Human activities contribute to climate change by causing changes in the atmosphere in the amount of greenhouse gases, aerosols and cloud cover. The largest known contribution comes from the burning of fossil fuels, which release significant amounts of carbon dioxide into the atmosphere. Greenhouse gases and aerosols influence the climate by altering the incoming solar radiation and outgoing infrared radiation that are part of the earth's energy balance. Changing the atmospheric abundance or properties of these gases and particles can lead to a warming or cooling of the climate system. The accumulation of greenhouse gases in the atmosphere has led to an increase in the natural greenhouse effect. It is precisely this increase in the human-induced greenhouse effect that is of concern due to the continued emissions of greenhouse gases that have the potential to warm the planet's climate to levels never experienced in the history of human civilization. Such climate changes represent an important issue for environmental concern in terms of the potentially dangerous effects they will have on the ecosystem...