A new study led by the Los Alamos National Laboratory has discovered that the Arctic is heating up over four times faster than the rate of global warming. The analysis revealed that this trend has stepped upward steeply twice in the past 50 years, a finding which was missed by all but four of the 39 existing climate models. According to the experts, these sudden increases were most likely caused by sea-ice and water-vapor feedbacks combined with changes in how atmospheric and oceanic heat move into the Arctic.
“Thirty years is considered the minimum to represent climate change,” said study lead author Petr Chylek, a physicist and climate researcher at the Los Alamos National Lab. “We decreased the time interval to 21 years. At that smaller time scale and, contrary to previous investigations that found the Arctic amplification index increases in a smooth way, we observed two distinct steps, one in 1986 and a second one in 1999.”
Since these trends identified by the scientists affect global weather and sea levels, and the melting of the Greenland ice sheet causes sea-level rises that threaten many coastal communities, accurately projecting climate change in smaller timeframes is crucial for planning any mitigation and adaptation strategies.
From the 39 climate change models in the widely used Coupled Model Intercomparison Project, the scientists found only four that reproduced the first step reasonably well around 1986, but none that reproduced the second step in 1999. “We attributed the first step to increasing concentrations of carbon dioxide and other pollutants in the atmosphere, because several models do it correctly, but the second step we think is due to climate variability because none of the models can reproduce it,” explained Professor Chylek.
The scientists aim to further investigate future Arctic climate projections using the four models that came closest to matching the observed Arctic warming trends. “Because the four models correctly reproduce at least the first step, we assume they’re a little better for future climate projection,” Chylek said. “People usually average all models and assume the ensemble is more reliable than any single model. We show the average does not work in this case.”
“People are not only interested in long-term climate change, but they are also interested in 10 years ahead, 20 years, 30 years. For decadal prediction our observation that the amplification index changed in the past in steps is quite important,” he concluded.
The study is published in the journal Geophysical Research Letters.