Global climate models have overstated warming in Antarctica

Washington, May 8 : A new research by scientists at the National Center for Atmospheric Research (NCAR) and Ohio State University has determined that computer analyses of global climate have consistently overstated warming in Antarctica.

The study marks the first time that scientists have been able to compare records of the past 50 to 100 years of Antarctic climate with simulations run on computer models. he researchers have used atmospheric observations to confirm that computer models are accurately simulating climate for the other six continents. The models, which are mathematical representations of Earth's climate system, are a primary method for scientists to project future climate.

"We can now compare computer simulations with observations of actual climate trends in Antarctica," said NCAR scientist Andrew Monaghan, the lead author of the study. This is showing us that, over the past century, most of Antarctica has not undergone the fairly dramatic warming that has affected the rest of the globe," he added.

The research team recently constructed temperature data sets from Antarctica, based on data from ice cores and ground weather stations, to 20th century simulations from computer models used by scientists to simulate global climate.

While the observed Antarctic temperatures rose by about 0.4 degrees Fahrenheit (0.2 degrees Celsius) over the past century, the climate models simulated increases in Antarctic temperatures during the same period of 1.4 degrees F (0.75 degrees C).

The error appeared to be caused by models overestimating the amount of water vapor in the Antarctic atmosphere, the new study concludes.

The reason may have to do with the cold Antarctic atmosphere handling moisture differently than the atmosphere over warmer regions.

That's why the researchers caution that model projections of future Antarctic climate may be unreliable.

"The current generation of climate models has improved over previous generations, but still leaves Antarctic surface temperature projections for the 21st century with a high degree of uncertainty," said NCAR scientist David Schneider.

"On a positive note, this study points out that water vapor appears to be the key cause of the problematic Antarctic temperature trends in the models, which will guide scientists as they work to improve the climate simulations," he added.

Part of the reason that Antarctica has barely warmed has to do with the ozone hole over the continent.

The lack of ozone is chilling the middle and upper atmosphere, altering wind patterns in a way that keeps comparatively warm air from reaching the surface.

The study can help scientists improve computer models and determine if Earth's southernmost continent will warm significantly this century, a major research question because of Antarctica's potential impact on global sea-level rise.

ANI