On RCP8.5 and "the Business as Usual" Scenario – Different beasts not to be confused

This weekend I finally got the opportunity to read Dr. Matt Ridley’s recent essay “The Climate War’s Damage to Science” in the Quadrant Online. As a fellow Lukewarmer I try to keep abreast of Dr. Ridley’s essays and articles and am seldom disappointed by his prose. This article, like most of his work, made for a very interesting read and I would recommend it to anyone interested in the topic of climate change politics. While reading the essay one particular paragraph jumped out at me. The paragraph described one of the Representative Concentration Pathways (RCPs) used in the IPCC Fifth Assessment Report. In the essay Dr. Ridley wrote:

What is more, in the small print describing the assumptions of the “representative concentration pathways”, it admits that the top of the range will only be reached if sensitivity to carbon dioxide is high (which is doubtful); if world population growth re-accelerates (which is unlikely); if carbon dioxide absorption by the oceans slows down (which is improbable); and if the world economy goes in a very odd direction, giving up gas but increasing coal use tenfold (which is implausible).

This paragraph reminded me that I had previously committed to writing about the IPCC RCPs and in particular about RCP8.5 which is often referred to, incorrectly, as the “Business as Usual Scenario”. The reason for my interest in this rather anodyne topic is that it actually represents a quite excellent example of how science is misrepresented to the public in the climate change debate.

As I describe in my post “Does the climate change debate need a reset? – on name calling in the climate change debate” one of the critical battles in any debate is control over the labelling of the actors. If you can apply the best possible label to yourself and the least agreeable label to your opponent you immediately gain the upper hand. In the climate change debate, the “Business as Usual” label has been used more times that I can count with activists from the folks at Skeptical Science to the Suzuki Foundation, and from the Pembina Institute to 350.org all finding some way to slip that phrase into their calls demanding immediate action (and of course donations to their cause). As this post will demonstrate, however, the “Business as Usual” descriptor used by the activists in the climate debate is nothing of the sort. Rather it is an artifact from earlier versions of the IPCC reports and was conspicuous by its absence in the most recent (Fifth Assessment) report.

Let’s start with some background. As anyone who has read my writing knows one of the ways to make science more reader-friendly is to use analogies and personal anecdotes. Of course the risk with analogies is that a bad analogy can distract from your narrative. Similarly, anecdotes can personalize your writing and make it more approachable but anecdotes are only valuable if they are subsequently supported by actual data since the old saw goes “the plural of anecdote is not data”. In this vein, the earliest IPCC reports used “Scenarios” to inform their modelling exercises. As they put it:

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. A set of scenarios assists in the understanding of possible future developments of complex systems. Some systems, those that are well understood and for which complete information is available, can be modeled with some certainty, as is frequently the case in the physical sciences, and their future states predicted. However, many physical and social systems are poorly understood, and information on the relevant variables is so incomplete that they can be appreciated only through intuition and are best communicated by images and stories. Prediction is not possible in such cases (ref).

I have neither the time nor the expertise to discuss the scenarios is a manner worthy of them and so will leave that to Dr. John Nielsen-Gammon from Texas A&M University who has prepared a brief breakdown on the history of the different scenarios used by the IPCC (ref). He also describes the process by which the most recent IPCC Report eliminated these scenarios. The reason for this is simple, by 2014, the older scenarios had outlived their usefulness. The public was no longer in need of spoon-feeding and instead the RCPs were rolled out. Four RCPs were generated for the Fifth Assessment report representing four different forcing pathways. A simplified definition of a “forcing” is the difference between the energy from the sun absorbed by the earth and that radiated out into space (ref). The four RCPs were labeled by the approximate radiative forcing (in watts per meters squared) expected to be reached by following the respective pathways during or near the end of the 21st century. The four pathways are RCP2.6, RCP4.5, RCP6.0, RCP8.5 (ref). The roles of the RCPs, therefore, were not to inform the public as much as to inform the modellers in the IPCC process. Specifically, they were intended to drive the climate model simulations that formed the basis of many of the future projections in the most recent IPCC report (ref). To put it another way, RCP8.5 was a pathway designed to model a set of conditions that could lead to a world where climate forcing by the year 2100 reached 8.5 watts per meter squared. It was essentially designed to provide a worst-case scenario [used in its traditional literary sense] if everything in the world went sideways or backwards (as I will detail later).

The problem with the IPCC retiring its old scenarios is that a lot of activists were very happy with the old paradigm and had no desire to change their tunes. They wanted something that they could sink their teeth into and use to scare the public and politicians. Since the IPCC had taken away their well-established tools they appear to have decided to re-label one of the new tools to suit their purposes. So they affixed the retired “Business as Usual” scenario label (some use the term “status quo”) to RCP8.5 and continued on their merry way scaring up new funding. The only problem is that, by definition, RCP8.5 was not a “Business as Usual” scenario, rather it was

developed to represent a high-end emissions scenario. “Compared to the scenario literature RCP8.5 depicts thus a relatively conservative business as usual case with low income, high population and high energy demand due to only modest improvements in energy intensity.” (Riahi et al. 2011 ref) RCP8.5 comes in around the 90th percentile of published business-as-usual (or equivalently, baseline) scenarios, so it is higher than most business-as-usual scenarios. (van Vuuren et al. 2011a ref)) – (Text ref)

What the activists call: “Business as Usual” actually represents the 90thpercentile of the scenarios prepared for the IPCC that involved little change in environmental and economic policies (sometimes referred colloquially as the “no significant action” scenarios). These scenarios represented the worst of the worst where governments and industry did not do anything to improve their lot. As such the no significant action scenarios could only be described as “business as normal” if you happened to be living in 1990 or 1996 when the IPCC prepared its original couple reports. That would be before we had spent 20 or so years learning about climate change; before the Kyoto Protocol and the world-wide drive to renewable energy; before the discovery of tight shale gas and the move away from coal as the primary source of future energy plants in much of North America, Europe and Asia. To put it simply, being at the 90thpercentile of that group put you in pretty impressive company and does not relate to anything that anyone in the real world would actually expects to happen. Rather, in a relative sense as the 90thpercentile of all those earlier estimates, it would be the scenario that comes just below the scenario where Godzilla emerges from the sea to burn Tokyo and the scenario where the atmosphere spontaneously combusts from the endless bursts of Hiroshima-bomb-powered forcings.

I have made a pretty bold statement that RCP8.5 is not really relevant in a real-world sense and I suppose it is time to back that up with data. In order to understand how RCP8.5 has already been trumped by history you need to look at the history and contents of RCP8.5. Readers interested in the details should read the paper by Riahi (et. al. 2011 ref). Dr. Riahi is one of the authors of the original IPCC Scenarios upon which RCP8.5 was based in 2007 (ref). At that time, consistent with the education theme each IPCC Scenario had a “Storyline”. The storyline described the assumptions of the scenario in easy to understand language. The “Storyline” for RCP8.5 originates from Scenario A2 in the Third IPCC Report but was further refined in Riahi (et. al. 2007 ref) as A2r. As recounted in the Third IPCC Report (and detailed in these references (ref ref and ref) the A2 storyline was characterized by:

  • lower trade flows, relatively slow capital stock turnover, and slower technological change;
  • less international cooperation than the A1 or B1 worlds. People, ideas, and capital are less mobile so that technology diffuses more slowly than in the other scenario families;
  • international disparities in productivity, and hence income per capita, are largely maintained or increased in absolute terms;
  • development of renewable energy technologies are delayed and are not shared widely between trade blocs;
  • delayed land use improvements for agriculture resulting in increased pollution and increased negative land use emissions until very late in the scenario (close to 2100);
  • a rebound in human population demographics resulting in human population of 15 billion in 2100; and
  • a 10 fold increase in the use of coal as a power source and a move away from natural gas as an energy source.

Looking at what the activists have labelled the “Business as Usual” scenario we see a slew of assumptions that are anything but business as usual. It is generally accepted in the demographic circles that the human population will max out at between 10 and 12 billion (ref) so the population estimate is off by around 25%. Rather than trade blocs hoarding technologies we are living in an increasingly international world where technological improvements move at the speed of the internet and new and improved renewable energy technologies are both being developed and shared worldwide. Coal use is decreasing as a percentage of our energy supply and the shale revolution and access to cheap and plentiful natural gas has resulted in an international market for liquefied natural gas and increases in energy intensities not decreases. To put it bluntly, virtually every one of the assumptions of the RCP8.5 have been demonstrated to be categorically wrong. No surprises here, when the IPCC picked a worst case scenario they went full bore on that approach.

I see I am running long so let’s summarize this post. When you see an abstract where the authors say something like:

We show that although the global mean number of days above freezing will increase by up to 7% by 2100 under “business as usual” (representative concentration pathway [RCP] 8.5), suitable growing days will actually decrease globally by up to 11%…. tropical areas could lose up to 200 suitable plant growing days per year….Human populations will also be affected, with up to ~2,100 million of the poorest people in the world (~30% of the world’s population) highly vulnerable to changes in the supply of plant-related goods and services (ref).

It is time to gently close the journal and back away slowly so as to not attract the author’s attention. By basing their study on RCP8.5 and specifically referring to it as the “business as usual” scenario the authors have told you all you need to know about the reliability of their paper. Similarly when an activist talks about “business as usual” in their sales pitch, it is time to put your wallet back in your pocket. If you are so inclined then it is it is time for you to find a group that is more serious about improving our planet and more in keeping with what the IPCC actually has to say. RCP8.5 is not a business as usual scenario but rather a future scenario that has been soundly invalidated by the conditions in the present.

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3 Responses to On RCP8.5 and "the Business as Usual" Scenario – Different beasts not to be confused

  1. Excellent! I've been complaining about RCP8.5 since I first saw it in 2013.

    By the way, I had an exchange with Nucittelli in which he coyly told me tagging the RCP8.5 as Business as Usual wasn't the IPCC's idea, that it emerged in the media. However, I found transcripts of presentations and talks by IPCC officials describing it as BAU.

    There's a huge number of studies using the RCP8.5 fed models to conduct research in quite a few associated fields. RCP8.5 results are used to induce “climate hysteria” in professional societies, government circles, and organized religion authorities. They hit a home run with their trick.


  2. CNY Roger says:

    “RCP 8.5 most closely approximates the current trend in greenhouse gas emissions and is generally considered to be the “business as usual” scenario.” This statement relative to your post exemplifies the sad state of “science” in New York State environmental regulations.

    This statement is from the NY Department of Environmental Conservation Summary for Stakeholders: 6 NYCRR Part 490, Projected Sea-level Rise. The document is part of the stakeholder process to “adopt regulations establishing science-based state sea-level rise projections” for the New York Community Risk and Resiliency Act. It does not get any better in the proposed regulation.

    Sad to say the quality of science in this document is probably better than the science used to justify the ban on hydro-fracking in New York. I am embarrassed by these actions.


  3. Pingback: On Linda McQuaig’s comments, Carbon budgets, and keeping oil sands “in the ground” | A Chemist in Langley

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