A new analysis of observed temperatures shows that the Arctic is warming more than four times faster than global warming. The trend has gone up steeply twice in the past 50 years, a finding missed by all but four of 39 climate models.
“Thirty years is considered the minimum to represent climate change,” said Petr Chylek, a physicist and climate researcher at Los Alamos National Laboratory and lead author of the study in Geophysical Survey Letters† “We have the time interval up to 21 years. On that smaller time scale, and in contrast to previous studies showing that the Arctic gain index increases in a smooth manner, we observed two distinct steps, one in 1986 and a second in 1999.”
Because the decade-to-decade episodic trend identified by Chylek and his collaborators affects global weather and sea levels, accurately projecting future climate change into smaller time frames is essential to planning for eventual impact mitigation and mitigation. developing adaptation strategies. The Arctic affects the world’s climate and weather, and the melting of the Greenland ice sheet is causing sea level rise that threatens many coastal communities.
The gain index in the study is the ratio of a 21-year Arctic temperature trend versus an overall 21-year global temperature trend.
The study calculated that the Arctic gain index in the early decades of the 21st century was greater than 4, four times faster than the global average and significantly faster than previously published research had determined using time intervals of 30 to 40 years. These previous studies linked the index between 2 and 3.
Of 39 climate change models in the widely used CMIP6 collection from the Coupled Model Intercomparison Project, the international research team found four that reproduced the first step fairly well around 1986, but none that reproduced the second step in 1999. CMIP is an international collaboration of climate models using a shared set of parameters. CMIP6 has been used to prepare a recent report by the Intergovernmental Panel on the Assessment of Climate Change.
“We attributed the first step to increasing concentrations of carbon dioxide and other pollutants in the atmosphere because several models are doing it correctly,” Chylek said, “but the second step is, we believe, due to climate variability because none of the models the second step.”
Short-term climate variability is typically not detected by climate models with their timescales over 30 years.
The study does not pinpoint a cause for these relatively sudden increases, but the authors speculate that the contributing causes are likely sea ice and water vapor feedbacks combined with changes in how atmospheric and oceanic heat enter the Arctic. Future increases in the Arctic gain index are likely to be smaller as the temperature difference between the Arctic and the tropics narrows.
Valuable for projecting change in the Arctic
Chylek said the research team will then study future Arctic climate projections using the four models closest to the observed warming trend, with the peaks.
“Since the four models correctly reproduce at least the first step, we assume they are a little better for future climate projection,” Chylek said. “People usually take the average of all models and assume that the ensemble is more reliable than each individual model. We show that the average doesn’t work in this case.”
The research team downloaded publicly available temperature data for the Arctic from the Internet and used simulations of climate models in the CMIP6 collection.
“People are not only interested in the long term climate change, but they are also interested in 10 years ahead, 20 years, 30 years. For the 10-year forecast, our observation that the amplification index has changed in steps in the past is quite important,” Chylek said.
The research team included members from Los Alamos, the University of East Anglia, PAR Associates, the University of Washington, the Pacific Marine Environmental Laboratory and Dalhousie University.
Petr Chylek et al, Annual mean arctic gain 1970-2020: observed and simulated by CMIP6 climate models, Geophysical Survey Letters (2022). DOI: 10.1029/2022GL099371
Los Alamos National Laboratory
Quote: Arctic temperatures rise four times faster than global warming (2022, July 5) retrieved July 5, 2022 from https://phys.org/news/2022-07-arctic-temperatures-faster-global.html
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