Mauna Loa Observatory. Image: NOAA
Here are a few numbers that should change the way that we think about how humans live on planet Earth: 400, 3,000,000, and 7.
And here is what they mean: The concentration of carbon dioxide in the atmosphere is on the brink of being 400 parts per million—the leading tracker of atmospheric carbon levels, at the Mauna Loa Observatory in Hawaii, has already taken a few 400 ppm readings, and it is just a matter of time before the new record level is confirmed. (If you are curious to see this modern-day doomsday clock tick onwards, in real-time the Scripps Institute of Oceanography has a website it updates daily.)
The last time that the concentration of carbon dioxide in the atmosphere was that high was 3,000,000 years ago. It was the Plioscene era, and things were a little bit more volatile back then. For one thing, sea levels were up to 40 meters higher in places, and the world was, on average, 5-7 degrees warmer, Fahrenheit. Yep, 7 degrees warmer. That is the difference between 32˚ F and 39˚ F. 83˚ F and 90˚ F. That is enough to radically disrupt ecosystems across the planet, and also whether or not you can bear doing manual labor outdoors on a given day.
Human beings have flourished—we learned how to farm, how to domesticate animals, how to build gadgets to do that stuff better, and ultimately, how to organize permanent communities with tall buildings and waste disposal and transportation networks—largely while carbon dioxide levels were at the pre-industrial levels of 280 parts per million.
Scientists tell us that 350 parts per million is the "safe" level of carbon to keep in the atmosphere, "safe" being a euphemism for "we really have no idea what might happen to civilization as we know it if we blow too far past this." That's why 350.org, the nation's leading climate activist group, is named after the number
We have now officially blown way past it. 400 ppm is a whole 'nother ball game. A whole new level of uncertainty. There is now 14.3% more carbon in the atmosphere than scientists say is safe to maintain a stable civilization.
''I wish it weren't true but it looks like the world is going to blow through the 400 ppm level without losing a beat,'' Ralph Keeling, a geologist with the Scripps told the Sydney Morning Herald. ''At this pace we'll hit 450 ppm within a few decades.''
Which, whoops. Humans have never lived on a planet with so much heat-trapping carbon stuffed into the atmosphere. As the Herald notes,
The 450 ppm level is considered to be the point at which the world has a 50 per cent chance of avoiding dangerous climate change. Any higher and the odds of avoiding searing temperature rises of 4 or 5 degrees by the end of the century become prohibitively risky.
Now, humans are pretty crafty, I admit, but are they crafty enough to stave off 50 meters of sea level rise? To re-organize societies in an orderly fashion as hundreds of millions of refugees pour in from now-inhospitable locales? Grow the same amount of food with far less arable land? Maybe. I guess we'll see! Because there's no indication whatsoever that we're slowing the flood of CO2 spewed forth from our factories, our coal plants, our internal combustion engines into the atmosphere.
Things are about to get interesting.