An Echo Chamber of Climate Change Denial
by Bob Ward, Policy and Communications Director, Grantham Research Institute on Climate Change and the Environment, Huffington Post, August 4, 2011
To understand this paper, you have to understand the difference between a 'forcing' and a 'feedback'. Forcings are imposed changes to the climate, while feedbacks are processes that respond to changes in the climate and amplify or ameliorate them. So the addition of carbon dioxide to the atmosphere by humans is a forcing - it is simply an imposition on the climate. Water vapour, on the other hand, is a feedback because the amount of water vapour is set by the surface temperature of the planet. As the planet warms, you get more water vapour in the atmosphere, and since water vapour is itself a greenhouse gas, this leads to additional warming.