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Earth's carbon dioxide levels permanently pass 400 parts per million

(Associated Press)

Our planet has hit a scary threshold.

We are now permanently over 400 parts per million of carbon dioxide in the atmosphere.

Although the planet has gone over this number before, this is the first time we have not dropped below that number in a year, and most scientists think we won’t see a number below it again.

“The natural range is usually about 180-200 parts per million,” says Professor Daniel Scott. “So we’ve pushed it outside that natural range through greenhouse gas emissions. Punching through that threshold is more of a symbolic reminder of the challenges ahead.”

Scott is the Executive Director of the Interdisciplinary Centre on Climate Change at the University of Waterloo.

He says that although some people are saying this number is some kind of point of no return, there are no drastic differences than when we were at 390ppm.

He does agree though, that we are now beyond healthy levels for the atmosphere.

“Some scientists and most governments agree that a safe concentration of carbon in the atmosphere would be about 350 parts per million,” he says. “So we have to peak our emissions and actually reduce carbon dioxide in the atmosphere over the next several decades.”

Scott says the reduction of carbon dioxide levels is possible, with natural carbon sinks in the oceans being a big help, but we have to stop levels from rising first.

“All the countries of the world, including Canada, have signed up to transition our economy to a low-carbon economy, and this [rising above 400ppm] is a reminder that we need to get to that and achieve our objectives and commitments to the Paris Agreement sooner rather than later.”

Scott says if everyhing with the Paris Climate Change Agreement goes well, he could see levels starting to stabalize at around 450ppm in the next several decades, but it will take a lot of work and will be a long road ahead.