Ocean temperatures for March reached near-record highs, the European Union’s Copernicus Climate Change Service said. The warmest March on record was 2024, when the El Nino cycle drove temperatures up; Copernicus says current records again point to “a likely transition toward El Nino conditions.”
The World Meteorological Organization has similarly forecast a shift this year: a cooling La Nina is expected to give way to neutral conditions before swinging into El Nino later in the year.
In the United States, March was the most abnormally hot month in 132 years of records, federal data show. The Associated Press quoted Shel Winkley, a meteorologist with nonprofit Climate Central, saying one reason for concern is “the sheer volume of records,” following what was the worst snow year and the hottest winter on record. Climate Central calculated that on March 20–21 about one-third of the US experienced unseasonable heat that would have been virtually impossible without human-caused climate change.
Under the 2015 Paris Agreement, countries aim to limit near-surface warming to 2°C, with a more ambitious 1.5°C target to avoid the worst impacts. Copernicus reports global surface air temperatures have risen about 1.3–1.4°C since the pre-industrial era.
La Nina and El Nino are opposing climate cycles in the tropical Pacific that cause short-term global temperature swings. El Nino conditions tend to amplify heat extremes on an already warming planet; the 2023–2024 El Nino contributed to those years becoming the second-hottest and hottest on record, respectively.
Arctic sea ice extent in March was 5.7% below average—the lowest on record for the month, Copernicus said. The area of ocean covered by ice is decreasing steadily year after year, a key indicator of rapid warming in the Arctic and Antarctica.
Oceans absorb most of the excess heat from human activities and play a central role in regulating climate. Warmer oceans expand thermally and accelerate polar ice melt, both contributing to sea level rise. Hotter seas also fuel stronger storms and heavier rainfall, which have become more frequent in recent years.
Edited by: Kieran Burke