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| q |
The atmospheric concentration of carbon dioxide (CO2) has
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increased by 31% since 1750. The present CO2 concentration
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has not been exceeded during the past 420,000 years and likely
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not during the past 20 million years. The current rate of increase
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is unprecedented during at least the past 20,000 years.
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| q |
About three-quarters of the anthropogenic emissions of CO2 to
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the atmosphere during
the past 20 years is due to fossil fuel
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burning. The rest
is predominantly due to land-use change,
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especially deforestation.
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| q |
Currently the ocean and the land together are taking up about
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half of the anthropogenic CO2 emissions. On land, the uptake of
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anthropogenic CO2 very likely exceeded the release of CO2 by
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deforestation during the 1990s.
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