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Coming on top of the previous years of extreme scarcity of food, however, the longer term economic implications were profound.

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A strong greenhouse effect will warm the oceans and partially melt glaciers, increasing ______.

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Ocean water also will expand if it warms, _______further to sea level rise.

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The clearing of land for agriculture, industry, and other human activities have increased ______ of greenhouse gases.

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Conjunctivitis caused by the common cold is very                  and can spread rapidly between people.

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Environmental groups want a substantial reduction in the emission of greenhouse gases.

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                is the gradual warming of the earth because of heat trapped by carbon dioxide and other gases in the atmosphere.