By Dr. Roger Pielke Jr.
In part one of this commentary I argued that the climate science community, broadly conceived, has been misusing scenarios, resulting in misleading and deeply flawed research and policy guidance. These problems reach deeply into leading climate science assessments such as the U.S. National Climate Assessment (NCA) and those of the Intergovernmental Panel on Climate Change (IPCC). If you haven’t yet read part one, please read it, and then come back for part two.
What would it mean for the climate science community, and those that use its work, to hit the reset button? Here I offer three suggestions.
The focus is on the IPCC and other leading scientific bodies, because their actions send powerful signals to the rest of the community, and also are a leading basis for climate policy making. Just as these bodies have played a role in the climate community getting off track, they can be essential in pressing the reset button.
First, the climate science community needs to more fully understand and implement proper methods of scenario planning. Two decades ago the IPCC explained accurately, “Scenarios are images of the future, or alternative futures. They are neither predictions nor forecasts. Rather, each scenario is one alternative image of how the future might unfold.” However, at some point in the intervening years the IPCC, U.S. NCA and a sizable part of the scientific literature decided to focus on a subset of scenarios to represent a “business as usual” future and then compare that baseline to an alternative future characterized by climate mitigation.
Make no mistake — decision makers and the media will surely continue to ask experts for forecasts on where the world is headed, and climate experts will continue to provide such forecasts, even if such prediction is impossible. The late Kenneth Arrow, a Nobel winning economist, related that when he served as a statistician in World War 2, he conveyed to his commanding general that his units’ long-term weather forecasts demonstrated no skill. The reply he received said, “The general is well aware that your forecasts are no good. However, they are required for planning purposes.”
Leading climate assessments can respond to such requests in two productive ways.
In the shorter term, looking several decades into the future, they might rely on scenarios produced by organizations such as the International Energy Agency, the U.S. Energy Information Agency and companies such as BP and ExxonMobil, among others. An advantage of such scenarios is that they are typically updated annually, based on new information, and they are produced by energy systems experts. Of course, these features certainly don’t guarantee accurate predictions, but they will be far more responsive to evolving knowledge than the scenarios of the IPCC generated by academics, which in some cases are based on data from 2005 or 2010, and are already wildly out of date.
For the longer term, such as looking out to the end of the century or longer, climate modelers exploring the physical climate system need not tie their work to long-term socio-economic scenarios. Such ties arguably lead to confusion among those who use this science in the media, or for impacts work and policy development. For instance, if scientists would like to explore the implications for climate variables of a forcing of 8.5 watts per meter2 or the impacts of a global temperature increase of 5 degrees Celsius, then they could readily do so without identifying those inputs as emerging from any particular set of socio-economic assumptions about how the world will evolve.
As a second reset, the climate community should dispense with the use of the concept of “business as usual” and its equivalencies — including reference scenario, baseline scenario and no-policy scenarios. In 2000 the IPCC reported “broad agreement that there could be no “best guess” scenarios; that the future is inherently unpredictable and that views will differ on which of the storylines could be more likely.” At that time the IPCC explained that all of its scenarios were to be viewed as equally likely outcomes. Such a change will prove enormously difficult as the IPCC has already identified two extreme scenarios to play the role of such baselines and asked researchers to prioritize the most extreme scenario in their work.
Leading scientific assessments beyond the IPCC and researchers following their cues routinely identify a high emissions extreme scenario as “business as usual” and pair it with a lower emissions scenario to represent a world with climate mitigation. The differences in impacts between the paired scenarios are then presented as benefits of mitigation policy. Such benefits however are completely illusory. Imagine that you and your partner decide to have 20 children, but then decide only have one. You cannot use the “benefit” of not having to pay the expenses of the 19 children who don’t exist to retire comfortably. You will still need to engage in retirement planning.
There is a strong incentive in climate advocacy for the use of extreme scenarios and to present them as forecasts of where the world is headed unless certain policies are adopted. Extreme scenarios show very large climate impacts in the distant future, and imagining the avoidance of those impacts comes with calculations of a large monetary benefit. For instance, in its 2018 report the US NCA identified more than $220 billion in benefits associated with moving from its extreme scenario (RCP8.5) to a middle-of the-road scenario (RCP4.5). There are no such benefits.
Ironically, under the logic of the US NCA mitigation policies in a RCP4.5 world would have no calculated benefits. Many climate analysts, myself included, would view mitigation action as necessary and beneficial even in a RCP4.5 world. The selling of mitigation policies to policy makers and the public will not have much potential for success if based on non-existent benefits resulting from asking policy makers to deviate from an impossible distant future. Instead, climate mitigation policies need to stand on their merits in the short –term, which is today, tomorrow and leading to the next election.
As a third reset, the IPCC should more explicitly discuss real-world policy options for mitigation and adaptation in support of near-term implementation. Too much of climate policy analysis has become about solving climate change in toy models – such as by inventing so-called negative emissions in the models – rather than in the real world.
Today, the risks posed increasing levels of greenhouse gases in the atmosphere, particularly carbon dioxide, are well understood and broadly accepted. Further, countries around the world have expressed varying levels of commitment to reduce emissions consistent with the stabilization of atmospheric carbon dioxide concentrations at low levels (e.g., such as consistent with a 1.5 or 2 degree Celsius temperature target). With respect to mitigation policy, the limiting factor today is not climate science, but viable policy options, including the availability at scale of a wide range of technologies.
Given the political momentum for climate policy implementation, the IPCC could assist policy makers by helping them to better understand what sorts of short-term actions are consistent with long-term aspirations. Scenario planning is particularly suited for such robust decision making.
The objective of the IPCC is “to provide governments at all levels with scientific information that they can use to develop climate policies.” It would seem obvious that one way to meet this objective would be to actually discuss specific policy options. However, the IPCC has long avoided such discussions behind a claim to being “policy-relevant and yet policy-neutral, never policy-prescriptive.” This stance has led the IPCC to be far less policy relevant than it might otherwise be. A good way to avoid being “policy prescriptive” is to provide decision makers with a large set of policy options — a policy smorgasbord — that can be employed to reach political goals.
The three recommendations made here – to return to actual scenario planning, to eschew the idea of using a baseline view of the future to ground policy analyses and expanding the IPCC role in discussing policy options – would represent a marked change from how the climate science community has evolved to support policy makers. But adopting these recommendations would also get climate science back on track and offer a much better chance for the invention, evaluation and ultimately implementation of policy options that help the world to accelerate decarbonization and prepare for an uncertain climate future.
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