Solving the climate dilemma: The budget approach

This recent report, from an esteemed German research shop with the acronym WBGU, is, despite its dry title, an important milestone on our collective path to the Big Climate Reckoning. Though you should be warned that Mark Hertsgaard, in Grist, reviewed it under the title A scary new climate study will have you saying Oh, shit!

Rather than rehashing Hertzgaard’s nice introduction to this report and its principle author, Hans Joachim Schellnhuber, let me simply add that, in essence, Solving the climate dilemma puts forward a version of the “carbon budget” analysis explored in another important paper, Greenhouse-gas emission targets for limiting global warming to 2C, published in April in Nature by Malte Meinshausen and friends. See our discussion of that paper here.

What’s important in this new study is that, in it, an influential group of top-tier scientists sets out to draw explicit political conclusions — about the shape of the necessary global climate accord — that are consistent with the implications of the budget approach, as they see them. More particularly, they set out to advocate a budget-sharing system that, they believe, is fair enough to serve as the basis of a global emergency mobilization. Here, to be clear, is their flat, terrifying, punchline:

“By the middle of the 21st century a maximum of approximately 750 Gt CO2 (billion metric tons) may be released into the Earths atmosphere if the [2C] guard rail is to be adhered to with a probability of 67%. If we raise the probability to 75%, the cumulative emissions within this period would even have to remain below 600 Gt CO2. In any case, only a small amount of CO2 may be emitted worldwide after 2050.”

In effect, this paper is supporting the 350 ppm stabilization trajectory, though it goes further on the path of advocating a specific kind of climate regime, and defending it in terms of the political logic of extreme stringency, than most any other 350 organizers have done. In particular, this paper quite explicitly argues that the emissions cuts that are needed are far beyond the bounds of political “realism” as we know it.

There are, basically, two models for thinking about cuts on this scale.

The first is the Greenhouse Development Rights framework, which is probably familiar to readers of this site. GDRs argues, in effect, that the wealthy countries must accept emissions cuts that rapidly rise to become much greater than 100%. That, more precisely, wealthy countries must accept emissions reductions obligations that are larger than their own domestic emissions, such that they can only meet those obligations by a) making extremely aggressive domestic emissions cuts, and b) paying (via finance and technology transfer) for additional cuts in the developing world.

The other is the budget-sharing approach, which Schellnhuber and his co-authors endorse. But rather than interpreting the budget with respect to a historical date — 1850, say, or even 1990 — they reject this option because “it would greatly limit the industrialized countries scope for action.” Rather,

The option favoured by the WBGU takes the historical responsibility of the industrialized countries into account, but above all it looks towards the future: the entire CO2 budget acceptable within the bounds of the 2C guard rail for the time between 2010 and 2050 is equally distributed across the various countries of the planet on a per-capita basis, taking 2010 as the demographic year of reference…

It’s an odd model of historical responsibility that starts the clock in 2010!

In effect, Schellenhuber and his mates, coming face to face with their own conclusions about the severity of the situation and the actions needed, have had their own “Oh, shit” moment. They balk, and do not seriously consider the possibility of a “historical responsibility” approach in which the budget to be shared between wealthy and industrialized countries is one that began accumulating long ago, with the North’s industrialization. And, unlike GDRs, which seeks to capture the past by way of a “capacity” factor that reflects the wealth that historical emissions helped to create, they hope instead that the developing countries, under tremendous pressure both environmental and political, will agree to start the clock right after Copenhagen.

It’s an odd failure of courage, particularly as it originates in such brave honesty about the situation itself.