Antarctica, the only place that had oddly seemed immune from climate change, is warming after all, according to a new study.
For years, Antarctica was an enigma to scientists who track the effects of global warming. Temperatures on much of the continent at the bottom of the world were staying the same or slightly cooling, previous research indicated.
The new study went back further than earlier work and filled in a massive gap in data with satellite information to find that Antarctica too is getting warmer, like the Earth's other six continents.
The findings were published in Thursday's issue of the journal Nature.
"Contrarians have sometime grabbed on to this idea that the entire continent of Antarctica is cooling, so how could we be talking about global warming?," said study co-author Michael Mann, director of the Earth System Science Center at Penn State University. "Now we can say: no, it's not true ... It is not bucking the trend."
The study does not point to man-made climate change as the cause of the Antarctic warming - doing so is a highly intricate scientific process - but a different and smaller study out late last year did make that connection.
"We can't pin it down, but it certainly is consistent with the influence of greenhouse gases," said NASA scientist Drew Shindell, another study co-author. Some of the effects also could be natural variability, he said.
The study showed that Antarctica - about one-and-a-half times bigger than the United States - remains a complicated weather picture, especially with only a handful of monitoring stations in its vast interior.
The researchers used satellite data and mathematical formulas to fill in missing information. That made outside scientists queasy about making large conclusions with such sparse information.
"This looks like a pretty good analysis, but I have to say I remain somewhat skeptical," Kevin Trenberth, climate analysis chief at the National Center for Atmospheric Research, said in an e-mail. "It is hard to make data where none exist."
Shindell said it was more comprehensive than past studies and jibed with computer models.
The research found that since 1957, the annual temperature for the entire continent of Antarctica has warmed by about 1 degree Fahrenheit (0.55 degrees Celsius) but still is 50 degrees below zero (-46 Celsius). West Antarctica, which is about 20 degrees (11 degrees Celsius) warmer than the east, has warmed nearly twice as fast, said study lead author Eric Steig of the University of Washington.
East Antarctica, which scientists had long thought to be cooling, is warming slightly when yearly averages are looked at over the past 50 years, said Steig.
However, autumn temperatures in east Antarctica are cooling over the long term. And east Antarctica from the late 1970s through the 1990s, cooled slightly, Steig said.
Some researchers skeptical about the magnitude of global warming overall said that the new study didn't match their measurements from satellites and that there appears to be no warming in Antarctica since 1980.
"It overstates what they have obtained from their analysis," said Roger Pielke Sr., a senior research scientist at the University of Colorado.
Steig said a different and independent study using ice cores drilled in west Antarctica found the same thing as his paper. And recent satellite data also confirms what this paper has found, Steig added.
The study has major ramifications for sea level rise, said Andrew Weaver at the University of Victoria in Canada. Most major sea level rise projections for the future counted on a cooling - not warming - Antarctica. This will make sea level rise much worse, Weaver said.