It isn't surprising that he would wait until his retirement to announce this. The professional consequences of being a denier can be serious with calls for more severe action. Such luminaries as Al Gore and Hansen have called for war crimes trials for skeptics and polluters.
So what does Theon really think?
My own belief concerning anthropogenic climate change is that the models do not realistically simulate the climate system because there are many very important sub-grid scale processes that the models either replicate poorly or completely omit. Furthermore, some scientists have manipulated the observed data to justify their model results. In doing so, they neither explain what they have modified in the observations, nor explain how they did it.Note - the part about manipulating the data is a direct dig at Hansen who has been adjusting actual temperature measurements going back decades but refuses to document his methodology.
They have resisted making their work transparent so that it can be replicated independently by other scientists. This is clearly contrary to how science should be done. Thus there is no rational justification for using climate model forecasts to determine public policy.
Theon is not the first scientist to wait until retirement to announce skepticism. While it is fashionable to look for links between skeptics and oil companies, billions of dollars in grants are available for climate research but only if you are a believer.
In the meantime, Hansen's letter to President Obama has been published. Among other things, Hansen calls for a carbon tax and for closing all coal-fired power plants. Obama is moving on allowing states to set CO2 emissions standards and Secretary of State Clinton has appointed a new envoy to the follow-up talks to the Kyoto treaty.
We are about to put our automobile makers out of business, raise the price of food, and start rolling brownouts over fraudulent science.