Mankind's impact on climate: The evolution of an awareness
The first inklings of an understanding of the role played by infraredabsorbing gases in maintaining the warmth of the surface of our planet were voiced early in the 19th century, and by the turn of this century quantitative calculations had been carried out that demonstrated how a change in atmospheric carbon dioxide would alter the earth's mean temperature. However, it was not until the 1960s that much attention was paid to this matter, and in the early 1970s two important summer studies dealing with environmental change fired the imagination of the scientific community. Since then the science (or art) of modeling the climate system has made great strides, aided by faster computers, greater knowledge of the factors involved, and global observations from space of the atmosphere, oceans, and biosphere. This effort has also been bolstered by studies of the behavior of the climate system in the past. There is now a strong consensus that the observed increase in the atmospheric concentrations of carbon dioxide and other infrared-absorbing trace gases is indeed warming the earth, and that this change is caused by mankind. The next set of questions are now being seriously addressed in national and international forums: what are the regional patterns of the changes to be anticipated, especially in terms of rainfall and soil moisture? And what should the countries of the world do about the situation? There is already a sharp debate between the activists, who would take action worldwide to avoid the climate change (or at least slow its advance), and those who would simply wait and see what happens and perhaps take what local measures are necessary to mitigate the effects.