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Ozone depletiondescribes two distinct but related phenomena observed since the late 1970s: a steady decline of about 4% in the total volume ofozoneinEarth'sstratosphere(theozone layer), and a much larger springtime decrease in stratospheric ozone around Earth's polar regions.[1]The latter phenomenon is referred to as theozone hole. In addition to these well-known stratospheric phenomena, there are also springtime polartropospheric ozone depletion events.
The details of polar ozone hole formation differ from that of mid-latitude thinning but the most important process in both iscatalyticdestruction of ozone by atomichalogens.[2]The main source of these halogen atoms in the stratosphere isphotodissociationof man-madehalocarbonrefrigerants,solvents,propellants, and foam-blowing agents(CFCs,HCFCs,freons,halons). These compounds are transported into the stratosphere by winds after being emitted at the surface.[3]Both types of ozone depletion were observed to increase as emissions of halocarbons increased.
CFCs and other contributory substances are referred to asozone-depleting substances(ODS). Since the ozone layer prevents most harmfulUVBwavelengths (280–315nm) ofultravioletlight (UV light) from passing through theEarth's atmosphere, observed and projected decreases in ozone generated worldwide concern, leading to adoption of theMontreal Protocolthat bans the production of CFCs, halons, and other ozone-depleting chemicals such ascarbon tetrachlorideandtrichloroethane. It is suspected that a variety of biological consequences such as increases insunburn,skin cancer,cataracts, damage to plants, and reduction ofplanktonpopulations in the ocean'sphotic zonemay result from the increased UV exposure due to ozone depletion.
Chinais the largest consumer ofcoalin the world,[1]and is about to become the largest user of coal-derived electricity, generating 1.95trillionkilowatt-hoursper year, or 68.7% of its electricity from coal as of 2006 (compared to 1.99trillionkilowatt-hoursper year, or 49% for theUS).[2][3]Hydroelectricpower supplied another 20.7% of China's electricity needs in 2006. Nuclear power is expected to rise from 2% to 4% of the energy mix.
With approximately 13percent of the world's proven reserves, there is debate as to how many years these reserves will last at current levels of consumption.[4]
Coal production rose 8.1% in 2006 over the previous year, reaching 2.38 billion tons, and the nation's largest coal enterprises saw their profits exceed 67billion yuan, or $8.75billion.[5]
Efforts to reduce emissions[edit]
Air pollution has gotten so bad that a study by the World Bank found that air pollution kills 750,000 people every year in China.[29]Issued in response to record-high levels of air pollution in 2012 and 2013, the State Council’s September 2013 Action Plan for the Prevention and Control of Air Pollution reiterated the need to reduce coal’s share in China’s energy mix to 65% by 2017.[30]Amidst growing public concern, social unrest incidents are growing around the country. For example, in December 2011 the government suspended plans to expand a coal-fired power plant in the city ofHaimenafter 30,000 local residents staged a violent protest against it, on the grounds that "the coal-fired power plant was behind a rise in the number of local cancer patients, environmental pollution and a drop in the local fishermen's catch."[31]
In addition to environmental and health costs at home, China's dependence on coal is cause for concern on a global scale. Due in large part to the emissions caused by burning coal, China is now the number one producer of carbon dioxide, responsible for a full quarter of the world's CO2 output.[32]According to a recent study, "even if American emissions were to suddenly disappear tomorrow, world emissions would be back at the same level within four years as a result of China’s growth alone."[33]The country has taken steps towards battling climate change by pledging to cut itscarbon intensity(the amount of CO2 produced per dollar of economic output) by about 40 per cent by 2020, compared to 2005 levels.[32]Reuters reports that "emissions and coal consumption will continue to rise through the 2020s, even though at a slower rate, barring a major intervention including a shift to cleaner burning gas from coal" - in other words, "meeting the carbon intensity target will require a significant change in trajectory for carbon emissions and coal consumption."[34]To that end, China has announced a plan to invest 2.3 trillion yuan ($376 billion) through 2015 in energy saving and carbon emission-reduction projects.[34]
China's first coal-fired power station employing theintegrated gasification combined cycle(IGCC), which is acoal gasificationprocess that turns coal into a gas before burning it, is planned to begin operations in 2009 atTianjinnear Beijing. Developed under a project calledGreenGen, this $5.7bn 650MW plant will be a joint venture between a group of state-owned enterprises andPeabody Energy.[35]In addition to these coal gasification projects, it is worth noting that on average, China's coal plants work more efficiently than those in the United States, due to their relative youth.[6]