题目内容
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A．The former was on teaching and the latter is on research.
B．The former was on teaching and the latter is on the combination of teaching and research.
C．The former was on the combination of teaching and research and the latter is on teaching
D．The former was on research and the latter is on teaching.
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更多“A．The former was on teaching and the latter is on research.B．The former was on teachin”相关的问题
A. reference
B. interdependence
C. independence
D. indifference
A、transportation
B、shuttle bus
C、vehicle
D、taxi stand
A、knowledge
B、beliefs
C、art
D、morals
Earth's climate has been changing constantly over its 5-billion-year history.
Sometimes, the climate has warmed so that the oceans have risen and covered much of the Earth. Each of the changes may seem extreme, but they usually occurred slowly over many thousands of years.
Ancient Climate History
The first people arrived in America between 15,000 and 30,000 years ago. During that time, much of North America was covered by great ice sheets. Some 14,000 years ago, the last ice sheet began to melt very quickly. By 7,000 years ago, the ice was gone. This end to the ice ages caused big changes on the Earth. The changes caused many kinds of plants and animals to die. For example, mastodons—elephant-like animals—and other large mammals that preferred cold climates may not have been able to live in the warmer, drier conditions.
The Little Ice Age
Starting in the 14th century, Europeans lived through what is known as the "Little Ice Age." The Little Ice Age lasted for several hundred years. During the Little Ice Age, the advance of glaciers along with hard winters and famines caused some people to starve and others to leave their homes.
Recent Climate History
The Earth has warmed about 1°F in the last 100 years. And the four warmest years of the 20th century all happened in the 1990s. Periods of increased heat from the sun may have helped make the Earth warmer. But many of the world's leading climatologists think that the greenhouse gases people produce are making the Earth warmer, too.
Scientists think the sea has risen partly because of melting glaciers and sea ice. When some glaciers melt, they release water into the sea and make it higher than it was before. Scientists also think that warmer temperatures in the sea make it rise even more. Heat makes water expand. When the ocean expands, it takes up more space.
What Might Happen？
Scientists are not fortune-tellers. They don't know exactly what will happen in the future. But they can use special computer programs to find out how the climate may change in the years ahead. And the computer programs tell us that the Earth may continue to get warmer.
Together, the melting glaciers, rising seas, and computer models provide some good clues. They tell us that the Earth's temperature will probably continue to rise as long as we continue increasing the amount of greenhouse gases in the atmosphere.
Scientists have to think like detectives. They look for clues to help them understand how the world works. Then they investigate the clues to find evidence—real facts that can give them a better idea of what is going on. Here are some of the ways that scientists gather evidence about climate, both past and present:
Weather Stations
Weather stations help us find out the temperature on the surface of the Earth. Weather stations use special thermometers that tell us the temperature. They can be set up almost anywhere on land. Weather stations also can tell us how fast the wind is moving and how much rain falls on the ground during a storm.
Weather Balloons
Almost everyone likes balloons—including scientists! Weather balloons are released to float high up into the atmosphere. They carry special instruments that send all kinds of information about the weather back to people on the ground.
Ocean Buoys
A buoy is an object that floats on water, and is often used to warn boats away from dangerous places in the ocean or on a river. But some buoys have special instruments on them. These buoys can tell us the temperature and other things about the conditions of the atmosphere.
Weather Satellites
Humans send satellites into space to travel around the Earth. The satellites send back
A．Y
B．N
C．NG
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