The Taming and Shaming of RCP8.5 – Climate Scientists Shrug Off Criticism And Carry On As Usual



In an epic climbdown, following a long campaign by sceptics to point out the routine misuse of the RCP8.5 IPCC Representative Concentration Pathway – and particularly owing to the dogged and determined efforts of Roger Pielke Jr. – the alarmist main stream media has finally conceded that scientists wrongly applied this worst case scenario in their research, often mis-labeling it as “business as usual”. Huge numbers of ‘impact studies’ have used this highly unlikely concentration pathway which have then been reported by the media without caveats (often because the researchers themselves have not bothered to provide perspective or have even hyped their own findings), giving the impression that climate change will be very bad or ‘worse than we thought’. So when the BBC’s Matt McGrath pens an article which is surprisingly contrite and factual, you know you are winning the war against climate crisis alarmism.

Now, there is huge confusion regarding the Representative Concentration Pathways – even among scientists themselves – and I’m not going to pretend that I understand all the nuances and intricacies involved in their development and use as tools for climate modelers, but some things seem clear – to me at least. The first is that even though they describe atmospheric concentrations of greenhouse gases by 2100, in ppm, they are, by necessity, intimately connected with emissions of GHGs. There are other factors which affect concentrations of course – like climate and carbon cycle feedbacks – but it seems pretty obvious that the quantity of GHGs which humans put into the atmosphere is a huge factor in determining the resulting concentrations of GHGs which accumulate in the atmosphere. Richard Betts on Twitter seems somewhat determined to underplay this fact in stressing the ‘huge difference’ between emissions and concentrations.

What it appears that Richard is trying to say (or at least give the impression) is that emissions are not a primary part of RCPs – which is of course pants.

On that last point, that the scenarios were originally defined purely as concentrations for use as input to climate models, not even the IPCC appears to agree:

The Representative Concentration Pathways (RCPs) describe four different 21st century pathways of greenhouse gas (GHG) emissions and atmospheric concentrations, air pollutant emissions and land use. The RCPs have been developed using Integrated Assessment Models (IAMs) as input to a wide range of climate model simulations to project their consequences for the climate system.

Zeke Haufather and Glen Peters in their Nature comment published yesterday on the misuse of RCP8.5 say:

In the lead-up to the 2014 IPCC Fifth Assessment Report (AR5), researchers developed four scenarios for what might happen to greenhouse-gas emissions and climate warming by 2100. They gave these scenarios a catchy title: Representative Concentration Pathways (RCPs).

It is a fact that there are many different scenarios that are compatible with very high GHG concentrations in 2100 and the resultant 8.5W/m² radiative forcing at the surface; indeed, a veritable plethora of them as  Zeke and Glen point out:

The plethora of future emissions scenarios poses a challenge to users of climate data — from policymakers to investors14. More than 1,200 mitigation scenarios were assessed in AR5 in 2014. Another 400 scenarios were used in the IPCC’s 2018 special report on 1.5 °C of warming.

However, what is certain is that RCP8.5 assumes high end emissions scenarios (nightmarishly unrealistic scenarios in fact), combined with little or no mitigation. That is why it was originally labeled ‘baseline’ by the IPCC, which somehow got translated to “business as usual”. You simply cannot get to very high GHG concentrations (1000ppm or more) in 2100 and a resulting 8.5W/m² radiative forcing at the surface using CMIP5 models without assuming very high emissions – even with strong climate and carbon feedbacks.

This paper summarizes the main characteristics of the RCP8.5 scenario. The RCP8.5 combines assumptions about high population and relatively slow income growth with modest rates of technological change and energy intensity improvements, leading in the long term to high energy demand and GHG emissions in absence of climate change policies. Compared to the total set of Representative Concentration Pathways (RCPs), RCP8.5 thus corresponds to the pathway with the highest greenhouse gas emissions.

The Representative Concentration Pathway (RCP) 8.5 corresponds to a high greenhouse gas emissions pathway compared to the scenario literature (Fisher et al. 2007; IPCC 2008), and hence also to the upper bound of the RCPs. RCP8.5 is a so-called ‘baseline’ scenario that does not include any specific climate mitigation target. The greenhouse gas emissions and concentrations in this scenario increase considerably over time, leading to a radiative forcing of 8.5 W/m2 at the end of the century.


Emissions scenarios (and climate change mitigation policies) are thus intimately connected with Representative Concentration Pathways and it’s not helpful that an award winning climate science communicator takes to Twitter to give the opposite impression. Why is Richard doing it? I don’t know, but damage limitation from the fallout of RCP8.5 being exposed as basically crap – not because of unrealistic assumptions about GHG concentrations but because of unrealistic socio-economic assumptions regarding the extreme use of coal in particular – springs to mind.

