E. And there is other evidence of warming to bolster the ACIAs case. For example, the report documents the widespread melting of glaciers and of sea ice, a trend already making life miserable for the polar bears and seals that depend on that ice. It also notes a shortening of the snow season. The most worrying finding, however, is the evidence still preliminary that the Greenland ice sheet may be melting faster than previously thought.
F. That points to one reason the world should pay attention to this weeks report. Like a canary in a coal mine, the hypersensitive Polar Regions may well experience the full force of global warming before the rest of the planet does. However, there is a second and bigger reason to pay attention. An unexpectedly rapid warming of the Arctic could also lead directly to greater climate change elsewhere on the planet.
G. Arctic warming may influence the global climate in several ways. One is that huge amounts of methane, a particularly potent greenhouse gas, are stored in the permafrost of the tundra. Although a thaw would allow forests to invade the tundra, which would tend to ameliorate any global warming that is going on , a melting of the permafrost might also lead to a lot of trapped methane being released into the atmosphere, more than offsetting the cooling effects of the new forests.
H. Another worry is that Arctic warming will influence ocean circulation in ways that are not fully understood. One link in the chain is the salinity of seawater, which is decreasing in the north Atlantic thanks to an increase in glacial melt waters. Because fresh water and salt water have different densities, this freshening of the ocean could change circulation patterns. said Dr. Thomson, a British climate expert. The most celebrated risk is to the mid-Atlantic Conveyor Belt, a current which brings warm water from the tropics to north-western Europe, and which is responsible for that regions unusually mild winters, he added. Some of the ACIAs experts are fretting over evidence of reduced density and salinity in waters near the Arctic that could adversely affect this current.
【雅思考试阅读材料:全球变暖问题】相关文章:
最新
2016-02-26
2016-02-26
2016-02-26
2016-02-26
2016-02-26
2016-02-26