Earth’s atmosphere will have the highest concentration of carbon dioxide in recorded human history any day now, according to scientists working on the problem of global warming.

Recent testing showed CO₂ levels reached 399.72 parts per million (ppm), leaving it all but certain that the 400ppm milestone will be reached.

“I wish it weren’t true but it looks like the world is going to blow through the 400ppm level without losing a beat. At this pace we’ll hit 450ppm within a few decades,” Ralph Keeling, a geologist with the Scripps Institution of Oceanography, said in a Scripps news release.

Tim Lueker, an oceanographer and carbon cycle researcher with the Scripps CO₂ Program, warned: “The 400ppm 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.”

The last time CO₂ levels were so high was likely between 3.2 million and 5 million years ago, during the Pliocene epoch, when the planet was much warmer than now. During the past 800,000 years, CO₂ levels had never exceeded 300ppm.

The tracking of these measurements was begun in March 1958—when the CO₂ level was 316ppm—by Scripps climate science pioneer Charles David Keeling, Ralph’s father.

-Noel Brinkerhoff

To Learn More:

Global Carbon Dioxide Levels on Pace to Hit ‘Sobering Milestone’ of 400ppm (by John Vidal, The Guardian)

Climate Collision Course: CO2 Levels About to Hit 400 PPM (by Andrea Germanos, Common Dreams)

As CO2 Approaches Symbolic Milestone, Scripps Launches Daily Keeling Curve Update (Scripps Institution of Oceanography)

The Keeling Curve (Scripps Institution of Oceanography)

U.S. Carbon Emissions to Hit 18-Year Low (by Matt Bewig, AllGov)       

U.S. Leads the World in Cutting CO2 Emissions…With Help from Fracking and Poor Economy (by Noel Brinkerhoff, AllGov)     

Big Coal Polluters Get a Pass in Obama’s Environmental Plan (by Noel Brinkerhoff, AllGov)