are lamenting the loss: instead of a dialogue between 'official' climate policy-makers and their activist critics, we are at risk to get just one side of that conversation. It is extremely useful, then, to read the advance critique of the conference agreement by Justin Gillis in today's New York Times. Gillis advances the notion of a 'carbon budget'--which may be the most important metric in the whole climate discussion, and one of the least contestable. A pointed conversation about that concept would indeed be useful, in the streets of Paris, on-line, or wherever, since it's not going to happen inside the conference hall.
Carbon budget? Scientists have pretty clearly identified a total quantity of carbon emissions which would keep temperature increases below 3.6 degrees F (2 degrees C). This is a measurable amount of fossil fuel--and 2/3 of it has been burned already. On the present post-Paris trajectory the world's economy will reach the limit by 2050 or sooner.
And when the 'budget' is all 'spent' ... ? Economic activity will not cease. Fossil fuels will still be consumed. Temperatures will rise beyond 3.6 F, perhaps as high as 6 or 8 degrees F in this century--and the planet will become a very different, quite possibly uninhabitable place. That is the inexorable logic of the carbon budget.
How certain is that cause-and-effect relation? Well, here's where it makes sense to say that 'climate is complex,' multiply determined, hard to be precise about. The key term here is 'carbon sensitivity': we know that carbon levels in the atmosphere will increase in direct proportion to fossil fuel consumption, but we don't know exactly how that will translate into temperature increases, and where, given the vagaries of ocean currents, carbon sinks, solar variability, and a host of other factors. But the 'carbon budget' assumption that fossil fuel consumption beyond a fixed level will take us beyond a 3.6 F temperature rise is widely accepted by scientists studying the question--most notably the UN's IPCC report in 2013.
So why not set a fixed carbon budget and mandate compliance from the world's nations, if that is the only way to guarantee tolerable carbon emissions limits? A sensible question, and maybe the only climate policy question that matters. The upper bound of carbon consumption can't really be finessed. It's real (even if the numbers can be slightly adjusted). But the process of allocating shares of dwindling carbon allotments has long been viewed as politically, diplomatically impossible--which is why the only truly meaningful way to measure success at Paris will not even be considered by the conferees.
And if a 'carbon budget' were implemented? The immediate problem, as Gillis makes clear, is a daunting question of justice, or equity: the US, China, and Europe have spent the vast share of that 'budget,' i.e. are responsible for most of the problem. We've used up our share, and the remaining consumption of fossil fuels by rights belongs to the less developed countries. In the short term, fossil-based growth should be permitted only to those historic under-users. In the longer term, the developed countries need to massively invest in conversion to renewables, at a much faster pace than previously imagined, both in our own economies and in the developing ones--including big ones like India. Effectively this would mean huge transfers--many trillions of dollars--of capital: from richer to poorer nations, from fossil-fuel producers to renewables, from one set of investors to another. The dislocations to the global economy would arguably be as catastrophic as big temperature increases unless carefully managed, in the framework of an international consensus.
Would market regulation of carbon do the same thing without the coercion of a fixed budget? It is true that carbon exchanges or taxes have more supporters than the global carbon budget idea, though these carbon market proposals seem to be excluded from the Paris talks as well. In theory, a carbon tax system could enforce a de facto budget, and exchanges (with huge subsidies) could address the equity issue by causing transfers to poorer nations. But would this happen? I observe that among the proponents are major corporations, including the big oil companies, as well as certain status-quo-oriented politicians. Why? Because all these market systems depend on the details of pricing, which would be endlessly negotiable. Low-priced exchanges such as the EU's have wasted valuable time and energy. Pricing that enforced stringent reductions in fossil fuels would meet all the same political resistance as a strict budget--but in a more complex, possibly covert forum. I like the simplicity of a fixed carbon budget--and so do a lot of climate scientists.
So what would it take? First, an acknowledgement of the equity issue by nations like the US, who have tended to promote a model of equal responsibility moving forward, with limited transfers of development funds. Second, a complete paradigm change, involving subordinating the economic interests of the rich and powerful to norms of equity that favor the poor--a tall order. And third, it would require the technical means to convert trillions in investment into rapid renewable energy generation--a scenario whose feasibility is debatable.
Alternatively? We can stumble along with the incremental approach inscribed in the Paris agreement (if it gets approved). We can press for the 'ratcheting up' over time of that agreement (and congratulate ourselves that 195 nations, including recalcitrants like China, the US, and India, are even in the conversation). We can hope 'climate sensitivity' coefficients are lower than most scientists think. Or we can fantasize about a techno-fix that some bright geo-engineer will invent tomorrow.
Personally I don't think any of the alternatives represent any security whatsoever for our children's and grandchildren's future. The rigid, top-down structure implied by 'carbon budget' logic presents a huge challenge to our frail human skills at diplomacy, negotiation, and enlightened self-interest. But truly, what choice do we have? Either Paris moves us a step closer to some real solution, based on absolute limitation, or it promotes a false sense of security that will haunt us in coming decades. I would like to believe in the former, but I suspect and fear the latter.