雅思阅读练习题：全球变暖_雅思
爱思学雅思网特为大家准备了雅思阅读练习题：全球变暖，供大家学习参考。雅思阅读备考阶段，同学们需要通过适量的练习题来检测自己的备考效果。希望以下内容能够对大家的雅思备考有所帮助!
The Arctic seems to be getting warmer. So what?
A. “Climate change in the Arctic is a reality now!” So insists Robert
Corell, an oceanographer with the American Meteorological Society. Wild-eyed
proclamations are all too common when it comes to global warming, but in this
case his assertion seems well founded.
B. At first sight, the ACIA’s (American Construction Inspectors
Association) report’s conclusions are not so surprising. After all, scientists
have long suspected that several factors lead to greater temperature swings at
the poles than elsewhere on the planet. One is albedo —the posh scientific name
for how much sunlight is absorbed by a planet’s surface, and how much is
reflected. Most of the Polar Regions are covered in snow and ice, which are much
more reflective than soil or ocean. If that snow melts, the exposure of dark
earth (which absorbs heat) acts as a feedback loop that accelerates warming. A
second factor that makes the poles special is that the atmosphere is thinner
there than at the equator, and so less energy is required to warm it up. A third
factor is that less solar energy is lost in evaporation at the frigid poles than
in the steamy tropics.
C. And yet the language of this week’s report is still eye-catching: “the
Arctic is now experiencing some of the most rapid and severe climate change on
Earth.” The last authoritative assessment of the topic was done by the UN’s
Intergovernmental Panel on Climate Change (IPCC) in 2001. That report made
headlines by predicting a rise in sea level of between 10cm (four inches) and
90cm, and a temperature rise of between 1.4°C and 5.8°C over this century.
However, its authors did not feel confident in predicting either rapid polar
warming or the speedy demise of the Greenland ice sheet. Pointing to evidence
gathered since the IPCC report, this week’s report suggests trouble lies
ahead.
D. The ACIA reckons that in recent decades average temperatures have
increased almost twice as fast in the Arctic as they have in the rest of the
world. Skeptics argue that there are places, such as the high latitudes of the
Greenland ice sheet and some buoys at sea, where temperatures seem to have
fallen. On the other hand, there are also places, such as parts of Alaska, where
they have risen far faster than average. Robin Bell, a geophysicist at Columbia
University who was not involved in the report’s compilation, believes that such
conflicting local trends point to the value of the international,
interdisciplinary approach of this week’s report. As he observes, “climate
change, like the weather, can be patchy and you can get fooled unless you look
at the whole picture.”
E. And there is other evidence of warming to bolster the ACIA’s 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 week’s
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
(since trees capture carbon dioxide, the greenhouse gas most talked about in the
context of climate change), 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 region’s unusually
mild winters,” he added. Some of the ACIA’s experts are fretting over evidence
of reduced density and salinity in waters near the Arctic that could adversely
affect this current.
I. The biggest popular worry, though, is that melting Arctic ice could lead
to a dramatic rise in sea level. Here, a few caveats are needed. For a start,
much of the ice in the Arctic is floating in the sea already. Archimedes’s
principle shows that the melting of this ice will make no immediate difference
to the sea’s level, although it would change its albedo. Second, if land ice,
such as that covering Greenland, does melt in large quantities, the process will
take centuries. And third, although the experts are indeed worried that global
warming might cause the oceans to rise, the main way they believe this will
happen is by thermal expansion of the water itself.
J. Nevertheless, there is some cause for nervousness. As the ACIA
researchers document, there are signs that the massive Greenland ice sheet might
be melting more rapidly than was thought a few years ago. Cracks in the sheet
appear to be allowing melt water to trickle to its base, explains Michael
Oppenheimer, a climatologist at Princeton University who was not one of the
report’s authors. That water may act as a lubricant, speeding up the sheet’s
movement into the sea. If the entire sheet melted, the sea might rise by 6-7
meters. But when will this kind of disastrous ice disintegration really happen?
While acknowledging it this century is still an unlikely outcome, Dr.
Oppenheimer argues that the evidence of the past few years suggests it is more
likely to happen over the next few centuries if the world does not reduce
emissions of greenhouse gases. He worries that an accelerating Arctic warming
trend may yet push the ice melt beyond an “irreversible on / off switch”.
K. That is scary stuff, but some scientists remain unimpressed. Patrick
Michaels, a climatologist at the University of Virginia, complains about the
ACIA’s data selection, which he believes may have produced evidence of “spurious
warming”. He also points out, in a new book, that even if Arctic temperatures
are rising, that need not lead directly to the ice melting. As he puts it,
“Under global warming, Greenland’s ice indeed might grow, especially if the
warming occurs mostly in winter. After all, warming the air ten degrees when the
temperature is dozens of degrees below freezing is likely to increase snowfall,
since warmer air is generally moister and precipitates more water.”
L. Nils-Axel Morner, a Swedish climate expert based at Stockholm
University, points out that observed rises in sea levels have not matched the
IPCC’s forecasts. Since this week’s report relies on many such IPCC assumptions,
he concludes it must be wrong. Others acknowledge that there is a warming trend
in the Arctic, but insist that the cause is natural variability and not the
burning of fossil fuels. Such folk point to the extraordinarily volatile history
of Arctic temperatures. These varied, often suddenly, long before sport-utility
vehicles were invented. However, some evidence also shows that the past few
millennia have been a period of unusual stability in the Arctic. It is just
possible that the current period of warming could tip the delicate Arctic
climate system out of balance, and so drag the rest of the planet with it.
M. Not everybody wants to hear a story like that. But what people truly
believe is happening can be seen in their actions better than in their words.
One of the report’s most confident predictions is that the breakup of Arctic ice
will open the region to long-distance shipping and, ironically, to drilling for
oil and gas. It is surely no coincidence, then, that the Danish government,
which controls Greenland, has just declared its intention to claim the mineral
rights under the North Pole. It, at least, clearly believes that the Arctic
ocean may soon be ice-free.
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