Human pollution may make earth’s natural “greenhouse” too warm.

The “greenhouse effect” is a process whereby gases and water vapor from the earth are naturally trapped in the earth’s atmosphere to create a type of blanket effect which allows the earth to retain heat necessary for life.

Many believe polluting gases such as carbon dioxide, methane, chlorofluorocarbons, and excessive water vapor, raise the temperature of the naturally occurring “greenhouse,” to cause detrimental “global warming.”

University of California, San Diego, has provided a readable explanation of the naturally occurring “greenhouse effect.

General Overview: The Greenhouse Effect

Introduction

The “greenhouse effect” is widely discussed in the media, and although its details are complicated, its principles are not difficult to understand. Without a greenhouse effect, radiation from the Sun (mostly in the form of visible light) would travel to Earth and be changed into heat, only to be lost to space. This scenario can be sketched as follows:

Sun’s radiation -> absorbed by Earth -> re-radiated to space as heat

The greenhouse effect is a process where energy from the sun readily penetrates into the lower atmosphere and onto the surface of Earth and is converted to heat, but then cannot freely leave the planet. This can be sketched as follows:

Sun’s radiation -> absorbed by Earth -> some re-radiated to space as heat -> some trapped by the atmosphere

Due to the presence of certain “greenhouse gases” that trap heat, like carbon dioxide, methane, water vapor, and CFCs [chlorofluorocarbons], the atmosphere retains the sun’s radiation and warms up the planet. By increasing the abundance of these gases in the atmosphere, humankind is increasing the overall warming of the Earth’s surface and lower atmosphere, a process called “global warming.” The figure below illustrates the radiation balance and the role of greenhouse effect.

The Radiation Balance

Another way to think about the greenhouse effect is to consider that, according to physics, the radiation we receive from the Sun must be equally balanced by the heat Earth radiates out to space. If we were to give back less energy than we receive, our planet would soon be too hot for life. Likewise, if we were to give back more energy that we receive, our planet would soon be too cold for life. This can be written as a balanced equation of radiation:

EQUATION: Solar radiation input to Earth = Earth’s output of re-radiated heat

If we were to measure the temperature of the Earth from space, the Earth’s “surface” would show a temperature appropriate for this requirement of energy balance: a measurement of roughly -18 degrees Celsius (about 0 ̊F). At this temperature, our planet radiates a quantity of heat into space that is equivalent to the amount of energy received from the Sun.

At this point you may be asking how we can speak of ‘global warming’ when we have just stated that the Earth (as seen from space) MUST stay at the same temperature’ And how is it that the temperature of the Earth’s surface is only a chilly 0̊F’ The key to understanding this apparent contradiction is to remember that we live at the bottom of the atmosphere. As far as the radiation balance is concerned, the lower atmosphere and the surface of Earth form part of a ‘warm interior’ of the planet.

To read the rest of this informative explanation from University of California, San Diego, and see the illustrations, click Explanation of “greenhouse effect”.

Click next page to see how global warming, as well as pollution from especially carbon dioxide, has affected the oceans.