The Scripps Institution of Oceanography at UCSD reported this week that atmospheric carbon dioxide averaged more than 400 ppm in April, a new milestone:
Every single daily carbon dioxide measurement in April 2014 was above 400 parts per million. That hasn’t happened in nearly a million years, and perhaps much longer. Climate scientists have proven that the rise in human-produced greenhouse gases like carbon dioxide are “extremely likely” to be the dominant cause of global climate change. The likelihood of dangerous impacts—like sea level rise, hotter heat waves, and certain types of extreme weather—increases with each incremental annual rise in atmospheric carbon dioxide.
Carbon dioxide levels have increased by more than 40 percent since humans first started burning fossil fuels in large quantities about 250 years ago. Once released, the carbon dioxide from coal, oil, and natural gas burning can remain in the atmosphere for centuries. Thus, the crux of the problem: There just hasn’t been enough time yet since those first coal-powered factories in Europe for the atmosphere to return to equilibrium. What’s more, the pace of fossil fuel burning has since dramatically quickened—there’ve been more greenhouse gas emissions in the last 40 years than over the previous 200—so carbon dioxide buildup keeps accelerating.
So what about the hockey stick? If you look at the last 800,000 years, the chart of CO2 concentration looks more like a brick wall: