From the least absurd models
A few days ago, I mentioned a paper that had looked at climate model simulation of clouds and found that the ones that did the best job of this narrow task produced the highest predictions of temperature rises. As I noted at the time this means that one can paraphrase the findings as "best cloud simulators are worst temperature predictors" but, as is normal in these circumstances, the headlines were all about global warming being "worse than we thought".
Yesterday Nature published a similar paper, this time looking at the El Nino phenomenon. It seems that if you take the models that best simulate extreme rainfall they predict that extreme Ninos will take place much more frequently in future, with all the floods and droughts and the like that accompany them.
The team identified 20 climate models — half of those available — that were capable of simulating extreme rainfall. They then used the models to compare the occurrence of extreme El Niños in a control period, 1891 to 1990, versus a warmer period extending from 1991 to 2090. Although the total number of El Niño events decreased, 17 out of the 20 models predicted more major El Niño events, with the average frequency increasing from once every 20 years to once per decade.
As an aside, it's notable that only half of the climate models were considered capable of simulating extreme rainfall, so one can reasonably wonder why we should base public policy on computer simulations that can't get even basic phenomena like heavy rain correct. One can also wonder at the paper's use of CMIP5 model runs, which don't incorporate the IPCC's latest estimates of aerosol forcings, and a perturbed physics ensemble, presumably the Sexton one, which has problems of its own. This is speculation though and I'll need to confirm when I get hold of the paper.
Of more immediate relevance to my point is the similarity in approach to the earlier paper - I think what we have here is a case of "the least absurd rainfall simulators predict a devastating increase in El Nino". Now you would think that, this being the case, the writers would have exercised a little restraint, perhaps mentioning uncertainties here and there. But not a bit of it. Here are a few of the headlines:
- Nature: Frequency of extreme El Niños to double as globe warms
- Guardian: Unchecked global warming 'will double extreme El Niño weather events'
- The Australian: 'Twice as many extreme El Ninos'
- Business Standard: Brace yourself for extreme El Ninos every 10 years
- New Scientist: Devastating El Niño events to double this century
Reader Comments (120)
If the models are based on earth / atmosphere physic, why is there a need for 20 or more models, when one model should be able to do the job?
Wasn't it Gavin Schmidt who said that no model gave similar answers but the average of the models gave the correct answer (or something like that)?
Richard Betts: Now that you're responsible for looking as assessing 'Climate Impacts' - I guess, based on your models, and as you seem to say on this thread that you don't see any alternative to the models (but you wish their outputs weren't so hyped by the MSM), I want to revisit a question I had for you from a previous thread:
"What are your thoughts on the fact that Governments are committing trillions of our money to something that may in fact turn out to be quite benign - and certainly not as 'catastrophic' as a long period of cooling that might be coming our way?
Are you aware of how your day job actually affects so many millions of people? Does it ever give you pause?"
The context this time is in the fact that you know your models are not as accurate as you'd like yet based on your and the MO's input to policy makers we are going to be taxed to death and driven back to the 18th Century in the process.
The reverence for models is something that separates the aged curmudgeons, male and female, on this blog from the cli sci community. Richard Betts asks what we're to do if we don't use models? And he's right, the complexity of the climate system and its chaotic nature make understanding it impossible by mere cogitation and observation. However, what appears to be happening in cli sci is tribal belief that the models produce reality or something near it. I note a certain amount of backpedalling where "uncertainties" are admitted, however the gist, to me is, that, "yeah right there are uncertainties but what else have you got". Whereas my view is the uncertainties are show stoppers, primarily because I have a primitive sceptical gene which tells me no one can foretell the future. Again Richard rightly points to the press hyping it all up before the cli scis get the chance to put the answers in perspective - and he's right. However, I well remember the cli sci community, or some 1700 of them, getting together a paper complaining about the attack on British science raised by the revelations of the Climategate emails - yes, I've heard it wasn't to support the scoundrels trying to silence their critics, hiding the decline or getting fellow scientists sacked for not agreeing with them, but it was pretty rapidly out together after the revelations. So how about a rapid response now from the cli sci community saying why Sherwood et al is important but that the conclusions about increased el Ninos is effectively cat poo?
