MSc. (Environmental Biology) Past Paper 2015
Q.9) Short descriptive note on:
a. Environmental Laws
b. MTBEs (Methyl Tertiary Butyl Ether)
c. Global Warming
Global warming is the term used to describe a gradual increase in the average temperature of the Earth's atmosphere and its oceans, a change that is believed to be permanently changing the Earth's climate.
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Global Warming Causes
Global warming is primarily a problem of too much carbon dioxide (CO2) in the atmosphere—which acts as a blanket, trapping heat and warming the planet. As we burn fossil fuels like coal, oil and natural gas for energy or cut down and burn forests to create pastures and plantations, carbon accumulates and overloads our atmosphere. Certain waste management and agricultural practices aggravate the problem by releasing other potent global warming gases, such as methane and nitrous oxide. See the pie chart for a breakdown of heat-trapping global warming emissions by economic sector.
Impacts of Global Warming
(Public level)
Health
Public health impacts include injuries and deaths from heat waves; more intense storms, floods, and wildfires; more severe and frequent bad-air days; and changes in disease pathways and allergen potency. Discover how global warming impacts our health.
Food
Climate change threatens crops, livestock, and fisheries owing to heat-induced declines in productivity, changes in rainfall timing and intensity, and shifts in the abundance and types of fish and pests. Learn about global warming effects on food.
Water use
A changing climate poses risks to the quality and supply of water for drinking, irrigation, shipping, and recreation. For example, rising seas can intrude into coastal groundwater used for drinking. Read about global warming effects on our water supply.
Costs
Climate impacts cost time and money by damaging critical infrastructure, disrupting economic activity, escalating medical expenses, losing work days, and requiring adaptations such as moving people out of harm's way. See how global warming affects the economy.
Cause of global warming
Almost 100% of the observed temperature increase over the last 50 years has been due to the increase in the atmosphere of greenhouse gas concentrations like water vapour, carbon dioxide (CO2), methane and ozone. Greenhouse gases are those gases that contribute to the greenhouse effect (see below). The largest contributing source of greenhouse gas is the burning of fossil fuels leading to the emission of carbon dioxide.
The greenhouse effect
When sunlight reaches Earth's surface some is absorbed and warms the earth and most of the rest is radiated back to the atmosphere at a longer wavelength than the sun light. Some of these longer wavelengths are absorbed by greenhouse gases in the atmosphere before they are lost to space. The absorption of this longwave radiant energy warms the atmosphere. These greenhouse gases act like a mirror and reflect back to the Earth some of the heat energy which would otherwise be lost to space. The reflecting back of heat energy by the atmosphere is called the "greenhouse effect".
The major natural greenhouse gases are water vapor, which causes about 36-70% of the greenhouse effect on Earth (not including clouds); carbon dioxide CO2, which causes 9-26%; methane, which causes 4-9%, and ozone, which causes 3-7%. It is not possible to state that a certain gas causes a certain percentage of the greenhouse effect, because the influences of the various gases are not additive. Other greenhouse gases include, but are not limited to, nitrous oxide, sulfur hexafluoride, hydrofluorocarbons, perfluorocarbons and chlorofluorocarbons.
Global warming causes by greenhouse effect
Greenhouse gases in the atmosphere (see above) act like a mirror and reflect back to the Earth a part of the heat radiation, which would otherwise be lost to space. The higher the concentration of green house gases like carbon dioxide in the atmosphere, the more heat energy is being reflected back to the Earth. The emission of carbon dioxide into the environment mainly from burning of fossil fuels (oil, gas, petrol, kerosene, etc.) has been increased dramatically over the past 50 years.
