There can be little doubt that major climate assessments and a significant portion of the underlying literature has slipped into misusing scenarios as predictions of the future.
In a remarkable essay last week titled, “We’re Getting a Clearer Picture of the Climate Future — and It’s Not as Bad as It Once Looked,” David Wallace-Wells of New York Magazine wrote, “the climate news might be better than you thought. It’s certainly better than I’ve thought.” The essay was remarkable because Wells, a self-described “alarmist,” is also the author of The Uninhabitable Earth, which describes an apocalyptic vision of the future, dominated by “elements of climate chaos.”
According to Wallace-Wells, his new-found optimism was the result of learning that much discussion of climate change is based on extreme but implausible scenarios of the future where the world burns massive amounts of coal. The implausibility of such scenarios is underscored by more recent assessments of global energy system trajectories of the International Energy Agency and United Nations, which suggest that carbon dioxide emissions from the burning of fossil fuels will be relatively flat over the next several decades, even before aggressive climate policies are implemented.
Scenarios of the future have long sat at the center of discussions of climate science, impacts and adaptation and mitigation policies. Scenario planning has a long history and can be traced to the RAND Corporation during World War 2 and, later (ironically enough) Shell, a fossil fuel company. Scenarios are not intended to be forecasts of the future, but rather to serve as an alternative to forecasting. Scenarios provide a description of possible futures contingent upon various factors, only some of which might be under the control of decision makers.Today In: Business
The climate community got off track by forgetting the distinctionbetween using scenarios as an exploratory tool for developing and evaluating policy options, and using scenarios as forecasts of where the world is headed. The scenario (or more precisely, the set of scenarios) that the climate community settled on as a baseline future for projecting future climate impacts and evaluating policy options biases how we think about climate impacts and policy responses. The point is not that climate analysts should have chosen a more realistic future as a baseline expectation, but rather, they should never have chosen a particular subset of futures for such a baseline.
The desire to predict the future is perfectly understandable. In climate science, scenarios were transformed from alternative visions of possible futures to a subset of predicted futures through the invention of a concept called “business as usual.” The Intergovernmental Panel on Climate Change explains that “business as usual” is “synonymous” with concepts such as “baseline scenario” or “reference scenario” or “no-policy scenario.” The IPCC used of the concept of “business as usual” (and equivalencies) in the 1990s, and then explicitly rejected it in the 2000s. It has returned with a vengeance in the 2010s. A reset is needed for the 2020s.
According to the IPCC, a “baseline” scenario refers to “the state against which change is measured” and for climate impacts and policy, is “based on the assumption that no mitigation policies or measures will be implemented beyond those that are already in force and/or are legislated or planned to be adopted.” The use of such a baseline is far more important for research on climate impacts and policy than it is for most research on the physical science of climate, as the latter need not necessarily be tied to socio-economic scenarios.
The IPCC warns, quite appropriately, “Baseline scenarios are not intended to be predictions of the future, but rather counterfactual constructions that can serve to highlight the level of emissions that would occur without further policy effort. Typically, baseline scenarios are then compared to mitigation scenarios that are constructed to meet different goals for greenhouse gas (GHG) emissions, atmosphereic (sic) concentrations, or temperature change.” Cost-benefit and effectiveness analyses in particular lend themselves to using a fixed baseline against which to evaluate an alternative, creating an incentive for the misuse of scenarios as predictions.
The IPCC warns against treating scenarios as predictions because they reach far into the future – for instance to 2100 and even beyond, and “the idea of business-as-usual in century-long socioeconomic projections is hard to fathom.” Humility in socio-economic prediction is also warranted because our collective track record in anticipating the future, especially when it comes to energy, is really quite poor.
It may seem confusing for the IPCC to recommend the use of baseline scenarios as a reference point for evaluating counterfactual futures and its parallel warning not to use reference scenarios as forecasts. The way for analysts to reconcile these two perspectives is to consider in research a very wide range of counterfactual futures as baselines. The instant an analyst decides that one particular scenario or a subset of scenarios is more likely than others, and then designates that subset of possible futures as a baseline or “business as usual,” then that analyst has started crossing the bridge to predicting the future. When a single scenario is chosen as a baseline, that bridge has been crossed.
There is of course generally nothing wrong with predicting the future as a basis for decision making. Indeed, a decision is a form of prediction about the future. However, in some contexts we may wish to rely more on decision making that is robust to ignorance and uncertainties (and thus less on forecasts), that might lead to desired outcomes across all scenarios of the future. For instance, if you build a house high on a bluff above a floodplain, you need not worry about flood predictions. In other settings, we may wish to optimize decisions based on a specific forecast of the future, such as evacuation before an advancing storm.
Climate science – and by that I mean broadly research on physical science, impacts, economics as well as policy-related research into adaptation and mitigation —- went off track when large parts of the community and leading assessment bodies like the IPCC decided to anoint a subset of futures (and one in particular) as the baseline against which impacts and policy would be evaluated.
This is best illustrated by a detailed example.