Dr. Howard D. Greyber wrote a letter to the (liberal) International Herald Tribune that is probably the best, very short summary of the global warming issue that I've seen. Here it is:

"When Thomas Friedman touts carbon dioxide as the cause of global warming in his column 'Doha and Dalian' (Sept. 20), I respond as a physicist that he cannot comprehend that it is still not proven that carbon dioxide emissions actually are causing global warming. Correlation does not prove Causation.

The Earth's climate changes all the time. Did carbon dioxide emissions cause the Medieval Warm Period, when Vikings raised crops on Greenland's coast? What caused the cold climate from 1700 to 1850? In 1975, articles were published predicting we were entering a New Ice Age.

Reputable scientists oppose this unwarranted alarmist hysteria. If fanatic leftists who hate America's progressive capitalistic system had not opposed the building of nuclear power plants by wild allegations and interminable lawsuits, the United States could have built dozens of safe, modern reactors. These provide plentiful, reliable energy and, incidentally, emit zero carbon dioxide.

Understanding climate change is an extremely difficult scientific problem. Giant computers generating climate models cannot be trusted so far. As any computer person knows, garbage in means garbage out. If research suggests subtle variations in our Sun's radiation reaching Earth are causing global climate change, what would Friedman recommend?"

Brilliant.