400 PPM Reached—But CO2 Isn’t the Only Gas to Worry About

The New York Times may have shuttered its Green Blog, but the on the reporting side of things, it continues to cover the depressing environmental news of the day. On Friday we learned that the daily level of atmospheric carbon dioxide reached 400 parts per million.

The Times reports:

The best available evidence suggests the amount of the gas in the air has not been this high for at least three million years, before humans evolved, and scientists believe the rise portends large changes in the climate and the level of the sea…

Ralph Keeling, who runs another monitoring program at the Scripps Institution of Oceanography in San Diego, said a continuing rise could be catastrophic. “It means we are quickly losing the possibility of keeping the climate below what people thought were possibly tolerable thresholds,” he said.

Once CO2 is released into the atmosphere it stays there for hundreds of years, making it by far the most important, and most permanent, contributor to climate change. However, there are greenhouse gases called short-lived climate pollutants (SCLPs), including black carbon, hydrofluorocarbons, methane and tropospheric ozone, that actually produce more warming, but are much more ephemeral, lasting days or years as opposed to centuries. As Grist’s David Roberts explains:

…reducing SLCPs can buy us some time, forestalling some near-term climate impacts while we get our [act] together to reduce CO2 in the long-term. A paper in Nature Climate Change finds that “mitigation of the four short-lived climate pollutants … has been shown to reduce the warming trend by about 50% by 2050.”

SLCP reduction is encouraging because the public health benefits will be more readily observable than reducing CO2 emissions, and efforts to curtail SLCPs don’t face the same Herculean political challenges that stand in the way of pricing carbon. One such promising effort is the UN Foundation’s initiative to eliminate black carbon-producing cookstoves, whose smoke kills millions of people a year, and contributes to climate change. While dramatically cutting CO2 emissions is the only way to address climate change in the long run, reducing SLCPs can mitigate the effects we see in the next few decades, and provide a huge boost to public health—especially in developing countries—as well.

Devin Castles

Devin Castles is an intern at the Washington Monthly.