Everything you always wanted to know about emissions trajectories…
Well, not everything. But you’ll find a good, almost definitive summary in The Emissions Gap Report: Are the Copenhagen Accord pledges sufficient to limit global warming to 2° C or 1.5° C? This report, organized by the UN Environment Program, basically consists of a meta-analysis of the various current studies of emissions pathways and their consequences. It’s focused on the Copenhagen pledges (which are judged to be way too weak) and is notable for taking proper account of 1.5ºC as well as 2ºC targets, for closely analyzing the loopholes by which the wealthy countries propose to avoid actually having to deliver on their nominal emission-reduction commitments, and for taking a good look at the need for “negative emissions” in the not too distant future. This is not a notion that realists usually dwell on, but here it’s even defined.
The tone is a little clinical. And there is a wee bit of soft-pedaling — for example, the range of 2020 emissions targets that is consistent with “likely” chance of holding the warming to 2ºC is judged to be 39-44 GtCO2 equivalent, which is not, actually, a range that can fairly be called “approximately 44.” But put this aside. The main point is that, after reading this report, you’ll know the key thing — if we’re going to squeak by, it’s going to be by way of a pathway that has no historical parallel. The necessary rate of annual, global emissions decline alone makes this crystal clear.
This report doesn’t go into the ethical-political failings that have stalled international progress, but this is no real surprise. These failings, though, cannot forever be set aside. Inevitably, they will be the focus of another round of increasingly visible analysis. They have to be. One way or another, we’re heading into a new world.