(Bloomberg) — The 10 hottest years on record have all occurred within the past decade, with 2024 likely to be the warmest yet. But the Arctic has warmed up at a faster rate than the planet as a whole during that period and its tundra is now releasing more carbon dioxide than it stores, according to scientists’ annual report card on the polar region.
The rapid heating on the top of the planet is set to continue as changes to sea ice, ocean temperatures and snow cover, among other factors, create feedback loops that amplify the effects of global warming.
“It’s not just that the Arctic is warming just like the rest of the world,” said Rich Thoman, a climate scientist at the University of Alaska Fairbanks. “Because of these changes in the frozen environment, we’re seeing this acceleration.” Thoman is co-editor of the 19th Arctic Report Card, a compilation of work from scientists around the world released Tuesday by the US National Oceanic and Atmospheric Administration.
One of the most worrying findings in this year’s report is that the interaction between Arctic wildfires — which are becoming more frequent and severe — and thawing permafrost has for the first time erased the beneficial role of the Arctic tundra as a carbon sink, turning it into a net source of CO2.
Arctic tundra has acted as a carbon sink for thousands of years, sequestering vast stores of the greenhouse gas in the frozen ground. While warmer temperatures may increase vegetation in the region, allowing plants to remove more CO2 from the atmosphere, it’s not enough to compensate for the increased emissions from high-latitude wildfires coupled with the carbon released from permafrost as it melts. (Thawing permafrost also releases methane, a highly potent greenhouse gas, which is not removed by plants.)
“When a wildfire comes through, it removes vegetation and it removes the insulating soil layer,” said Sue Natali, a scientist at the Woodwell Climate Research Center in Falmouth, Massachusetts, who contributed to the report. “It’s like opening the top of a cooler. What we are seeing is that after a wildfire, the ground will stay more thawed for years and sometimes decades.” Whether the permafrost can eventually recover from the combined, interrelated impact of wildfires and atmospheric warming is not known, she said.
Between October 2023 and September 2024, the area above the Arctic Circle was 1.2C warmer than the mean global temperature between 1991 and 2020. By comparison, the entire planet warmed 0.7C over the same period, Thoman said. (The global temperature rise will likely exceed 1.5C this year for the first time, compared to a pre-industrial baseline.)
The report examines eight “vital signs” to gauge the Arctic’s health. While variability exists from year to year in different parts of the region, the following are among the other broad trends highlighted in the report.
While new records may not be set every year, data suggests the Arctic has entered a “new regime” in which the baseline for its vital signs has shifted. That doesn’t mean the region has stabilized under human-caused warming, the report stresses: “Projections of climate change for the next several decades are clear: change will continue.”
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