The Arctic is warming four times faster than the rest of the world. Scientists at the Los Alamos National Geosciences and Environmental Sciences Laboratory have revealed that the causes of this phenomenon, called Arctic amplification, are both anthropogenic forcing and internal climate variability, which has not yet been reproduced by models. The researchers’ article was published in the journal Geophysical Research Letters.
Between the 1970s and 2000s, the average annual Arctic amplification index fluctuated from two to three, which means that the climate of the Arctic region was two to three times more sensitive to global temperature rise than in other regions. However, over the course of the 21st century, the index rose to four. In addition, over the entire period of observation, the Arctic amplification did not change smoothly, but in the form of two sharp jumps approximately in 1986 and 1999, when the rate of increase in surface air temperature remained constant, but increased in the Arctic.
The researchers analyzed the available Arctic temperature data and looked at how it is reproduced by various CMIP climate models.
. Four climate change models out of 39 CMIP6 models predict an increase in the amplification index in the 1980s, but they miss the sharp increase in warming in the Arctic after 1999. According to the authors of the paper, this suggests that the initial push to increase the temperature is associated with anthropogenic greenhouse gas emissions, but subsequently the heating of the Arctic intensified due to internal climatic mechanisms. Typically, models cannot reproduce short-term climate variability as they target time periods greater than 30 years.
The probable causes of the second jump may be feedbacks between the melting of sea ice and the content of water vapor in the atmosphere (water vapor enhances the greenhouse effect), as well as the transfer of atmospheric and oceanic heat from the Atlantic to the Arctic, resulting in the atlantization of the Arctic climate. Most likely, the index will continue to increase, but at a lower rate due to the decrease in the difference in temperatures between the Arctic and southern latitudes.
According to the authors of the work, those models that predict the first jump are more suitable for future climate forecasts. Climatologists usually average the results of different climate models, assuming that the overall result is better than individual predictions, but in this case, averaging misses a phenomenon that could significantly affect the climate in the future.