The term greenhouse effect is used to describe the warming effect that certain gases have on the temperature of the earth's atmosphere under normal conditions.


Facts on Global Warming (Part 1)

Posted by Imran H Khan on Feb 11, 2007, 06:01


Global warming (also called the greenhouse effect) describes the gradual increase of the air temperature in the earth's lower atmosphere.

Why is this called the Greenhouse Effect?

A greenhouse is made entirely of glass. When sunlight (shortwave radiation) strikes the glass, most of it passes through and warms up the plants, soil and air inside the greenhouse. As these objects warm up they give off heat, but these heat waves have a much longer wavelength than the incoming rays from the sun. This longwave radiation cannot easily pass through glass; it is re-radiated into the greenhouse, causing everything in it to heat up.

The term greenhouse effect is used to describe the warming effect that certain gases have on the temperature of the earth's atmosphere under normal conditions.

Sunlight (shortwave radiation) passes easily through the earth's atmosphere. Once it strikes and warms the earth's surface, longwave radiation is given off and goes back into the atmosphere. While some of this longwave radiation or heat escapes into space, most of it is absorbed or held by carbon dioxide and other gases that exist in small quantities in the atmosphere. Thus these gases form a `blanket' that keeps the earth an average of 33 degrees centigrade warmer than it would be if this greenhouse effect did not occur. Without these gases the whole planet would be an icy wasteland with an average temperature of 16 degrees centigrade below freezing!

Human population growth and related industrial expansion, have led to greater air pollution and a change in the composition of the earth's atmosphere. Some pollutants enhance the natural greenhouse effect, resulting in increased global atmospheric temperatures.

The gases that are responsible for the increase in the greenhouse effect are:

Carbon dioxide (CO2) is the pollutant most responsible for increased global warming. It is released into the atmosphere mainly through burning of fossil fuels (e.g. coal, petrol, diesel). In addition, widespread destruction of natural vegetation, particularly forests, has contributed to increased atmospheric CO2 levels (. This has occurred for two reasons. First, plants take up CO2 through the process of photosynthesis. The destruction of vegetation, as occurs in deforestation, reduces the amount of CO2 that is removed from the atmosphere. Second, when forests are cleared, and burnt or left to rot, CO2 is released.

Methane (CH4) has doubled in concentration, mainly as a result of agricultural activities, between 1750 and 1990.

Nitrous oxide (N2O), also a product of burning fossil fuel, has increased by 8% over the same period.
Chlorofluorocarbons (CFCs), in addition to damaging the ozone layer, are potent greenhouse gases. Their concentrations in the atmosphere are increasing by about 4% every year.

Therefore, the average global temperature is about 0,5 degrees centigrade warmer than it was 100 years ago. Snow and ice-cover has decreased this century, deep ocean temperatures have increased, and cloud cover over North America has also increased over this period. The latter indicates increased atmospheric water vapor. Over the last century, global sea levels have risen by between 100 mm and 200 mm. Rising sea levels cause water to expand as it warms and glaciers melt, adding water to the oceans, thus scientists expect widespread flooding of coastal areas as sea levels rise. If current pollution trends continue, scientists conclude that the earth could probably be about 1 degree centigrade warmer by 2025 and 3 degrees centigrade warmer by 2100.

This rapid temperature rise could have several effects:

"There maybe a greater frequency and scale of extreme weather conditions, e.g. drought and flood as being experience by most regions of the world.
"Changes in the distribution of disease-bearing organisms so that people, domestic animals, and crops might be exposed to diseases previously absent from an area.
"These changes in global temperature, although apparently small, could cause very large changes in climate. For example, the last Ice Age, which ended approximately 15 000 years ago, was only 5 degrees centigrade colder than current temperatures, but the resulting climate changes were massive: most of North America was covered in a layer of ice about 1,5 km thick.
Although I am not an expert on the issue the aforementioned facts make incredible reading and this is just the basic stuff. Therefore, in conclusion to this part I can honestly say the facts are worrying and a definite cause for concern. The facts I have quoted are readily available on any number of given reputable websites and books. The analysis I provide here is not an opinion or personal point of view but facts. Thus in order to truly understand the issue one must observe and correlate the entire picture of human civilization on Earth. Next week I examine the political, social and economic hurdles that have contributed to the Global Warming effect and the steps required to negotiate with this grave concern that affects the whole of humanity now and for future generations.

Facts and statistics obtained from:
United Nations Framework Convention on Climate Change;
Institute for Biodiversity and Conservation;
National Oceanic and Atmospheric Administration
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