landfall in Jamaica with maximum sustained winds of 160 knots. Central Texas received 180-300 millimeters of rain within three hours during a July event that exceeded the estimated 1-in-1,000-year probability. Flooding in central North China affected more than 7 million people and caused US$25 billion in direct economic losses, and drought endangered more than 10 million people across Somalia, Ethiopia, and Kenya in need of humanitarian food assistance. For governments, infrastructure owners, insurers, and investors, the findings reinforce the value of Climate Risk Intelligence™ that connects long-term climate trends with localized exposure, vulnerability, asset life, and financial consequences.
Frequently Asked Questions (FAQs)
- How warm was 2025 globally? The five assessed datasets ranked 2025 as the second- or third-warmest year since 1850.
- Did the Paris Agreement’s 1.5°C threshold fail in 2025? No. The report estimates that 2025 was 1.33°C-1.41°C above the preindustrial reference period, and the Paris threshold applies to long-term average warming rather than a single year.
- What greenhouse-gas records were set? Carbon dioxide, methane, and nitrous oxide reached annual global averages of 425.6 ppm, 1,935.7 parts per billion, and 338.9 parts per billion, respectively.
- What were the changes to global sea level? It reached 111.2 millimeters above the 1993 baseline, marking a 14th consecutive annual record.
- Why does the report matter for decision-makers? Its observation-based indicators provide evidence for updating risk assessments, infrastructure standards, adaptation priorities, emergency planning, and long-term capital decisions.
(Source: Blunden, J., & Reagan, J. (Eds.). (2026). State of the climate in 2025. Bulletin of the American Meteorological Society, 107*(8), Si-S512. https://doi.org/10.1175/2026BAMSStateoftheClimate.)
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