I am reminded of The Hitchhikers Guide to the Galaxy when I see the discussions of climate models The Hitchhikers Guide effectively hold all the secrets of the universe within it and has the words "DON'T PANIC" written on the front page, it does have an explanation of how what's in it which is as follows:
“The Hitchhiker’s Guide to the Galaxy is an indispensable companion to all those who are keen to make sense of life in an infinitely complex universe, for although it cannot hope to be useful, or informative, on all matters, it does at least make the reassuring claim that where it is inaccurate it is at least definitively inaccurate. In cases of major discrepancy it’s always reality that’s wrong.”
Prescience from the late and much missed Douglas Adams.
"You can follow the precautionary principle and hope for the best while planning for the worst."
The worst of what?
There is a very real possibility that the 'precautionary measures' will cause more damage than the 'worst' they are implemented to prevent.
How many extra thousand winter deaths were there because of fuel prices?
How many extra thousand deaths would there be if the world warmed another 2 degrees? (Would we even notice)?
John Marshall
Depends on the clouds. All types of cloud reflect incoming sunlight back upwards and infra-red from below back downwards, but to different extents.
Overall, low clouds reflect more sunlight than IR and produce a net cooling effect, a negative forcing.
High clouds reflects more IR than sunlight and produce a net warming effect, a positive forcing.
Research into trends in cloud cover is ongoing. The International Satellite Cloud Climatology Project (ISCCP) has seen a decrease in both total cloud cover and high clouds.Others have seen a small increase in high cloud. Sherwood's recent paper described a shift towards an increasing proportion of high cloud. As with many other fields, detailed data is only avaliable for recent decades and a longer timeline would be useful.
The huge advances in computing capability coincided with the AGW obsession and as a consequence there has never been any serious climate modelling that does not include carbon dioxide as a major driver of our climate. So there are no models that have been validated with just "natural" variability, no base line against which AGW can be measured or judged. Furthermore, I suspect that over recent decades there has been negligible research on ocean oscillations and solar activity compared with the huge resources thrown at carbon dioxide induced temperature rise.
Today, the scientists are clinging to their failed models and tinkering around the edges in the hope that they can discover a magic explanation for the "pause" that preserves their alarmist claims. Unfortunately, we are now seeing a succession of alarmist papers that do nothing to restore credibility, quite the opposite.
The reality is that our climate is not understood. We all know that it might cool or it might warm. It will not stay constant for long. Perhaps our understanding would have been much better today if the IPCC had not hijacked the science for decades.
Nial
If the science is correct, we are already committed to more than 2C. This is regarded as the tipping point between net benefit and net damage. How far the climate goes beyond 2C will determine the cost in lives.
I can understand your position; it is human nature to value current lives more than future lives.
I do not agree with it. If extensive climate change happens the net effect would be to reduce the carrying capacity of our planet as it reaches peak population. You would have traded thousands of lives now for millions of deaths a hundred years hence.
Schrodinger's Cat
The code for the models is available. If cAGW were wrong, then I would expect sceptic scientists to be publishing model results which show that increasing CO2 does not affect climate. Instead all we have is an embarassing silence.
Are you saying that all the models are consistent with CAGW?
Just 'breaking a few eggs' to make that omelette eh? Have you no shame?
EM
Nial made the point ahead of me but I'll add this. The trouble with the "precautionary principle" is that it has come to be so roundly abused that it is worthless as a guide. Applied as the activists (in climate directly but also in other related environmental fields) would wish it means that nobody would ever do anything and — to extend the argument — we would all stay at home and probably in bed in spite of the fact that the majority of accidents occur in the home.There has to be some balance.