We can get another clue as to what might be going on by this tweet from JPascal van Ypersele, IPCC vice-chair for AR5, in response to Richard’s thread on RCP8.5:

Having been roundly criticised for misusing RCP8.5 as “business as usual”, climate scientists now appear to be changing tack and diverting criticism by claiming that high end scenarios (even nightmarishly unrealistic ones) are essential when considering risk management. Glen Peters and Zeke Hausfather echo this sentiment in the BBC article:

Does this mean that our projections about future temperature rises are wrong?

Not necessarily.

However, the authors are at pains to point out that the lower temperatures aren’t guaranteed.

That’s because scientists are still uncertain as to how sensitive temperatures are to CO2. New models are being used for the next set of major projections due from the IPCC next year. Those models are said to show that temperatures are more sensitive to CO2 than previously thought.

There is also the question of climate feedbacks. Although emissions from human activities might level off over this century, warming could see more permafrost melt which will push more methane and CO2 into the air, putting upward pressure on temperatures.

“I don’t think we can rule out a world of four degrees or above, because of these uncertainties in climate sensitivity and the uncertainties in carbon cycle feedbacks,” said Zeke Hausfather.

“So even under a lower emission scenario, you could have higher sea level rise, higher warming impacts, if climate sensitivity ends up being on the high end.”

“If you think of climate as a problem of risk management, you don’t necessarily just want to plan for the most likely outcome, You want to plan for sort of the tail risk, the relatively low probability but high impact scenario.”

You can immediately see where this is going, can’t you? Having finally been publicly exposed for unnecessarily scaring the pants off of people by abusing an extremely unlikely worst case emissions scenario for years, scientists are now seeking to divert attention from their failings by resurrecting the discredited precautionary principle and relying upon equally highly unlikely hyper-sensitive AR6 climate models and theoretical carbon cycle feedbacks to claim that ‘risk management’ demands a robust real world policy response to fantasy projected climate warmings. Business as usual, in other words, in the whacky world of policy advocating alarmist climate science.


Zeke Hausfather further enlightens us on the likelihood (or not) of RCP8.5/SSP5-8.5:

Screenshot_2020-01-30 Zeke Hausfather on Twitter For this reason while we think that the RCP8 5 SSP5-8 5 emissions scenario[...]




  1. So the BBC admits that the BBC was wrong and Jaime Jessop was right (see ‘related post’ link to lies… Part II).
    Will they issue a correction and an apology for misleading viewers?

    Liked by 1 person

  2. Business as usual then, for the foreseeable future.


  3. Zeke almost recovered a shred of integrity.
    Reading the apologists for the continued use of provably false scenarios shows amazing banality and bloody mindedness. Their unwillingness to back down in the face of plain fact is only comparable with religious fundamentalists and communist true believers who will undertake any rationalization to cling to their faith, no matter at what cost.

    Liked by 1 person

  4. Thanks for summarising the current debate so well Jaime.

    Bishop Hill kicked off a Twitter thread ten days ago on why the MSM, not least the BBC, weren’t covering the RCP8.5 story, tagging Shukman and Harrabin but not McGrath. Knowing Roger personally from the 1990s I chipped in:

    Later I also paid brief tribute to the man who we all agree deserves great credit for bringing the scandal to light, not least through his new regular Forbes column, Roger Pielke Jr. (When you say we are “winning the war against climate crisis alarmism” the importance of that decision by Forbes, and the way Roger has used it, after the debacle of his sacking by Nate Silver at in 2014, as various shadowy players tried to silence him completely, should not be overlooked.)

    The Bish then did tag McGrath:

    and I made what I think is the key point we should now all focus on:

    We all agreed that there were twelve things missing from that flagship BBC effort, just one of which was the implausibility of RCP8.5, on which I relied on your piece on the subject mentioned by Paul, Climate Change – The Lies, Propaganda, Misinformation, Disinformation and Emotional Blackmail. Part II posted on 19 Apr 19.

    I didn’t predict that RCP8.5 would be the first of the twelve pillars to fall but I strongly believe we should be going back to the others with the key people in the corporation. The imbalance of their output on this crucial subject in April 2019, for the whole country, including the new climate assembly, has to be faced up to and publicly. (And then all the other output!) But kudos to Matt McGrath for this first step.

