LOS ALAMOS, New Mexico — A chilling new study reveals that temperatures in the Arctic are rising four times faster than the current rate of global warming. The researchers say an analysis of observed temperatures revealed two jumps that most climate models have missed over the past 50 years.
“Thirty years is considered the minimum to represent climate change,” said study lead author Petr Chylek, a physicist and climate researcher at Los Alamos National Laboratory, in a statement. Press release. “We have reduced the time interval to 21 years. At this smaller timescale and unlike previous surveys which found the Arctic Amplification Index to increase steadily, we observed two distinct steps, one in 1986 and a second in 1999.”
The amplification index used in this study is the ratio of a 21-year Arctic temperature trend to a 21-year global global temperature trend.
Researchers found that the Arctic Amplification Index was greater than four (4) during the first decades of the 21st century, which means four times faster than the global average and much faster than previous research had determined in using time intervals of 30 to 40 years. Previous studies have calculated the index to be closer to two (2) or three (3).
Of the 39 climate change models used in the Coupled Model Intercomparison Project’s CMIP6 collection, the researchers found four that reproduced the first stage reasonably well around 1986, but none that reproduced the second stage in 1999.
“We attributed the first stage to increasing concentrations of carbon dioxide and other pollutants in the atmosphere, because several models do this correctly,” notes Chylek, “but the second stage, we believe, is due to climate variability because none of the models can reproduce the second stage.
What causes temperatures to skyrocket?
Scientists say that short-term climate variability is generally not detectable by climate models with their 30-year time scales.
Although the team could not find a cause for these sudden increases, the researchers believe that contributing factors include feedbacks from sea ice and water vapor, combined with changes in the way the heat atmospheric and oceanic shifts in the Arctic.
“Future increases in the Arctic Amplification Index will likely be smaller as the temperature difference between the Arctic and the tropics decreases,” the researchers add.
The team uses the four models that come closest to the observed warming trend for future Arctic climate projections.
“Because all four models correctly reproduce at least the first step, we assume they are somewhat better for future climate projection,” Chylek says. “People usually average all models and assume that the ensemble is more reliable than any single model. We show that averaging doesn’t work in this case.
The authors of the study downloaded temperature data from the Arctic and used simulations from climate models in the CMIP6 collection.
“People are not only interested in long-term climate change, but they are also interested in the next 10 years, 20 years, 30 years. For the decadal prediction, our observation that the amplification index has changed stepwise in the past is quite important,” says Chylek.
The results appear in the journal Geophysical Research Letters.