Your contention that "we are already committed to more than 2C" is both contentious and meaningless. 2C as compared with what? Starting from when? By when? And you are assuming positive feedback. And you are ignoring the fact that we are nearly half way to a doubling of pre-industrial CO2 levels (according to the IPCC) and the effects of CO2 are logarithmic and where are all the nasty things that ought to be starting to happen by now and what are they anyway?
And since the earth has frequently been at +2C compared with now and the effect has been largely beneficial where is the evidence that "this time it's different"? (And I'm thinking of starting to put a ™ sign on that statement as well!)
And humanity has always valued current lives more than future lives as a general principle because that is all we have and it's always been right to do so because mankind — especially during times when the climate has been warm — has always moved forward in his social, intellectual, and industrial development. Not to mention his ability the better to cope with the various problems that those leaps forward have brought with them.
And, provided we don't impoverish her with our insane energy policies and obsession with endless warming while ignoring the real possibility of cooling, I fully expect my grand-daughter and her generation to be just as able to face their difficulties as we and our grandparents have been.
Always assuming we aren't so bloody arrogant as to decide now what those problems will be in 30+ years time and take action now to prevent them because, like generals always planning to fight the last war, we will be wrong!
Richard Betts says:
Validate! Validate! Validate!
Selecting models that predict rainfall reliably and then claiming that they are therefore valid for predicting frequency of el nino's is a non-sequitor. If the same models that predict rainfall are unreliable for other parameters (eg temperature) then to claim they are better for some third variable which has not been validated is pure hokum.
And if you compare enough different runs of random noise generators, you will eventually get a correlation with your target variable. This is called spurious correlation and is trivial to test for with a Student T Test. Selecting the best prediction is in itself a bias - even with random noise, one prediction will always be "better".
Finally, the more comparisons you make of the output (from different model runs) until selecting the one that agrees with your data, the more likely you are to find a spurious correlation. The statistical test for spurious correlation becomes more and more onerous and is in proportion to the POWER of the number of the comparisons you make. For a (reasonably) lay description of this see the article by Kalkomey, 1997 in the publication The Leading Edge.
I have to smile because one of the key tenets of warmism is about saving the planet for future generations. As EM shows all too clearly, the real motive is to screw over the current population by causing deaths which may be unnecessary. It is always good to see greenism in its pure form.
EM says:
And if the science is wrong, then we are not.
Wils:[2007] from the Climategate emails:
Richard Betts
"We don't know what's going to happen.."
That isn't a message that seems to get much traction. :-(
EM:
"Think of it as spread betting."
- This is an idiotic comparison that serves you very badly.
- Spread betting requires hedging. To hedge you bet in both directions and across both related and unrelated investments. The profit is made in ensuring that you're hunch nudges in just enough of the correct overall direction across bets that you make at least a modest profit. If you were particularly certain of anything, you wouldn't spread bet but would invest most of your capital in an appropriate instrument that you were sure was going to move one direction or the other.
@Richard Betts "While it is an important conclusion and well-articulated in the paper, the media have, unfortunately, done their usual thing in hyping it up and ignoring uncertainties."
So I take it that you will be writing to the various arms of the media, in a formal capacity, in to correct this?
Richard:
"While it is an important conclusion and well-articulated in the paper, the media have, unfortunately, done their usual thing in hyping it up and ignoring uncertainties."
- Have you consulted Matt Collins' twitter output? What's his excuse?
- At least it answers something for me. At the Royal Society meeting, Collins was expressing concern about 'getting the message out there' especially vis a vis sceptics. I asked why they didn't focus instead on reining in the irresponsible hysterics. He said "not my problem". That makes more sense now. He's one of those irresponsible hysterics.
EM -
"You can follow the precautionary principle and hope for the best while planning for the worst."
- The precautionary principle can be invoked for anything and its use is often quite arbitrary. When you invoke it you open yourself to the objection that you need to justify why excessive precaution should be given to your pet issue and not others.
- For example: Where is our asteroid defence system?
EM -
"The code for the models is available."
- Really? Can you enlighten us as to where? I spent some time trying to dig this out for myself. The majority of the models are not publicly available AFAICT.
