考研考试

【单选题】The United States experienced some of the most extreme weather events in its history this spring, including deadly outbreaks of tornadoes, near-record flooding, drought and wildfires.Damages from these disasters have already passed $ 32 billion, and the hurricane season, which is just beginning, is projected to be above average, according to the National Oceanic andAtmosphericAdministration.
Government scientists said Wednesday that the frequency of extreme weather has increased over the past two decades, in part as a result of global warming caused by the accumulation of carbon dioxide in the atmosphere.But they were careful not to blame humans for this year’s rash of deadly events, saying that in some ways weather patterns were returning to those seen at the beginning of the last century. "Looking at long-term patterns since 1980, indeed, extreme climatological and meteorological events have increased," said Thomas R. Karl, director of NOAA’s NationalClimaticDataCenter. "But in the early part of the 20th century, there was also a tendency for more extreme events followed by a quiet couple of decades. "
Presenting a new NOA
A、report on 2011 extreme weather,Dr. Karl said that extremes of precipitation have increased as the planet warms and more water evaporates from the oceans. He also said models suggest that as carbon dioxide builds up in the atmosphere and heats the planet, droughts will increase in frequency and intensity. "But it is difficult and unlikely to discern a human fingerprint, if there is one, on the drought record of the United States," he saiD、
Some other climate scientists were more categorical about the human contribution to extreme climate events. Kevin Trenberth, distinguished senior scientist at the NationalCenter forAtmospheric Research, said that when the greenhouse effect caused by burning fossil fuels is added to the natural variability of climate, weather disasters can be expected to occur more frequently. "Global warming is contributing to an increased incidence of extreme weather because the environment in which all storms form has changed from human activities,"Dr. Trenberth said in a telephone interview Wednesday. "Records are not just broken, they are smasheD、It is as clear a warning as we are going to get about prospects for the future. "
April was a particularly devastating month for tornadoes and rainfall, with 875 tornadoes reported during the month and heavy rain and snowmelt contributing to Mississippi River flooding later in the spring that surpassed the historic floods of 1927 and 1937. So far this year, there have been nearly 1,400 preliminary tornado reports nationwide; those reports will most likely be whittled down to about 900 confirmed tornadoes, the second-highest annual total recorded in modern times. The record is 1,011 confirmed tornadoes in 2008. The year also is on track to be one of the deadliest, with 536 fatalities so far from tornadoes, placing 2011 in sixth place in United States history and the deadliest since 1936.
According toDr. Karl, extreme weather is mainly attributable to
A、arbitrary human activities.
B．changing weather patterns.

C、an increase in climatological events.
D．human failure to control the weather.

网考网参考答案：B
网考网解析：
Karl博士不认为极端天气的频繁出现是人的所作所为造成的。文章的第二、三段提到了他的观点。在他看来。如果从长期的气象模式来看，目前的模式类似于20世纪早期的气象模式。Karl博士又在第三段指出，在美国干旱的历史上很难找到人类的“指纹”，根据上文，这里的意思是：干旱是天气自身的规律性变化决定的，而不带有人类的痕迹，即不是人类的活动或行为——如二氧化碳的排放——造成的。 document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>