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  3. The Role of the Ocean in Controlling Climate P1: Computer models are one of the tools that scientists use to understand the clim

The Role of the Ocean in Controlling Climate P1: Computer models are one of the tools that scientists use to understand the clim

admin2019-03-10  30
问题 The Role of the Ocean in Controlling Climate
P1: Computer models are one of the tools that scientists use to understand the climate and make projections about how it will respond to changes such as rising greenhouse gas levels. The computer models used to predict climate change are far more sophisticated than the one that forecasts the weather. They are multi-layered programs in which scientists try to replicate the physics behind things such as rainfall, ocean currents, and the melting of sea ice. Because of their complexity and size, supercomputers are used to run full-scale climate models. Much of the uncertainty in their outputs comes from the way that various aspects of the climate are represented by different models, and even more so, because there are aspects of climate that are not well understood—one of which is how the ocean impacts climate.
P2: As one of the planet’s principal carbon absorbers, the ocean soaks up roughly one-third of all human carbon emissions, reducing the amount of atmospheric carbon dioxide and its associated global effects. This benefit stems from the fact that numerous marine plants and algae, especially phytoplankton, are photosynthetic, meaning they have the ability to use sunlight to convert carbon dioxide and water into energy. Then what controls the amount of phytoplankton? There are several limiting factors, but results from a recent experiment suggest that in areas of the ocean where other nutrients are plentiful, iron may be one of the most important and, until recently, unrecognized variables controlling phytoplankton production. Some researchers claimed that adding iron to the sea could induce phytoplankton blooms, which might alleviate the impact of global warming by consuming a significant amount of carbon dioxide in the atmosphere. But this radical approach was rather controversial. It was demonstrated for the first time after research conducted by the University of Liverpool that carbon, absorbed by algae in an iron-fertilized bloom, can sink to the ocean bed, where scientists believe it will remain in a fluff layer for many centuries or longer.
P3: In the ocean, carbon dioxide is also removed and placed into long term storage by the burial of sedimentary strata, especially coal and black shale, which stores organic carbon from undecayed biomass and carbonate rocks like limestone. However, when deposits of limestone become exposed and weathered on land or are recycled in the sea, carbon dioxide is released back into the atmosphere. Gas hydrates are another threat to global warming. Gas hydrates are crystalline solids of water, which release massive amounts of methane gas when ocean temperatures increase. Consequently, massive hydrate dissolution events are possible causes of some of the abrupt increases in temperature seen in the geologic record. Besides, localized melt-downs have caused massive continental slope failure, which can present a geological hazard for shelf oil and gas production.
P4: The ocean is also a great reservoir and transporter of heat. Heat from the ocean warms the atmosphere and fuels tropical storms. Heat is transported by currents from the equator to the poles. Evaporation from the ocean also supplies the precipitation that creates fields of snow and ice at high latitudes. Snow and ice coverage change the reflectivity of Earth’s surface and are an important influence on how much incoming radiation is either absorbed or reflected. Furthermore, clouds and water vapor in the atmosphere come mainly from the sea and strongly influence climate. Surprisingly, clouds are one of the least understood and most poorly modeled parts of the climate change equation. Most climate modeling grids fail to take into account common-sized cloud formations. To accurately depict how individual clouds form and disappear, for instance, the computers that model climate change would need to be a million times faster. For now, the effects of clouds have to be estimated. But scientists say complexity doesn’t guarantee accuracy and the best test of a model is to check it against reality.
P3: In the ocean, carbon dioxide is also removed and placed into long term storage by the burial of sedimentary strata, especially coal and black shale, which stores organic carbon from undecayed biomass and carbonate rocks like limestone. ■ However, when deposits of limestone become exposed and weathered on land or are recycled in the sea, carbon dioxide is released back into the atmosphere.■ Gas hydrates are another threat to global warming. ■ Gas hydrates are crystalline solids of water, which release massive amounts of methane gas when ocean temperatures increase. ■ Consequently, massive hydrate dissolution events are possible causes of some of the abrupt increases in temperature seen in the geologic record. Besides, localized melt-downs have caused massive continental slope failure, which can present a geological hazard for shelf oil and gas production.
According to paragraph 3, why are gas hydrates a possible threat to the global climate?
选项 A、If disturbed by offshore drilling, they can destroy limestone deposits.
B、They can replace regular ice at certain locations.
C、If melted, they may release a lot of carbon dioxide into the atmosphere.
D、They contain a lot of methane, which may be released as the ocean warms.
答案D
解析 【事实信息题】第4句提到天然气水合物是固态的水，当海洋温度升高时，它将释放大量的甲烷气体，所以天然气水合物是全球变暖的另一个威胁。
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