H umanity and climate are interconnected. A prehistoric climate shift that turned moist forests into dry savannas in Africa may have sparked the evolutionary shift to upright walking. 2 Rainfall, temperature and sea level have always governed where people live, trade and grow their food.
People also influence climate, defined as the prevailing or average pattern of weather.
And as we approach a new millennium the growing scale of human activity threatens to raise global average temperatures through the emission of gases that amplify the greenhouse effect, which traps solar heat in the lower atmosphere. The physical laws governing the greenhouse effect are well understood, and there is no question the atmosphere's capacity for trapping heat is growing stronger as a result of human activities. Nonetheless, to consider how changes in human population could influence climate change is to bring together two of the most controversial environmental topics. The word population is not even mentioned in the Framework Convention on Climate Change, an international treaty ratified by 57 countries that went into effect in March 1994. This is perhaps not surprising.