Scientists for the United Nations Intergovernmental Panel on Climate Change, or IPCC, say the group's latest findings on global warming show rapidly increasing carbon dioxide emissions and quickly shrinking Arctic ice.  To compound matters, a separate study released on Wednesday finds that the melting of polar ice is more severe than previously thought. 

The Chairman of the IPCC, RK Pachauri, said 11 of the last 12 years were among the warmest for global surface temperature in recorded history.  Pachauri testified before the Senate Committee on Environment and Public Works on the IPCC's latest  findings on global warming.

He said climate change will impact some parts of the world more severely than others.

"In Africa, for instance, by 2020 our projections show that 75 to 250 million people would be affected by water stress on account of climate change, and crop revenues could drop very rapidly," said R.K. Pachauri. "We are really causing major distortions and disparities in economic development and growth throughout the world."

Pachauri's testimony coincided with another study by the U.N.-backed International Polar Year program, which found that icecaps at both the North and South Poles are melting at unprecedented rate.  The report, compiled by scientists from more than 60 countries, also says that the shrinking of polar and Greenland ice is fueling a rise in sea levels and the potential for dramatic changes in the global climate system.

The authors say the Arctic permafrost also reveals larger amounts of carbon than expected that, with further melting, could release more greenhouse gasses into the atmosphere.

Christopher Field, a contributor to the IPCC report, told the Senate Committee that temperatures at the South Pole are rising faster than expected.

"Just within the last few months we've seen confirmation that the continent of Antarctica has been warming," he said. "And it's been warming at a rate of almost 0.2 degrees Fahrenheit per decade, comparable in pace to much of the rest of the Southern Hemisphere."

Pachauri and Field say the costs of mitigating human generated carbon dioxide, or CO2, emissions are modest compared to the costs of doing nothing.  Field adds that the U.N.'s Intergovernmental Panel on Climate Change says if CO2 levels are left unchecked, the earth's temperature could rise several degrees by the end of the century.

Scientists who are skeptical of the severity of global warming contend that there is no way to measure the impact of human activity on climate and that no one knows how much warming will occur or how it might affect the earth.  Some experts suggest that global warming may be part of natural climate cycles that humans can do little about.