A study from 2021 found that the Arctic, long believed to be warming at two times the rate of the rest of the planet, was underestimated.
The research finds that the rate of acceleration has been at four times the global average since roughly 1990 as the Arctic has a considerable swing in damage from the heating of the Earth by fossil fuel emissions and what seems newly identified feedback loops that are not included in climate models. Peter Jacobs, NASA Goddard, describes the importance of the data for climate modeling. “When something is changing as quickly as the climate, numbers can get old and outdated quickly before you realize it, you’re misinforming people by a factor of two.”
Many scientists doubted the 2 celsius average for some time. Changes have come too quickly and are evident from satellite data and research on the ground.
It’s almost a mantra in climate science: The Arctic is warming twice as fast as the rest of the world. But that figure, found in scientific studies, advocacy reports, the popular press, and even the 2021 U.N. climate assessment, is incorrect, obscuring the true toll of global warming on the north, a team of climate scientists reports this week. In fact, the researchers say, the Arctic is warming four times faster than the global average.
“Everybody knows [the Arctic] is a canary when it comes to climate change,” says Peter Jacobs, a climate scientist at NASA’s Goddard Space Flight Center, who presented the work on 13 December at a meeting of the American Geophysical Union. “Yet we’re misreporting it by a factor of two. Which is just bananas.”
Researchers have long known the world warms faster in the far north, because of a phenomenon known as Arctic amplification. The drivers of amplification include increased solar heating, as dark ocean water replaces reflective sea ice, along with occasional intrusions of tropical heat, carried to the Arctic by “atmospheric rivers,” narrow parades of dense clouds that drag water vapor northward.
The researchers found Arctic warming has been underestimated for a couple of reasons. One is climate scientists’ tendency to chop each hemisphere into thirds and label the area above 60°N as the “Arctic”—an area that would include, for example, most of Scandinavia. But the true definition of the Arctic is defined by Earth’s tilt. And, as has been known for centuries, the Arctic Circle is a line starting at 66.6°N. When researchers lump in the lower latitudes, “you’re diluting the amount of Arctic warming you’re getting,” Jacobs says. “That is not a trivial thing.”
The other difference is the choice of time periods over which the warming rate is calculated. Jacobs and his colleagues focused on the past 30 years, when a linear warming trend emerged for the Arctic. Analyses that look at longer term trends see less divergence between the Arctic and the world. That’s because before 1990, the Arctic’s temperatures fluctuated, and even cooled for decades because of air pollution, including light-blocking sulfate aerosols that swept in from the northern midlatitudes, says Mark England, a climate scientist at the University of California, Santa Cruz, who is unaffiliated with the new work. As the world moves off fossil fuels and curbs pollution, he says, “this scenario is not going to repeat itself again.”
What happens in the Arctic doesn't stay in the Arctic.