RCP 8.5: Foundation of Current Climate Discussions

This really is just about the worst post ever. I’m leaving it up as I hope to update it with better information. Read on at your own risk…

Picking up where we left off yesterday, Judith Curry thinks we should take the ‘plausible worst case scenario’ on which to base our plans for living with climate change in the 21st century.

The IPCC has a case that they are putting forward as just such a worst case scenario. It is called RCP 8.5. It is based on what the IPCC says are ‘internally consistent set of economic assumptions’ and is one of four such scenarios. RCP 8.5 is the most pessimistic.

RCP stands for ‘Representative Concentration Pathway’. It attempts to chart the increase in forcings on our atmosphere, measured in watts per square meter. Most of the assumptions are adopted wholesale from the scenarios that RCP replaced–the SREs used in prior versions of IPCC reports AR3 and AR4 .

RCP 8.5 uses assumptions from the most pessimistic SRE, variant A1F1 if you believe Skeptical Science or A2r if you believe the RCP database.

RCP 8.5’s answers to the important question are, emissions will more than triple during this century, radiative forcing will quadruple and temperatures will rise 4.9C over the pre-industrial period.

To evaluate its fitness for purpose we need to examine the assumptions involved. We should be aware of the worst case scenario, but it has to be plausible.

These assumptions don’t appear to be in any one place, either by the term RCP 8.5, SRES A1F1 or SRES Ar2. If anyone can help me find them I will be forever in your debt.

At Climate Change National Forum, John Nielsen-Gammon describes RCP 8.5: “RCP8.5 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) 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).”

Here are the assumptions underlying RCP 8.5:

Population: They assume population will reach 12 billion by 2100. This is well above the UN median projection of 10.1 billion, but less than their high variation of 15.8 billion.

Urbanization: SRES A2r assumes 85% urbanization by 2100

Emissions: RCP 8.5 assumes peak emissions in 2090 at 27.5 PgC (petagrams of carbon)

Concentrations: RCP 8.5 assumes CO2 concentrations reaching 950 ppm by 2100, more than double current concentrations of 400 ppm.

GDP: Skeptical Science has a chart saying that RCP 8.5 shows global GDP growth to a little less than $200 trillion in US 2000 dollars, which is bizarre, because everybody else shows results in 2005 US dollars. I can’t trust them, but it’s really hard to find these figures. (Help!) The US DOE Energy Information Administration predicts global GDP to reach $200 trillion by 2040…

Energy Consumption: It appears that RCP 8.5 projects energy consumption to reach 1,657 quads by 2100. In 2010 the globe consumed 523 quads. Sadly, I think they have underestimated consumption–as faithful readers know, my projection for energy consumption at my other blog serves as its title–I project consumption to reach 3000 quads by 2075, before stabilizing.

Okay, I don’t even know if I should publish this post. In population, RCP 8.5 looks mid-range, if somewhat pessimistic. They really think GDP is going to grow slowly. But energy consumption? That looks low.

I confess I need help with this. If help arrives I will update this. Quickly, as it is a bit of an embarrassment.

Ah, well–work in progress.

25 responses to “RCP 8.5: Foundation of Current Climate Discussions

  1. Be careful with Skeptical Science. I’ve discussed these issues with them in the past, pointed out the economic development inconsistencies and the fossil fuel problem.

    • Yes, I don’t trust them at all. But who’s right? Is it A1F1 or Ar2?

      • I don’t know. I don’t to IAM models. ive run dynamic models, but nothing as ambitious. Besides, it’s all a bit goofy, this system has way too many degrees of freedom. I do know the fossil side, though.

        I don’t know if I told you, but in the early 1990’s I worked on something which yielded a really grim outlook for oil and gas exploration. I realize they like to tout technology, but most of the new technology is enabled by higher prices. In other words, those horizontal wells with 30 large hydraulic fractures don’t yield an acceptable profit unless they exist in a high price environment. The same applies to deep water, the heavy oil, arctic, enhanced oil recovery.

        When I look at this problem I think of specific countries I know about. Sometimes I lived there, sometimes I worked there, or I researched them.

        If I may suggest, try a mental game: make a run for a country like Egypt. Take their economy, their population growth, their energy, and run the clock forward. When you finish you’ll see a horde of Egyptians taking boats across the Med.

        Jamaica is next. I know a bit about it. I researched it because I read comments from a Jamaican who is big into plugging solar for Jamaica (he wrote the Jamaica solar for Wikipedia). I think the guy is nuts, but I try to help him. I even researched how to connect Jamaica to Cuba by subsea cable (the two islands are separated by a submarine trench with really nasty sea floor terrain).

        Then try Pakistan. That’s a really hard nut to crack.