    Liked by 1 person

  5. I have at once to disagree with myself:

    I made what I think is the key point we should now all focus on …

    RCP8.5 is of course bigger than the BBC and the debate that Jaime summarises is much wider than anything Matt McGrath wrote yesterday, right or only slightly wrong. (Those well-known scientific lawyers – Nitpick, Look Squirrel and Partners – are really out in strength on this one.)

    The first step is, of course, to put the bed the soft soaping (says the Cliscep master of mixed metaphors):

    and lay into all weaselly fellow-travellers:

    But, just on Pielke and the importance of his Forbes column after the suspension of his brief gig six years ago at, here’s a Polish software engineer, resident in London, who I’ve met at Ruby events and really like, last February:

    I couldn’t help myself, though my language was I hope measured, as I think is befitting with those one assumes are neophytes in this strange area:

    No response but at least Tomasz didn’t block me. (Many very good software people have felt that need during the last ten years, starting with @david_harvey in November 2009, a veteran software thinker I used to like and respect a lot. To everyone’s detriment.)

    Then I thought I’d look back to Forbes and how long Roger’s been writing regularly there. So to the page Roger Pielke Contributor. He only began in September, with the last of six that month being typically fact-filled and trenchant: Net-Zero Carbon Dioxide Emissions By 2050 Requires A New Nuclear Power Plant Every Day. Is that all Rog? 🙂 And he’s now done 31 articles in all – about three every two weeks. I don’t think Forbes would have made this commitment if Donald Trump wasn’t President – a man Roger despises, as far as I can tell. But he’s used the platform brilliantly, in conjunction with Twitter, perhaps now with world-changing consequences.


  6. OLDBREW says:
    30 Jan 20 at 10:42 pm
    The bottom line is to keep greenhouse gas mythology alive.

    There is no reason to exaggerate scary scenarios for Climate Science funding cuts.


  7. I have to ask why there is this fixation on emissions when there is compelling analysis that emissions do not control concentrations. ( ) The recent rise in CO2 concentration is nearly all natural an has been nearly constant for the last 30 years while emissions increased steadily until 2012 than leveled off for several years. Harde, Berry , and Salby demonstrate these relationships but the consensus group ignore their work and run with the falsified IPCC assertion that all the rise in concentration is due to human use of fossil fuels.


  8. Schneider all over again:

    On the one hand, as scientists we are ethically bound to the scientific method, in effect promising to tell the truth, the whole truth, and nothing but – which means that we must include all doubts, the caveats, the ifs, ands and buts. On the other hand, we are not just scientists but human beings as well. And like most people we’d like to see the world a better place, which in this context translates into our working to reduce the risk of potentially disastrous climate change. To do that we need to get some broad based support, to capture the public’s imagination. That, of course, means getting loads of media coverage. So we have to offer up scary scenarios, make simplified, dramatic statements, and make little mention of any doubts we might have. This “double ethical bind” we frequently find ourselves in cannot be solved by any formula. Each of us has to decide what the right balance is between being effective and being honest. I hope that means being both.

    Frankly, Schneider’s “other hand” is not science.


  9. Michael Liebreich has been getting involved in a technical discussion on carbon feedbacks with Zeke Hausfather and others.


  10. “Does this mean that our projections about future temperature rises are wrong?

    Not necessarily.”

    I have seen this approach used before to explain away why things predicted weren’t happening. They don’t say “No” of course, even thought that has to be the case.

    The Met Office were so worried in 2006 about the credibility of global warming theory in the face of contrary experience with then current weather patterns, and the coldest winter for many years, that they felt it necessary to draw the attention of the public to the question. The original forecast in September 2005 said:

    “Our latest predictions indicate a colder-than-average winter for much of Europe. If this holds true, parts of the UK – especially southern regions – are expected to have temperatures below normal. The last eight winters have been relatively mild and perhaps have given the impression that these are ‘normal’. The balance of probability is for a winter colder than those experienced since 1995/6.”

    A subsequent web page said: “why are we predicting a colder than average winter when we are at the same time talking about climate change”. They even produced an FAQ on the subject, including a pertinent “belief-related” question and answer:

    Q) So, does it mean that global warming is on hold?

    A) No. The forecast of a colder-than-average winter is based on the prediction of atmospheric circulation patterns that change from year to year. Increased frequencies of easterly and northerly winds are expected this year. Basically, it is the direction of the wind that brings the lower-than-average temperatures.”

    Professor Betts is required to back up the government line. The government line is to follow the UN and they have no wish to be labelled as “Trumpian Climate Deniers” with COP 26 on the stocks for November. Having declared a Climate Emergency, they cannot now say “sorry, as you were.”


