The Various Misuses of RCP 8.5

Fernando Leanme has been all over the RCP 8.5 story. He’s commented on it here frequently but also at his own blog, a blog with a great masthead picture. Even if you don’t agree with Fernando or myself, it’s worth a look.

Representative Concentration Pathways replace the IPCC’s Special Report on Emission Scenarios (SRES). There are four RCPs named after the additional forcing in watts per square meter they are anticipated to have by 2100 compared to pre-industrial forcings. The four are 2.6, 4.5, 6.0 and 8.5.

Each RCP was developed by a different team. They also used different models. They cannot be compared to each other head to head.

The first important thing to know about RCPs comes to use directly from the IPCC. Writing in a document titled, ‘IPCC Scenario Process for AR5’ they say “The goal of working with scenarios is not to predict the future but to better understand uncertainties and alternative futures, in order to consider how robust different decisions or options may be under a wide range of possible futures”. The IPCC decided to act only as a catalyst for the process–in essence they commissioned independent scientific teams to generate the RCPs.

Maybe they used these good folks:


As stand alone products, the RCPs have limited usefulness to other research communities. First and foremost, they were selected with the sole purpose of providing data to climate models, taking into consideration the limitations in climate models differentiating levels of radiative forcing. They lack associated socioeconomic and ecological data. They were developed using idealized assumptions about policy instruments and the timing of participation by the international community.”

They used information from the previous SRES developed for AR3 and AR4–they didn’t want to just throw numbers out there–but they did not develop the emissions narratives and economic assumptions themselves.

They are not predictions. RCP 8.5 essentially says ‘if you want to get to this level of forcing by 2100, here’s a pathway that will get you there.’ It is not the end result of a scientific look at the fuels we will burn, the emissions they will cause, the sensitivity of the atmosphere and the results of the interactions between those and other factors. It is a reasonable-sounding trajectory that will get you to that result. It is meant to feed into climate models to keep the data consistent. It is not meant to be used as a prediction to form other scientific work or policy.

But that is how they are being used. See here, here, here, here, here and here.

And here. And here. And here. I could go on…

The problem is that RCP 8.5 is being used as a ‘business as usual’ scenario with the force of a prediction. People are using it in scientific papers as if it were the worst case scenario with their sketchy numbers borrowed from previous work being treated as if it were the sober judgment of scientists working in 2014, as opposed to scenarios created back in 2000.

RCP 8.5 comes up with these assumptions to get them to their goal–not vice versa:

“RCP 8.5 – High emissions This RCP is consistent with a future with no policy changes to reduce emissions. It was developed by the International Institute for Applied System Analysis in Austria and is characterised by increasing greenhouse gas emissions that lead to high greenhouse gas concentrations over time. Comparable SRES scenario A1 F1 This future is consistent with:  Three times today’s CO2 emissions by 2100  Rapid increase in methane emissions  Increased use of croplands and grassland which is driven by an increase in population  A world population of 12 billion by 2100  Lower rate of technology development  Heavy reliance on fossil fuels  High energy intensity  No implementation of climate policies.”

Is it possible? Sure. Is it likely? I don’t know. Is it a prediction of the future?

Hell no.

Therefore, there is a need to develop socioeconomic and climate impact scenarios that draw on the RCPs and associated climate change projections in the scenario process. Referencing the RCP and  climate  change projections has two potential benefits; they would facilitate comparison across research results in the CM, IAM, and IAV communities, and facilitate use of new climate modeling results in conjunction with IAV research.

“The parallel phase has several components. Within CMIP5, CM teams are using the RCPs as an input for model ensemble projections of future climate change. These projections will form the backbone of the IPCC’s Working Group I assessment of future climate change in the 5th Assessment Report (AR5).   The IAM community has begun exploring new socioeconomic scenarios and producing so-called RCP replications that study the range of socioeconomic scenarios leading to the various RCP radiative forcing levels. In the meantime, IAV analyses based on existing emission scenarios (SRES) and climate projections (CMIP3) continue.

“In the integration phase, consistent climate and socioeconomic scenarios will inform IAM and IAV studies.  For example, IAV researchers can use the new scenarios to project impacts, to explore the extent to which adaptation and mitigation could reduce projected impacts, and to estimate the costs of action and inaction. Also, mitigation researchers can use the global scenarios as “boundary conditions” to assess the cost and effectiveness of local mitigation measures, such as land-use planning in cities or changes in regional energy systems.

“These scenarios need to supply quantitative and qualitative narrative descriptions of potential socioeconomic and ecosystem reference conditions that underlie challenges to mitigation and adaptation. And they have to be flexible enough to provide a framework for comparison within which regional or local studies of adaptation and vulnerability could build their own narratives. The defining  socioeconomic conditions of these scenarios have been designated Shared Socioeconomic reference Pathways (SSPs).”

