Like street comer prophets proclaiming that tile end is near, scientists who study the earth’s atmosphere have been issuing predictions of impending doom for the past few years without offering any concrete proof. So far even the experts have had to admit that no solid evidence has emerged that this is anything but a natural phenomenon. And the uncertainty has given skeptics-especially Gingrichian politicians--plenty of ammunition to argue against taking the difficult, expensive steps required to stave off a largely hypothetical calamity.
Until now, A draft report currently circulating on the Internet asserts that the global temperature rise can now be blamed, at least in part, on human activity. Statements like this have been made before by individual researchers-who have been criticized for going too far beyond the scientific consensus. But this report comes from the International Panel on Climate Change (IPCC), a respected UN sponsored body made up of more than 1,300 leading climate experts from 40 nations. This shift in scientific consensus is based not so much on new data as on improvements in the complex computer models that climatologists use to test their theories. Unlike chemists or molecular biologists, climate experts have no way to do lab experiments on their specialty. So they simulate them on supercomputers and look at what happens when human generated gases-carbon dioxide from industry and auto exhaust, methane from agriculture, chlorofluoro carbons from leaky refrigerators and spray cans-are pumped into the models virtual atmospheres.
Until recently, the computer models weren’t working very well. When the scientists tried to simulate what they believe has been happening over the past century or so, the results didn’t mesh with reality; the models said the world should now he warmer than it actually is. The reason is that the computer models had been overlooking an important factor affecting global temperatures: sulfur dioxides that are produced along with CO2 when fossil fuels are burned in cars and power plants. Aerosols actually cool the planet by blocking sunlight and mask the effects of global warmning. Once the scientists factored in aerosols, their models began looking more like the real world. The improved performance of the simulations was demonstrated in 1991, when they successfully predicted temperature changes in the aftermath of the massive Mount Pinatubo eruption in the Philippines. A number of studies since have added to the scientists confidence that they finally know what they are talking about-and can predict what may happen if greenhouse gases continue to be pumped into the atmosphere unchecked.
The computer models failed to picture reality because______.

A:they only simulate what has happened over the past century B:they are wrongly programmed C:scientists didn’t take aerosols into consideration D:too many chemicals are produced along with CO2

Wind, wave and tides all suffer from the fact that they are variable sources of power output. For example, there will be times when due to windless days or calm seas—and both can occur for periods of several days even in the winter time—they are producing little or no power.
Insofar as this shortfall has to be made up by electricity from conventional power stations, these newer energy sources would not necessarily reduce the installed capacity of such conventional stations needed to meet the total demand on windless or calm days. What the newer sources will do is to save fuel that would otherwise be burned in conventional power stations.
Pumped storage reservoirs could in principle be used to counter this effect, but there 1 is not enough additional reservoir capacity available. We therefore face the same type of storage problem as in solar energy. Thus, unless some new method of energy storage can be developed or we move to the widespread use of a fuel like hydrogen, the wind and wave schemes will be at an economic disadvantage.

The energy produced by the sun （）

A:is easy to store B:poses similar problems to the other newer energy sources C:poses very few problems D:poses different problems from the other newer energy sources

Wind, wave and tides all suffer from the fact that they are variable sources of power output. For example, there will be times when due to windless days or calm seas—and both can occur for periods of several days even in the winter time—they are producing little or no power.
Insofar as this shortfall has to be made up by electricity from conventional power stations, these newer energy sources would not necessarily reduce the installed capacity of such conventional stations needed to meet the total demand on windless or calm days. What the newer sources will do is to save fuel that would otherwise be burned in conventional power stations.
Pumped storage reservoirs could in principle be used to counter this effect, but there 1 is not enough additional reservoir capacity available. We therefore face the same type of storage problem as in solar energy. Thus, unless some new method of energy storage can be developed or we move to the widespread use of a fuel like hydrogen, the wind and wave schemes will be at an economic disadvantage.

