In an article released online on Monday, author Lauren Morello makes the case for 350 ppm as the upper limit of carbon dioxide in the atmosphere. With temperature increase predictions ranging from 2 to 6 degrees Celsius in the next 90 years, 450 ppm (the current target) is no longer considered realistic. Yet her research leads her to conclusions beyond any final, exact concentration. As she says, "Some scientists mapping out Earth's potential futures say both targets are arbitrary. What's essential, they insist, is that countries start cutting their greenhouse gas emissions soon and stay flexible in case the planet behaves in unexpected ways."
Very smart people, including Gavin Schmidt from NASA's Goddard Institute for Space Studies, Steven Schneider, from Stanford's Woods Institute for the Environment, and Jason Lowe, from Met Office's Hadley Center, contributed to the story.
Thanks to these bright minds, we know the time to start cutting emissions is now. And remember - for motivation's sake - any bit of press that the most important number on the planet can garner in the months leading up to Copenhagen is a positive indication that our efforts are succeeding.