On May 10, researchers at the Mauna Loa Observatory, an atmospheric monitoring facility, sounded the alarm that carbon dioxide levels in the air had now passed 400 parts per million, an arbitrary marker, but signifying the rapidly growing share of the atmosphere that carbon dioxide is claiming—and getting climate change back into the public debate.
In light of that ignominious achievement, commentators are revisiting what exactly that means for a global population of 7 billion humans, who weren’t around 3 million years ago, the last time there was this much carbon dioxide in the atmosphere, and a time of zero arctic ice, higher ocean levels, and much hotter weather. The Guardian spoke with climate change expert Lord Nicholas Stern, who issued some severe warnings about what the future could look like, assuming nothing changes.
"Hundreds of millions of people will be forced to leave their homelands because their crops and animals will have died. The trouble will come when they try to migrate into new lands, however. That will bring them into armed conflict with people already living there. Nor will it be an occasional occurrence. It could become a permanent feature of life on Earth."
The paper also points out that carbon dioxide is entering the atmosphere faster than ever, at a rate of 2.1 ppm per year, as opposed to 0.7 ppm per year in the 1960s.
Agricultural failure, more conflict, the uprooting of rural people from the land, and no solutions in sight. Happy 400 ppm, everybody.