Alternative sources of energy （）

A:could not possibly reduce the installed capacity of conventional power stations B:might not reduce the installed capacity of conventional power stations C:would automatically reduce the installed capacity of conventional power stations D:would make it necessary to reduce the installed capacity of conventional power stations

Wind, wave and tides all suffer from the fact that they are variable sources of power output. For example, there will be times when due to windless days or calm seas—and both can occur for periods of several days even in the winter time—they are producing little or no power.
Insofar as this shortfall has to be made up by electricity from conventional power stations, these newer energy sources would not necessarily reduce the installed capacity of such conventional stations needed to meet the total demand on windless or calm days. What the newer sources will do is to save fuel that would otherwise be burned in conventional power stations.
Pumped storage reservoirs could in principle be used to counter this effect, but there 1 is not enough additional reservoir capacity available. We therefore face the same type of storage problem as in solar energy. Thus, unless some new method of energy storage can be developed or we move to the widespread use of a fuel like hydrogen, the wind and wave schemes will be at an economic disadvantage.

The power produced by the waves, tide and wind（）

A:is not as consistent as it should be B:is generally less in winter than in summer C:is never likely to be very great D:is consistent

Wind, wave and tides all suffer from the fact that they are variable sources of power output. For example, there will be times when due to windless days or calm seas—and both can occur for periods of several days even in the winter time—they are producing little or no power.
Insofar as this shortfall has to be made up by electricity from conventional power stations, these newer energy sources would not necessarily reduce the installed capacity of such conventional stations needed to meet the total demand on windless or calm days. What the newer sources will do is to save fuel that would otherwise be burned in conventional power stations.
Pumped storage reservoirs could in principle be used to counter this effect, but there 1 is not enough additional reservoir capacity available. We therefore face the same type of storage problem as in solar energy. Thus, unless some new method of energy storage can be developed or we move to the widespread use of a fuel like hydrogen, the wind and wave schemes will be at an economic disadvantage.

What, according to this passage, would be the major impact of the newer energy sources（）

A:A reduction of the fuel consumed by conventional power stations. B:A reduction of the manpower required by conventional power stations. C:The total replacement of conventional power stations. D:The total replacement of conventional energy sources.

Wind, wave and tides all suffer from the fact that they are variable sources of power output. For example, there will be times when due to windless days or calm seas—and both can occur for periods of several days even in the winter time—they are producing little or no power.
Insofar as this shortfall has to be made up by electricity from conventional power stations, these newer energy sources would not necessarily reduce the installed capacity of such conventional stations needed to meet the total demand on windless or calm days. What the newer sources will do is to save fuel that would otherwise be burned in conventional power stations.
Pumped storage reservoirs could in principle be used to counter this effect, but there 1 is not enough additional reservoir capacity available. We therefore face the same type of storage problem as in solar energy. Thus, unless some new method of energy storage can be developed or we move to the widespread use of a fuel like hydrogen, the wind and wave schemes will be at an economic disadvantage.

Hydrogen （）

A:is a widely-used fuel B:is not yet in general use as a fuel C:is not a particularly easy fuel to store D:is a more economical fuel than wind energy

Central heating became popular only after the Civil War. Typically, coal-burning furnaces (火炉) fueled the early systems. Natural gas had developed into the leading fuel by 1960. Its acceptance resulted in part from its wide uses. Because it comes primarily from U.S. and Canadian fields, natural gas is also less vulnerable (脆弱的) than oil is to War. Oil remains the most important fuel in a few areas, such as New England.
Electric heating dominates most areas with mild winters and cheap electricity, including the South and the Northwest. It was made popular at least in the South by the low cost of adding electric heating to new houses built with air-conditioning. Bottled gas, which is somewhat more expensive than utility gas, is the fuel of choice in rural areas not served by utility pipelines. Wood is the leading heating fuel in just a few rural counties.
Home heating, which accounts for less than 7 percent of all energy consumed in the U.S., has had a commendable (值得赞扬的) efficiency record: from 1978 to 1997, the amount of fuel consumed for this purpose declined 44 percent despite a 33 percent increase in the number of housing units and an increase in house size. The U.S. Department of Energy, however, forecasts that energy used in home heating will rise by 14 percent over the next two decades. That rise is small considering an expected 21 percent increase in the number of houses and the trend toward larger houses.
Natural gas and electricity will probably dominate the home heating market for the next two decades. Solar (太阳的) heating never became popular because of cost and limited winter sunlight in most areas; in 2000 only 47,000 homes relied on it.
The word "consumed" in paragraph 3 could be best replaced by ______.

