[font face=Serif][font size=5]Why We Can’t Ditch the 2 C Warming Goal[/font]

Jonathan Koomey | October 27, 2014 9:42 am

[font size=3]On Oct. 1, David G. Victor and Charles F. Kennel wrote an opinion piece that appeared in the journal Nature, Ditch the 2 C warming goal (1). The provocative title, which accurately conveyed the point of view of the authors, led to several responses, two from Joe Romm at Climate Progress (here and here), one from Stefan Rahmstorf at Real Climate, one from William Hare at Climate Analytics and one from David Roberts at Grist. Victor wrote a long reply to the Romm and Rahmstorf pieces that appeared on Andy Revkin’s New York Times Dot Earth blog.

For those interested in digging in, I found the longer Victor response to be clearer than the very condensed Nature article. The Roberts response is the easiest read for those who are less technical, while the Romm, Hare and Rahmstorf pieces go into a lot more detail about the problems with the Nature article, which are many and varied.

I’m not going to get into a blow-by-blow analysis of the discussion. Instead, I’d like to explore some key aspects of the 2 C limit that Victor (and others) seem to misunderstand, because of the importance of this concept to making the case for urgent action on climate.

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The 2 C warming limit is more than just a number (or a goal to be agreed on in international negotiations). It embodies a way of thinking about the climate problem that yields real insights (2). The warming limit approach, which can also be described as “working forward toward a goal,” involves assessing the cost effectiveness of different paths for meeting a normatively-determined target. It has its origins in the realization that stabilizing the climate at a certain temperature (e.g., a warming limit of 2 Celsius degrees above pre-industrial times) implies a particular emissions budget, which represents the total cumulative greenhouse gas emissions compatible with that temperature goal. That budget also implies a set of emissions pathways that are well defined and tightly constrained (particularly now that we’ve squandered the past two decades by not reducing emissions).

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