英语翻译In the long run,the greatest health impacts may not be f

英语翻译In the long run,the greatest health impacts may not be from acute shocks,such as natural disasters or epidemics,but from the accumulated effects of a changing climate on those systems that sustain health,and which are already under stress in much of the developing world.Increasing temperatures and more variable precipitation are expected to reduce crop yields in many tropical developing regions.In some African countries,yields from rain-fed agriculture could be reduced by up to 50 percent by 2020.This is likely to aggravate the burden of undernutrition in developing countries.Extreme high air temperatures can kill directly; it has been estimated that more than 70,000 excess deaths were recorded in the extreme heat of the summer of 2003 in Europe.By the second half of this century,such extreme temperatures will be the norm.In addition,rising air temperatures will increase levels of important air pollutants,such as ground-level ozone,particularly in areas that are already polluted.