Scientists have long warned that some level of global warming is a done deal—due in large part to heat-trapping greenhouse gases humans already have pumped skyward. Now, however, researchers are fleshing out how much future warming and sea-level rise the world has triggered. The implicit message: "We can’t stop this, so how do we live with it" says Thomas Wigley, a climate researcher at NCAR.
One group, led by Gerald Meehl at NCAR, used two state-of-the-art climate models to explore what could happen if the world had held atmospheric concentrations of greenhouse gases steady since 2000. The results: Even if the world had slammed on the brakes five years ago, global average temperatures would rise by about 1 degree Fahrenheit by the end of the 21st century. Sea levels would rise by another 4 inches over 20th-century increases. Rising sea-levels would continue well beyond 2100, even without adding water from melting glaciers and ice sheets. The rise highlights the oceans’ enormous capacity to absorb heat and its slow reaction to changes in atmospheric conditions.
The team ran each model several times with a range of "what if" concentrations, as well as observed concentrations, for comparison. Temperatures eventually level out, Dr. Meehl says in reviewing his team’s results. "But sea-level increases keep ongoing. The relentless nature of sea-level rise is pretty daunting." Dr. Wigley took a slightly different approach with a simpler model. He ran simulations that capped concentrations, at 2000 levels. If concentrations are held constant, warming could exceed 1.8 degrees F. by 2400. The two researchers add that far from holding steady, concentrations of greenhouse gases continue to rise. Thus, at best, the results point to the least change people can expect, they say.
The idea that some level of global climate change from human activities is inevitable is not new. But the word has been slow to make its way into the broader debate. "Many people don’t realize we are committed right now to a significant amount of global warming and sea-level rise. The longer we wait, the more climate change we are committed to in the future," Meehl says.
While the concept of climate-change commitment isn’t new, these fresh results "tell us what’s possible and what’s realistic" and that for the immediate future, "prevention is not on the table," says Roger Pielke Jr., director of the Center for Science and Technology Policy Research. To Pielke and others, this means adaptation should be given a much higher priority that it’s received to date. "There’s a cultural bias in favor of prevention," he says. But any sound policy includes preparation as well, he adds. "We have the scientific and technological knowledge we need to improve adaptation and apply that knowledge globally./
By "at best, the results point to the least change people can expect", (Lines 7～8, Paragraph 3) the researchers try to tell us that

A:the impact of climate change is relatively minor. B:the global warming is inevitable in the near future. C:concentrations of greenhouse gases cannot be held steady. D:the atmospheric conditions will be better than people think.

There will be a steady trend toward vegetarianism. A given quantity of ground can provide plant food for man or it can provide plant food for animals which are later killed for meat. 　　In converting the tissues of food into the tissues of the feeder, up to 90 per cent is used for reasons other than tissue maintenance and growth. This means that one hundred pounds of plant food will support ten pounds of human tissue―while one hundred pounds of plant food will support ten pounds of animal tissue, which will then support one pound of human tissue. In other words, land devoted to plant food will support ten times as many human beings as land devoted to animal food. 　　It is this (far more than food preferences or religious directions ) that forces overcrowded populations into vegetarianism. And it will be the direction in which the United States of 2001 will be moving―not by presidential order, but through the force of a steady rise in meat prices as compared with other kinds of food. 　　This, in turn, will come about because our herds will decrease as the food demand causes more and more meadow to be turned to farmland, and as land producing corn and other animal food is converted to providing food directly for man. 　　Another point is that it is not only energy that is in short supply. A shortage of oil means a shortage of plastics; a shortage of electricity means a shortage of aluminium. We are also experiencing a shortage of paper and most other raw materials. 　　This means that, for one thing, our generosity in wrapping, bagging and packaging will have to recede. There will have to be at least a partial return in supermarkets to the old days where goods were supplied in bulk and given out in bags to order. It may even become necessary to return bags, as we once returned bottles, or pay for new ones. 　　A decline in per-capita energy use will make it necessary to resort to human muscle again, so that the delivery man will make a comeback (his price added to that of the food, of course).Since energy shortages will cause unemployment in many sectors of the economy, there will be idle hands to do the manual work that will become necessary. 　　From an energy-saving standpoint, it would make far more sense to order by phone and have a single truck deliver food to many homes, than for a member of each home to drive an automobile, round-trip, to pick up a one-family food supply. 　　To be sure, it will not all be retrogression. Even assuming that Earth is in a desperate battle of survival through a crisis of still rising population and dwindling energy reserves, there should still continue to be technological advances in those directions that don’’t depend on wasteful bulk use of energy. There will be continuing advances in the direction of "sophistication", in other words. The shortage of energy will result in

A:a steady decrease in the feeding of herds. B:a continual drop in recycling used packages. C:a forced return to an early stage of certain jobs. D:a great reduction in the kinds of motor vehicles.

There will be a steady trend toward vegetarianism. A given quantity of ground can provide plant food for man or it can provide plant food for animals which are later killed for meat. 　　In converting the tissues of food into the tissues of the feeder, up to 90 per cent is used for reasons other than tissue maintenance and growth. This means that one hundred pounds of plant food will support ten pounds of human tissue―while one hundred pounds of plant food will support ten pounds of animal tissue, which will then support one pound of human tissue. In other words, land devoted to plant food will support ten times as many human beings as land devoted to animal food. 　　It is this (far more than food preferences or religious directions ) that forces overcrowded populations into vegetarianism. And it will be the direction in which the United States of 2001 will be moving―not by presidential order, but through the force of a steady rise in meat prices as compared with other kinds of food. 　　This, in turn, will come about because our herds will decrease as the food demand causes more and more meadow to be turned to farmland, and as land producing corn and other animal food is converted to providing food directly for man. 　　Another point is that it is not only energy that is in short supply. A shortage of oil means a shortage of plastics; a shortage of electricity means a shortage of aluminium. We are also experiencing a shortage of paper and most other raw materials. 　　This means that, for one thing, our generosity in wrapping, bagging and packaging will have to recede. There will have to be at least a partial return in supermarkets to the old days where goods were supplied in bulk and given out in bags to order. It may even become necessary to return bags, as we once returned bottles, or pay for new ones. 　　A decline in per-capita energy use will make it necessary to resort to human muscle again, so that the delivery man will make a comeback (his price added to that of the food, of course).Since energy shortages will cause unemployment in many sectors of the economy, there will be idle hands to do the manual work that will become necessary. 　　From an energy-saving standpoint, it would make far more sense to order by phone and have a single truck deliver food to many homes, than for a member of each home to drive an automobile, round-trip, to pick up a one-family food supply. 　　To be sure, it will not all be retrogression. Even assuming that Earth is in a desperate battle of survival through a crisis of still rising population and dwindling energy reserves, there should still continue to be technological advances in those directions that don’’t depend on wasteful bulk use of energy. There will be continuing advances in the direction of "sophistication", in other words. The shortage of energy will result in

A:a steady decrease in the feeding of herds. B:a continual drop in recycling used packages. C:a forced return to an early stage of certain jobs. D:a great reduction in the kinds of motor vehicles.

There will be a steady trend toward vegetarianism. A given quantity of ground can provide plant food for man or it can provide plant food for animals which are later killed for meat. 　　In converting the tissues of food into the tissues of the feeder, up to 90 per cent is used for reasons other than tissue maintenance and growth. This means that one hundred pounds of plant food will support ten pounds of human tissue―while one hundred pounds of plant food will support ten pounds of animal tissue, which will then support one pound of human tissue. In other words, land devoted to plant food will support ten times as many human beings as land devoted to animal food. 　　It is this (far more than food preferences or religious directions ) that forces overcrowded populations into vegetarianism. And it will be the direction in which the United States of 2001 will be moving―not by presidential order, but through the force of a steady rise in meat prices as compared with other kinds of food. 　　This, in turn, will come about because our herds will decrease as the food demand causes more and more meadow to be turned to farmland, and as land producing corn and other animal food is converted to providing food directly for man. 　　Another point is that it is not only energy that is in short supply. A shortage of oil means a shortage of plastics; a shortage of electricity means a shortage of aluminium. We are also experiencing a shortage of paper and most other raw materials. 　　This means that, for one thing, our generosity in wrapping, bagging and packaging will have to recede. There will have to be at least a partial return in supermarkets to the old days where goods were supplied in bulk and given out in bags to order. It may even become necessary to return bags, as we once returned bottles, or pay for new ones. 　　A decline in per-capita energy use will make it necessary to resort to human muscle again, so that the delivery man will make a comeback (his price added to that of the food, of course).Since energy shortages will cause unemployment in many sectors of the economy, there will be idle hands to do the manual work that will become necessary. 　　From an energy-saving standpoint, it would make far more sense to order by phone and have a single truck deliver food to many homes, than for a member of each home to drive an automobile, round-trip, to pick up a one-family food supply. 　　To be sure, it will not all be retrogression. Even assuming that Earth is in a desperate battle of survival through a crisis of still rising population and dwindling energy reserves, there should still continue to be technological advances in those directions that don’’t depend on wasteful bulk use of energy. There will be continuing advances in the direction of "sophistication", in other words. The shortage of energy will result in

A:a steady decrease in the feeding of herds. B:a continual drop in recycling used packages. C:a forced return to an early stage of certain jobs. D:a great reduction in the kinds of motor vehicles.

Many scientists today are convinced that life exists elsewhere in the universe-life probably much like that on our own planet. They reason in the following way.
As far as astronomers can determine, the entire universe is built of the same matter. They have no reason to doubt that matter obeys the same laws in every part of the universe. Therefore, it is reasonable to guess that other stars, with their own planets, were born in the same way as our own solar system. What we know of life on earth suggests that life will arise wherever the proper conditions exist.
Life requires the right amount and kind of atmosphere. This eliminates all those planets in the universe that are not about the same size and weight as the earth. A smaller planet would lose its atmosphere; a larger one would hold too much of it.
Life also requires a steady supply of heat and light. This eliminates double stars, or stars that flare up suddenly. Only single stars that are steady sources of heat and light like our sun would qualify.
Finally, life could evolve only if the planet is just the right distance from its sun. With a weaker sun than our own, the planet would have to be closer to it. With a stronger sun, it would have to be farther away.
If we suppose that every star in the universe has a family of planets, then how many planets might support life First, eliminate those stars that are not like our sun. Next eliminate most of their planets; they are either too far from or too close to their suns. Then eliminate all those planets which are not the same size and weight as the earth. Finally, remember that the proper conditions do not necessarily mean that life actually does exist on a planet. It may not have begun yet, or it may have already died out.
This process of elimination seems to leave very few planets on which earthlike life might be found. However, even if life could exist on only one planet in a million, there are so many billions of planets that this would still leave a vast number on which life could exist.
The existence of life depends on all of the following factors EXCEPF ______.

A:the right amount of atmosphere B:our own solar system C:steady heat and light D:the right distance from the sun

{{B}}第三篇{{/B}}

According to the author, it is best for asthmatics to take their medicines ______

A:at steady rates B:each morning and evening C:when the disease occur D:at midafternoon