Carbon dioxide hits a level not seen for 3 million years. Here's what that means for climate change — and humanity

https://www.nbcnews.com/mach/science/carbon-dioxide-hits-level-not-seen-3-million-years-here-ncna1005231?fbclid=IwAR238O-JT1VffXhuV5-8fvhHQZSTfc2rlz7sYDPD5_tBsEjcz12NVYgZxd0

May 14, 2019, 4:39 AM EDT
By Denise Chow

In the latest bit of bad news for a planet beset by climate change, the concentration of carbon dioxide in Earth’s atmosphere has climbed to a level last seen more than 3 million years ago — before humans even appeared on the rocky ball we call home.

On Saturday, sensors at the Mauna Loa Observatory in Hawaii indicated that concentrations of the greenhouse gas — a byproduct of the burning of fossil fuels — had reached 415 parts per million (ppm), meaning that for every 1 million molecules of gas in the atmosphere, 415 were of carbon dioxide.

Carbon dioxide traps heat from the sun, and higher levels are associated with higher global temperatures and other effects of climate change, such as rising seas and unusual weather patterns.

The level of CO2 in the atmosphere has risen an average of 2.5 ppm per year over the past decade, reaching 400 ppm in 2013 — and the level appears likely to go higher from here.

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The last time levels of atmospheric carbon dioxide were this high came during the Pliocene Epoch, which extended from about 5.3 million to 2.6 million years ago. During that period, average sea levels were about 50 feet higher than they are today and forests grew as far north as the Arctic, said Rob Jackson, a professor of earth system science at Stanford University. “Earth was a very different place,” he said. “You would hardly recognize the land surface, and my gosh, we don’t want to go there.”

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If the current trajectory continues, levels of CO2 could hit 500 ppm within 30 years, a number that could mean an increase in global temperatures of at least 2 degrees Celsius (about 3.6 degrees Fahrenheit).

“At the present pace, we could reach that well within a lot of people’s lifetimes,” Keeling said of the grim milestone ahead.

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