  11. OldBrew,

    Climate science saved the world from 5C; we should all now just let climate scientactivists get on with saving the world from 3C.

    Liked by 1 person

  12. and a climate activist is very unhappy …. with Tamsin Edwards (click on the tweet and see the whole conversation)

    The activist is an independant mayoral candidate for London, who wants to ban all cars in London (including electric ones..

    Mark and Greta will be fun.. Greta: you scientists have done nothing
    Mark: we’ve save the world from 5-6 C

    that will end well


    COP26 is going to be so much fun watching

    Liked by 2 people

  13. “it seems pretty obvious that the quantity of GHGs which humans put into the atmosphere is a huge factor in determining the resulting concentrations of GHGs which accumulate in the atmosphere.”

    Actually, what’s now clear is just the reverse: The role of “GHGs which humans put into the atmosphere’ is Not Huge but Tiny. The fallacy follows from the presumption that GHGs “accumulate in the atmosphere”. They Don’t – It’s now been shown that GHGs (like those put in by nature) are removed from the atmosphere almost as fast as they are put in.

    The house of cards collapses.


  14. Where’s the downside to making alarmist predictions that fail miserably?

    In eight years’ time, when the planet hasn’t disappeared in a cloud of toxic gas, presumably Greta will throw up her arms and say: ‘Sorry guys. Looked like I was wrong about you ruining my childhood. I’m now going to become a flight attendant.’

    But, weirdly, that never happens. No matter how often these ‘experts’ are shown to be no better at forecasting than Paul the Octopus — worse, actually — they just carry on as if nothing has happened.


  15. They don’t come much more unhinged than Nutticelli. This is completely insane. I’m starting to think, because of the response from mainstream climate science, that the RCP 8.5 debacle is probably the most significant public airing of bad practice by the climate science community since climategate.


  16. So Tamsin Edwards reveals herself as a priestess, not a scientist.
    We could have spent none of the billions on “climate science” and the huge climate consensus promotion industries that feed off it. We could have done literally nothing but to continue with nuke, gas and cleaner coal. And the climate, the weather, SLR, Bushfires, Arctic sea ice, etc., etc., etc. would be the same as now.


  17. Those apologists choosing the tactic of defending RCP8.5 as a minor bit of semantics that doesn’t impact “the science” only show they either never understood the science or never cared about the science.

    Liked by 2 people

  18. Jeremy, I have always been somewhat sceptical of the Bern Model of accumulating anthropogenic CO2 and in particular the consensus narrative that CO2 has increased from 280ppm pre-industrial to 410ppm now, almost entirely because of anthropogenic emissions. I don’t buy into the claim that atmospheric CO2 is the highest it’s been for 800,000 years because chemical analyses and plant stomatal proxy data tell a very different story than Antarctic ice cores.

    That particular debate was recently re-ignited by John Shade, but essentially it’s not relevant to my post here because mainstream climate science maintains that emissions are driving global warming by increasing atmospheric concentrations of GHGs. To model future concentrations, they invented these four RCP scenarios which are, by their own admission, intimately connected to emissions. Because they have now been revealed to have misused RCP 8.5, which is an unrealistically high end emissions scenario, what they are trying to do is de-empahsise the role of emissions by claiming that concentrations are also significantly affected by carbon cycle feedbacks and hence RCP8.5 is possible even with lower emissions.

    Liked by 1 person

  19. I think Murry Salby has the CO2 bookkeeping wrong, annual revenue is not the same as net profit, e.g. my guinea pigs have a huge annual CO2 revenue, but still act as a carbon sink.

    Liked by 1 person

  20. Interesting post from Roy Spencer who uses a simple carbon model to project future increases in atmospheric CO2 concentrations using IEA’s latest estimates of emissions throughout the century. The model (which closely matches the Mauna Loa data) suggests that the fraction of CO2 removed increases significantly as temperatures increase and more CO2 is released into the atmosphere, resulting in a leveling off of CO2 at just 541ppm in 2240, half of what RCP8.5 projects for 2100 even. This implies that the carbon feedbacks do the complete opposite of what Richard Betts and others are suggesting, taking more, not less CO2 from the atmosphere as emissions increase. Ironically then, this would mean that Richard is in fact right: there is a huge difference between emissions and concentrations! Right in completely the opposite direction though, making RCP8.5 look even more vanishingly improbable.

