Writing at Boing Boing, Saul Griffith has come up with a good analysis of President Barack Obama’s recently pledged climate change mitigation target of “17 percent below 2005 levels by 2020 and 83 percent by 2050:”
As you’ll note, a 17% reduction over 2005 levels means only a 0.3% reduction over 1990 levels.
What you’ll also see is that Obama is making a commitment to emit 59 Gigatons from the US alone from 2010-2020, and a further 88 Gigatons from 2020-2050, for a total of 147 Gigatons of CO2. This is 22.7% of the 650 Gigaton limit implied by Meinshausen. This helps to see why it’s hard to get an agreement in Copenhagen. In order to avoid “dangerous levels of climate change” the US is committing to reduce its output to “only” 22.7% of global emissions, despite having only 4.5% of the global population. The other point to note is that even these reductions don’t satisfy the “emissions go to zero” aspect of this CO2 budget, as the US would still be emitting a gigaton of CO2 per year in 2050 under this plan.
As discussed here before, crafting a global emissions pathway to keep warming below 2°C is very challenging, particularly because of how countries with high per-capita emissions need to begin deep cuts very quickly. There is still an enormous gap between what is physically necessary to prevent dangerous climate change and the commitments that governments and politicians are willing to make.
That said, Obama’s target can legitimately be seen as part of an iterative process: a recognition that America cannot continue to emit greenhouse gasses in an unrestrained way. Eventually, however, the proposed cuts are going to need to get much deeper, or we are all going to have to start bracing for the changed world that more than 2°C of climate change would produce.