Penguins

Around 18,000 years ago, as the earth emerged from the Pleistocene Ice Age, the earth's climate began changing. Global temperatures have risen, glaciers have melted and ecosystems around the world have been altered.

By the start of the 20th Century, millions of tons of greenhouse gases have been released into the atmosphere, primarily carbon dioxide and methane. Carbon dioxide builds up from fossil fuels, industry, and transport.

According to the National Academy of Sciences, in the past century the Earth's surface temperature has risen about 1Ð'o F in the past century. There is strong evidence attributing human activities for the warming over the last 50 years. Such activities have altered the atmosphere through the buildup of greenhouse gases.

The polar ice caps are an area of concern due to the rising temperatures. Global warming could cause the Antarctic ice sheet and the Greenland ice cap to gradually melt away, eventually raising sea levels by up to 30 feet, according to a report given by the German Advisory Council on Global Change.

Raising sea levels would submerge vast areas of land and key cities worldwide. New York, Miami, London and Tokyo would be among those largely submerged.

Today, global warming is a hot topic in our world. Government officials, business leaders, environmental activists, concerned scientists and citizens worldwide are acting fast to combat climate change.

Curt Davis, croft professor of electrical and computer engineering, said snowfall-driven growth in the Antarctic ice sheet is a cause for recent sea-level rise. Davis believes global warming has a direct effect on rising sea level.

Anthony Lupo, associate professor of atmospheric sciences at the University of Missouri, believes global warming has increased temperatures in the Arctic, but not to a substantial level. There are not a lot of people who agree with what Lupo said, "global warming is no big deal."

New York Attorney General Eliot Spitzer warned, "global warming threatens our health, our economy, our natural resources, and our children's future. It is clear we must act."

An international team of scientists, who reported their findings in the journal Science, have been using satellite radar measurements on the Antarctic ice sheet to seek evidence for ice sheet melting. The scientists and Lupo agree that global warming is occurring, but they all suggest that it is not having an effect on the Antarctic ice sheet.

"The west Antarctic ice sheet is not melting rapidly, is reasonably stable and has been so for more than a century", said the international team of scientists. C.K. Shum, an associate professor of civil and environmental engineering and geodetic science at Ohio State University, said based on our short, five-year period of observation of the interior of Antarctica, we do not detect the ice to be melting more than one centimeter per year.

"That would mean that the interior Antarctic ice sheet does not seem to be contributing to sea level rise more than 1 millimeter per year," said Shum. A one-centimeter decrease in Antarctic ice sheet volume roughly converts into a one-millimeter rise in global sea level, said Shum.

Curt Davis, of the University of Missouri, disagrees with Shum's and Lupo's findings that the polar ice caps are not melting away.

Davis is all about the facts and his studies are the most recent observation-based estimate of Antarctica's effect on sea level. During his studies, Davis found that the Antarctic ice sheet gained about 45 billion metric tons a year.

Global warming would lead to an increase in snow fall over the Antarctic, because warmer air leads to more evaporation and precipitation, researchers said in a report in the journal Science.

Snowfall over Antarctica will decrease indefinitely due to a warming world, but the rising temperatures will begin to melt the ice, Davis said. "Since sea levels are rising, that would be a reasonable assumption to make, although we don't know for sure," added Davis.

There is no direct evidence that links global warming to the rising sea levels. Yet, Antarctica is seeing a rise in temperatures and a decrease in its overall mass.

Antarctica is the world's largest store of ice. The west Antarctic ice sheet is much drier than the east Antarctic ice sheet, which is below sea level. Changes in the east Antarctic sheet would not affect sea levels as much.