    Given the large uncertainties in how the global carbon cycle responds to more CO2 in the atmosphere, it is entirely reasonable to hypothesize that the rate at which the ocean and land removes CO2 from the atmosphere is simply proportional to how high the atmospheric concentration gets above some baseline value. This simple hypothesis does not necessarily imply that the processes controlling CO2 sources and sinks are also simple; only that the net global rate of removal of atmospheric CO2 can be parameterized in a very simple form.

    The Mauna Loa CO2 data clearly supports that hypothesis (Fig. 1 and Fig. 2). And the result is that, given the latest projections of CO2 emissions, future CO2 concentrations will not only be well below the RCP8.5 scenario, but might not even be as high as RCP4.5, with atmospheric CO2 concentrations possibly not even reach a doubling (560 ppm) of estimated pre-Industrial levels (280 ppm) before leveling off. This result is even without future reductions in CO2 emissions, which is a possibility as new energy technologies become available.

    Very awkward times ahead for climate alarmists methinks, in particular RCP8.5 enthusiasts.

    Liked by 1 person

  21. What Pielke has illustrated and finally gotten the larger world to finally realize is something skeptics have said for many years. But we are denialist scum to be ignored. Frankly this shows the climate consensus, as pimped by Mann, Lewandowsky, Hansen, ATTP, Gore, Greta, Merkel, ER, HRH Prince of Wales, Kayhoe, etc. ad nauseum, is a scam.
    People should be really, really pissed off.
    Trillions of dollars have been pissed away.


  22. Richard still insistent that RCP8.5 is relevant to risk management (and hence policy). Roger Pielke maintaining that it is not. The climate consensus is fighting very hard to rescue the credibility of RCP8.5. They’ve realised that an awful lot depends on it, e.g. the US National Climate Assessment 4 used RCP8.5 as a ‘business as usual’ scenario. Could get quite nasty.


  23. The European Commission’s Director-General of its Director-Generalship for Budget (DG DG BUDG), a Dutchman, reckons that because 45% of Dutch people have said that climate change is the most important issue facing the EU a quarter of the EU’s 2021-2027 budget should ‘go on climate’.

    Somewhat odd logic, no?

    And, as it happens, it’s odd logic that has been applied to a misrepresented poll. The 45% comes from the latest Standard Eurobarometer (#92) and is in fact the percentage of Dutch people who mentioned climate change when asked to name the two most important issues facing the EU. They weren’t asked to rank their answers, so it’s not possible to use that poll to say how many Dutch people think that climate change is ‘the N1 issue for the #EU to address’.

    You can say which was the issue mentioned most often by Dutch respondents, which is a very similar thing, I suppose. The trouble is, that wasn’t climate change. It was immigration (48%). Will the Commission be calling for ~€300 billion of EC funds to be spent on immigration in 2021-2027? Er, probably not.

    They perhaps should, though, if they are going to base the EU’s spending priorities on opinion polls. Immigration was the most frequently mentioned issue in 26 of the EU’s then-28 member states. Climate change came top in only three: Sweden, Ireland and Austria (where it was joint top with CC).

    (Saintly Ireland, eh? With its per-cap emissions nearly twice the UK’s. Too-ra loo-ra loo-ra CO2 CH4 N2O-oorah, bejesus, by crikey.)


  24. Vinny,
    Blarny (Irish premium) is, at the very least, 97% CO2 emissions.
    Will Gert Jan Koopman impose a hypothecated tax that will selectively affect the saintly Irish? Westminster might dodge a bullet if it acts on time.


  25. Alan, I had to google ‘hypothecated tax’. A handy term. Thanks.

    As for dodging bullets… I gave up reading about the UK’s Brexit negotiations almost as soon as they started. Speculation upon speculation about speculation…


    Gert-Jan Koopman was Neil Kinnock’s top advisor during his two terms as a European Commissioner, so if Koopman is involved on the EU side in the Brexit negotiations then Britain might do quite well. Unless it’s decided that we were kicked out for fraud, that is, in which case we’ll be forced to re-join, a la Kinnock.



  26. Roger has sadly deactivated his account on Twitter because he got fed up with all the SkS fanatics harrassing him. But the argument still rumbles on. Michael Liebreich has taken Richard to task over his insistence that you can get to RCP8.5 concentrations from lower emissions scenarios. It’s an interesting thread. I recommend you read all the tweets. This is the most significant for me:

    At this point it’s worth noting that the latest UKCP18 regional climate projections provided by the Met Office for Britain are based on RCP8.5, so the Met Office is heavily invested still in the use of this scenario, just like NCA4.

    Liked by 1 person

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