The United States has thus far refused to sign the Kyoto Protocol, a treaty that requires countries to cut emissions of carbon dioxide and other greenhouse gasses — the primary causes of global warming.

The United States, which is the world’s top polluter, contributing almost 25 percent of the world’s total emissions, and Australia, are the only countries that have not signed. The treaty, which opened for signatures in 1998, became legally binding on Feb. 16, after Russia’s ratification pushed the treaty over the 55 percent greenhouse gas emissions mark — the target percentage for the treaty to go into effect.

While President George W. Bush has not signed the Kyoto Protocol, he has, however, pushed for the Clear Skies Act, which has yet to be passed. The act is designed to reduce sulfur dioxide, mercury, and nitrogen oxides emissions.

“All the measures help in a small way,” said Brenda Ekwurzel, a climate scientist for the Union of Concerned Scientists. “But they don’t go far enough. Every method we have at our disposal, we need to put to use.”

The Clear Skies Act has also come into criticism from environmental groups who argue the act is less restrictive than its predecessor.

Ekwurzel said perhaps the biggest contributors to the emissions are automobiles, especially those that get poor gas mileage.

Global warming is a problem that arose in the late 1800s after the industrial revolution, during which time people began to burn fossil fuels, such as coal and oil, for industrial purposes. The burning of these materials increases levels of greenhouse gases, such as carbon dioxide, methane, the bad kind of ozone and nitrous oxide, released into the atmosphere, which traps heat.

Carbon dioxide levels have increased by 30 percent, and the average temperature has increased by approximately two degrees over the past 100 years, both of which are contributing factors to global warming, said Helen Cox, assistant geography professor at CSUN.

However, she said there is no proof that global warming has contributed to changes in actual weather patterns.

“(Global warming) is serious,” Cox said. “Once you increase emissions, it stays in the air for a long time.”

Ekwurzel said emissions can remain in the air anywhere from 50 to 200 years, and the molecules they are made of can float around for 1,000 years.

One of the problems repeatedly attributed to global warming is increased temperature, which has led to the melting of polar ice caps. This can lead to increase in sea levels, causing coastal erosion, and can also pose severe flooding threats to coastal areas at or close to sea level.

“Entire cities can be wiped out (by the potential flooding)” said Cox, who added that Florida, Amsterdam and London are three of the areas at highest risk. However, this is something that is not likely to happen for at least another century. Louisiana is also at risk because it has been sinking progressively due to the unstable and not completely solid land it sits on.

Over the past 50 years, in icy regions such as Alaska, the equivalent of 450 cubic kilometers of water has been melted from the ice caps. If spread out one foot deep, that is enough water to cover California, Nevada, Arizona, New Mexico, Utah and Colorado. Over the past 30 years, sea ice has decreased by between 16 and 20 percent, Ekwurzel said.

Some animals are also at risk for extinction, such as polar bears, whose diets consist almost entirely of ringed seals. The seals are completely dependent on sea ice for their survival, Ekwurzel said.

The increase in heat could also threaten areas that are good for agriculture, which would put more of a burden on the water supply, Cox said.