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IT #8
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Ozone depletion describes two distinct but related phenomena observed since the late 1970s: a steady decline of
about 4% in the total volume of ozone in Earth's stratosphere (the ozone layer), and a much larger springtime
decrease in stratospheric ozone around Earth's polar regions.[1] The latter phenomenon is referred to as the ozone
hole. In addition to these well-known stratospheric phenomena, there are also springtime polar tropospheric ozone
depletion events.
The details of polar ozone hole formation differ from that of mid-latitude thinning but the most important process in
both is catalytic destruction of ozone by atomic halogens.[2] The main source of these halogen atoms in the
stratosphere is photodissociation of man-made halocarbon refrigerants, 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 as ozone-depleting substances (ODS). Since the ozone
layer prevents most harmful UVB wavelengths (280–315 nm) of ultraviolet light (UV light) from passing through
the Earth's atmosphere, observed and projected decreases in ozone generated worldwide concern, leading to
adoption of the Montreal Protocol that bans the production of CFCs, halons, and other ozone-depleting chemicals
such as carbon tetrachloride and trichloroethane. It is suspected that a variety of biological consequences such as
increases in sunburn, skin cancer, cataracts, damage to plants, and reduction of plankton populations in the
ocean's photic zone may result from the increased UV exposure due to ozone depletion.
China is the largest consumer of coal in the world,
[1]
and is about to become the largest user of
coal-derived electricity, generating 1.95 trillion kilowatt-hours per year, or 68.7% of its electricity from coal as of 2006
(compared to 1.99 trillion kilowatt-hours per year, or 49% for the US).[2][3] Hydroelectric power 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 13 percent 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 67 billion yuan, or $8.75 billion.[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 of Haimen after 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 its carbon 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 the integrated gasification combined cycle (IGCC), which is a coal
gasification process that turns coal into a gas before burning it, is planned to begin operations in 2009
at Tianjin near Beijing. Developed under a project called GreenGen, this $5.7 bn 650 MW plant will be a joint
venture between a group of state-owned enterprises and Peabody 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]