FROM THE ARTICLE:
"Somehow in the last 50 ppm we melted the Arctic," said environmentalist and founder of activist group 350.org Bill McKibben, who called today's news a "grim but predictable milestone" and has long used the symbolic number as a rallying call for climate action. "We'll see what happens in the next 50."
We could find out soon enough: With the East Coast still recovering from Superstorm Sandy and the West gearing up for what promises to be a nasty fire season, University of California ecologist Max Moritz says milestones like these are "an excuse for us to take a good hard look at where we are," especially as the carbon concentration shows no signs of reversing course.
Scientists first saw the carbon scale tip past 400 ppm last summer, but only briefly; the record reported today by NOAA is the first time a daily average has surpassed that point. For the last several years concentrations have hovered in the 390s, and we're still not to the point where the carbon concentration will stay above the 400 ppm threshold permanently. But that's just around the corner, said J. Marshall Shepherd, president of the American Meteorological Society.
"It's clear that sometime next year we'll see 400 consistently," he said. "Avoiding the future warming will require a large and rapid reduction in greenhouse gases."