Earth's Greenhouse Gas Levels Approach Milestone

The ratio of carbon dioxide in Earth’s atmosphere is approaching with 400 parts per million. This amount of carbon dioxide in the atmosphere has not been seen since about 2.5 million to 5 million year ago. Scientists are alarmed that CO₂ levels are also rising in places far from pollution sources. The Los Angeles Times reports:

"The 400-ppm threshold is a sobering milestone, and should serve as a wake-up call for all of us to support clean-energy technology and reduce emissions of greenhouse gases, before it's too late for our children and grandchildren," said Tim Lueker, an oceanographer and carbon cycle researcher who is a longtime member of the Scripps CO₂ Group.

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