Adding insult to Copenhagen injury, a new study shows that the increases in atmospheric CO2 taking place today could have a much larger effect on global temperatures than previously thought.
How so? Well, only a relatively small rise in CO2 in the Pliocene era 3 to 5 million years ago drove temperatures a whopping 3 to 4 degrees Celsius higher. Peak temperatures were reached at CO2 concentrations between 365 and 415 parts per million. Today’s CO2 stands at about 386 ppm.
The problems with the current models (and the resulting 350 target) is they take into account only the faster feedbacks, like changes in atmospheric water vapor and the distribution of sea ice, clouds, and aerosols.
The new study assessed long-term feedbacks, including changes in continental ice-sheets, shifting terrestrial ecosystems, and the impacts of greenhouse gases other than CO2. Lead author Mark Pagani tells Yale:
"This work and other ancient climate reconstructions reveal that Earth’s climate is more sensitive to atmospheric carbon dioxide than is discussed in policy circles. Since there is no indication that the future will behave differently than the past, we should expect a couple of degrees of continued warming even if we held CO2 concentrations at the current level."
Of course, not only is policy discussing the wrong numbers, it's still discussing. The failure of Copenhagen makes me realize we need to look at ways to exit the rut of discussion and enter the age of meaningful action. Especially now that the 15 minutes of media coverage are over.