Amid increasing evidence of global warming, scientists have pointed to thawing polar icecaps in Antarctica and rising sea levels that threaten to flood low-lying islands the world over as side effects of the planet heating up.

But new evidence from Antarctica published today in the journal Science indicates the thawing of at least one major ice field is a natural event that has little to do with global warming.

Aside from challenging accepted theories behind global warming, these findings illustrate the complexities that go along with predicting how the earth will react to high levels of carbon-fuel consumption and deforestation, supposedly the two main causes of global warming.

At issue is the West Antarctic Ice Sheet. This frozen wasteland measures 360,000 square miles, an area larger than Texas and Colorado combined. The WAIS is one of the largest ice sheets on the planet, and for that reason, it could have an enormous effect on sea levels worldwide.

Unlike any other ice sheet, the WAIS is anchored to land below sea level - what's known as a marine ice sheet. Because of its ocean exposure and position on the sea floor, scientists say it is potentially unstable and could be more affected by changes in sea level or ocean temperature than other ice fields.

Sure enough, the WAIS is changing faster than any other ice sheet. It has shrunk at a rate of about 400 feet per year during the past 7,600 years, according to the scientists.