Have our climate models been wrong?

Have our climate models been wrong? This is the title of a new episode of the BBC World Service’s “The Inquiry”, available here on BBC sounds. It’s about the emphasis on RCP 8.5, often misleadingly referred to as “business as usual”.

After introducing the topic via James Hansen’s call to action in 1988, and the formation of the IPCC, the presenter says that some scientists are saying too much emphasis has been put on the worst case scenarios.

Four expert witnesses are presented. The first is Chelsea Harvey, a reporter for E&E News, who introduces the RCP scenarios, explaining that RCP 8.5 is a worst case scenario based on rapid expansion of coal use. She says it’s human nature to be attracted to the worst case scenario.

Expert number two is Justin Ritchie, who says he started to question why RCP 8.5 was getting so much attention while he was doing his PhD.

Next up is Roger Pielke Jr, who says the proliferation of use of RCP 8.5 is a prime example of the misuse of science.

We got off track when we started treating scenarios not as scenarios of the future but as predictions or projections of the future.

When academics such as myself publish papers and university press offices put out press releases, you can be guaranteed that the most notable newsy studies will be those that employ RCP 8.5, and somewhere – I don’t think any of this is conscious, but somewhere along the way we take a scenario that is highly improbable, highly unlikely, and it goes through the process and  shows up on the BBC or the front page of the New York Times as “where we’re headed” stripped of all the context and details, because it is a complicated topic, and if we repeat that hundreds of times, every year for the last decade, we get a picture of climate change that is not necessarily in conformance to what the broader literature actually says.

The analogy I often use in these situations was the decision to go to war in Iraq. In the short term there was a lot of fear generated by raising concerns of weapons of mass destruction and in fact it did lead to short term action with long term consequences – the invasion of Iraq.  Later when it was discovered that the intelligence wasn’t quite sound, and may have had some political influence, there was a lot of lost credibility among the intelligence community, but also those politicians and policy makers who had pushed very hard for action based on the science. We shouldn’t evaluate science buy the worthiness of the cause, because that doesn’t lead to good decision making.

The continued use of RCP 8.5, and presenting it as business as usual, gives ample fodder for those who are opposed to action on climate change to criticise the scientific community, and they will be in real respects standing on solid ground when they do so.

Does he have debates with scientists who say, can you stop talking this down?

Oh absolutely, all the time. It is interesting that for some people, they say, well climate change is far too important to air the questions, uncertainties, course corrections, going on within science, and I have exactly the opposite view: climate change is far too important not to have those discussions. Because science is messy, it’s course correcting, which is one of its strengths, and climate change is one of the critical challenges of this generation, and if we don’t have the science right I can’t think we’re ever going to get the policy right.

Finally we hear from Richard Betts, who attempts to defend the continued use of RCP 8.5.

The way you’re framing the question is, have we been looking at the wrong scenarios, and I don’t think so, because we need to account for a whole range of future possibilities, and it’s very important to guard against overconfidence, and thinking that we can predict the future perfectly, when we can’t.

Richard tries to claim that even with lower emissions we could still get to RCP8.5’s higher CO2 concentrations. Because when you mow your lawn, it decomposes and the carbon dioxide goes back into the atmosphere. Or perhaps the ocean might somehow stop absorbing carbon dioxide. The programme didn’t mention the almost 12 million euros of grant funding, mostly from the EU, that Richard and colleagues received specifically to study “High End Climate Impacts and Extremes” (HELIX).

The narrator ends with this summary:

Have our climate models been wrong? All our expert witnesses say treating the most severe trajectory, RCP 8.5, as the “business as usual” baseline scenario was wrong.  That placed us in the spotlight and as a result, our climate modelling has put too much emphasis on an unlikely scenario.  The truth is, there are many paths we could take into the future. None of them look easy, and some look horrendous.


HT Bishop Hill. Another possible explanation for the rather desperate attempt to keep RCP 8.5 alive is that the Met Office’s UK predictions, UKCP 18, make use of RCP 8.5, see documents here and here. Excerpts:



  1. Ha, if that’s not a weasel-worded summary I don’t know what is! They obviously hate the fact that they got it wrong and that they have been shown to have got it wrong, so they’re squirming in discomfort. Also, Richard keep banging on about a lower emissions/concentration scenario possibly leading to RCP8.5 concentrations is embarrassing. RCP8.5 is rubbish, but it’s being blatantly used by the Met Office to make regional, local and global projections of climate change in UKCP18.


