In the American Thinker, James Lewis comments on a News-of-the-Week feature in Science, the official journal of the American Association for the Advancement of Science.
The Science news item, Another Global Warming Icon Comes Under Attack, notes that "mainstream atmospheric scientists" are disputing the reliability of the computer models used to predict future warming, and " researchers are giving some ground."
The Intergovernmental Panel on Climate Change, a United Nations committee, has produced a series of reports that have become a Holy Bible of sorts for the global warming alarmists. The reports contain an analysis of current computer global climate models.
The latest IPCC report averaged the results of 14 different computer models and compared the numbers to actual temperature readings throughout the last century. While there is a fair match between actual temperatures and some of the computer predictions, there are uncertainties factor unaccounted for in the IPCC's analysis.
Science's James Kerr writes, "Greenhouse gas changes are well known... but not so the counteracting cooling of pollutant hazes, called aerosols. Aerosols cool the planet by reflecting away sunlight and increasing the reflectivity of clouds. Somehow... modelers failed to draw on all the uncertainty inherent in aerosols so that the 20th-century simulations look more certain than they should."
Bottom line: Aerosols cool the earth. It is uncertain exactly how much they cool the earth. Climate models make predictions which are used to scare the public about global warming. However, the models do not account for the large uncertainty in the amount of cooling from aerosols, including clouds.
The warming effects of greenhouse gases are said to be well-understood and are widely reported. The cooling effects of aerosols are poorly understood, hardly ever reported, and this is not fully explained in the United Nations' official IPCC reports on climate change. What is wrong with this picture?
How can we make rational decisions about public policy when one of the major factors affecting global cooling is not well-understood and not properly taken into account in predictions of climate warming? The answer, obviously, is that we can't.
This new analysis is extremely important, and will be dealt with in one or more future installments on the Global Warming Swindle blog.
NOTE: What are aerosols? "Aerosols are tiny particles suspended in the air. Some occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels and the alteration of natural surface cover, also generate aerosols." (from http://earthobservatory.nasa.gov/Library/Aerosols) Aerosols play an important part in cloud formation. Clouds exert a cooling effect by reflecting solar radiation back into space.
Man can produce greenhouse gases which warm the planet, and he also produces aerosols which lead to cooling. However, in both cases, man's contributions are less a factor in earth's temperature than nature itself, especially solar activity.