One of the world's greatest scientists, Richard Feynman said (The Meaning of it All, 1999):
The exception proves that the rule is wrong. That is the principle of science. If there is an exception to any rule, and if it can be proved by observation, that rule is wrong.
The dominant argument for AGW contradicts Feynman's "principle of science". This dominant argument is that a majority of scientists, a consensus, support it. There are many recent papers which are "exceptions" to AGW; any one of these papers satisfies Feynman's principle that a consensus is defeated by just one bit of evidence.
AGW is the increase in global average temperature [GAT]. AGW relies on 2 processes to cause this increase in GAT; forcings and feedbacks.
A forcing is a factor external to or introduced to the climate system which affects the radiative balance at the Tropopause, the boundary between the Troposphere and the Stratosphere. The IPCC recognises 2 main types of forcings; greenhouse gases, the most dominant one being CO2, and solar radiation. A feedback is a change in another quantity in the climate system as a response to a change in a forcing. The IPCC assumes that an increase in forcing from an increase in anthropogenic CO2 causes a feedback by an increase in water vapour [AR4, FAQ 1.3]. This process is measured by the change in GAT.
The following papers clarify AGW's uncertainty between forcings and feedbacks and show that AGW science is not clear about the distinction or effects. The papers show the IPCC assumptions about the role of CO2 and water vapor, particularly in the form of clouds, are incorrect and that the IPCC conclusions about GAT are both exaggerated and wrong. In doing so, these papers also vindicate Feynman's principle.
If global warming is going to happen it will be due to feedbacks. If the feedbacks are positive it means that as the world warms, atmospheric conditions would have to change to keep even more of the sun's energy inside our system. But Richard Lindzen and Yong-Sang Choi show that as the world warms Earth's dynamic system changes to let more of the infra red or long-wave energy out to space. It's like a safety release valve. This means that the system has negative feedbacks (like almost all known natural systems). The changes dampen the effects of extra CO2. If there is no net amplifying positive feedback there is no catastrophe. Because Lindzen & Choi are looking at long-wave radiation leaving the planet, this is a way of assessing all forms of feedbacks at once. They don't isolate which part of the system is responsible: clouds, humidity, ice-cover or vegetation, but we know the net effect of all of them together is that when the world warms, more energy escapes from the planet.
2 Spencer and Braswell
Spencer & Braswell's papers in 2008, 2010 and 2011 took a different approach to Lindzen & Choi. Spencer & Braswell looked more closely at the nature of feedbacks and forcings and the difficulty of putting a value on feedbacks. The IPCC models assume that clouds change in response to GAT, so they are a "feedback" [AR4, WG1, 22.214.171.124]. But as Spencer & Braswell show in their papers clouds can be a forcing factor as well. This means that if something other than temperature affects cloud cover (like changes in ocean currents or air circulation) the change in clouds would then force the GAT to change in the opposite direction.
Spencer and Braswell found that the forcing and feedback effect of clouds on GAT are both negative to increases in GAT.
Anthony Cox is a lawyer and secretary of The Climate Sceptics.
Joanne Nova wrote The Skeptics Handbook, 160,000 copies of which have been distributed in four nations and translated by volunteers into six languages. She's a freelance writer, blogger and also an analyst for The Science and Public Policy Institute in the USA. She was a prize winning graduate of molecular biology, and a former associate lecturer in Science Communication at the ANU. Her new blog, JoNova, has reached 140,000 people already this year with over 400,000 page views and 6000 comments. She has spoken about climate science communication in New York and to Senate Staffers in Washington, and attended the UNFCCC in Bali, 2007. Joanne has done over 200 radio interviews, and hosted a science series for children on Channel Nine.