“People are not only interested in long-term climate change, but also 10 years, 20 years, 30 years. »
Climate change is upon us, but not all regions of the world are experiencing it at the same rate. The polar regions have been hit particularly hard by warming temperatures and a new analysis of temperature rises in the Arctic shows just how much.
An international team of researchers has found that temperatures in the Arctic are rising more than four times faster than the average rate of global warming. Not only that, but in the last half century the trend has accelerated twice in a few peaks (in 1986 and 1999) ignored by most climate models.
“Thirty years is considered the minimum to represent climate change,” says Petr Chylek, physicist and climate researcher at Los Alamos National Laboratory.
“We have reduced the time interval to 21 years. At this smaller timescale, and unlike previous surveys which showed the Arctic Amplification Index to increase steadily, we observed two distinct stages, one in 1986 and a second in 1999,” he explains. .
The scientists examined the 39 climate change models in the Coupled Model Intercomparison Project’s widely used CMIP6 international collaborative collection and found only four models that reproduced the first step reasonably well around 1986.
However, all models in the database failed 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,” Chylek says, “but we think the second stage is due to the climate variability because none of the models can reproduce the second stage.”
Scientists speculate that the sudden spikes were caused by sea ice and water vapor feedbacks combined with changes in the way atmospheric and ocean heat moves in the Arctic.
Their new study now estimates that the Arctic Amplification Index is above 4 in the first decades of the 21st century, which is four times faster than the global average. This rate of warming is also faster than previous estimates based on intervals of 30 to 40 years, which placed the index between 2 and 3, the scientists explain in a press release on their findings.
Warming in the Arctic is affecting weather and sea levels around the world and scientists’ new decade-by-decade survey may help us better predict the true rate of warming in the polar region, as models climates based on time scales of several decades generally fail to detect short periods. long-term climate variability.
This is why projecting future rates of climate change at shorter timescales will be essential for planning climate change mitigation and developing adaptation strategies, the scientists point out.
Researchers are currently studying future Arctic climate projections using the four models that come closest to the observed warming trend with the two peaks.
“Because all four models correctly reproduce at least the first step, we assume they are somewhat better for projecting future climate. People usually average all models and assume that the ensemble is more reliable than n “any single model. We show that averaging doesn’t work in this case,” Chylek says.
“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,” adds the scientist.