Kevin Trenberth is head of the large US National Centre for Atmospheric Research and one of the advisory high priests of the UN’s Intergovernmental Panel on Climate Change (IPCC).
A New Zealander by birth, Trenberth has had a distinguished career as a climate scientist with interests in the use of computer General Circulation Models (GCMs), the basis for most of the public alarm about dangerous global warming.
When such a person gives an opinion about the scientific value of GCMs as predictive tools, it is obviously wise to pay attention.
In a remarkable contribution to Nature magazine’s Climate Feedback blog, Trenberth concedes GCMs cannot predict future climate and claims the IPCC is not in the business of climate prediction. This might be news to some people.
Among other things, Trenberth asserts “. . . there are no (climate) predictions by IPCC at all. And there never have been”. Instead, there are only “what if” projections of future climate that correspond to certain emissions scenarios.
According to Trenberth, GCMs “. . . do not consider many things like the recovery of the ozone layer, for instance, or observed trends in forcing agents”.
“None of the models used by IPCC is initialised to the observed state and none of the climate states in the models corresponds even remotely to the current observed climate.
“The state of the oceans, sea ice and soil moisture has no relationship to the observed state at any recent time in any of the IPCC models.
“There is neither an El Nino sequence nor any Pacific Decadal Oscillation that replicates the recent past; yet these are critical modes of variability that affect Pacific rim countries and beyond . . . the starting climate state in several of the models may depart significantly from the real climate owing to model errors” and “regional climate change is impossible to deal with properly unless the models are initialised”.
GCMs “assume linearity” which “works for global forced variations, but it cannot work for many aspects of climate, especially those related to the water cycle . . . the science is not done because we do not have reliable or regional predictions of climate”.
Strange that. I could have sworn that I heard somewhere that the science was supposed to be settled.
One wonders whether anyone has told CSIRO that their much-vaunted regional climate models are worthless predictive tools. Perhaps someone will ask the CSIRO to refund the swingeing amounts state governments and others have paid for useless regional “climate forecasts”?
Trenberth’s statements are a direct admission of the validity of similar criticisms that have been made of GCMs and the IPCC by climate rationalists for many years.
Of course, his tail-covering assertion that the IPCC doesn’t make climate predictions or forecasts anyway has to be taken with a grain of salt. In a paper being presented at the 27th International Symposium on Forecasting in New York this week, Scott Armstrong and Kesten Green audit the relevant chapter in the IPCC’s latest report. They find that “in apparent contradiction to claims by some climate experts that the IPCC provides ‘projections’ and not ‘forecasts’, the word ‘forecast’ and its derivatives occurred 37 times, and ‘predict’ and its derivatives occur 90 times” in the chapter.
Strange that the public has this misimpression that the IPCC predicts future climate, isn’t it?
Having analysed the IPCC’s approach in detail, Armstrong and Kesten conclude that “because the forecasting processes . . . overlook scientific evidence on forecasting, the IPCC forecasts of climate change are not scientific”.
Like Trenberth’s advice, this also may well be news to some people.
In a third devastating blow to the credibility of climate forecasting, a lead author of the IPCC Working Group 1 science report, Jim Renwick, recently admitted “climate prediction is hard, half of the variability in the climate system is not predictable, so we don’t expect to do terrifically well”.
Renwick was responding to an audit showing the climate forecasts issued by New Zealand’s National Institute of Water and Atmosphere were accurate only 48 per cent of the time.
In other words, one can do just as well by tossing a coin.
These various criticisms of climate modelling can be summed up in the following statement – there is no predictive value in the current generation of computer GCMs and therefore the alarmist IPCC statements about human-caused global warming are unjustified. Yet Australia has an Opposition and a Government that profess to set their climate policies on the basis of IPCC advice. Both also seem determined to impose an inefficient, ineffective and costly carbon trading or taxation system on the economy, for the aspirational absurdity of “stopping climate change”.
Perhaps someone should tell Prime Minister John Howard that dangerous global warming has been called off.
Professor Bob Carter is a James Cook University geologist who studies ancient environments and climate. His website is at: http://members.iinet.net.au/~glrmc/new_page_1.htm
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First published in The Courier Mail. Republished with permission.
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
I don’t think the IPCC predicts the future, I think they give us the best guess we can get. CO2 is a greenhouse gas, it’s increasing due to us, the predicted feedback is happening.
