What is the Greenhouse Effect?
The greenhouse effect is an important natural process that makes life on earth possible. Because the atmosphere always contains heat-trapping gases like carbon dioxide, water vapor, and methane, much of the heat from the sun’s radiation is “trapped” in the atmosphere rather than radiating back into space — much like how the panes of glass in a greenhouse hold heat inside the greenhouse. As a result, the atmosphere remains warm enough to support human, plant, and animal life as we know it. Without greenhouse gases, Earth would be about 60 degrees (F) colder and uninhabitable. Unfortunately, as humans burn fossil fuels like coal, oil and natural gas, we are increasing the amount of carbon dioxide and other greenhouse gases in the atmosphere. This is causing more of the sun’s heat to be trapped, thus causing the intensification of the greenhouse effect known as global warming.
When sunlight hits the earth, the earth is warmed and radiates some of that heat back towards space. Certain gases in the atmosphere (known as “greenhouse gases”) can absorb some of that radiation, preventing it from escaping. The earth retains more heat from the sun than it would in the absence of these gases, making the earth about 35°C warmer than it would be otherwise. Without this greenhouse effect, the earth would likely be a giant ice ball. Life as we know it would not exist. The planet Venus (earth’s “sister planet” ) provides a striking example of the impact of the greenhouse effect. It has a surface temperature of 750° K, hot enough to melt lead. The surface temperature is twice that of Mercury, even though Mercury is much closer to the sun. This is because Venus has a “runaway greenhouse effect” due to its dense atmosphere of 96% CO2 . This effect is estimated to raise the surface temperature of Venus 400° K.
