I have become increasingly concerned that EPA has itself paid too little attention to the science of global warming. EPA and others have tended to accept the findings reached by outside groups, particularly the IPCC and the CCSP, as being correct without a careful and critical examination of their conclusions and documentation. If they should be found to be incorrect at a later date, however, and EPA is found not to have made a really careful independent review of them before reaching its decisions on endangerment, it appears likely that it is EPA rather than these other groups that may be blamed for any errors. Restricting the source of inputs into the process to these these two sources may make EPA’s current task easier but it may come with enormous costs later if they should result in policies that may not be scientifically supportable. I do not maintain that I or anyone else have all the answers needed to take action now. Some of the conclusions reached in these comments may well be shown to be incorrect by future research. My conclusions do represent the best science in the sense of most closely corresponding to available observations that I currently know of, however, and are sufficiently at variance with those of the IPCC, CCSP, and the Draft TSD that I believe they support my increasing concern that EPA has not critically reviewed the findings by these other groups. As discussed in these comments, I believe my concerns and reservations are sufficiently important to warrant a serious review of the science by EPA before any attempt is made to reach conclusions on the subject of endangerment from GHGs. I believe that this review should start immediately and be a continuing effort as long as there is a serious possibility that EPA may be called upon to implement regulations designed to reduce global warming. The science has and undoubtedly will continue to change and EPA must have the capability to keep abreast of these changes if it is to successfully discharge its responsibilities. The Draft TSD suggests to me that we do not yet have that capability or that we have not used what we have. 2009