2020-09-27 22:20:37   来源:环球教育在线   评论:0 点击:

  In the ramshackle apartment blocks and sooty cement homes that line the dusty roads of urban India,there is a new status symbol on proud display.An air-conditioner has become a sign of middle-class status in developing nations,a must-have dowry item.


  It is cheaper than a car,and arguably more life-changing in steamy regions,where cooling can make it easier for a child to study or a worker to sleep.


  The earth also has the cause of air conditioning disease


  But as air-conditioners sprout from windows and storefronts across the world,scientists are becoming increasingly alarmed about the impact of the gases on which they run.All are potent agents of global warming.



  Air-conditioning sales are growing 20 percent a year in China and India,as middle classes grow,units become more affordable and temperatures rise with climate change.The potential cooling demands of upwardly mobile Mumbai,India,alone have been estimated to be a quarter of those of the United States.


  Air-conditioning gases are regulated primarily though a 1987 treaty called the Montreal Protocol,created to protect the ozone layer.It has reduced damage to that vital shield,which blocks cancer-causing ultraviolet rays,by mandating the use of progressively more benign gases.The oldest CFC coolants,which are highly damaging to the ozone layer,have been largely eliminated from use;and the newest ones,used widely in industrialized nations,have little or no effect on it.


  But these gases have an impact the ozone treaty largely ignores.Pound for pound,they contribute to global warming thousands of times more than does CO2,the standard greenhouse gas.


  Concentrations of CFC-12,which had been growing rapidly since the 1960s,have tapered off since 2003,thanks to the treaty’s strict phaseout schedule.In 2006,NASA scientists concluded that the ozone layer was on the mend.


  But that sense of victory has been eclipsed by the potentially disastrous growth in emissions from the newer air-conditioning gases.While a healthier ozone layer itself leads to some warming,far more warming results from the tendency of these coolant gases to reflect back heat radiating off the Earth.


  When the treaty set its rules in the mid-1980s,global warming was poorly understood,the cooling industry was anchored in the West,and demand for cooling was minuscule in developing nations.



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