Source: A framework for a new generation of socioeconomic scenarios for climate change impact, adaptation, vulnerability, and mitigation research; Arnell, Kram, Carter

15 responses to “The Various Misuses of RCP 8.5

  1. What is wrong with using SRES?

    • Hans, I happen to have considerable expertise in the fossil fuel resource area, and I’m familiar with dynamic models, such as the Integrated Assessment Models used to flesh out these pathways or scenarios.

      I find the RCP8.5 (and by association the SRS A1F1) to be infantile when it comes to fossil resources we can exploit during the course of the 21st century. It would take me several days to outline the basics of what I know, so let me give you an analogy: to me, what they do when they prepare those models is similar to taking the sea level rise rate of change over the last 10 years and using that to project sea level in 2075.

      The key is to understand that fossil fuels are NOT renewable. This in turn leads to an ever increasing degree of difficulty in finding and extracting them. Oil in particular is a big problem. I also want to point out I’m fully aware of the claims that new technology allows them to extract ever increasing amounts of oil. But that’s a bit backwards. Higher prices allow us to search for and implement technologies we knew about many years ago. Most of what we do is fairly old, but a higher price environment allows us to refine and get better at it.

      Some think higher prices are fine, people pay, life goes on. But higher prices don’t allow third world or developing economies to grow, or survive. I like to use Jamaica, Egypt, and Pakistan as examples. They won’t do very well when oil reaches $150 per barrel. Thus we are inexorably approaching a point when oil will be too expensive.

      The interesting fact is that economic models show oil peaks at a point when oil prices dip down, which reduces industry activity, which in turn leads to lower production. Lower production then drives prices up, but the industry is unable to catch up, and production just fails to satisfy demand. At that point prices zoom, and either a replacement source takes over, or large portions of the world collapse (as in Jared Diamond’s “Collapse”). Maybe you have an alternate model in mind. But I’m pretty sure those who stack endless fossil fuel flows into these models don’t really know the basics. And please don’t quote me peer reviewed literature on this subject, what I have seen is garbage.

      • I am with you, all I was musing about was why were the plausible SRES abandoned for the impossible RCP? RCP8.5 reminds me of the old continuous 1% increase scenario: useful for climate model testing but no relevance to the real world. We are still on the SRES A1B BAU, which gives a low warming with 1.3 transient sensitivity. No panic needed.

      • Hans, I’ve read the older scenario descriptions, including the A1 family’s. It sure looks like a giant faux pas to write so much verbiage, and negkect a description and information about the fossil fuel resources, and how they compete (or fail to do so) with other energy sources.

        I’ve noticed this whole process is dominated by climate types and economists who failed to understand the full system dynamics, or thought it was so complex they didn’t dare to include this interplay within the model flowchart.

        There is an incredible amount of effort being wasted until this topic is fully addressed and understood. And the individuals who try to tackle it need to be aware that resource depletion is a very touchy subject for fossil fuel companies, OPEC nations, and the full range of experts who make a living peddling the surreal idea that fossil fuels will last forever.

      • Fernando,
        You keep coming back to the end of days scenario, but why is the prediction now more useful than the ones going back to the post WWI era?
        The boom-bust cycle you describe- and which drives the economic life of my hometown, Houston- is not really any different than that of any other commodity. When (if) oil actually becomes scarce in a secular sense, we can move on to the rational alternatives that are out there.
        As to costs- As David Yergin pointed out, oil was the great game changer. Even though it has been much higher and lower in price than today in constant dollars. it is the value added from it that makes economies flourish, not its price per se.
        It is not like gold, whose value is based on a consensual illusion. It is the providential mineral that is a true cornucopia for innovative technically literate societies.
        In other words, I think we will muddle through pretty well.

  2. No one has been able to make meaningful predictions more than a few years out ever, even before the climate obsession. And we have done pretty darn well.
    With the motivated reasoning and institutional corruption endemic in the climate obsessed community there is no reason to believe that any of their predictions will be useful for honest policy making.
    There is no more reason to believe the end of the world predictions of the climate community any more than there are to believe in the prophecies of televangelists and the end of the world.

    Tom, Is this what divestment is really about?

    • Marty,
      Please excuse my stepping up to answer. I noticed that and could not help but to wonder the same thing. I do not believe that the CO2 obsession is making people less cynical..

    • Hiya Marty. Wow. Is that the most tone deaf investment in history?

      • Tom,
        Surely there is another possible explanation for why one of the savviest and manipulative people of our time has done this?

    • Hiya hunter

      Well, if the calculations I made over at are even close to accurate, his investment in fossil fuels will be highly lucrative.

      • Exactly. Tone deaf? Not in an age when a convicted crook and open schemer is barely discussed in the public square, much less held accountable. For many, the climate obsession is about the money.

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