Abstract
The problem of determining the causes of climatic change is outlined and some possible causes are suggested. The effect on climate of changes in the CO2 concentration and in the particulate content of the atmosphere are discussed with reference to the physical and statistical/historical data. The possible effects on climate of sunspots, the Milankovitch effect and long-term solar variability are also discussed and it is concluded that vulcanism and the Milankovitch effect were the two major causes of climatic change in the pre-industrial era. Industrial pollution both cools the climate by increasing the particulate content of the atmosphere and warms it by increasing the CO2 concentration. It is uncertain which of these two is the larger effect.