Greenhouse Effect - An essay

The Greenhouse Effect is a naturally occurring process that results in the heating of the earth’s surface and atmosphere. This is due to the particular property of certain atmosphere gases like carbon dioxide, nitrous oxide, methane etc. These gases allow the heat from the sun to reach the earth but absorb some of the outgoing heat energy, as the heat radiated by the earth is at a lower frequency than that of the incident energy. This is somewhat like the action of glass panels in a glass house. Without this natural green house effect, temperatures on earth would have been much lower and life would not have been possible. Due to this effect, earth’s temperatures are more hospitable at about 15C instead of -18C.

The matter of concern now is that since the industrial revolution, the atmospheric concentrations of these gases are on the rise. Over the past three centuries, atmospheric concentrations of carbon dioxide have increased 30% (from 280 ppm to 360 ppm), methane concentrations have more than doubled (from 0.7 ppm to 1.7 ppm), and nitrous oxide compounds have risen by 15 % (280 ppm to 310 ppm). In the absence of emission control policies carbon dioxide concentrations are projected to b 30 – 150 % higher in 2100 than today’s levels. The other gases involved in the green house effect are chlorofluorocarbons and tropospheric ozone. Of all the green house gases, carbon dioxide accounts for 55% of the enhancement in the earth’s green house effect. The contributions of other gases are: 25% by chlorofluorocarbons, 15% by methane, 5% by nitrous oxide. Ozone’s contribution to the enhancement of greenhouse effect is yet to be qualified.

Why are the greenhouse gas concentrations increasing? Scientists generally agree that the combustion of fossil fuels and other human activities are the primary reasons for this increase. The concentrations of carbon dioxide have increased due to several activities of humans after the industrial revolution. The major causes for the increased emission of this gas include (i) combustion of fossil fuels by industries, transportation, space heating, electricity generation, cooking (ii) vegetation changes in natural pairs, woodland and forest ecosystems. Emission from fossil fuel combustion accounts for 65% of the extra carbon dioxide now found in the atmosphere. The remaining 35% comes from the conversion of prairie woodland and forested ecosystems primarily into agricultural systems, as natural ecosystems can hold 20 – 100 times more carbon dioxide per unit area than agricultural systems. The major reasons for the additional methane in the environment are rice cultivation, domestic grazing animals, termites, land fills, coal mining, oil and gas extraction etc. The causes for the increase in nitrous oxide concentrations are land use conversions, fossil fuel combustion, biomass burning, soil fertilization. Most of the nitrous oxide added to the environment comes from deforestation and conversion of forest, savanna, grassland ecosystems into agricultural fields and range land. Both of these processes reduce the amount of nitrogen stored in the living vegetation and soil through the decomposition of organic matter. Greenhouse gases that are not naturally occurring are chlorofluorocarbons. They are byproducts generated by industrial processes such as foam production, refrigeration and air conditioning. Each greenhouse gas differs in its ability to absorb heat in the atmosphere. Chlorofluorocarbons have the highest capacity. Methane traps over 21 times more heat than carbon dioxide, and nitrous oxide absorbs 270 times as much as carbon dioxide.

The increase in the concentration of these greenhouse gases in the environment, also increases the heat trapping capacity of the earth, which effects many factors like temperature, precipitation, sea level, climatic condition etc. Global temperatures are found to be rising. Observations collected over the last century suggest that the average land surface temperature has risen by about 0.45C – 0.6C. Predictions of future climate indicate that by the middle of the next century earth’s global temperature may be 1C – 3 C higher than today. Precipitation has increased by about 1% over the world’s continents in the last century. High latitude areas are tending to see more significant increases in rainfall, but in some places precipitation has decreased too. These dry areas may become drier and wet areas wetter. Dude to the increasing global temperatures, the sea level has risen approximately 15 – 20 cms in the last century. Approximately 2 -5 cms of this rise has resulted by the melting of the mountain glaciers. Another 2 – 7 cms has resulted by the expansion of ocean water that results in warmer ocean climate. Rising sea level inundates wet lands and other low lying lands, erodes beaches, intensifies floods, salinity of rivers, bays and groundwater tables.

