Letter: Goodbye to 399 ppm carbon dioxide

Tuesday, November 8 2016

In April 2014, the level of carbon dioxide(CO2) in the atmosphere—as measured at the Keeling Laboratory on Mauna Loa, Hawaii—first passed through the threshold of 400 ppm (parts per million). Over the past two years the CO2 level has fluctuated, as it always does, dropping through the spring and summer until late September and increasing over the fall and winter and spring until April. 

Late this past September, the CO2 level dropped to 401 ppm, and in early October it started rising again. Never again in my lifetime, or yours, or your children’s or your grandchildren’s, or even their grandchildren’s, will the CO2 level drop below 400 ppm. Not even the Paris Accord will change that. That should be of great concern to all of us, because the natural CO2 level for the climate that we’ve grown up with is less than 300 ppm, and the climate that eventually comes into equilibrium with over 400 ppm will be seriously different from what we have today. Get used to it, and think seriously about leaving your car at home.

~ Steven Earle