“you’ve got to ask yourself a question: Do I feel lucky? Well, do ya, punk? ”
Could we have a link to the actual source?
In response to devastating fact, SJT responds with the first stanza of the AGW Believers Creed.
Richard Lindzen,(his detractors may howl, but they can’t dismiss him as a crank frome the fringe of climate science), also speaks with great clarity about the workings and intrigues of the IPCC.
http://www.canada.com/nationalpost/story.html?id=63ab844f-Sc55-4059-9ad8-89de085af53&k=0
Sorry, typo.
http://www.canada.com/nationalpost/story.html?id-63ab844f-8c55-4059-9ad8-89de085af353&k=0
More here:
Comment on the Nature Weblog By Kevin Trenberth Entitled “Predictions of climate”
http://climatesci.colorado.edu/2007/06/18/comment-on-the-nature-weblog-by-kevin-trenberth-entitled-predictions-of-climate/
IPCC “give us the best guess we can get”
Try guessing a little harder.
Given that it’s based on advanced physics and understanding of complex fluid behaviour, it’s a damn sight better than the alternative. The validation of even the much more primitive models by Hansen in the 1990’s indicates to me that even if there are anomolies, the overall prediction will be in the right direction.
If external forcings are stable (which they are), then current warming is explained by CO2. Given that glaciers, the arctic and other feedback mechanisms are on track, as predicted, I think the best guess is a lot better than the ostrich approach.
More trouble for observations and models here:
New Study On The Prediction Skill Of The Multi-Decadal Global Climate Models
http://climatesci.colorado.edu/2007/06/28/new-study-on-the-prediction-skill-of-the-multi-decadal-global-models/
What a amazingly silly post. Climate forecasting blended together with scenario generation.
Of course the IPCC runs are not predictions in the true sense intialised exactly at a current system state.
So what?
The question to ask Trenberth is does he use GCMs in his climate science as valuable tools and whether he thinks AGW is a major issue.
e.g. http://www.sciencemag.org/cgi/reprint/302/5651/1719.pdf
Global Warming Surpassed Natural Cycles in Fueling 2005 Hurricane Season, NCAR Scientists Conclude
June 22, 2006
BOULDER—Global warming accounted for around half of the extra hurricane-fueling warmth in the waters of the tropical North Atlantic in 2005, while natural cycles were only a minor factor, according to a new analysis by Kevin Trenberth and Dennis Shea of the National Center for Atmospheric Research (NCAR). The study will appear in the June 27 issue of Geophysical Research Letters, published by the American Geophysical Union.
So Pielke is prepared to admit the world is warming?
Pielke’s preferred metric is ocean heat content:
http://climatesci.colorado.edu/2007/06/27/simulated-and-observed-variability-in-ocean-temperature-and-heat-content-by-achutarao-et-al/
Bob,
I was surprised Trenberth expressed himself so forthrightly.
Highlighting the colossal dislocation between on one hand, the media deluge of pro-IPCC puff plus policy and on the other hand, the science.
Additional to Renwick’s candid comments re the NIWA forecasts that have little value.
Have you seen Prof Andrew Vizards paper where he looks at BoM rainfall Outlooks (produced monthly looking ahead 3 months).
Quoted in an ABC article, “Professor Vizard says weather bureau predictions of a 50 per cent chance of rain are “totally useless”.”
http://www.warwickhughes.com/blog/?p=107
I have been critical of the BoM Outlooks, both rainfall and temperature, for years now.
The reality with seasonal forecasts (in general) is that the methods do not have a lot of skill at various times and places (called reality – limits of the methods). For areas and periods they do. 50% probability of exceeding the median may not be helpful when it is forecast – but is precise mathematical description of what the probabilities are for the methods involved which use the historical record.
The comment is really “I’m not happy with that”.
I really want 80% probability of exceeding the median. Or 10% probability.
But yes if you want wet or dry skill – a 50% chance forecast isn’t that informative.
Anyway why would you believe Hughes site – you only ever get one side of it – do we see an invited comment from the Bureau and why not ? – no comparitive point of view.
and I’m yet to see him retract anything incorrect e.g. the Philipona paper slag off.
Just another uncritical take-all propaganda dump. e.g. the regrettable Archibald piece.
Anyway all a diversion from Trenberth and climate change modelling.
Subtle spin….
“the science is not done because we do not have reliable or regional predictions of climate”.
is very different from what is implied by
“Strange that. I could have sworn that I heard somewhere that the science was supposed to be settled.”
