(AFP) – Dec 15, 2007
WASHINGTON (AFP) — A small group of US experts stubbornly insist that, contrary to what the vast majority of their colleagues believe, humans may not be responsible for the warming of the planet Earth.
These experts believe that global warming is a natural phenomenon, and they point to reams of data they say support their assertions.
These conclusions are in sharp contradiction to those of the United Nations Intergovernmental Panel on Climate Change (IPCC), which reached its conclusions using largely similar data.
The UN body of about 3,000 experts, including several renowned US scientists, adopted a landmark report in mid-November stating that the evidence of a human role in the warming of the planet was now "unequivocal."
Retreating glaciers and loss of snow in Alpine regions, thinning Arctic summer sea ice and thawing permafrost shows that climate change is already on the march, the report said.
Carbon pollution, emitted especially by the burning of oil, gas and coal, traps heat from the Sun, thus warming the Earth's surface and inflicting changes to weather systems.
A group of US scientists however disagree, and have written an article on their views that is published in The International Journal of Climatology, a publication of Britain's Royal Meteorological Society.
"The observed pattern of warming, comparing surface and atmospheric temperature trends, doesn't show the characteristic fingerprint associated with greenhouse warming," wrote lead author David Douglas, a climate expert from the University of Rochester, in New York state.
"The inescapable conclusion is that human contribution is not significant and that observed increases in carbon dioxide and other greenhouse gases make only a negligible contribution to climate warming," Douglas wrote.
According to co-author John Christi from the University of Alabama, satellite data "and independent balloon data agree that the atmospheric warming trends do not exceed those of the surface," while greenhouse models "demand that atmospheric trend values be two to three times greater."
Data from satellite observations "suggest that greenhouse models ignore negative feedback produced by clouds and by water vapor, that diminish the warming effects" of human carbon dioxide emissions.
The journal authors "have good reason, therefore, to believe that current climate models greatly overestimate the effects of greenhouse gases."
For Fred Singer, a climatologist at the University of Virginia and another co-author, the current warming "trend is simply part of a natural cycle of climate warming and cooling that has been seen in ice cores, deep sea sediments and stalagmites . . . and published in hundreds of papers in peer reviewed journals."
How these cyclical climate take place is still unknown, but they "are most likely caused by variations in the solar wind and associated magnetic fields that affect the flux of cosmic rays incident on cloudiness, and thereby control the amount of sunlight reaching the earth's surface and thus the climate."
Singer said at a recent National Press Club meeting in Washington that there is still no definite proof that humans can produce climate change.
The available data is ambiguous, Singer said: global temperatures, for example, rose between 1900 and 1940, well before humans began to burn the enormous quantities of hydrocarbons they do today. Then they dropped between 1940 and 1975, when the use of oil and coal increased, he said.
Singer believes that other factors -- like variations of solar winds and terrestrial magnetic field that impact cloud formations and the amount of sunlight reaching the Earth's surface, and thus determining the temperature -- are much more influential than human-generated greenhouse gas emissions.
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