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Are Levels of Greenhouse Gases Increasing?

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Question: Are Levels of Greenhouse Gases Increasing?
Answer: Human activity is increasing the concentration of greenhouse gases in the atmosphere at a rate that has probably never been seen before in the planet's history. There is no serious scientific disagreement or debate on this point.

Greenhouse Gases at Record Levels
Prior to the start of the Industrial Revolution, the levels of carbon dioxide in the atmosphere were about 280 parts per million by volume (ppmv). Current levels are about 370 ppmv. The concentration of carbon dioxide and other key greenhouse gases in our atmosphere today is higher than at any time in the past 650,000 years, and probably higher than in the past 20 million years.

The Accumulation of Greenhouse Gases Continues
According to the Special Report on Emission Scenarios (SRES) from the Intergovernmental Panel on Climate Change, by the end of the 21st century we could expect to see carbon dioxide concentrations of anywhere from 490 ppmv to 1260 ppmv if we don't act now to lower greenhouse gas emissions that contribute to global warming. That's between 75 percent and 350 percent above pre-industrial concentrations.

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