March 28 (UPI) -- The Intergovernmental Panel on Climate Change reports what they call new and stronger evidence to support the conclusion that humans are contributing to global warming.

 "Studies consistently find evidence for an anthropogenic signal (human-caused effect) in the climate record of the last 35 to 50 years," the Geneva, Switzerland-based consortium of climate experts concluded. It is an established scientific principle that heat from the sun is trapped on Earth by gases in the atmosphere, similar to what happens in a glass-enclosed greenhouse.

 Documented increases in global temperature and greenhouse gases coincide with the increased use of fossil fuels such as coal, natural gas, gasoline and fuel oil. In the last 30 years, worldwide annual emissions of carbon dioxide, the gas that makes the greatest contribution to global warming, have increased 61 percent, to about 6 billion tons per year. Experts predict a pattern of increasing emissions.

 The United States Department of Energy projects the following annual data for 2020:

 -- worldwide energy use twice what it is today;
 -- worldwide CO2 emissions to rise by 63 percent
 -- carbon dioxide emissions from Asia to increase approximately 80 percent, to 3.8 billion tons;
 -- U.S. emissions to increase about 30 percent, to 2.3 billion tons, 23 percent of the projected world total.

Observations of how much heat is escaping Earth, using spectrographic data gathered by satellites, were recently published in the journal Nature. Scientists at the Space and Atmospheric Physics Group at Imperial College in London reported obtaining "direct experimental evidence for a significant increase in the Earth's greenhouse effect."

 Helen Brindley, an atmospheric physicist and one of the lead authors, told United Press International, "You see a reduction in the amount of outgoing longwave radiation, a reduction in the amount of energy that's escaping to space."

 Jerry Mahlman, a climate specialist who recently retired from the National Oceanic and Atmospheric Administration, told UPI, "The consensus now on global warming is very strong. There's lots of people, including many from industry, saying, 'Look, you can't fight this.'"

"The catch is that the really bad stuff happens maybe a century from now. And of course today's mentality is, 'Who gives a damn about a century from now?,'" added Mahlman, who was director of NOAA's geophysical fluid dynamics laboratory.

"There is now strong evidence that particularly the warming of the last 30or 40 years is associated with anthropogenic activity," said Peter Stone, professor of climate dynamics at Massachusetts Institute of Technology, Cambridge. "Most scientists in the field would agree that there is a problem worth worrying about."

However, Stone added, prediction uncertainties still exist, particularly in computer models for climate projections as well as in economic uncertainties about what energy use in the future will look like. For example, "cloud changes are a major uncertainty," he said. "Nobody has really put it all together to come up with some overall understanding how clouds might affect warming going into the future." The IPCC believes the signal of human contribution to global warming has emerged. Stone shares the view. "We are seeing the signal in the temperature patterns," he said.

For those who don't see the signal yet, Russ Schnell, director of NOAA's meteorological baseline observatory operations for more than 40 stations around the world, told UPI, "When the snow line recedes from all the mountains in Colorado and there's no more skiing, then they'll see the signal. To some people, that's what it'll be."

The IPCC report, titled "Climate Change 2001: The Scientific Basis,"states the following:

 -- Earth's temperature in the last 100 years has increased by about 0.6degrees Celsius (1 degree Fahrenheit).
-- The temperature increase during the 20th century was likely (probability of 66 percent to 90 percent) the greatest in 1,000 years.
 -- Since the 1960s, global snow cover has decreased by about 10 percent and many rivers and lakes have about two weeks less of ice.
 -- Analysis of ice-core samples going back 1,000 years show greenhouse gases carbon dioxide, methane, nitrous oxide and sulfates at constant levels until the beginning of the industrial revolution, when the heavy use of fossil fuels began.
 -- Since 1800, the gas increases have been: carbon dioxide 32 percent, methane 130 percent, nitrous oxide 15 percent, sulfates about 200 percent. Carbon dioxide in the atmosphere has increased from 280 parts per million to370 ppm.

The IPCC reports states, "The present carbon dioxide concentration has not been exceeded in the past 420,000 years and likely (66 to 90 percent) not during the past 20 million years. The current rate of increase is unprecedented during at least the past 20,000 years."

About three-quarters of the human contribution to carbon dioxide increasing the last 20 years is due to the burning of fossil fuels and the remainder due to the burning of forests.

The IPCC projects that carbon dioxide levels in the atmosphere will go higher and probably double in the next 100 years, barring some radical change in fossil fuel use. It presents a range of estimates of future global temperature increases, using six different global models with varying social, industrial and energy scenarios. The predicted range of global temperature increase is from 1.3 to 5.8 degrees Celsius (2.3 to 10.4 degrees Fahrenheit) with a cumulative average of about 3 degrees Celsius (5.4degrees Fahrenheit).

The IPCC report is the product of more than 3,000 experts and the report summary was approved by all of the more than 100 participating countries, Narasimhan Sundararaman, secretary of the IPCC, told UPI. The IPCC itself was established in 1988 by the World Meteorological Organization, a United Nations agency, and the U.N. Environmental Program.

Whenever experts disagreed on how likely or unlikely a conclusion was, issues were carefully discussed, Sundararaman said, adding, "On the issue of uncertainty there is usually a very lusty argument and then people come to an agreement on how to represent it."

The report summary is available on the Internet at www.ipcc.ch

.Copyright 2001 by United Press International.