The greenhouse effect is a mixed blessing. Without it the earth would be about 60º cooler than it is today. The natural greenhouse effect provides an insulating layer of greenhouse gases—water vapor, CO2, ozone, and several others that help to keep the earth warm. When something happens to upset the natural balance, climate change can result.
In normal circumstances, changes in the earth's temperature are so gradual as to be practically undetectable. Over the last few hundred years mankind has changed the natural balance of the greenhouse effect by burning fossil fuels and cutting down forests. Much of the carbon that was stored over millions of years has been returned to the atmosphere as CO2 far faster than natural processes are equipped to remove it. Deforestation, the loss of millions of acres of trees and their CO2 absorbing capability, amplifies the effect of burning coal, oil and natural gas.
The greenhouse effect concerns us now because the greenhouse properties have become exaggerated and we have an excess of greenhouse gases trapping heat that would normally radiate out into space. As the atmospheric concentrations of these gases rise, more heat is radiated back and the average temperature of the lower atmosphere increases. This is global warming.
It is not a one way street. If something cataclysmic should happen to block sunlight or to dramatically reduce the volume of water vapor and CO2 in the atmosphere, the greenhouse effect would be reversed, the earth would cool and a new set of climate change concerns would face us: global cooling.
(Photo credit: Torley Olmstead, Flickr, Second Life)
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