A seal rests on an ice floe in the western Antarctic peninsula, on March 5, 2016
- Trend toward warmer temperatures in the region paused in 1990s
- Changes may be in step with natural variation, researchers say
One of the most rapidly warming places on Earth in the past half century actually cooled in the past 20 years, according to research that may be seized on by those who have doubts about global warming.
Temperatures on the Antarctic Peninsula have reversed course, dropping by an average of about 0.5 degree Celsius per decade since the late 1990s while the rest of the world experienced record heat, 10 researchers from the British Antarctic Survey concluded in an article published in the journal “Nature” on Wednesday.
The report’s authors didn’t make a conclusion about what their findings mean for the debate about global warming, saying the changes they noticed could fit at the extreme end of natural climate variations. That suggests it may take years and further research to determine the direction of temperatures in the Antarctic and what they mean for the world. Climate scientists said the report should be treated with caution.
“That a very small part of the planet shows a short-term cooling is not in any way a surprise,” said Ed Hawkins of the National Center for Atmospheric Science at the University of Reading in England. “It’s what we expect from natural variation in the atmospheric circulation interacting with a long-term warming trend.”
The findings will feed the debate about the significance of a slowdown in the pace of global warming seen since 1998.
The authors noted their study covered 1 percent of the Antarctic continent, a region that has warmed in the spring in the 1970s because of a hole in the atmosphere’s Ozone layer of the atmosphere. That gap now is starting to close, with an uncertain impact.
“This study certainly does not suggest that global warming has been halted,” said Martin Siegert, co-director of the Grantham Institute at Imperial College London.
The authors neglected to mention the role of warmer oceans in melting the peninsula’s glaciers, which would have put the findings into a broader context, said University College London Professor of Climate Science Chris Rapley. This, he said, could give fuel to skeptics who say climate change is overstated. A separate paper also by the British Antarctic Survey published earlier this month in “Science” showed ocean warming is the primary cause of glacier retreat on the western Antarctic Peninsula.
“It is important not to interpret the cooling of this small area of Antarctica as evidence that the climate is not warming,” said Martyn Tranter at the University of Bristol. “The cooling here has very little influence on global climate change. The overwhelming evidence is that the global climate is warming.”
Andrew Shepherd, director of the Center for Polar Observation and Modeling at the University of Leeds in England, said scientists should turn their attention to the warming of the oceans, which “has triggered widespread loss of ice just around the corner in West Antarctica.”
“We should not lose sight of that because there are early signs in the satellite record of similar effects at the Peninsula too,” he said.