The Antarctic Peninsula, regarded as a “global warming hot spot”, has been cooling for almost 20 years.
The Antarctic Peninsula has cooled (blue line) since 1998 — Robert Mulvaney/British Antarctic Survey
Natural variability was responsible both for the decades-long warming since the 1950s and more recent cooling, according to research published today in Nature.
The research, led by John Turner from the British Antarctic Survey, said while the start of Antarctic Peninsula cooling in 1998 had coincided with the so-called “global warming hiatus”, the two were not connected.
Scientists were quick to declare the results of the Turner et al paper, which covered 1 per cent of the Antarctic continent, did not negate a long-term warming because of man-made climate change.
Rather, they said, the ozone hole, changing wind patterns and natural variability had masked the long-term warming trend.
“Climate model projections forced with medium emission scenarios indicate the emergence of a large anthropogenic regional warming signal, comparable in magnitude to the late-20th-century peninsula warming, during the latter part of the current century,” the Turner research concluded.
In addition, temperatures on the Antarctic Peninsula remained higher than measured during the middle of the 20th century, so glaciers were still retreating in the Antarctic region.
Nonetheless, the findings have put into sharp relief the long-term cycles of natural variability in an area popularised in the climate change narrative by dramatic images of calving ice sheets and retreating glaciers.
Prior to the paper’s publication, science media organisations around the world were ready with quotes from climate scientists to ensure the Turner paper was not misinterpreted.
Martin Siegert, co-director of the Grantham Institute, London, said the Antarctic Peninsula was one of the regions of the world where warming was greatest over the past 100 years, and now it had levelled off whilst other areas continued warming. “The study does not suggest that global warming has been halted however, and it must not be misconstrued as such,” Professor Siegert said.
The Turner research found temperatures had decreased as a consequence of a greater frequency of cold, east-to-southeast winds, resulting from more cyclonic conditions in the northern Weddell Sea associated with a mid-latitude jet.