Scientists unveiled evidence yesterday to suggest global warming is affecting all of Antarctica, home to the world’s mightiest store of ice.
The average temperature across the White Continent has been rising for the last half century and the finger of blame points at the greenhouse effect, they said.
The research, published in the British journal Nature, takes a fresh look at one of the great unknowns — and dreads — in climate science.
Any significant thaw of Antarctica could drown many coastal cities and delta regions. Bigger than Australia, Antarctica holds enough ice to raise global sea levels by 57m.
Previous monitoring has already pinpointed the Antarctic Peninsula — the tongue that juts 800km toward South America — as a “hotspot” where hundreds of glaciers have been in retreat since the start of the decade.
But until now the news has been reassuring regarding Antarctica’s two massive icesheets.
A common belief is that the icy slabs have even cooled slightly and possibly thickened, partly in response to the chilling seasonal effects of the ozone hole over the South Pole.
Not so, the new study says.
It calculates that West Antarctica has been warming by 0.17ºC per decade over the past 50 years.
This is even more than the Peninsula, where the average rise is estimated as 0.11ºC per decade.
There has indeed been some cooling in East Antarctica, but this was mainly in the autumn, and occurred as a result of the ozone hole. There was also a period of strong cooling between 1970 and 2000.
But, overall and when calculated over 50 years, East Antarctica has warmed too — by an average of 0.1ºC per decade, a figure that the authors describe as “significant.”
“The sense of ‘Oh, it’s cooling in East Antarctica,’ is based essentially on the 1970-2000 period, and it’s warmed since then — although we don’t have a lot of data for the most recent period — and it definitely warmed prior to the 1970s,” said Eric Steig, a professor of Earth and space sciences at the University of Washington. “When you look at the big picture on that, the average [trend in East Antarctica] is actually warming.”
Put together, the average temperature rise for Antarctica is put at 0.12ºC per decade, the study said.
The work is based on a 25-year archive of observations by satellites measuring the intensity of infrared light radiated by the snow pack. These were buttressed by data from automated weather stations deployed around the Antarctic coast since 1957.
The paper does not venture any estimate about ice loss or predict the icesheets’ stability, but says only global warming can logically explain the temperature trend.
“This shouldn’t cause anyone to worry more than they did before. But what it does do is kill off the rather silly and careless statements out there from some people to the effect that Antarctica’s cooling,” Steig said.
Comments such as that “put into question all the other science that supports the idea that there is warming and it’s human beings’ fault,” he said.
There could be bad news a few decades down the road, when efforts to fix the ozone hole bear fruit, Steig said.
“The hole could be eliminated by the middle of this century. If that happens, all of Antarctica could begin warming on a par with the rest of the world,” he said.
The West Antarctic icesheet, which holds enough ice to boost global sea levels by up to 6m, lies at an average height of about 1,800m.