Good to see Richard Betts commentating. He says - ' it is rarely correct to say "will"when talking about climate projections- "could or "may" are usually about as confident as you can get '.
Precisely the point everyone is making. I hope Dr Betts will communicate his uncertainty immediately to Cameron, Clegg, Davey etc. and convince them that the information they currently have about future climate is not suitable to base energy policy on. That is what worries so many here.
Several respected scientists, on evidence from PDO, sun activity etc, suggest there 'may' be a period of cooling for the next 30 yrs which 'could' have a marked effect on food production.
After 15+ years of no global warming despite rising CO2 maybe policy makers should listen more to the 'coolists' rather than the 'warmists'.
G.Watkins
"After 15+ years of no global warming despite rising CO2 maybe policy makers should listen more to the 'coolists' rather than the 'warmists'."
- Problem is that there is something of a credibility (or epistemological) crisis here as some of those 'coolists' were very recently 'warmists'. And I think by now most people, including our Dear Leaders, must be doubly confused by the assertions that AGW is now consistent with cooling periods and major extreme cold weather events.
Entropic Man
In recent days this is the third time you've indirectly admitted to incomplete knowledge by CliSci on important inputs to their incomplete models. Yet you insist on
The science says 2'C warming
The precautionary principle says stop burning fossil fuels Now
Can't say you've convinced me of either with that amount of vagueness.
Mike Haseler
Just completed your survey.
I noticed that one question referred to "catastrophic global warming".
Your political Freudian slip is showing. I can only recall seeing that phrase used by sceptics.
EM -
"I noticed that one question referred to "catastrophic global warming".
Your political Freudian slip is showing. I can only recall seeing that phrase used by sceptics."
- If it isn't catastrophic, perhaps we shouldn't worry about it then?
Email 0149 John Davies (foe) to Phil Jones
Email 0230 Ecologist climate declaration
Guardian Unlimited November 27th 2007
UNEP press release November 1998 (COP4)
etc etc.
As all current models do not accurately predict reality with respect to temperatures (which for some reason has adopted the name climate change), can I suggest: as all models have a strong bias with CO2 impact, to disregard CO2 in future calculations.
In their 3rd assessment the IPCC showed their knowledge of solar, water vapour and med/low cloud was very low.
As a simple person, I would scrap all current models and go back to basics. Surely, one should start with the known greatest impacts; solar, water vapour and med/low cloud and gain better knowledge. Only once that understanding has reached a suitable level, should a base model be built. The effects of all other GHG can then be adequately measured using this base model.
Dr Betts perhaps this may be too simple for you, but I have found the many fundamental scientific discoveries have been based on simple principals. Gaining a better knowledge of the main climate drivers may be a good place to start.
Climate science is just a mess. Some of the temperature datasets have been corrected and homogenized so much that I wouldn't rely on them for anything.
Now the models are shown to be wrong. When will these people realise that science starts with proper observation and measurement? The taxpayers are paying out billions for people to sit in front of their screens playing sophisticated games with insufficient, inadequate and suspect data in an attempt to model a hugely complex system which they barely understand.
Now I could even stomach some of that were it not for the fact that they feed the half-baked results to the press and politicians in order to make the most far reaching policy decisions in the history of the planet.
Katabasis, Terry S, Neilc
Source code has to be available, allowing replication by other researchers. Try here for the NASA models.
http://www.giss.nasa.gov/tools/modelE/
There's a download directly available from the page.
Dr. Spencer has a simple Excel model on his own sceptic website. Neilc could start with that and work up
"Where is our asteroid defence system?"
In the same place as effective climate change mitigation. Both are large but distant risks. People, and the politicians they elect, are good at reacting to immediate obvious threats. They tend to ignore, or at best postpone, anything that will not affect them before the next election.
"catastrophic"
Here I am told that CAGW stands for Catastrophic Anthropogenic Climate Change. It tends to be used as a sarcastic term. In the trade cAGW stands for carbon dioxide induced anthropogenic climate change.
