The Greenhouse Effect

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What is the greenhouse effect?Let's give a familiar example. You know what happens if you park your car in the parking lot on a hout summer day without opening the windows.When you get back inside your car,it is hot as an oven.This rapid warm-up is due to a greenhouse effect:The sun's radiant energy wasily passes through the car's windows,and some of this energy is then converted into heat or infaraed radiation.Since this radiation can not readily escape back through the windows,it is trapped inside ,and the car warms up. Molecules of greenhouse gases,such as carbon dioxide,behave every much like the glass in car windows or in a greenhouse .In a sense,the greenhouse gases form a"glass window"over the earth.They trap heat that other otherwise would escape from the the earth'ssurface into outer space. Scientists have used several different techniques to determine the atmospheric carbon dioxide levels of past centuries.For example,they have analyzed air bubbles trapped in ice and have examined wood from century-old tress.Since 1958,carbon dioxide levels have been continuously monitored with sensitive instruments atop mauna loa,a 13667-foot volcanic mountain on the island of hawaii.