For the first time in about 5 million years, the amount of carbon dioxide in the Earth’s atmosphere is forecast to top 400 parts per million next month.
Human ancestors were just learning how to walk on two feet about that time, on a world that was much warmer than the one we walk on today.
Carbon dioxide is the greenhouse gas that is responsible for 63 percent of the warming attributable to all greenhouse gases, according to the National Oceanic and Atmospheric Administration’s Earth System Research Lab.
This latest report comes from the Scripps Institution of Oceanography, keepers of the famed “Keeling Curve,” the longest continuous record of carbon dioxide measurements on the planet. The record was begun in 1958 by Scripps climate scientist Charles Keeling.
When Keeling first began his measurements, the amount of CO2 was 316 parts per million. As of Tuesday, the reading was 398.44 ppm.
Increasing amounts of carbon dioxide and other gases caused by the burning of the oil, gas and coal that power our world are enhancing the natural “greenhouse effect,” causing the planet to warm to levels that climate scientists say can’t be linked to natural forces.
Carbon dioxide levels were around 280 ppm before the Industrial Revolution, when we first began releasing large amounts into the atmosphere by burning fossil fuels.
For the last 800,000 years, CO2 levels never exceeded 300 parts per million, according to Scripps, which measures CO2 levels along with several other agencies, including NOAA.
“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, a Scripps oceanographer.
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