According to a new study, temperatures at the South Pole have been rising three times faster than the global average since 1989. The authors see the main causes of warming in natural climate fluctuations between the tropical Pacific ocean and the Weddell Sea. However, scientists believe that the increase in greenhouse gas concentrations in the atmosphere intensifies the warming.
On the Antarctic continent, enormous temperature differences can be observed over the course of a year, with great regional contrasts. The highest temperature ever measured in Antarctica was recorded this past February at 20.75°C on Seymour Island east of the Antarctic Peninsula. This contrasts with the low winter temperatures in the interior of the continent with the lowest ever recorded temperature of -89.2°C in July 1983 at the Russian Vostok station.
The impact of climate change is most evident in West Antarctica and the Antarctic Peninsula. In the region around the Geographic South Pole, which lies at an altitude of 2,835 meters, a cooling had been observed for a long time.
However, as a team of scientists from New Zealand, the UK and the US found in their new study, the South Pole has been warming rapidly since the late 1980s compared to global temperature rise. The researchers attribute the warming to a combination of natural and anthropogenic influences, although the individual contribution of each factor is not yet well understood and difficult to determine precisely.
The research team used climate models to analyze changes in air temperature that have been recorded at the American Amundsen-Scott station at the South Pole since 1957. Their analyses show that the South Pole is now warming at a rate of about 0.6°C a decade, compared to a rate of about 0.2°C for the rest of the planet.
“Research over the past couple decades revealed the Antarctic plateau, the coldest and one of the most remote places on Earth, had been cooling while global temperatures were increasing. … Our study has found that this is no longer the case. The south pole is now one of the fastest warming regions on the planet, warming at an incredible three times faster than the global average rate.”Lead author Dr Kyle Clem, a polar researcher at Victoria University of Wellington in New Zealand
The authors of the study, published in the journal Nature Climate Change, blame natural climate fluctuations related to the phenomenon of the “Interdecadal Pacific Oscillation” (IPO) as the dominant driving factor for warming. The IPO cycle lasts about 15 to 30 years and alternates between a “positive” state in which the tropical Pacific is warmer and the northern Pacific is colder than average, and a “negative” state in which the temperature anomaly is reversed. At the beginning of the century, the IPO has tipped into a “negative” cycle, which has led to stronger storms in the Weddell Sea. Clem explains that this allowed more warm and humid air to be transported towards the South Pole.
The researchers do not know with certainty how great the influence of anthropogenic climate change is. “Our results suggest that global climate change has most likely played a role, but it has not been the dominant driver”, says Clem.
The researchers ran the climate models with different scenarios, including one without man-made greenhouse gas emissions. According to this one scenario, the warming of the South Pole in recent decades would have been possible in a world without greenhouse gas emissions — but only just, says Clem.
“The observed south-pole warming during the past 30 years exceeded 99.9% of all possible 30-year temperature trends at the south pole simulated in climate models without increased greenhouse gases included. Therefore, while natural changes chiefly caused the recent south pole warming, it appears very likely that it worked in tandem with human-caused warming.”Dr. Kyle Clem
Understanding warming at the South Pole is a complex issue, says Dr Ella Gilbert, a climate scientist with the British Antarctic Survey who was not involved in the study.
“This is a really interesting study because it shows how complex the causes of warming trends in Antarctica are. It’s clear from these results that remote linkages extending far beyond the Antarctic…contribute in a major way to regional climate over the south pole by influencing the amount of heat that can travel inland.”Dr Ella Gilbert
The research shows that the rate of warming at the South Pole was seven times higher than on the continent as a whole. “The warming trend at the south pole is much larger than at other stations, but this study shows that it’s only larger because natural factors are amplifying the underlying climate change signal”, Gilbert adds.
Julia Hager, PolarJournal
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