The exceptional warmth that first enveloped the planet last summer has continued into this year with last month clocked as the hottest January ever measured, according to the European Union’s climate monitor.
It was the hottest January on record for the oceans, too, according to the European Union’s Copernicus Climate Change Service.
Sea surface temperatures were just slightly lower than those recorded last August, the oceans’ warmest month on the books. Sea temperatures kept on climbing in the first few days of February, surpassing the daily records set last August.
The oceans absorb the great majority of the extra heat that greenhouse gases in the atmosphere trap near Earth’s surface, making them a reliable gauge of how much and how quickly the planet is warming. Warmer oceans provide more fuel for hurricanes and atmospheric river storms, and can disrupt marine life.
January makes eight months in a row that average air temperatures, across the continents as well as the seas, have topped all prior records for the time of year. All in all, 2023 was Earth’s hottest year in more than a century and a half.
The principal driver of all this warmth is no mystery to scientists: The burning of fossil fuels, deforestation and other human activities have driven temperatures steadily upward for more than a century. The current El Nino weather cycle is also allowing more ocean heat to be released into the atmosphere.
Yet, precisely why Earth has been this hot, for this long, in recent months remains a matter of some debate among researchers, who are waiting for more data to come in to see whether other, less predictable and perhaps less understood factors might also be at work around the margins.
“Rapid reductions in greenhouse gas emissions are the only way to stop global temperatures increasing,” Samantha Burgess, Copernicus’ deputy director, said in a statement.
“Not only is it the warmest January on record but we have also just experienced a 12-month period of more than 1.5 degrees celsius above the pre-industrial reference period.”
According to Copernicus’ data, temperatures in January were well above average in eastern Canada, northwestern Africa, the Middle East and Central Asia, though much of the inland United States was colder than usual. Parts of South America were warmer than normal and dry, contributing to the recent forest fires that devastated central Chile.
The intensity of recent underwater heat waves prompted the National Oceanic and Atmospheric Administration in December to add three new levels to its system of ocean heat alerts for indicating where corals might be bleaching or dying.
An El Nino pattern like the one currently observed in the Pacific is associated with warmer years for the planet, as well as a swath of effects on rainfall and temperatures in specific regions.
But as humans heat up the planet, the effects that forecasters could once confidently expect El Nino to have on local temperatures are no longer so predictable, said Michelle L’Heureux, a NOAA scientist who studies El Nino and its opposite phase, La Nina.
“For regions that previously tended to have below-average temperatures during El Nino, you almost never see that anymore,” Ms L’Heureux said. “You see something that’s more near-average, or even still tilting above average.”
This article originally appeared in The New York Times.
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