Earth’s atmosphere just crossed another troubling climate change threshold

For the first time since humans have been monitoring, atmospheric concentrations of carbon dioxide have exceeded 410 parts per million averaged across an entire month, a threshold that pushes the planet ever closer to warming beyond levels that scientists and the international community have deemed “safe.”

The reading from the Mauna Loa Observatory in Hawaii finds that concentrations of the climate-warming gas averaged above 410 parts per million throughout April. The first time readings crossed 410 at all occurred on April 18, 2017, or just about a year ago.

Carbon dioxide concentrations — whose “greenhouse gas effect” traps heat and drives climate change — were around 280 parts per million circa 1880, at the dawn of the industrial revolution. They’re now 46 percent higher.

As you can see in the famed “saw-toothed curve” graph above, more formally known as the Keeling Curve, concentrations have ticked upward in an unbroken progression for many decades. But they also go up and down on an annual cycle that’s controlled by the patterns and seasonality of plant growth around the planet.

The rate of growth is about 2.5 parts per million per year, said Ralph Keeling, who directs the CO2 program at the Scripps Institution of Oceanography, which monitors the readings. The rate has been increasing, with the decade of the 2010s rising faster than the 2000s.

“It’s another milestone in the upward increase in CO2 over time,” Keeling said of the newest measurements. “It puts us closer to some targets we don’t really want to get to, like getting over 450 or 500 ppm. That’s pretty much dangerous territory.”

via Earth’s atmosphere just crossed another troubling climate change threshold – The Washington Post