A:used B:burned C:delivered D:pumped

Home Heating
Central heating became popular only after the Civil War. Typically, coal-burning furnaces (火炉) fueled the early systems. Natural gas had developed into the leading fuel by 1960. Its acceptance resulted in part from its wide uses. Because it comes primarily from U.S. and Canadian fields, natural gas is also less vulnerable (脆弱的) than oil is to war. Oil remains the most important fuel in a few areas, such as New England.
Electric heating dominates most areas with mild winters and cheap electricity, including the South and the Northwest. It was made popular at least in the South by the Iow cost of adding electric heating to new houses built with air-conditioning. Bottled gas, which is somewhat more expensive than utility gas, is the fuel of choice in rural areas not served by utility pipelines. Wood is the leading heating fuel in just a few rural counties.
Home heating, which accounts for less than 7 percent of all energy consumed in the U.S., has had a commendable (值得赞扬的) efficiency record: from 1978 to 1997, the amount of fuel consumed for this purpose declined 44 percent despite a 33 percent increase in the number of housing units and an increase in house size. The U. S. Department of Energy, however, forecasts that energy used in home heating will rise by 14 percent over the next two decades. That rise is small considering an expected 21 percent increase in the number of houses and the trend toward larger houses.
Natural gas and electricity will probably dominate the home heating market for the next two decades. Solar (太阳的) heating never became popular because of cost and limited winter sunlight in most areas; in 2000 only 47, 000 homes relied on it.
The word "consumed" in paragraph 3 could be best replaced by

A:used. B:burned. C:delivered. D:pumped.

{{B}}第二篇{{/B}}

The word "consumed" in paragraph 3 could be best replaced by

A:used. B:burned. C:delivered. D:pumped.

第二篇 Home Heating Central heating became popular only after the Civil War. Typically, coal—burning furnaces(火炉)fueled the early systems．Natural gas had developed into the leading fuel by 1960.Its acceptance resulted in part from its wide uses．Because it comes primarily from U．S．and Canadian fields，natural gas is also less vulnerable(脆弱的)than oil is to War．Oil remains the most important fuel in a few areas．such as New England． Electric heating dominates most areas with mild winters and cheap electricity, including the South and the Northwest．It was made popular at least in the South by the low cost of adding electric heating to new houses built with air．conditioning．Bottled gas．which is somewhat more expensive than utility gas，is the fuel of choice in rural areas not served by utility pipelines．Wood is the leading heating fuel in just a few rural counties． Home heating，which accounts for less than 7 percent of a11 energy consumed in the U．S．，has had a commendable(值得赞扬的)efficiency record：from 1978 to 1997，the amount of fuel consumed for this purpose declined 44 percent despite a 33 percent increase in the number of housing units and an increase in house size．The U．S．Department of Energy。however, forecasts mat energy used in home heating will rise by 14 percent over the next two decades．That rise is small considering an expected 2 1 percent increase in the number of houses and the trend toward larger houses． Natural gas and electricity will probably dominate the home heating market for the next two decades．Solar(太阳的)heating never became popular because of cost and limited winter sunlight in most areas；in 2000 only 47.000 homes relied on it． The word “consumed’’ in paragraph 3 could be best replaced by

A:used． B:burned． C:delivered． D:pumped．