We have no agreed definition for the term "catastrophic". At what threshold of kilodeaths, megadeaths or gigadeaths does the term become applicable?
Sandy S
Can you describe the level of evidence that would tip you from sceptic to acceptor? Is that threshold reachable scientifically or so high that nothing would change your mind?
Remember that all science is ultimately limited to probabilities. There is no 100% certainty outside mathematics.
In Northern Ireland I meet people every week with this unlimited certainty about politics and/or religion. "My mind is made up. Dont confuse me with facts!".
"In Northern Ireland I meet people every week with this unlimited certainty........... "My mind is made up. Dont confuse me with facts!"."
Aye, every morning when you look in the mirror.
Nope. Ask Harold W. I am willing to change my mind on topic when the evidence is strong enough.
I sincerely hope that Doug McNeall, Richard Betts and even Entropic Man will keep posting here as much as possible.
Watching the game of "Logic Twister" that they have to perform every time they communicate will, I hope, be a source of great enlightenment to future classrooms.
To those mentioned above: This is just starting to look sad. Do you really, honestly, not see it? I mean, take this for example:
"Ignoring information that you gain from climate models in policy is folly."
I really wonder if we all inhabit the same universe sometimes.
Why would anyone take the models even slightly seriously? They. Don't. Work.
You can give us some cute schtick about how no models work, if you like. But actually, many models work incredibly well. The climate models don't. Obviously they don't. They are rubbish. They are dead. They are ex-models.
However, these models encapsulate our scientific understanding of the climate system. So my request to the scientists would be that they STFU until they actually have something useful to say.
"Can you describe the level of evidence that would tip you from sceptic to acceptor?"
Accept what?
Here's a good example of climate models in action:
http://www.metoffice.gov.uk/news/releases/archive/2009/tropical-storm-forecast
Fast forward to 2013.
http://www.metoffice.gov.uk/weather/tropicalcyclone/seasonal/northatlantic2013
Outturn for 2013:
Two hurricanes (versus 9 in forecast), ACE (Accumulated Cyclone Energy) 33 (versus 130 in forecast)
2013 was the 11th least active year for hurricanes since 1851 and the 15th= since 1851 for ACE.
Even when you think you have a 'skilful' model, nature has a habit of making you look inept (in as little as 5 years!).
The forecast verification and analysis report is a masterpiece in damage limitation:
http://www.metoffice.gov.uk/media/pdf/b/0/verification2013.pdf
It should be borne in mind that these models are only looking 6 months ahead - not a hundred years.
> Which models are at the intersection of "best climate model simulation of clouds" and "best climate model simulation of extreme rainfall" ?
I was also wondering that. So I've cross-referred between the new Cai et al. ENSO/extreme rainfall paper, and the recent Sherwood et al. paper tracing the spread in climate sensitivity to atmospheric convective mixing and implying therefrom that climate sensitivity is over 3°C.
The Cai paper analyses 40 CMIP3(last generation - AR4) and CMIP5 (latest generation - AR5) models. Out of those 40, it selects 20 that are able to produce the high rainfall skewness and high rainfall over the Nino3 region (Supplementary Tables 1 and 2). It finds that those 20 models generate twice as many extreme ENSO events in the 100 years after 1990 than the 100 years before 1990.
The Sherwood paper shows 7 CMIP3 and CMIP5 models that have a lower-tropospheric mixing index, their chosen measure, falling within their observational uncertainty range (Figure 5(c)). It takes a little effort to work out which models they are, as some of the colour codes used differ little. For the record, I make them to be: ACCESS1-3, CSIRO-Mk3-6-0, FGOALS-s2, HadGEM1, IPSL-CM5A-LR, MIROC3-2-HIRES and MIROC-ESM.
Two of the seven models that Sherwood's analysis favours are not included in the Cai paper. Of the other five, by chance you might typically expect two or three to be in the 50% (20 out of 40) of models that Cai's analysis favours. But in fact not one of those five models is.
