Why the Arctic is warming four times faster than the rest of the world

All of the extra heat from the summer is also trapped in the Arctic Ocean and then released throughout the winter. “Most of the warming in the Arctic occurs in winter, which may surprise people because summer is when sea ice melts the most,” says Hahn of the University of Washington. “That’s when you have incident sunlight. But the idea is that there is seasonal ocean heat storage.” It’s like a giant radiator that warms a room even when it’s off.

At the same time, storms transport moisture from lower latitudes to the Arctic and promote cloud formation. And injections of warmer water from the south, brought north by ocean currents, continue to melt the sea ice. “When it melts, water evaporates and increases humidity, which causes cloud cover to increase in winter, and we have infrared radiation coming to the surface from those clouds,” says Chylek. “This is a feedback loop that can result in increased Arctic temperature, and we believe this is one of the reasons we are seeing this temperature increase around the year 2000.”

University of Washington climate scientist Cecilia Bitz, who studies Arctic strengthening but was not involved in the new research, points out that there has been a lag in the response of high-latitude areas to greenhouse gases compared to the rest of the planet Has. It took some time for the sea ice to melt, but now that it has, the Arctic heat feedback loop has deteriorated and the rate of change has become much more noticeable. “The tropics warmed faster at first, and now the poles are catching up, and that’s why you’re seeing a trend,” she says.

The consequences are already massive and far-reaching. First of all, more melting—particularly in Greenland, which loses a quarter trillion tons of ice each year—means higher sea levels. Also, warmer bodies of water become physically larger, a phenomenon known as thermal expansion, causing sea levels to continue to rise.

The landscape also undergoes a literal and metaphorical upheaval. Warming temperatures are thawing frozen ground known as permafrost. As this permafrost loses water, it collapses, taking with it any infrastructure in or above it, like pipelines, roads, and buildings. “There is persons in the Arctic,” says Bitz. “They have done very little to deserve to live in this dangerous environment.”

The exploding temperatures also green this landscape. Shrub species are marching north, and vegetation is catching more snow on the ground. This prevents the cold of winter from penetrating and possibly accelerating the thawing of the permafrost. All this extra vegetation is also darker – just like the sea itself is darker than its ice – and therefore absorbs more solar radiation.

Put simply, the Arctic is sinking into climatological and ecological uncertainty. “Each summer when my field research team travels to the Arctic, we don’t know exactly what to expect,” says Isla Myers-Smith, a global change ecologist at the University of Edinburgh, who was not involved in the new research. “This year we arrived in Inuvik, Canada, in a heat dome with temperatures reaching 32 degrees Celsius [90 degrees Fahrenheit]but out on the coast there was still a lot of sea ice, which kept temperatures much cooler locally.”

This type of variability makes it difficult for models to determine how the Arctic is changing and how those changes will affect the larger climate system. That’s why it’s so important that scientists revise their understanding that the Arctic is in fact more than warming four times as fast as the rest of the planet.

A key concern is the potential for the climate system to reach an inflection point where warming initiates rapid change. For example, if the Arctic warms sufficiently, melting in Greenland could accelerate rapidly. “I don’t think it’s really known with any certainty — if these turning points exist — what level of warming would trigger such rapid changes,” says Michael Previdi, a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory, who wasn’t at it involved in the new newspaper. But, he continues, in theory, a larger gain factor “increases the odds of passing one of those turning points.”

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