  2. Richard accepts that RCP8.5 cannot possibly be reached through carbon emissions as originally envisaged (coal fever). His new argument is that the carbon cycle breaks down such that airborne fraction increases (currently 0.45) just enough to keep us on RCP8.5 trajectory. So maybe you’re right that the HELIX study is all based on RCP8.5. The problem with that argument is that the airborne fraction has been remarkably constant for the last 30 years and shows no sign of increasing.

    It seems (perhaps misinterpreted by the host) that he also proposed that warmer oceans lead to more clouds which “warm” (i.e. add forcing) to keep us on the RCP8.5 track. I think this is nonsense since more clouds lead instead to higher albedo and a reduction in forcing. That is why rainfall follows the sun.


  3. The clouds arguments are tricky, because you get more albedo in daytime but on the other hand less heat loss at night. Do models treat the overall effect as zero?


  4. The evidence thus far is that land sinks are expanding to accommodate the extra CO2, also that recently the oceans are absorbing more CO2 because of changes in global circulation. The historical Mauna Loa record does not support the suggestion that carbon sinks are declining with increasing concentrations, so it’s all speculation based on little or no evidence. Alarmism in other words. It’s doubtful the atmosphere will be anywhere near 1000-1300ppm concentration by 2100.

    Liked by 2 people

  5. Clouds react to temperature. In the tropics the day starts with clear skies. As the heat builds up clouds form until by afternoon in sky is mostly covered by clouds shading the sun. Late afternoon there is a thunderstorm releasing latent heat energy and overnight the clouds disperse so that the land cools down through IR.

    Clouds overall are a thermostat control on climate.

    Liked by 1 person

  6. Is everyone aware of this piece by Roy Spencer last month, questioning whether we’ll ever even reach a doubling of CO2 in the atmosphere? He summarises thus:

    In my experience, the main complaint about the current model will be that it is “too simple” and therefore probably incorrect. But I would ask the reader to examine how well the simple model assumptions explain 60 years of CO2 observations (Figs. 1 & 2).

    Also, I would recall the faulty predictions many years ago by the global carbon cycle modelers that the Earth system could not handle so much atmospheric CO2, and that the fraction which is removed over time would start to decrease. As Fig. 2 (above) shows, that has not happened. Maybe when it comes to photosynthesis, more life begets still more life, leading to a slowly increasing ability of the biosphere to remove excess CO2 from the atmosphere.

    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.

    I think this is at least as important an issue to discuss as the implausibility (impossibility?) of the RCP8.5 scenario. And it raises the question of just how good the carbon cycle models are that the UN IPCC depends upon to translate anthropogenic emissions to atmospheric CO2 observations.

    Something else I know I don’t grok – the carbon cycle.

    How nice it must be to have an infusion of HELIX money to make one sure.


  7. Schneider redux:

    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 the 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 climatic change. To do that we need to get some broad based support, to capture the public’s imagination. That, of course, entails 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.

    Obviously only “effective” research wins grants.


  8. This comparison of scenarios shows how out of line RCP 8.5 is with business as usual:

    The latest IEA emission esitimate for 2040 is only 37 GtCO2, (current 33)

    Liked by 1 person

  9. Have our climate models been wrong? Have they ever been right?

    In 2007, Professor Lenny Smith, a statistician at the London School of Economics, warned about the “naïve realism” of current climate modelling. “Our models are being over-interpreted and misinterpreted. Over-interpretation of models is already leading to poor financial decision-making, Smith says. “We need to drop the pretence that they are nearly perfect.”

    He singled out for criticism the British government’s UK Climate Impacts Programme and the Met Office. He accused both of making detailed climate projections for regions of the UK when global climate models disagree strongly about how climate change will affect the British Isles.” (From New Scientist magazine, 16 August 2007.)

    In 2007, Defra was congratulating its scientists in sharing in the Nobel Peace Prize with Al Gore:

    “Defra provides financial support to the co-chairs and their supporting secretariats. As such the UK has provided underpinning funding for almost one-third of the major scientific reports produced by the IPCC, which the Nobel committee believes have “created an ever-broader informed consensus about the connection between human activities and global warming.”

