By Brian Merchant
16 May 2013
(Motherboard) – It already ranks as one of the grimmest measurements ever taken.
Climate scientists found that for the first time in approximately three million years, the level of carbon dioxide in the atmosphere has reached 400 parts per million. The reason that figure was splashed across the front page of the New York Times—and why top White House advisors find it "truly frightening"—should be well understood by now. Carbon dioxide is a powerful greenhouse gas, and the more that accumulates in the atmosphere, the more sunlight it traps—and the more the globe warms.
We've now added enough CO2 to the atmosphere to change the lives of every human on the planet. This isn't an exaggeration. An increasingly large portion of the CO2 clogging our atmosphere comes from human activity—from our coal-fired power plants, our petroleum burning cars, our factories. Before we had any of those, carbon dioxide accounted for just 280 ppm. That means we've already turned up the dial on the planet's central heating by some 42 percent.
As with most heating units, it will take a little time for the temperatures to catch up with the new setting. But many of those changes are already under way. Life in a world where carbon accounts for 400 ppm is going to be quite different from the old 280 ppm world. The climate is now fundamentally different than it was 40, 30, even 20 years ago.
When I was born, in the mid-1980s, the amount of CO2 that had accumulated in the atmosphere was just enough to account for 350 ppm—the amount climatologists like NASA's Dr. James Hansen have identified as the threshold between a stable climate and an unpredictable, potentially volatile one. Between the 1800s and then, humans—mostly the United States and Europe—had built enough carbon-belching power plants and factories to add 70 ppm to the atmosphere.
Yet in my short life alone, human activity has pumped enough carbon pollution into our skies to raise the bar a full 50 ppm more. That's a huge change—out of the 120 ppm humans have added in total, nearly half of it has occurred in just under 30 years. That's the rest of the world following suit, building fossil fueled power plants and industrializing; the same way the U.S. did.
And that's enough carbon to transform our climate to the point that it better resembles another geologic era entirely: The Pliocene. That era, which took place from 5.8 to 2.6 million years ago, was the last time there was so much CO2 was blanketing the planet. According to the geological record, the CO2 levels of 360-400 ppm that marked the Pliocene made the world a drastically different place than the one that you and I grew up in.
Here are some characteristics of the 400 ppm world then—and those that are likely to be reprised in coming years:
- Sea levels were, on average, between 50 and 82 feet higher.
- Temperatures were 2-3˚C higher, or about 4-6 ˚F, than they are today.
- Arctic temperatures were between 10-20 ˚C hotter.
- Many species of both plants and animals existed several hundred kilometers north of where their nearest relatives exist today.
- Vast swaths of land turned into swamps. [more]