Imperfect models do not mean we are not getting emission driven warming. Nor do they mean that the science on anthropegenic warming is not fundamentallty correct.
Imperfect models also do not mean that dangerous warmig will not occur. In fact, is it not as or more reasonable to assume that if the models are imperfect, they have underestimated the extent and effect of warming?
As we cannot model weather too well, then that means we have even more difficulty modelling climate, and derived from that even greater problems modelling climate change, especially when we don’t really understand or know the natural variations that cause climate change.
During the earth’s geological history climate has always changed, often catastrophically, but no one really understands why.
As these forcings are absent in the GCM’s, one is forced to conclude that we really cannot model climate at all since the most important one that occurred in the past remain unknown, unknowns.
In any case no one has offered a good explanation why temperatures increased up to 1942, since the present rise seems similar. Now its rising. Hence CO2 is irrelevant and something else is causing the temperature increase. Solar connection? Or have we missed something and it is to be found as the cause of past climate changes on the earth?
I think the issue boils down to the people confusing scientists making forecasts, and scientific forecasts. The two are not necessarily the same. In the case of the IPCC, it is probably the former where meteorologists, who have no background in climate but are experts in the physics of weather, plus a handful of climate specialists, plus the rest who are computer modelling experts, and this means that the IPCC is in the business of having scientists making forecasts.
In any case there are serious doubts about the way the global temperature is aggregated according to grid cells – it actually is really no different to averaging the telephone numbers in the same grid cells – both are meaningless numbers.
O degrees C applies equally to an ice cube from your fridge and a billion tonne iceberg floating in the sea. So simply pontificating about temperature means physically nothing. It may as well be a telephone number.
That means to me that we actually do not have any sound physical metrics to determine what the thermal state of the earth has been over the past 100 years. Ie we don’t have the data to know whether it is cooling, static or warming.
“no one has offered a good explanation why temperatures increased up to 1942” – umm yes they have.
“has always changed, often catastrophically, but no one really understands why” – mmm – only a few dominant hypotheses that seem to have a lot of paleo backup
The old can’t do the weather so how can you do climate ruse. Sigh ! Let’s try a climate prediction – each winter will be colder than summer on average for the next 20 years. But I can’t tell you about each day .. .. Was it something about boundary conditions.
“who have no background in climate but are experts in the physics of weather, plus a handful of climate specialists, plus the rest who are computer modelling experts” ROTFL and LMAO
Anyway let’s go with Louis – the world is cooling – that’s why the Artic and glaciers are melting. Makes sense.
Luke: Give over a bit there, a lot of stuff Aat Jen’s becomes a big peeing contest and some blokes can’t resist. Hey; it seems we can dump on almost any thread lately, Jen is scratching to hold back the tide of public opinion.
Since this latest Carter prose tries to stitch holes in the beach net against the trend expect another surge in dead kelp from other half baked geologists and similar ilk on GCM’s, IPCC etc. I noted someone had our climate man David – Evans not Jones backed up with a bunch of sceptics as evidence of our failure.
IMO Carter, Biggs, Hughes & co here, are so far off the real planet in their observations they don’t count at home. It’s no wonder they get invited to this place for mutual comfort.
Motty; the last word on climate change does not begin in QLD. I keep saying we need to watch the dynamics, not the max min and routines. Yesterday we had a chap on ABC from Eastern Victoria involved in the emergency saying he had never seen the flood water so high. Another commentator this week said the number of deep lows this season was also abnormal.
This morning we had John Ives on ABC 666 radio discussing soils in drought, carbon loss, ideal ground cover under extreme conditions, bidirectional flow of info between farmers and researchers and the pending Grassland Society conference in Queanbeyan. I think he comes from Yass which like Goulburn was totally dried out until this month.
I see current the current flash flooding as another uncommon impact in parched lands.
Hard headed Heffernan was also on 666 today with the outline for his Northern Tack Force. In my understanding of his comments today he has no illusions regarding our need to compensate for major change to our climate. His prediction was for shift in agricultural biz greater than the Snowy Scheme.
Dear patient and gentle Gavin – I yield to your sensibility.
SJT says, “Given that it’s based on advanced physics and understanding of complex fluid behaviour…” For a most interesting take on what one of the brightest new stars in advanced physics thinks about the fundamental physics of greenhouse warming see:
http://motls.blogspot.com/2007/06/realclimate-saturated-confusion.html
It appears he must not understand the physics like the Warmers do. It is time we give Warming Theory its just recognition as a whole new area of advanced physics, that is so arcane even a leading light of string theory can’t comprehend it.
