The computer at the National Center for Atmospheric Research projects that temperatures could rise by 2.6 degrees Celsius (4.7 degrees Fahrenheit) if countries continue to emit large amounts of carbon dioxide.

The previous estimates were a rise of about two degrees Celsiusdegrees Fahrenheit).

Information from the Community Climate System Model, known as CCSM3, will be presented to the Intergovernmental Panel On Climate Change, an international body of experts established by the United Nations to assess the environmental impact of climate change.

According to the US National Science Foundation (NSF), a variety of models in the past have been used to understand the effects of carbon dioxide, a common greenhouse gas emitted by cars and power plants.

Atmospheric levels of carbon dioxide have increased significantly in recent decades to about 370 million parts per million today and levels are continuing to rise.

If carbon dioxide emissions were to double, most scientific models agree that this would signifigantly increase global temperatures.

But, the models have been unable to produce consistent results in trying to determine the impact of other sources global warming, such as radiation from clouds or thunderstorms and the effect aerosol gases have on the environment.

Clifford Jacobs, an NSF scientist, said that with the new models "the degree of uncertainty has narrowed."

"We have a higher degree of confidence in these results than in the previous results."

Jacobs said scientists now hope their models will become sophisticated enough to predict how climate change will affect specific regions, such as in Africa or the American Midwest.

He hopes the scientific breakthrough will "better inform the ongoing debate" over global warming.

"The key question is: How much of the change is a natural variability and how much of the change is caused by activities of mankind on the face of planet," he said.

TERRA.WIRE