Monday, October 19, 2015

The heat is on, folks…

The math on staying below 2°C of global warming looks increasingly brutal

Updated by Brad Plumer on October 19, 2015, 1:20 p.m. ET,

Here's a capsule summary of the big UN climate talks this year:

1) The good news: Every country is submitting a detailed pledge to curb greenhouse gas emissions.

2) The bad: Those pledges, added together, aren't enough to keep us below 2°C of global warming. Without drastic changes, we're in for some serious shit.

Point 2 can be tricky to conceptualize, since it involves so many moving parts. For more detail, I'd recommend this new paper in Environmental Research Letters by Glen Peters, Robbie Andrew, Susan Solomon, and Pierre Friedlingstein. It's the clearest presentation I've seen of how far off course the world is from its 2°C climate goal. And it explains why the United States, Europe, China, and even India would need to radically rethink their climate policies if we wanted to stay below that target.
The US, Europe, and China will use up the world's carbon budget by 2030

The science here is pretty straightforward: If we want decent odds of avoiding more than 2°C (or 3.6°F) of global warming — which has long been the goal — then there's only so much more carbon dioxide we can put into the atmosphere. The world's annual CO2 emissions will need to shrink to zero to stay within this "carbon budget."

In their paper, Peters and his co-authors sketch out a plausible carbon budget if we want a 66 percent chance of staying below 2°C. (Because there's some uncertainty around climate sensitivity, this is couched in terms of probabilities.) Roughly speaking, the world has just 765 gigatons of CO2 left to emit. We currently emit about 35 gigatons per year.

The authors then compared this carbon budget (the dark line) with what the United States, the European Union, and China* are currently promising to do on emissions between now and 2030:

(Continued here.)


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