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Messing with the Earth's Breath
Why reaching 400 ppm is more than just crossing some arbitrary climate change threshold.

In grad school, one of my professors, the journalist Jonathan Weiner, told us the story of visiting Hawaii's Mauna Loa earth observatory in the mid-1980s while researching his book The Next One Hundred Years. Atop an active volcano, Jonathan was asked to breathe on a new intake valve as part of an informal test of the equipment that, since 1958, has kept continuous track of the average daily concentration of carbon dioxide in the earth’s atmosphere.

The exhalation from my professor’s lungs was enough to show a momentary spike on the station’s monitors to a CO2 level of 378 parts per million (don’t worry, climate skepticsthe scientists filtered out the tiny anomaly from the long-term readings). The experience helped inspire Jonathan’s memorable description of the Mauna Loa observatory measuring “the breathing of the world.”

Last week, those same monitors showed that the world’s breath has grown increasingly dangerous to the other life cycles of our planet. For the first time since the Pliocene Epoch, when sea levels were at least 30 feet higher than today and camels roamed the Arctic, the average daily concentration of atmospheric CO2 has topped 400 ppm. And unlike in the past, when natural cycles caused carbon dioxide levels to rise and fall over periods of hundreds of thousandsand sometimes millionsof years, we’ve seen an extreme shift of more than 100 ppm in less than a century. That’s a swing that, as far as scientists know, is pretty much unprecedented.

Of course, just because we’ve crossed the arbitrary threshold of some big, round number doesn’t mean we’ll suddenly start seeing vineyards in Siberia and high tides on 34th Street. CO2 levels have been rising, resulting in slow but steady worldwide climate shifts, since coal dust started spewing into the atmosphere in the early days of the Industrial Revolution. But the 20th century saw a huge increase in fossil fuel burning, and the atmosphere and oceans have responded in kind. Deserts expand, Arctic ice shrinks, crop ranges wander, and extreme storms become routine. That doesn’t mean we won’t still see a cold winter every now and again, but it does mean that our grandchildren will grow up under very different conditions than those experienced by our grandparents and their grandparentsand a long line of grandparents going all the way back to cave painting times.

Human activity has dramatically altered the world’s breath; how can we possibly expect the rest of the world not to change along with it?

If crossing the 400 ppm threshold does anything, it should add a further sense of urgency to efforts to halt and, if possible, reverse the effects of our own activity. “Ultimately, we have to invent our way out,” writes Nicholas Thompson at the New Yorker, expressing the technological optimist’s perspective. “Everything we use that emits carbon dioxide needs to be replaced with something that doesn’t, whether a car or a cooking stove.” Then there are the related options of using less than we do now, or making everything that we do use that much more efficient.

The truth is, we need to utilize every option available to us, and ensure that 400 ppm isn’t just a number that historians one day look back on as a milestone we crossed and left far behind. It’s a number that we need to strive to reach againthis time, when we’re headed in the other direction, back down to the numbers our grandparents and their grandparents would find familiar.

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image of Scott Dodd
Scott Dodd is the editorial director of NRDC, which publishes OnEarth. He was a newspaper reporter for 12 years, contributing to coverage of Hurricane Katrina that won a Pulitzer Prize, and has written for Scientific American, Slate, and other publications. CJR praised his expansion of OnEarth.org as an outlet for "bang-up investigative journalism." He also teaches at Columbia University. MORE STORIES ➔