These skeptics aren't run of the mill pseudo-scientists or scientists commenting upon an issue outside their field of expertise. These are climatologists, meteorologists, geologist, solar astronomers, paleontologists, environmental chemists, and a host of others from a number of related scientific disciplines weighing in on the issue.
Quotes from just a few of the 650 scientists expressing skepticism about AGW, including some formerly supporters of the AGW theories:
“I am a skeptic…Global warming has become a new religion.” - Nobel Prize Winner for Physics, Ivar Giaever.
“Since I am no longer affiliated with any organization nor receiving any funding, I can speak quite frankly….As a scientist I remain skeptical...The main basis of the claim that man’s release of greenhouse gases is the cause of the warming is based almost entirely upon climate models. We all know the frailty of models concerning the air-surface system.” - Atmospheric Scientist Dr. Joanne Simpson, the first woman in the world to receive a PhD in meteorology, and formerly of NASA, who has authored more than 190 studies and has been called “among the most preeminent scientists of the last 100 years.”
Warming fears are the “worst scientific scandal in the history…When people come to know what the truth is, they will feel deceived by science and scientists.” - UN IPCC Japanese Scientist Dr. Kiminori Itoh, an award-winning PhD environmental physical chemist.
“The IPCC has actually become a closed circuit; it doesn’t listen to others. It doesn’t have open minds… I am really amazed that the Nobel Peace Prize has been given on scientifically incorrect conclusions by people who are not geologists.” - Indian geologist Dr. Arun D. Ahluwalia at Punjab University and a board member of the UN-supported International Year of the Planet
“Anyone who claims that the debate is over and the conclusions are firm has a fundamentally unscientific approach to one of the most momentous issues of our time.”- Solar physicist Dr. Pal Brekke, senior advisor to the Norwegian Space Centre in Oslo. Brekke has published more than 40 peer-reviewed scientific articles on the sun and solar interaction with the Earth.
“It is a blatant lie put forth in the media that makes it seem there is only a fringe of scientists who don’t buy into anthropogenic global warming.” - U.S Government Atmospheric Scientist Stanley B. Goldenberg of the Hurricane Research Division of NOAA.
“The Kyoto theorists have put the cart before the horse. It is global warming that triggers higher levels of carbon dioxide in the atmosphere, not the other way round…A large number of critical documents submitted at the 1995 U.N. conference in Madrid vanished without a trace. As a result, the discussion was one-sided and heavily biased, and the U.N. declared global warming to be a scientific fact,” Andrei Kapitsa, a Russian geographer and Antarctic ice core researcher.
“Gore prompted me to start delving into the science again and I quickly found myself solidly in the skeptic camp…Climate models can at best be useful for explaining climate changes after the fact.” - Meteorologist Hajo Smit of Holland, who reversed his belief in man-made warming to become a skeptic, is a former member of the Dutch UN IPCC committee.
“All those urging action to curb global warming need to take off the blinkers and give some thought to what we should do if we are facing global cooling instead.” - Geophysicist Dr. Phil Chapman, an astronautical engineer and former NASA astronaut, served as staff physicist at MIT (Massachusetts Institute of Technology)
More information can be found in the full minority report which can be downloaded as a PDF.
There's plenty of rebuttal that can be viewed, such as this post on the New York Times Dot Earth blog.
Andrew Revkin supports that AGW is a fact, claims of the skeptics to the contrary, and that something must be done now to forestall the catastrophic effects of AGW. The comments are telling, with those trying to open the debate being labeled as “mindless contrarians”, “denialists, “distractors”, “delayers”, “crybabies”, “lowly”, “vulgar”, and “stupid”. So much for open discourse. Read the comments to the to post and you'll see what I mean. Far too many of those dismissing the skeptics out of hand appear to be letting emotion rule their opinions rather than data, evidence, a actual debate. That's never a good sign.