Ultimately, climate change is the result of a change in the balance between the solar energy trapped by the Earth and its atmosphere and the solar energy released into outer space. As this energy balance changes, so changes the climate.
The Earth’s atmosphere contains trace amounts of gases that absorb and emit long-wave radiation (heat). The “greenhouse gases” play a powerful role in maintaining the Earth’s energy balance. Greenhouse gases act like a blanket around the earth: by trapping heat they keep the planet some 30 degrees C (54 degrees Fahrenheit) warmer than it would be otherwise. Up to a certain point, this “greenhouse effect” is a very good thing. Indeed, without some greenhouse gases in the atmosphere, temperatures would plummet and life as we know it would cease to exist!
However, the Earth can definitely get too much of a good thing! Numerous human activities are making the atmospheric blanket “thicker”, trapping heat and raising the planet’s temperature. Prior to industrial revolution, for example, greenhouse gas levels in the atmosphere remained relatively constant over time. Since the mid-18th century, however, carbon dioxide levels in the atmosphere have risen by 30%, and are increasing at an average rate of 0.4% per year. Not surprisingly, in the last century the average global temperature rose by 0.6 degrees C (1.1 degrees Fahrenheit) and will continue to climb.
Even small rises in temperature can be expected to produce major climatic alterations, such as changes in cloud cover, precipitation levels and patterns, the length of seasons and wind patterns. While there is still significant scientific uncertainty about what exactly the effects of climate change will be, some climate change is now inevitable because of past and current emissions. Changes, at a minimum, will be difficult and disruptive; some scientists fear that they may be catastrophic.
