【気候】南極半島が温暖化していないのは自然変動の範囲内

The Antarctic Peninsula warmed for much of the twentieth century, but beginning in the late 1990s, the warming trend switched to cooling, finds a paper published in Nature this week. These findings are within natural variability of regional atmospheric circulation and do not imply more general cooling in Antarctica or elsewhere.

Research stations on the Antarctic Peninsula have recorded warming near-surface air temperatures since the 1950s with several interlinked processes suggested as contributing to the warming, including sea-ice loss, westerly winds and stratospheric ozone depletion.

John Turner and colleagues use a stacked temperature record from six stations in the northern Antarctic Peninsula to investigate broad-scale temperature changes in the region since 1979. They find that there has been an absence of regional warming since the late 1990s up to 2014, with the annual mean temperature decreasing at a statistically significant rate. The most rapid cooling occurs during the Southern Hemisphere summer, they note. They consider this cooling trend to be a consequence of a greater frequency of cold, easterly to southeasterly winds resulting from more cyclonic conditions in the northern Weddell Sea, in turn associated with a strengthening mid-latitude jet stream.

The authors stress that their findings cover only one per cent of the Antarctic continent and emphasise that these decadal temperature changes in the region are not primarily associated with the drivers of global temperature change, and instead reflect the extreme natural internal variability of the regional atmospheric circulation.