Antarctic Temperatures Disagree with Climate Model Predictions

February 15, 2007

A new report on climate over the world’s southernmost continent shows that temperatures during the late 20th century did not climb as had been predicted by many global climate models.

This comes soon after the latest report by the Intergovernmental Panel on Climate Change that strongly supports the conclusion that the Earth’s climate as a whole is warming, largely due to human activity.

It also follows a similar finding from last summer by the same research group that showed no increase in precipitation over Antarctica in the last 50 years. Most models predict that both precipitation and temperature will increase over Antarctica with a warming of the planet.

David Bromwich, professor of geography and researcher with the Byrd Polar Research Center at Ohio State University, reported on this work at the annual meeting of the American Association for the Advancement of Science at San Francisco.

“It’s hard to see a global warming signal from the mainland of Antarctica right now,” he said. “Part of the reason is that there is a lot of variability there. It’s very hard in these polar latitudes to demonstrate a global warming signal. This is in marked contrast to the northern tip of the Antarctic Peninsula that is one of the most rapidly warming parts of the Earth.”

Bromwich says that the problem rises from several complications. The continent is vast, as large as the United States and Mexico combined. Only a small amount of detailed data is available – there are perhaps only 100 weather stations on that continent compared to the thousands spread across the U.S. and Europe. And the records that we have only date back a half-century.

“The best we can say right now is that the climate models are somewhat inconsistent with the evidence that we have for the last 50 years from continental Antarctica.

“We’re looking for a small signal that represents the impact of human activity and it is hard to find it at the moment,” he said.

Last year, Bromwich’s research group reported in the journal Science that Antarctic snowfall hadn’t increased in the last 50 years. “What we see now is that the temperature regime is broadly similar to what we saw before with snowfall. In the last decade or so, both have gone down,” he said.

In addition to the new temperature records and earlier precipitation records, Bromwich’s team also looked at the behavior of the circumpolar westerlies, the broad system of winds that surround the Antarctic continent.

“The westerlies have intensified over the last four decades of so, increasing in strength by as much as perhaps 10 to 20 percent,” he said. “This is a huge amount of ocean north of Antarctica and we’re only now understanding just how important the winds are for things like mixing in the Southern Ocean.” The ocean mixing both dissipates heat and absorbs carbon dioxide, one of the key greenhouse gases linked to global warming.

Some researchers are suggesting that the strengthening of the westerlies may be playing a role in the collapse of ice shelves along the Antarctic Peninsula.

“The peninsula is the most northern point of Antarctica and it sticks out into the westerlies,” Bromwich says. “If there is an increase in the westerly winds, it will have a warming impact on that part of the continent, thus helping to break up the ice shelves, he said.

“Farther south, the impact would be modest, or even non-existent.”

Bromwich said that the increase in the ozone hole above the central Antarctic continent may also be affecting temperatures on the mainland. “If you have less ozone, there’s less absorption of the ultraviolet light and the stratosphere doesn’t warm as much.”

That would mean that winter-like conditions would remain later in the spring than normal, lowering temperatures.

“In some sense, we might have competing effects going on in Antarctica where there is low-level CO2 warming but that may be swamped by the effects of ozone depletion,” he said. “The year 2006 was the all-time maximum for ozone depletion over the Antarctic.”

Bromwich said the disagreement between climate model predictions and the snowfall and temperature records doesn’t necessarily mean that the models are wrong.

“It isn’t surprising that these models are not doing as well in these remote parts of the world. These are global models and shouldn’t be expected to be equally exact for all locations,” he said.

Source: Ohio State University

Explore further: Polar tourists see an icy world melt

Related Stories

Polar tourists see an icy world melt

November 26, 2015

They go to paddle between glistening icebergs or ski on blinding white ice, but a rising number of polar tourists get to see something else, too: the monumental changes wrought by global warming.

Climate is changing fast in West Antarctica

November 23, 2015

When the ship pulls up at Palmer Station each Antarctic spring, the arriving scientists glance up at the massive glacier that covers most of Anvers Island. It has been retreating about 7 meters per year, and this year is ...

Recommended for you

Don't forget plankton in climate change models, says study

November 26, 2015

A new study from the University of Exeter, published in the journal Ecology Letters, found that phytoplankton - microscopic water-borne plants - can rapidly evolve tolerance to elevated water temperatures. Globally, phytoplankton ...

Can Paris pledges avert severe climate change?

November 26, 2015

More than 190 countries are meeting in Paris next week to create a durable framework for addressing climate change and to implement a process to reduce greenhouse gases over time. A key part of this agreement would be the ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.