Select your localized edition:

Close ×

More Ways to Connect

Discover one of our 28 local entrepreneurial communities »

Be the first to know as we launch in new countries and markets around the globe.

Interested in bringing MIT Technology Review to your local market?

MIT Technology ReviewMIT Technology Review - logo

 

Unsupported browser: Your browser does not meet modern web standards. See how it scores »

{ action.text }

The National Oceanic and Atmospheric Administration and Scripps Institution of Oceanography say that the carbon dioxide concentration in the atmosphere hit the symbolic milestone of 400 parts per million yesterday, up from about 280, the level it was at for thousands of years before the Industrial Revolution.

There are two things to keep in mind about carbon dioxide. First, it stays in the atmosphere for a long time—hundreds to thousands of years. If we stopped burning fossil fuels today, the concentration of carbon dioxide will start falling, but it will take over a thousand years to get back to pre-industrial levels (see “Climate Change: The Moral Choices”).

The second is that it takes a long time for the earth to respond to higher levels and reach a new state of equilibrium. So we won’t know for many decades—or even over a hundred years– what impact 400 parts per million will have.

That means that, while it will be a long time before we know what 400 parts per million will do to the planet, whatever it does we’ll be stuck with for a long time.

Here’s the takeaway from Scripps:  “There’s no stopping CO2 from reaching 400 ppm,” said Ralph Keeling [a geochemist at Scripps ]. “That’s now a done deal. But what happens from here on still matters to climate, and it’s still under our control. It mainly comes down to how much we continue to rely on fossil fuels for energy.”

48 comments. Share your thoughts »

Tagged: Energy, climate change, carbon dioxide, greenhouse gases, global warming

Reprints and Permissions | Send feedback to the editor

From the Archives

Close

Introducing MIT Technology Review Insider.

Already a Magazine subscriber?

You're automatically an Insider. It's easy to activate or upgrade your account.

Activate Your Account

Become an Insider

It's the new way to subscribe. Get even more of the tech news, research, and discoveries you crave.

Sign Up

Learn More

Find out why MIT Technology Review Insider is for you and explore your options.

Show Me