        The thing is, given what I know about future fossil fuel prices, and renewables lacking the horsepower to pull the weight, those three countries are in deep doodoo. You don’t have to run a worldwide model or reach as far as 2100. The problem isn’t global warming. That’s a peanuts issue. The problem is overpopulation and lack of cheap energy.

  2. van Vuuren et al. write, “the RCP8.5 was based on a revised version of the SRES A2 scenario.” Figures 6 & 9 compare RCP8.5 emissions/concentrations to other scenarios. Unfortunately the SRES scenarios aren’t identified.

    On the other hand, this class assignment asserts that “the A1FI scenario has cumulative emissions similar to RCP8.5.”

    P.S. Figure 2 of van Vuuren et al. shows GDP trajectories for the RCP scenarios. It’s surprising to me that RCP2.6 comes out on top the entire century. For 2015, it’s perhaps a third higher than RCP8.5, 60-ish to 45-ish.

    • The RCPs are done by different groups. They were given instructions to arrive at the four designated forcings, and each chose the ingredients. The 8.5 required extreme emissions. Check their methane concentrations. Methane can be used to jazz up a model. But there’s no discussion about the methane emissions model itself. Maybe they assume everybody starts eating lots of rice?

  3. By the way, this is a good reference to keep handy


    You can download this’s, it’s van Buuren et al 2011

  4. Another link for your collection, an IPCC press conference where RCP8.5 is referred to as business as usual (start at minute 18 and 53 seconds). This may have to be copied because they have a tendency to erase this type of faux pas.

  5. Here are the sres emission tables in IPCC TAR
    Below a comparison of sres and rcp 8.5 emissions, note that rcp8.5 is very similar to A1FI, be aware that rcp8.5 continues high emission for another century after 2100.

    • I prepared a CO2 concentration estimate using what I felt were likely fossil fuel resources, it’s like the AIB cases. The key to fossil fuel resources is the price it takes to justify extraction. By 2050 the price is so high the renewables start to erode market share. One issue I can’t handle at all is what happens to third world country economies when oil prices go above $150 per barrel in today’s dollars. I think Countries like Jamaica, Pakistan, and Egypt will be highly unstable at those prices.

      The EIA has an oil price forecast going up to $150 per barrel. I suppose the IPCC must think price will be $500 per barrel to justify the RCP8.5 projections.

      • Coal to liquids is somewhere at $50-70/bbl cost price. If the oil price goes permanently above $100 that becomes lucrative. Currently the price is completely determined how far OPEC is willing to open the tap.

      • Hans, if coal to liquids were that cheap we would have a CTL plant in Santa Marta, Colombia. Do you know why that plant wasn’t built? We couldn’t make it fly at $80 about 9 years ago. Given what I see, I would run THAT plant at $100. But today’s costs are also a lot higher. It won’t fly.

        When we look at this issue we do assume we will see some CTL, and GTL too of course. But when we pull hard on the feedstock we drive up feedstock prices. There’s going to be peak gas, and peak coal. That’s the problem we see, all of them hit peak by 2050 if we keep trying to use them at increasing rates. If we don’t pull on gas to make liquids then we can’t satisfy the liquids market. If we pull on gas we drive gas prices higher. Coal works the same way.

  6. Fernando,
    Your claims about energy seem very similar to those made about food in the 1960’s and early 70’s. What is the difference?

    • hunter, as I understand it (and if I do understand it, I agree), it’s not that we’re going to run out of fossil fuels. It’s that petroleum will get so expensive to get out of the Arctic and pre sal deposits in Brazil that we will start liquefying coal and using natural gas to power cars and it will all get too expensive.

      • The incoming projects aren’t really Arctic or presalt offshore Brazil. Those will never amount to that much (check the EIA forecast for Brazil if you wish). I’ve worked on Arctic projects, they have enormous layers of complexity caused by the environment, which means they take 10 to 20 years to go on stream. By the time a significant Arctic contribution shows up to play the other production will be way down.

        The real oil is found in extremely marginal reservoirs, low permeability rocks such as the Texas Wolfcamp, and in the so called “shales” (which aren’t really shales). The most highly regarded are the Bakken, Eagle Ford, Bazhenov (Western Siberia) and Vaca Muerta (Argentina).

        The other major source of new oil is the extra heavy in Canada and Venezuela. But that crude requires a lot of work and heavy investment to produce. It also requires oil upgrading, or refinery modifications.

        Another point: today the world produces slightly less than 80 million barrels of oil per day. The decline rate for this developed oil is about 4 % per year. This means that EVERY YEAR we have to put on stream about 3.2 million BOPD to make up for decline.

        I don’t think we will ever reach 90 million BOPD simply because to get there we would have to add 10 million BOPD of capacity on top of the 3.2 to 3.6 million BOPD we would have to add every year. And yet, we see government agencies making predictions as high as 100 mmbopd. So how can we get to such numbers? We would have to charge a lot. And we would have to hire and train millions of personnel we don’t have.

