On August 11, 2022, a study was published in Nature Communications Earth & Environment on Arctic amplification (AA), the relatively higher rate of warming in the Arctic compared to all other parts of the globe. AA, also known as polar amplification, is thought to be due to feedback from reduced cold-season ice and snow cover.
In other words, ice loss in the Arctic causes the region to have greater temperature change averages than the rest of the planet. Though this fact has been well established in previous literature, authors of “The Arctic Has Warmed Nearly Four Times Faster Than the Globe Since 1979” declare that AA is presently happening at higher ratios than what’s been reported in the past.
According to authors Mika Rantanen, Alexey Karpechko, Antti Lipponen, Kalle Nordling, Otto Hyvärinen, Kimmo Ruosteenoja, Timo Vihma, and Ari Laaksonen, warming ratios from previous studies are based on possibly outdated estimates that do not include the most recent observations. If true, previous studies will have likely underestimated present-day Arctic heating rates.
Mika Rantanen and colleagues used several observational datasets for the Arctic region to more accurately quantify the current magnitude of AA. They included four climate models in their calculations: NASA’s Goddard Institute for Space Studies Surface Temperature version 4 (GISTEMP), the Berkeley Earth temperature dataset (BEST), the Met Office Hadley Centre/Climatic Research Unit version 126.96.36.199 (HadCRUT5) and ERA5 reanalysis.
Rantanen’s team claims that “the period of interest and the area of the Arctic can be defined in multiple ways”. To put it another way, AA estimates will vary according to the timeframe studied and the definition of what qualifies as the geographic area of the Arctic. Rantanen’s team primarily defined the Arctic using the Arctic Circle as the southern boundary (66.5∘–90∘N, the area located above 66.5 degrees latitude) and focus on warming trends for the last 43 years.
During the last 43 years, more accurate satellite remote sensing data and observations on atmospheric variables and sea ice concentration have become available. This period is crucial for AA calculations, as 1979–2021 is thought to be a period of relatively strong Arctic warming.
Their results are evidence that major portions of the Arctic Ocean warmed nearly four times faster than the globe from the years 1979–2021, whereas previous studies report the Arctic warming at nearly twice, or about twice as quickly as the global average. AA was most severe in Novaya Zemlya sea areas, which warmed up to seven times as fast as the global average.
There are multiple reasons for accelerated Arctic heating. Human-caused global warming is likely an integral cause of recent heating trends. On top of that, ice loss within the Arctic Circle plays a role. Ice that was once frozen for all or most of the year, is increasingly shrinking. Sea ice loss reinforces global warming because melting ice gives way to a darker ocean. Brightly colored snow and ice surfaces reflect sunlight back into space at a higher rate than the surfaces of darkly colored seawater, which are more efficient at absorbing sunlight and heat energy.