True about global warming is
Ans. is 'a' i.e. C02 is the major greenhouse gas CO2 and water vapour are the two most important and major greenhouse gases.Global warming is a vast topic to be discussed in detail here. So we will deal with it briefly in context of the given options.Global warming:Global warming is the increase in the temperature of earth's near-surface air and oceans.The global surface temperature has increased approximately 0.6 degC (1.3 degF) since the mid 20th century.This increase in temperature is caused by increasing concentration of greenhouse gases.Effects of global warmingWarming is expected to affect the Arctic most, and would be associated with continuing retreat of glaciers, permafrost and sea ice.Rising of sea levelExpansion of subtropical desertsChanges in the frequency and intensity of extreme weather events (like flood, storm etc.)Species extinctionsChanges in agricultural yield.Greenhouse gasesIn order, Earth's most abundant greenhouse gases are -Water vapour =60-70%Carbon dioxide = 55% (option a)Atmospheric methaneNitrous oxideOzoneChlorofluorocarbons (CFC)The main sources of greenhouse gases d/t human activity areBurning of fossil fuels & deforestation - | CO2Enteric fermentation in ruminant animals, paddy rice farming and covered vented garbage landfill emissions, drilling for oil and natural gas- | methane.Use of CFCs in refrigerator & use of CFC & halons in fire suppression systems.Use of fertilizers in agriculture | N2O.Greenhouse effect'Greenhouse effect' is the heating of the Earth d/t presence of greenhouse gases.It is named this way because of a similar effect produced by the glass panes of a green house.The shorter wavelength radiation from sun, is absorbed by the surface of the earth, causing it to worm. Part of the absorbed energy is then re-radiated back to atmosphere as long wave infrared radiation.The greenhouse gases selectively transmit the infrared waves, allowing some to pass through into space and some are absorbed. The absorbed waves are re-emitted downward, causing the lower atmosphere to warm.The greenhouse effect is essential for living beings on earth, as it makes the earth warm enough to live. (Without the greenhouse effect the earth surface would be 33 degC colder than at present!!!)But it is the 'enhanced' greenhouse effect due to increased concentration of greenhouse gases that is causing global warming.The clouds are the major non-gas contributor to the Earth's greenhouse effect.Ozone layers of atmosphereStratosphereIt is the highest level of ozone.It is spread b/w 10 km and 50 km above the Earth surfaceIt contains 90% of ozone of the atmosphereStratosphere is beneficial as it filters out the harmful ultraviolet rays from sun (option b)TroposphereIt is the lower most atmospheric layer extending from the surface to 10 km (18 km at poles).The troposphere contains ~ 80% mass of atmosphere.The ozone present in this layer is an atmospheric pollutant & also produces greenhouse effect.In recent decades the amount of ozone in the stratosphere has been declining mostly because of emissions of CFCs and similar chlorinated & brominated organic molecules (option c)Kyoto protocol:It is a protocol to the United Nations Framework Convention on Climate Change (UNFCCC).Aim is to stabilising greenhouse gas concentration to fight global warming.The protocol was initially adopted on 11th Dec 1997 in Kyoto, Japan & entered into force on 16th Feb 2005. By Nov 2009, 187 states have signed the protocol.Under this protocol 37 industrialised countries commit to reduce greenhouse gas emission by 5.2% from the 1990 level by 2008-2012(option d).Rest of the member countries have given general commitment to reduce greenhouse gas emission.Also knowGlobal dimming, in simple words, is a phenomenon which produces forces opposite to global warming. Global dimming causes the amount of sun's rays reaching the earth's atmosphere to reduce & causes a drop of temperatures around the globe. It is thought to have been caused by an increase in atmospheric aerosols in the atmosphere due to human action.
CO2 is the major greenhouse gas
Stratosphere ozone layer is harmful
CFC increases stratosphere ozone layer
Kyoto protocol called for 20% reduction in greenhouse effect.
Environment and Health