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[简答题]As evidence that the Earth’s atmosphere is warming continues to accumulate, scientists are making slow progress toward an answer to the big question raised by the evidence: (89) How much of the warming is due to human activity and how much to natural causes
The UN Intergovernmental Panel on Climate Change, (90) the group of scientists widely considered the most authoritative voice on the subject, has already concluded that there is a "discernible human influence" on the global climate. Now the panel is deep into another of its periodic full-scale scientific assessments of global climate change.
(91) Some experts on the problem say the human imprint on climate is becoming clearer, and may even have been the dominant factor in the global warming of recent decades. Not everyone agrees and virtually all experts say that in any case, a reliable estimate of the human imprint’s magnitude still remains some distance off.
A number of influences, both n
[简答题] How Global Warming Works
Gases in the Earth’’s atmosphere act like glass in a greenhouse-trapping heat and making life on Earth possible. But there is a delicate balance. Burning coal, oil and natural gas increases atmospheric concentrations of these gases. Over the past century, increases in industry, transportation, and electricity production have increased gas concentrations in the atmosphere faster than natural processes can remove them leading to human-caused warming of the globe.
The Sources Of Global Warming
The major source of global warming is carbon dioxide pollution from power plants, auto mobiles, and industry. Another source is global deforestation.
●Power plants are responsible for more than a third of U. S. CO2 emissions, yet there are no caps on CO2 emissions from power plants or any other industry.
●Gas guzzling cars and light trucks are also responsible for a third of U.S. CO2 emissions. Current regulations allow fo
