What Do We Know About the Science of Climate Change? Climate science is extremely complex for three reasons, according to the climate scientists at our conference—Carl Wunsch (Professor of Oceanography at ), David Chapman (Professor of Geology and Geophysics at the University of Utah), William Gray (Professor Emeritus of Atmospheric Science at Colorado State) and Richard Lindzen (Professor of Meteorology at ). First, it is an immature science. The observational records cover a time period that is dwarfed by the relevant geologic time scales. Given the current state of understanding, accurate prediction is not possible. … [M]odern climate science relies on large, complicated models that seek to describe and predict the climate system, but these models are inherently unreliable and unstable. … Evidence abounds to suggest that  is far from the most important contributor to global warming. Previous interglacial periods were much warmer and had far lower concentrations of  in the atmosphere; and it might eventually be demonstrated that  concentrations lag temperature increases. When the temperature change is within a few tenths of a degree, it is difficult to identify the particular causes. … The ’s views on global warming are widely portrayed as representing an objective, scientific consensus, but David Henderson (a former chief economist at the , now at the University of Westminster, ) demonstrated that the  reporting process is flawed and lacks rigor, inclusiveness, and impartiality… . Environmental economist Ross McKitrick (University of Guelph, Ontario) affirmed Henderson’s analysis with an account of his own experience with the . … The challenge is not, ‘Either we believe in global warming and rescue the planet or we all die.’ It is largely a choice between how much action to take now and how much in the future; and a choice between preventing or adapting to it. The science is still young. Some people take uncertainty as a reason to act, others take it as a reason to proceed slowly. Future generations will have the benefit of greater scientific knowledge, better technology, and greater wealth… . . The range of views expressed at our conference suggests that the debate is far from being over, and that there is still time for much-needed rational discussion.