The heat caused by infrared radiation from the sun which escapes from the Earth’s outer surface, is absorbed by “greenhouse gases” which trap the heat forming a kind of blanket of warm air that surround the planet. This occurrence is called the “green house effect”. It is suggested that the temperature on average would have been much lower compared to what is now. Survival of the ecosystem would have been difficult in such extreme condition.

UNDERSTANDING THE GREENHOUSE EFFECT

In the natural greenhouse effect, the type of topograpyh the sunlight falls plays a key role. Different types of surfaces absorb or radiate heat differently. For example, white glaciers reflect maximum sunlight resulting in minimum heating of the surface and the lower atmosphere. On the other hand, sunlight is absorbed the maximum by dark desert soil causing more heating of the surface and the lower atmosphere. Clouds that cover the sky reduce the amount of solar radiation penetrating onto the earth’s surface and also reduce the amount of radiation emitted into space.

BASIC MECHANISM

About 50% of the solar radiation is absorbed by the earth’s surface and the rest is emitted as infrared radiation by the surface of earth. Green house gases absorb most of the infrared radiation and pass on to the other atmospheric gases by molecular interaction. The greenhouse gases too radiate some heat. Heat is radiated both upwards and downwards with some escaping into the space and some getting back to the earth surface. The earth surface and the lower atmosphere is thus aiding to the survival of life on earth.

Greenhouse gases such as carbon dioxide, methane, water vapor, nitrous oxide etc. are molecules formed by two atoms which are loosely bound and are thereby easily excited by solar radiation. The loose atoms then pass on the heat to other gases by molecular interaction. Major components of the atmosphere such as oxygen and nitrogen are formed my tightly bound atoms which are not easily excited and thus do not absorb heat.

EFFECTS ON GLOBAL WARMING

Though greenhouse effect is an essential environmental phenomenon, the trouble begins when human activities disturb or accelerate the natural process by creating more of the green house gases necessary for the optimum warming of the earth surface and thus raising the surface temperature above ideal one.

Higher the concentration of the green house gases more is the heat radiation towards the earth. The emission of green house gas such as carbon dioxide is mainly due to burning of fossil fuels such as oil, gas, petrol, kerosene etc.
Higher concentration of such man-made greenhouse gas causes considerable warming of the earth and the sea resulting in Global Warming.

HUMAN CONTRIBUTION

• Level of carbon dioxide is increased by burning of natural gas, coal, oil, petrol etc.
• Some agricultural and land-use methods increase the level of methane and nitrous oxide in atmosphere.
• Industrial wastes and gases contribute substantially to the green house effect and thus adding to global warming.
• Deforestation is one of the major causes of global warming today.
• Population explosion is another prime factor contributing towards global warming.

While most people accept global warming as a fact, some still deny that humans play a significant role. Unfortunately politics are often involved, and while I don’t intent to try to change anyone’s mind, it’s worthwhile to look at some statistical facts. These come from the Intergovernmental Panel on Climate Change’s (IPCC) 2007 working group assessment report, which is available for free online. The IPCC is a scientific panel under the United Nations.

The average surface temperature of the planet has increased 1.33 degrees Fahrenheit between 1905 and 2005.

Over the last fifty years, the warming trend is almost twice that of the previous fifty years, so the rate of temperature rise is increasing.

Eleven of the past twelve years are among the twelve warmest years since 1850. This is a shocking fact!

Also, the Environmental Protection Agency reports that the sea level along the Gulf and Mid Atlantic has risen five to six inches more than the average in the last century. Glaciers and snow cover are decreasing on both sides on the equator.

Clearly the earth is warming and with this warming, snow and ice are melting and the seas are rising. Yes, the earth has cooled and warmed many times before there were humans, and one may even argue that humans alone are not to blame, as though blame matters anyways. Humans and our activities are contributing to the rapid rise in temperature, and the only questions that remain is how serious is it and how should we react.

I for one am no alarmist, but it’s tough to argue with the facts presented above. I’m trying to do my part to help combat global warming and suggest everyone else do what they can as well.

Harry Baldwin writes on many topics including green issues and photography. Visit Canon Photo Printer and Canon Selphy Printers to see his latest.

Harry has started riding his bike to work and to run errands as well. What are you doing?