Global Warming

Global Warming

Introduction

"We must no longer think of human progress as a matter of imposing ourselves on the natural environment. The world--the climate and all living things-- is a closed system; what we do has consequences that eventually will come back to affect us." - UNEP

Climate change is one of the most ardently debated topics on globe at present. The frequency and intensity of extreme climactic change such as changing composition of earth atmosphere, unprecedented melting of glaciers and rise in the level of sea, increasing numbers of hurricanes and other anomalous events have forced scientists, researchers, and policymakers to believe that the earth is going through major climatic change. Experts argue that the changes in the global temperature are becoming excessive and wayward enough that something other than natural causes is driving them. Many researchers assert that human activities such as deforestation and the emission of greenhouse gases such as carbon dioxide and chlorofluorocarbons (CFCs) into the atmosphere are to blame for the present and predictably for the future changes in the earth's climate.

Experts believe that the condition of the atmosphere has worsened to such a level that the implementation of suggested protocols would only lower insignificant amount of green house gases from the atmosphere.

Greenhouse Effect

The greenhouse effect is a natural component of the Earth's geophysical balance necessary for the existence of the biological sphere of Earth. It is the rise in temperature that the Earth experiences because of gases like water vapor, carbon dioxide, nitrous oxide, methane and others in the atmosphere that traps energy from the sun. Because of how they warm up the Earth, these gases are referred to as greenhouse gases. Without these gases, heat would escape back into space and Earth's average temperature would be about 60Ñ"F colder. In other words, without a natural greenhouse effect, the temperature of the Earth would be about zero degrees F (-18oC) instead of its present 57oF (14oC). Earth absorbs not all of the sun's energy entering the atmosphere. Approximately, 30 percent of the total solar energy that strikes the Earth is reflected back into space by clouds, atmospheric aerosols, reflective ground surfaces, and ocean surf. The land, air, and the oceans absorb the remaining 70 percent.

Basically, the flow of solar energy to and from the earth is a natural phenomenon and the reason for life on earth, but the balance must be maintained for the temperature to remain constant at this beneficial level. The absorbed light is mostly in the form of ultraviolet, visible, and near-infrared solar radiation. However, it is understood that the greenhouse and other gases produced by human activity reflect a proportion of the outgoing energy back to the earth upsetting the equilibrium by increasing the temperature of the Earth.

Figure 1: The greenhouse effect (Source: The woods Hole Research Center)

Greenhouse gases act like an insulator or blanket above the earth, keeping the heat in. Increasing the concentration of these gases in the atmosphere increases the atmosphere's ability to block the escape of infrared radiation. Therefore too great a concentration of greenhouse gases can have striking effects on climate and significant repercussions upon the world.

Scientific Evidence

Global warming is now a well documented and accepted by scientists as fact. So, the concern is not with the fact that we have a greenhouse effect, but whether human activities are leading to an enhancement of the greenhouse effect. A panel convened by the U.S National Research Council, the nation's leading science policy body, in June 2006 voiced that Earth is the hottest it has been in at least 400 years, and possibly even the last 2,000 years. Studies indicate that the average global surface temperature has increased by approximately 0.7-1.4oF over the last century. This is the largest increase in surface temperature in the last 1,000 years and scientists are predicting an even greater increase over this century. Many experts estimate that the average temperature will rise an additional 2.5 to 10.4 degrees F by 2100. This warming is largely attributed to the increase of greenhouse gases, primarily carbon dioxide and methane, in the Earth's upper atmosphere caused by exceptional human burning of fossil fuels, industrial, farming, and deforestation activities.

The enhanced greenhouse effect cannot be definitively tied to greenhouse gas emissions as yet. The risk of further danger and impact can be considered severe. The causes and impacts of global climate change, human-induced or not, touch every aspect of human society. The issue of global warming is not only a scientific, political, or economic but a human issue requiring immediate action (David Easterling and Tom Karl, National Climatic Data Center, Asheville, N.C. 28801).

Increasing greenhouse gases

Human activity has been increasing the concentration of greenhouse gases in the atmosphere mostly carbon dioxide from combustion of coal, oil, and gas; plus a few other trace gases. There is no scientific debate on this point. Pre-industrial levels of carbon dioxide (prior to the start of the Industrial Revolution) were about 280 parts per million by volume (ppmv), and current levels are about 370 ppmv. Study shows that the concentration of CO2 in our atmosphere today has not been exceeded in the last 420,000 years, and likely not in the last 20 million years. According to the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES), by the end of the 21st century, the concentration of carbon dioxide concentrations could be anywhere from 490 to 1260 ppm, which is 75-350% above the pre-industrial concentration.

Other evidence of the reality of global warming continues to accumulate. Consistent with predictions of the IPCC since 1990, global average temperatures have been rising while atmospheric CO2 increases at a rate of approximately 1.6ppm per year. Figure 2 below shows the average global temperature and carbon dioxide concentration in the atmosphere.

Figure 2: The global average temperature and carbon dioxide concentration, 1800-2004 (Source: IPCC)

Climate warming

Increasing the amount of greenhouse gases intensifies the greenhouse effect meaning that the higher concentrations of carbon dioxide