So the answer is that there are NO MODELS at the intersection of "best lower-tropospheric mixing" and "best simulation of extreme rainfall etc".
So, if the Sherwood and Cai analyses are valid, it looks as if with CMIP3 and CMIP5 models you have a choice. You can find selected models that have realistic lower-tropospheric mixing, strong positive low cloud feedback and high climate sensitivity. Or you can choose models that produce realistically high rainfall skewness and rainfall over the Nino3 region and generate a large increase in extreme ENSO events with global warming. But you can't have both at once.
Of course, the real world climate system may differ so much from that simulated by any CMIP3 or CMIP5 model that the Sherwood and Cai results have little relevance.
FWIW, if one assumes a binomial distribution with each of the five models favoured by Sherwood's analysis having a 50% chance of being favoured by Cai's analysis (no better or worse than average), then I calculate there would be only a 3% probability of none of the five models being so favoured.
Entropic man
Personally I'd say you were the one whose mind is made up and who cannot be persuaded he's wrong or even likely to be.
To me the case against CO2 is not proven, and at the current state of knowledge is likely to end up on the scrap heap of scientific theories alongside Luminiferous aether, Miasma theory of disease,Caloric theory, Phlogiston theory, Stress and Ulcers, Emission theory of vision,Rutherford atomic model, Bohr atomic model, Geocentric universe, Heliocentric universe , Newtonian gravity, Steady State Theory, and Alchemy amongst others.
BTW I did check a few via DuckDuckGo.
Bishop Hill
I disagree that "empirical studies suggest climate sensitivity is low". Sure, Nic Lewis's study suggests this, and fair play to him for publishing it in a journal, but it's only one study, and others like Aldrin et al are much less confident on low CS. Their mean CS was 2.0 (don't know what Nic's was) and their 90% confidence interval was 1.5 to 3.5. Of course (as I've said before here) we can't actually measure CS anyway - these "empirical studies" are still only estimates, and rely on extrapolating things into the future in the assumption in a linear fashion, which is basically still just making a model.
Palaeo studies of warmer worlds in the past suggest higher CS.
You don't have to make predictions in order to assess risks - you just need to look objectively at possible outcomes, consider the implications of these, and make a judgement. Process-based numerical models can clearly represent atmospheric processes well enough to simulate the global atmosphere pretty well, in terms of the global atmospheric circulation, general rainfall patterns, etc, and this is why it is possible to provide useful weather forecasts. Yes the models disagree widely on future changes due to increased GHGs, and also have a long way to go in being able to predict specific features of internal climate variability, but they can give a guide to the range of changes that could occur.
I do not share your confidence that the future can be predicted so easily, especially on the basis of a couple of variables estimated over a relatively short period in the past.
Richard Betts:
"You don't have to make predictions in order to assess risks - you just need to look objectively at possible outcomes, consider the implications of these, and make a judgement."
I'm only a layman Richard, but an engineer where the practice of looking at possible outcomes entails looking at what happened in the past. So we both have the goal posts in the same place I am assuming that he IPCC possible outcome for climate sensitivity is 1.5 - 4.5C, a range identified from just two computer models one (Hansen's) predicted an ECS of 4C and the other by a chap whose name I've forgotten suggested an ECS of 2C, Charney ( for it was he) decided that they could both be wrong by 0.5C so introduced the range 1.5C - 4.5C which has stubbornly repulsed $100bn of scientific research and stands to this day, except for a small blip in AR4.
With this in mind it seems to me that the best way of tracking down ECS, or indeed TCS, isn't, as you rightly, in my view anyway, point out by measuring it because of the myriad interacting processes that could screen out reality, but by looking in the paleoclimate records for temperature rises of 1C and seeing if the temperature rose by 3C immediately after that event. Although not decisive in engineering terms, in terms of climate science the existence of such a post hoc rise would prove the case. It would be a simple step forward from there to identify what actually happened to the Earth's ecosystem with a 3C rise in temperature.