    The Science:
    The Climate Prediction Programme was not an academic research programme; its work plan and deliverables was driven by Defra’s requirements for science to inform UK government policy on climate change mitigation and adaptation. As the policy requirements changed, so did the research programme objectives. The Met Office will focus on research that contributes to UK government policy objectives and will communicate the results to government and the public.”

    In 1999, there was a series of seminars in Europe focusing on “Uncertainty in Climate Models,” known as the ECLAT series, “Representing Uncertainty in Climate Change Scenarios and Impact Studies” published by CRU: Mike Hulme and others said:

    “Even with perfect models and unlimited computing power, for a given forcing scenario, a range of future climates will always be simulated. It is for this reason that the Intergovernmental Panel on Climate Change (IPCC) have always adopted the term ‘projection’.” Not any longer, as Jaime recently pointed out and Pielke Jnr is also highlighting.

    Stabilising Climate to Avoid Dangerous Climate Change — A Summary of Relevant Research at the Hadley Centre January 2005. Richard Betts was a co-author:

    “What constitutes ‘dangerous’ climate change, in the context of the UN Framework Convention on Climate Change, remains open to debate.

    Once we decide what degree of (for example) temperature rise the world can tolerate, we then have to estimate what greenhouse gas concentrations in the atmosphere should be limited to, and how quickly they should be allowed to change. (how would they know?)

    These are very uncertain because we do not know exactly how the climate system responds to greenhouse gases.

    The next stage is to calculate what emissions of greenhouse gases would be allowable, in order to keep below the limit of greenhouse gas concentrations.

    This is even more uncertain, thanks to our imperfect understanding of the carbon cycle (and chemical cycles) and how this feeds back into the climate system.”

    This was just before Tony Blair’s “Conference on Dangerous Climate Change,” at the new Exeter Met Office HQ. One poor Australian reporter was so overwhelmed by the disaster scenarios, that she reported: “Some of the research being presented at the latest conference, Avoiding Dangerous Climate Change, in Exeter in England, are (sic) enough to prompt nightmares about the end of the world.” And so they have been presenting their computer modelling ever since.

    Who can forget Kevin Trenberth’s angst over climate modelling in 2007? Oops, it seems everybody has:


    Liked by 2 people

  10. Richard is not even right about grass. Here is an experiment. Mow your lawn. Take a handful of grass clippings and place them on a concrete path in a protected area where they will not blow away. It will take them a very long time to oxidise and return to the atmosphere as CO2. The clippings left on your lawn will disappear much faster. Why? Because earthworms will take some portion of them underground. There they will undergo all sorts of processes, and sure some CO2 production will occur. But some portion will also end up as labile carbon, and some portion will end up combined in humic substances which are quite resistant to decomposition, as long as you don’t dig up the lawn.
    Plus, when you mowed the lawn a portion of the roots about equal in quantity to the amount of grass you mowed will shed off the active root system,die,and undergo the same processes of decomposition, and the same short and long term storage of some of the carbon.
    Plus if you let your lawn grow rather long, its photosynthetic efficiency increases. Any energy used for photosynthesis can have less immediate heating effect, so the ambient temperature will be less than, say for bare ground. Then when you finally mow it, a greater quantity quantity of roots are shed underground.

    Liked by 1 person

  11. “Because science is messy, it’s course correcting, which is one of its strengths, and climate change is one of the critical challenges of this generation, and if we don’t have the science right I can’t think we’re ever going to get the policy right.”

    Climate Science is a mess because it is NOT self correcting. Peer Review has proved its weakness.

    Having proved the weakness of Climate Science, Peer Review has continued to be a lucrative enterprise, as the situation remains” Business, as usual”


  12. Most dead plant material decays within one year. There are plenty of studies using litter bags that show this. Some plants drop litter that is resistant to decay. However, thanks to our fungi friends, even wood is not a permanent store, er, unless it is made into furniture.

    A classic example of recalcitrant plant material is Sphagnum moss in peat bogs. The anoxic state of the peat means that rather than decaying rapidly, the dead material takes thousands of years to decay. Note: this is not a permanent store because the bog reaches an equilibrium, like a glacier; it may end up metres deep but new material will be added at the same rate it is lost unless the bog is building.

    That is why I have been fascinated to work out how much carbon fixed by phytoplankton rains down into the ocean depths, becoming first sediment and eventually shale – but from what I have read this is as low as 1%. I find this hard to believe, and intend to delve deeper to find out the basis of the number.