Greenhouse effect may also alter the regional climate, which in turn could alter forests, crop yield, water supplies, harm birds, fish and many types of ecosystems. Hurricanes, El-nino effects, forest fires are likely to become more frequent and severe as the earth becomes warmer. Throughout the world the prevalence of a particular disease and other threats to human health depend largely on the local climate. Extreme temperatures can directly cause the loss of life. Moreover, several serious diseases occur only in warm areas. Warm temperatures can increase air and water pollution which in turn harms human health. Higher air temperatures increase the concentration of ozone at ground level. The natural layer of ozone in the upper surface of the atmosphere blocks the harmful ultra violet radiation from reaching the earth’s surface, but in the lower atmosphere ozone is a harmful pollutant. It damages lung tissue, and causes particular problems for people with asthma and other lung diseases.

However, it must be pointed out that there is so unanimity in the scientific community regarding the impacts of the greenhouse effect. Figuring out to what extent the human induced accumulation of greenhouse gases since pre-industrial times is responsible for the global warming trend is not easy. This is because other factors, both natural and human affect the planet’s temperature. When the American Association for the Advancement of Science tried to get all the world’s leading climatologists to sign a paper affirming global warming, only 1% signed. In Leipzig, Germany at a global conference 80% of the climatologists said that there was not enough evidence to prove global warming.

There are scientists who believe that alternate scenarios could also emerge. One such argument is that, even though some areas may get affected by the sea rise, farming areas may open up farther north and areas like Russia could benefit. Farmers in Canada could have a longer growing season. Hence from an overall perspective the human race may gain rather than lose due to this effect. Another interesting view is that, we are presently in an inter-glacier period of an ice-age. The inter-glacier period started 16,000 years ago, and may soon be about up, with a return of glaciers covering the lands. If this was really correct, then rising seas does not seem as bad as glaciers marching towards lands and wiping out countries as they flow down south. Global warming may well prevent the ice age from returning. A third argument goes like this: if the Arctic cap melted, the sea level would not rise one inch because the Arctic ice is floating on the water just like an ice cube in a glass. Greenhouse effect warns of a 3C – 5C average temperature rise but it would take a 55C rise worldwide for 1000 years to melt the ice of the Antarctic. Finally the Sun heats the earth and not man. The Sun’s energy changes not only in short term sun-spot cycles, but also in long term 200 year cycles. According to fossil evidence the Sun is entering a cooling period that should max about the beginning of the 22nd century.

It is true that a section of scientists have identified that our health, agriculture, water, resources, forest, wild life, and coastal areas are vulnerable to the changes that global warming may bring. But projecting what exact changes will be over the 21st century remains very difficult. This is especially true, when one asks how a specified local region will be affected. Some of the greatest uncertainties are associated with events that pose a great risk to human societies.

Even with all these diverging views, we know for certain that human activities are changing the composition of the earth’s atmosphere. It is well accepted that greenhouse gases trap heat in the earth’s atmosphere and tend to warm the planet. By increasing the levels of greenhouse gases in the atmosphere, human activities are strengthening earth’s natural greenhouse effect.

True, there is no unanimity regarding the impact of Greenhouse Effect. Yet, there is no reason for us to be complacent about it. It is necessary to recognize that Greenhouse Effect is the manifestation of our activities upsetting the equilibrium of the earth’s atmosphere. We have to be proactive in maintaining its delicate balance. Afforestation and decreasing our dependence on fossil fuels based energy are the two major principles that should drive our future actions. Governments should discourage deforestation and actively pursue an agenda of afforestation. Populations throughout the world need to be sensitized, so that afforestation becomes a mass movement and hence successful. Decreasing our dependence on fossil fuel based energy is possible through two main approaches. One is reducing our energy consumption through conservation. The developed countries who are mainly responsible for the green house effect must take the lead in this regard. Sometimes this may call for some life-style changes. But they should be made to understand that the sacrifices needed (for the life style changes) are a small price to pay in order to sustain life on our planet. The second approach is developing an environment friendly energy sources such as wind, solar, micro hydel systems. The government and scientific community must concentrate their effects in this direction.

Our understanding of the Greenhouse Effect has a very important message –
'Development is important, but what is more important is Sustainable Development.'

PS:

• This essay was originally written when I was in the 9th standard.
• Everywhere in the essay, the degree part of the temperature needs to be assumed, as it is missing.
• This won the second prize in the essay competition conducted by IISc.
• Strangely, the results were announced and I got the award more than a year later. The only proof that I had got the second prize was a small piece of paper with the IISc stamp, with my name and II written on it. No idea what happened to it though.