the publication of Volume 100 of Climatic Change

In order to mark the 100th volume of Climatic Change, I will go back to the time of the first issue of Climatic Change, in 1977, and outline the state of knowledge concerning the climate science of global warming and of potential impacts such as existed at that time. I will argue that the science then concerning the climatic consequences of anthropogenic CO2 emissions was sufficient to have justified what could, at the time, have been regarded as “precautionary ” action. In the 33 years since the first issue of Climatic Change, the climate science has become substantially stronger, we have began to see happening what were mere predictions when the first issue of Climatic Change was published, and we have come to realize that the ecological and social consequences of the projected future warming will be worse than thought even 10 years ago. Action now to restrain and then reduce emissions of CO2 and other greenhouse gas can therefore no longer be regarded as “precautionary”. An appropriate term for what are still, unfortunately, only hypothetical emission reductions would be “reactive”, as action at this late date will merely serve to reduce the magnitude of harm that we now clearly face