Dr. Spencer Weart

Dr. Weart will discuss Global Warming.

The story in a nutshell: From ancient times people suspected that human activity could change the climate. For example, in the 19th century many Americans believed that cutting down forests brought more rainfall to a region. The discovery of ice ages in the distant past proved that climate could change all by itself, and radically. But what caused these changes — was it variations in the heat of the Sun? Volcanoes erupting clouds of smoke? The raising and lowering of mountain ranges, which diverted wind patterns and ocean currents? Or could it be changes in the composition of the air itself?