        So what’s the trick? Why am I disagreeing with the U.S. energy information agency? Because I don’t think many poor countries will be able to afford such prices. Or renewables will kick in. Or they’ll genocide each other. Or we will do it to them.

    • Hunter, I didn’t make claims about food in the 1960’s and 1970’s. Are you aware of a special technology we can use to breed oil fields or add some sort of fertilizer? Those of us who work in this area are out of ideas, unless we get to charge you really high prices

    • Price increases were part of the solution to food shortages.
      High priced energy is a natural, beneficial outcome. The prices drive innovations, in both energy sourcing and generation as well as usage efficiency.
      My question was in light of the utter failure of the Ehrlich predictions his entire life. He not only predicted food shortages, but resource shortages worldwide.
      Ehrlich is categorically wrong in each of his predictions yet you seem to imply they have credibility.

  7. Any sentence that uses both “4.9oC increase” and “realistic” is fictional. It is astonishing to me that as we are now well into the third decade of the climate obsession the fanatics have still not noticed that not one of the doom scenarios have happened as predicted.
    And many of the climate doom prophecies were confidently predicted to have already happened by now.
    This is the time for the grownups to take back the conversation and to stand against the madness of climate hype.

  8. Hunter, I never read Erlich. I’ve been focused on other topics. I started getting concerned in the early 90s, but I was working for a giant energy multinational and I had to keep my thoughts private. I did have a little influence, which led to a more pessimistic outlook about exploration and started focusing us on other targets (heavy oil, coal degas, shale gas, and buying other companies).

    When you attribute my position to Erlich you ignore what I wrote.

    • Fernando,
      I apologize if I mistakenly made it appear I am implying you are directly utilizing Ehrlich.
      I guess what I am seeing is that Ehrlich’s influence has been to shape the discussion environment so that terrible outcomes are accepted as likely, despite the lack of those predictions coming true.
      I find your work insightful and your point of view interesting. As someone who was fortunate enough to marry into a S. American family and to have known several Cuban refugees from the Castro revolution, your ideas and life experiences are particularly intriguing.

      • Hunter, my training as an engineer taught me to expect terrible outcomes if we didn’t watch out for every little detail. In this case we would have to define “terrible”. I see fossil fuel depletion as a natural phenomenon. It’s not “terrible”

        At first the stuff is there, then we take it out, and eventually we run out. We move elsewhere and find more, take it out, etc. if you want me to extract stuff from 3000 meters under the ocean’s surface I want to get paid more.

        But there’s a limit. We can’t find anything beyond about 4000 meters water depth. We can’t find oil that’s worth producing at all under about 6000 meters of rock. In other words, there’s a limit to the locations/regions we have left. Thus we concentrate in really low quality rocks and low quality high viscosity fluids. And those require huge amounts of money. There’s nothing terrible about it. It’s just a fact.

  9. Lukewarmer,

    According to Van Vuuren et al., Climatic Change (2011) 109:5–31 DOI 10.1007/s10584-011-0148-z (not paywalled, if memory serves) “The RCPs should not be interpreted as forecasts”. So far as I can tell, the key assumption in RCP8.5 is that forcing will be 8.5 W/m^2 in 2100; everything else works back from there. The forcing values in 2100 were chosen based on the range found in the literature with, it appears, no attempt at critical review.

    Also from Van Vuuren: “The socio-economic scenarios underlying the RCPs cannot be treated as a set with an overarching internal logic”.

    RCP8.5 assumes a very large increase in population and that most additional energy comes from coal. That requires burning twice as much coal as is known to exist (follow the links in Judith Curry’s post for this and a deconstruction of RCP8.5). Even the other scenarios have modest contributions from non-fossil energy sources (about 20% in RCP6, see Fig. 3 in van Vuuren et al.).

    Within the van Vuuren paper, there are indications that serious attempts at forecasting, whether based on fossil fuel availability forecasts or on econometrics modelling, come out in the range of RCP4.5 to RCP 6.0. But they don’t really discuss that.

    If you just extrapolate the trend in forcing since 1950, you get something like 5.3 W/m^2 in 2100. If there are breakthroughs in solar or nuclear before then, the forcing should be less.

    Do not forget that IPCC is in the same relationship to science as a paid expert witness in a court case.

  10. Under these high emissions scenarios, that means you have lots of economic growth, particularly in poor countries. Yet WG2 goes ahead and declares that high warming would devastate those countries, ignoring the part where they are no longer so poor.
    Indeed, they are frequently given growth rates higher than the US in the 19th and 20th centuries.

  11. WORST POST EVER. I must immediately go on the internet to vent my frustration.

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