I understand that if you go too far back we have a completely geographically different Earth, so why not take a look at the effect of the Minoan, Roman and Medieval warm periods and estimate the climate sensitivity from these events, and the concomitant catastrophes that followed?
Or am I talking cat poo again?
Jaysus wept, Billy Liar 9.47pm - you weren't wrong about the UK Met Office obfuscating and trying to paper over their spectacularly bad 2013 North Atlantic tropical storm hurricane forecast. That doc is astonishing. Crafting a narrative of Met Office forecasting success when observations reveal total failure. needless to say - but I will anyway - the excuse is something to with win shear and blah blah, something natural that the Met office stupidly fialed to forecast. Climate Science 101 - absolute tosh from go to whoa.
Richard Betts: "others like Aldrin et al are much less confident on low CS. Their mean CS was 2.0 (don't know what Nic's was) "
Otto et al. (of which Nic Lewis was a co-author) wrote, "The most likely value of equilibrium climate sensitivity based on the energy budget of the most recent decade is 2.0 °C, with a 5–95% confidence interval of 1.2–3.9 °C"
Nic Lewis wrote, "The 1.6 K mode for climate sensitivity I obtain is identical to the modes from Aldrin et al. (2012) and (using the same, HadCRUT4, observational dataset) Ring et al. (2012)." Aldrin's distribution is quite skewed (see figure 6a), no doubt influenced by the uniform prior distribution. For such a distribution, the median would be a more meaningful value to cite than the mean, if one must reduce it to a single value. [The median was about 1.8 K, according to Nic writing here.]
Post-script to the aside in my previous comment about the uniform prior distribution of Aldrin et al., I notice that Aldrin's figure 6(f) shows the effect of a prior which is uniform in 1/S, resulting in a much more confined posterior distribution, with a mean and median of approx. 1.5 K (by eye).
Richard Betts wrote: "others like Aldrin et al are much less confident on low CS. Their mean CS was 2.0 (don't know what Nic's was) "
That's because AR5, sensibly, only gives medians, and not means or modes, both of which are misleading central values for skewed distributions. One could work out the mean from the PDF itself.
As HaroldW writes, the Aldrin 2012 median based on their uniform-in-sensitivity (S) prior was about 1.8 K; I make it 1.76 K actually. Using a uniform-in-1/S prior it was between 1.5 and 1.6 K. Both those medians were biased upwards by use of a prior for aerosol forcing that reflected the highish AR4 aerosol forcing estimated distribution.
AR5 indicates that the most reliable means of estimating ECS is from multidecadal warming over the instrumental period, which Aldrin 2012, Ring 2012, Lewis 2013 and Otto 2013 all did, and obtained lowish median estimates (1.6 - 2.0 K, taking for Ring et al the average of its four estimates). The uncertainties in estimating ECS (and TCR), which remain substantial, stem primarily from the difficulty in constraining aerosol forcing.
Richard
I've discussed the "single paper" meme before. It's simply not true.
For the avoidance of doubt I am assuming that 1C increase from any source would cause feedbacks caused by increased water vapour. I have yet to figure out how the ecosystem knows that the 1C increase caused by a doubling of CO2 is able to differentiate the heat that in the past has clearly arisen from other sources.
Richard Betts statements are in blockquotes below:
While it is true that you can sit in groups dreaming up outlandish (or even realistic) scenarios of what the future might look like, to evaluate risks you have to be able to place a quantitative "chance of occurence" on the events. Without this, you cannot compare the events and what the appropriate response might be. If the cost of some future scenario is very, very high but the risk is vanishingly small then it would be ludricous to take preventative action. Otherwise we would all being living in fear of the time of the "The Coming of the Great White Handkerchief" and trying to take preventative action. Without a reliable predictive model your statement belongs in the fantasy world of committees dreaming up scary scenarios, without a clue as to how likely they may be.
Challenge 1: Name me a single historical example of a future risk predicted and prevented in this way.