    Of course plankton are limited by trace nutrients, so I don’t know if there is much hope that increasing concentrations of CO2 in the atmosphere will increase productivity and sequestration. If I recall right, the experimental addition of limiting elements to the ocean did not boost productivity (another thing to look up in more detail…)

    Liked by 1 person

  13. Yer masquerade, yer burlesque. yer pantomime, why did the BBC not stick to this, … (ter wit, in this age of political correction requiring a snowflake warning,) ‘The Goodies’ and ‘The Travelling Instant Five Minute Christmas’ …


  14. A very pertinent article by Fabius Maximus:

    He has a nice reminder of Richard Betts’ piece for the BBC in 2010:

    “Climate scientists need to take more responsibility about how their work is presented to the public, suggests the Met Office’s Richard Betts. In this week’s Green Room, he says it is vital to prevent climate science being misunderstood or misused.

    The focus on climate change is now so huge that everybody seems to need to have some link to climate change if they are to attract attention and funding.

    Hence the increasing tendency to link everything to climate change – whether scientifically proven or not.

    The question is: do climate scientists do enough to counter this? Or are we guilty of turning a blind eye to these things because we think they are on “our side” against the climate sceptics?

    It’s easy to blame the media and I don’t intend to make generalisations here, but I have quite literally had journalists phone me up during an unusually warm spell of weather and ask “is this a result of global warming?”

    When I say “no, not really, it is just weather”, they’ve thanked me very much and then phoned somebody else, and kept trying until they got someone to say yes it was.”

    Fabius Maximus continues, with links to show his claims are true: “In 2015 I wrote one of the early critiques of the RCP8.5 scenario (perhaps the first): Is our certain fate a coal-burning climate apocalypse? No! I followed with Manufacturing climate nightmares: misusing science to create horrific predictions. Afterwards, I tried to find a climate scientist to coauthor an article in EOS or WSJ op-ed about the misuse of RCP8.5 – when it might have had an impact. But the ones I contacted were too smart to do so.

    Now even Nature and the hard-core alarmist BBC says this. But RCP8.5 – and more broadly, climate science – no longer matter. The debate has moved beyond science to the exaggerations of the Climate Emergency and the fictions of the Extinction Rebellion. It is all politics and mass hysteria.”

    Worth reading the whole piece.

    Liked by 3 people

  15. “Richard tries to claim that even with lower emissions we could still get to RCP8.5’s higher CO2 concentrations. Because when you mow your lawn, it decomposes and the carbon dioxide goes back into the atmosphere. Or perhaps the ocean might somehow stop absorbing carbon dioxide.”
    Richard unwittingly got this sort of right. Our emissions almost do not change the atmospheric concentration (https://tambonthongchai.com/2018/12/19/co2responsiveness/) so the recent rise in concentration is substantially all natural ( Harde2017 and 2019, Berry 2019). The point Richard misses is that : If our emissions are not the cause of CO2 concentration changes we have no way to “control” the climate by curtailing them. It seems to me he has stumbled into a fact and doesn’t notice that it eradicates his intent.


  16. This Betts fellow might be good with book larning, but he knows nowt about grass. It’s true that the cut grass will decompose and release carbon dioxide back to the atmosphere, but by the time you’ve put the lawnmower away, the grass in the lawn will have started to regrow and, by the time the cut grass has decomposed, it will have absorbed enough CO2 for it to need cutting again.

    Liked by 1 person

  17. GEOFF CRUICKSHANK 07 Mar 2020 10.14am

    The clippings left on your lawn will disappear much faster. Why? Because earthworms will take some portion of them underground. There they will undergo all sorts of processes, and sure some CO2 production will occur. But some portion will also end up as labile carbon, and some portion will end up combined in humic substances which are quite resistant to decomposition..

    Geoff’s explanation of the carbon cycle haunts me every time I go into the garden. I hardly dare pull up a weed. Should I concrete the lot over to make parking space for a third petrol guzzler “before they are forever banned”?

    The BBC has no idea of the repercussions this kind of scepticism about the settled science may generate. A butterfly gets into a flap at Broadcasting House, and a thousand snowflakes in Wokingham go into meltdown. Meanwhile the rest of us hope the weather turns out nice enough for a barbecue.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.