Walter gave us a danm good lead er read there I even had a soft spot for the physics. I particularly liked THAT story of the shifting goal posts.
We may indeed have atmospheric temp limits due to greenhouse gas effects but in this real world I’m more concerned about the historic margins of ice and water on our actual climate. Fluid dynamics include some differentials beyond his gas equations.
After working with a few practical scientists including the odd physicist down the track I realised when this guy was not completely over the top it was mostly spray from his far end so I smiled about the gullibility of those left behind him in academia.
We should feel sorry for Ken and Ender too…
Walter
Motl is one more dunce who thinks he has debunked global warming by realising that the climate sensitivity is not linear, but logarithmic. Unfortunately, he his just one more in a long line to realise this, and the scientists working on the topic knew all about it right from the start. What a complete and utter waste of time, but it does it’s job, it sows confustion, which is all that is needed. Just look at the creationists.
The issue, and I wish we could start there, rather than being dragged back to this inanity all the time.
The issue is the slight rise in temperature caused by the large rise in CO2 kicking off positive feedback effects, such as melting ice changing the albedo of the earth. Such feedback effects are already being observed. Now could nongs like him please stop wasting everybodies time.
SJT,
Your characterization of Motl as a dunce suggests you must feel you have have a much superior understanding of the radiative physics than he does. An explanation of why you think his estimates for warming are wrong and setting out of your superior ones would be enlightening.
As for positive feedbacks turning a small temperature change from increased CO2 into a much larger one, why would the larger ones then not induce still greater ones in runaway fashion? Surely there must also be negative feedbacks that have maintained the remarkably narrow range of tropical sea surface temperatures over millions of years exhibited in oceanic sediment cores. The delicate balance of climate sensitivity you postulate does not appear to accord with the available evidence.
When any evidence a situation may not be as serious as feared provokes fierce rejection rather than interest it suggests a greater commitment to the threat than to its rational assessment.
Well Walter actually recent published paleo studies looking at these sort of things put the median estimate for 2X CO2 at 2.9C – pretty well spot on.
Walter
The earth has had higher concentrations of CO2 before, and there hasn’t been a runaway Venus effect. There will probably be a negative feedback limit that will be reached. That isn’t happening yet, though. At the present it’s going as predicted.
So far, there have been several references to the statements made by Trenberth, only paraphrasing and claims. Id’ liek to see what he actually said, without the spin.
SJT,
Here’s the URL for Trenberth’s comments.
http://blogs.nature.com/climatefeedback/2007/06/predictions_of_climate.html
You will see that Carter has quoted from them accurately, selecting the quotations appropriate to a discussion of the validity of models – which was the focus of his article.
Trenberth’s other comments are interesting, especially where he lapses back into IPCC propaganda mode – in effect saying that human-caused global warming has been demonstrated. He must live on a different planet to me.
Cathy
Carter has not quoted accurately, he has cherry picked the bits he wants to hear, and left out the conclusion.
“So if the science is settled, then what are we planning for and adapting to? A consensus has emerged that “warming of the climate system is unequivocal” to quote the 2007 IPCC Fourth Assessment Working Group I Summary for Policy Makers (pdf) and the science is convincing that humans are the cause. Hence mitigation of the problem: stopping or slowing greenhouse gas emissions into the atmosphere is essential. The science is clear in this respect.”
I repeat
“Hence mitigation of the problem: stopping or slowing greenhouse gas emissions into the atmosphere is essential. The science is clear in this respect.”
He is saying in much more precise and scientific language what I was saying. It’s our best guess so far, in the sense that we aren’t able to model the future climate accurately, but we can model scenarios, as a guide to action on warming. Businesses do this all the time, and no-one dumps on them. It would be a large business that would be immediately downgraded for not undertakings such tasks. “What if”, given that we cannot predict such factors as future fossil fuel usage.
For him there are parts of the issue that are settled, unambiguously, there are other parts that we need to work on, but these cannot wait for action.
So Carter is spinning, Hughes is cherry picking. Both are aghast that science is not some magical power to predict the future.
Another post, more mythical claims being spun.
Isn’t anyone getting tired of it?
Cathy is the last gasp for a particular lobby