Claim 3. Carbon dioxide is important because it has a forcing effect on other factors such as water vapor which magnify warming effects.
Truth: Since the atmospheric absorption of CO2 is already near saturation, (see previous post), very little additional heating can take place due to increased CO2. Contrary to AGW advocates, increased water vapor from warming doesn’t stay as vapor to trap heat near the surface. It forms low altitude clouds that strongly reflect solar heat back out into space, overwhelming any trapped re-radiation from the Earth and having an overall cooling effect. The models, which assume water vapor remains as vapor, predict an atmospheric “hot spot” at middle altitudes. Weather balloons and satellites have failed to find this assumed hot spot, which is the signature of atmospheric forcing of global warming in computer models. Due to low altitude clouds reflecting sunlight back into space, any feedback is negative (cooling), not positive (warming) as assumed in computer models. For earlier posts, go to http:realscienceblog.com
Source of Figure: “The Skeptic’s Handbook” at http://www.Joannenova.com.au