Researchers have reconstructed the Arctic amplification index over the past 1,000 years and found that the index has decreased during the time range, according to the Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences.

The Arctic has warmed more than twice the global average since the preindustrial era, a phenomenon known as Arctic amplification. The Arctic amplification index is the slope of a regression equation linking pan-Arctic and mid-low latitudes' temperature anomalies.

The decreased Arctic amplification index showed that the Arctic experienced faster variability than the mid-low latitudes during the past millennium but the variability difference between the two regions gradually reduced, according to the researchers.

Arctic amplification and its driving mechanism is a hot and cutting-edge topic in polar climatology. At present, the research on Arctic amplification is mainly limited to its seasonal and interannual changes over the past few decades. Scientists hope to identify the changes of the Arctic amplification on a longer time scale to deeply understand its driving mechanism.

The researchers from the Chinese Academy of Sciences, Lund University and the University of Gothenburg in Sweden reconstructed an annual mean temperature data of the Northern Hemisphere in the past millennium by assimilating climate proxy data such as tree rings, ice core and lake sediments.

The study extended the time scale of the research on the Arctic amplification from decades to one thousand years and from seasonal to multi-decadal.

At the millennium scale, there is a significant correlation between the Arctic amplification and the two factors of the Atlantic Multidecadal Oscillation and greenhouse gases, according to the study.

The research article has been published in the journal Nature Communications. (Xinhua)