Different Projections, Different Stories, Same Goals
On September 28th, the New York Times published an article on its front page trumpeting an analysis carried out by Climate Interactive, an environmental NGO tied closely to UN climate proceedings. Despite our best efforts in Paris, their analysis suggests, global climate will warm more than 3.5˚C (6˚F) by 2100 — far short of our 2˚C target. The Climate Interactive analysis was more pessimistic than most other official analyses, and I imagine those concerned with the outcomes of Paris would not be pleased.
Scenes came to mind from mid-brow cli-fi (a personal weakness) — I imagined a spin-doctor, a dark-suited bureaucrat charged with controlling the discourse surrounding the Paris climate conference, calling from deep within a government building to threaten an objective scientist for not conforming to the official point-of-view. Like most things, however, this discrepancy is colored by subtler hues. In fact, the answer to that simple question — how much will our planet warm? — depends on what is ultimately being asked.
As brief background, the ticket to entry at the 21st conference of parties (COP21) in Paris is an Intended Nationally Determined Contribution (INDC) from each participating party. These individual plans for emissions reductions form a new strategy for global agreement in the wake of the widely publicized failures of the Copenhagen COP, and are the focal point of discussions leading up to the conference. The UNEP Emissions Gap Report compiled various studies in order to assess the climatological implications of the INDCs. There is of course no single, compact answer. Kelly Lavin and Taryn Fransen or the World Resources Institute published a lovely and comprehensive piece, entitled “Why are INDC Studies Reaching Different Temperature Estimates?” explaining the spread of estimates for temperature increases given current INDCs. Anyone interested in this topic should read this piece — the authors separate out and discuss the various sources of discrepancies in terms of three categories: inclusion of different INDCs, assumption about the INDCs, and assumptions about what happens after the INDCs.
The Climate Interactive analysis was special for its treatment of the last category. Climate Interactive ran their model using a concrete and strict emissions scenario. As the stated ambition of most INDCs end around 2030 (2050 for USA, EU, and Japan), with no further information, their model assumes a flat-line emissions trajectory after that. No policy analysis, they argue, would ever include a “projected policy” component. As an example, imagine a law that establishes continuously increasing safety standards for automobiles on some time horizon, say to 2030. We would never assess the benefit of such a policy by looking at fatalities in some later year, say 2050. Furthermore, it seems laughable to assume increased safety standards in the 2030–2050 interim in order to make that assessment. Similarly, Climate Interactive argues, it would be misleading to include assumed emissions decreases outside the scope of the INDC in any INDC benefit analysis.
Despite this sound reasoning, most other analyses do include some projection of future strictness. Climate Action Tracker (CAT), for instance, assumes a “level of effort equal to that implied by the INDCs” after the INDCs, by matching the INDC reductions to emissions scenarios that have already been presented in the literature. The International Energy Agency (IEA) also matches “climate ambition” to emissions scenarios out to 2100 in order to model temperature increase. On the other hand, some prudent studies do not extend at all past the end of INDCs, or 2030.
None of these is a perfect approach. Steering the climate is a bit like what I imagine it is like to steer an ocean liner. There is serious lag, and inputs take time to make their way through the massive system. Because of this, ending an analysis at 2030 does not tell us what we want to know; our actions have impacts for centuries to come. At the same time, we have set a target for 85 years from now, but our policies exist on a 15-year time horizon. What about those remaining 70 years? The solution is to demand policies that clearly describe emissions that far into the future. This is clearly impossible. Incorporating assumed future policies into projections introduces a level of uncertainty that is uncomfortable. However, assuming a flat line post-INDC is equally arbitrary — no one expects the discussion in Paris to produce a final solution. In fact, the message-people have taken painstaking efforts to make sure we see it as the beginning.
The Climate Interactive approach to assessing the success of Paris sees the purpose of these meetings differently from other approaches — it does not contradict other official findings. Is Paris a meeting to set the definitive policy, or is it the beginning of further global commitment to reining in our runaway impacts on climate? It is both. Kelly Lavin and Taryn Fransen wrote, “The Paris Agreement can help bend the curve further before 2030 and ensure greater ambition after 2030 by including clear long-term and short-term signals.”
The climate projections answer more specific questions than might be obvious at first glance. What will happen if this is all we do? Climate Interactive has the answer. What is possible given the path these agreements set us on? IEA and CAT answer that. What can we be sure about given these policies? The short-term studies answer that. All science — physical and social (this problem is both) — only takes meaning through both the framing and the answering of questions. When thinking about Paris, it is important to keep this in mind, or we might get lost in the dark, thinking about who wants what instead of what we all want: an unprecedented global solution to an unprecedented global problem.