The future is not the present extrapolated. Richard, if you believe that it is possible to properly and realistically quantify risks in this way then I am sure there is a brilliant future for you in other disciplines, eg oil exploration, where you can make your predictions against nature and then actually have them tested by reality. You might find a healthy dose of reality pleasantly sobering and learn, as geologists and geophysicists do regularly, that nature is a cruel mistress, we know far less than we think and a little humility goes a long way. Unless you are prepared to bet and lose an awful lot of money, of course. Gamblers ruin doesn't just apply to casinos: it applies to any risk-based decision making where money is involved.
Yes, the numerical models do pretty well on the circulation patterns, as Freeman Dyson pointed out as recently as 2007: "The models solve the equations of fluid dynamics, and they do a very good job of describing the fluid motions of the atmosphere and the oceans." But Dyson went on to say this about climate models: "They do a very poor job of describing the clouds, the dust, the chemistry and the biology of fields and farms and forests. They do not begin to describe the real world we live in."
Over short timescales the models are okay for weather forecasts, with event horizons of maybe 3 - 5 days (I am being generous). But that is not the question and "these are not the droids we are looking for". This is a classic misdirect and I am sure Julia Slingo will be proud of you.
Put bluntly, the models spectacularly fail to predict internal variabiltiy such as Enso, PDO etc and after just a short time have been shown to be all running too hot. They cannot predict temperature reliably over 15 years, so why on earth would you suggest they can give a guide to the range of changes that could occur 50 - 100 years in the future?
Challenge 2: Show me a model run, or suite of runs, initialised in the year 1910 and with no other information on aerosols, solar measurements etc, that can reliably predict the temperature response and internal climate variability out to 2010. You can have volcanic eruptions over the prediction period to help you, but nothing else.
To suggest (eg as Susan Solomon does) that we should have faith in a GCM to predict the climate in 100 years when it cannot even manage 10 - 15 years, in full knowledge that climate interactions are chaotic and that error terms grow exponentially over time, is absurd. A trivial error in the initial conditions will render the model nothing more than an expanding noise bubble as it predicts further into the future. Averaging noise using multiple model runs, as is done, simply returns the forced transient response of the internal model ie the CO2 warming effect. And as that seems to disagree with reality after just 15 years, why would any right-minded person believe these predictions, much less base eye-wateringly expensive policy decisions on them?
EM Wrote: "Here I am told that CAGW stands for Catastrophic Anthropogenic Climate Change. It tends to be used as a sarcastic term. In the trade cAGW stands for carbon dioxide induced anthropogenic climate change."
Sorry, I can't let that slide, you're trying to change history. Try a google of CAGW and see what you get.
Or what trade is that you're talking about? The guild of human hating lying b*stards who'll keep changing the story to keep the CAGW myth alive?
EM
Interesting you live in Northern Ireland. I'm from Belfast myself but have lived in Blighty for over 12 years.
That pigheadedness that we have as a people comes in very handy as a scientist. Especially when people obfuscate and don't provide evidence for their claims.
At some point someone (maybe even me) will produce an IR forcing curve for water in the lab so we can all see how efficient this forcing really is at low power densities. As for mathematics being 100% correct, surely a slip of the tongue. Kurt Godel showed this to be false in 1931 with his Incompleteness Theorem.
Sorry, I can't let that slide, you're trying to change history. Try a google of CAGW and see what you get.(...)
Jan 21, 2014 at 12:17 PM Nial
Nial - save your keystrokes.
EM is a naive man who has swallowed the CAGW story whole. He'll believe anything that seems to back it up and if he can't find it, he'll make it up. From that point on, his own BS becomes his reality.
He presents his naive banalities as if they were profundities, presumably a habit acquired teaching schoolchildren.
You would have traded thousands of lives now for millions of deaths a hundred years hence.
Jan 20, 2014 at 1:41 PM Entropic man
A characteristic of religions is their willingness to kill people on the basis of the beliefs of the believers.
Sorry for swearing all, this just makes me really angry.
What makes it worse is I'm also from Norn Iron (before moving to England then Scotland) and am embarrassed that one of my fellow countrymen is promulgating such b*llshit.