Climate change skeptics often shrug off the pesky facts scientists present by pointing to the big, over-simplified picture. Climate is always changing, they say. Nature goes through cycles.
True enough, but there’s nothing all-natural about the cycle in this chart. It shows the amount of carbon dioxide in the earth’s atmosphere. For the last 800,000 years, it has oscillated between 180 and 250-280 parts per million.
Then came the industrial revolution. Since then, the amount of CO2 in the atmosphere has increased by 41 percent. And on May 9, the tracking station at Mauna Loa that has been measuring fresh air just off the Pacific Ocean for more than 50 years, registered its first daily average CO2 concentration over 400 ppm.
Carbon dioxide, though still a small percentage of the atmosphere, is the most important of the heat-trapping greenhouse gases. To think that humans could make such a dramatic change in the chemical composition of the Earth’s atmosphere without consequences is an act of ignorance and arrogance.
The last time CO2 levels were this high, scientists say, was 3 million years ago, during the Pliocene Epoch. The climate was far warmer then, the polar ice caps far smaller, and sea levels as much as 60 to 80 feet higher. Of course there were no people then, living in highly developed seacoast cities, and the wooly mammoths presumably had an easier time moving inland.
The carbon dioxide milestone “feels like the inevitable march toward disaster,” Columbia scientist Maureen E. Raymo told The New York Times. As I note in a Sunday editorial, there are lots of things happening more important than the scandals obsessing the Washington press corps and the political commentariat, none of them more significant than the milestone recorded at Mauna Loa.