Guest Post by Steven Goddard
Global Climate Models (GCM’s) are very complex computer models containing millions of lines of code, which attempt to model cosmic, atmospheric and oceanic processes that affect the earth’s climate. This have been built over the last few decades by groups of very bright scientists, including many of the top climate scientists in the world.
During the 1980s and 1990s, the earth warmed at a faster rate than it did earlier in the century. This led some climate scientists to develop a high degree of confidence in models which predicted accelerated warming, as reflected in IPCC reports. However, during the last decade the accelerated warming trend has slowed or reversed. Many climate scientists have acknowledged this and explained it as “natural variability” or “natural variations.” Some believe that the pause in warming may last as long as 30 years, as recently reported by The Discover Channel.
But just what’s causing the cooling is a mystery. Sinking water currents in the north Atlantic Ocean could be sucking heat down into the depths. Or an overabundance of tropical clouds may be reflecting more of the sun’s energy than usual back out into space.
“It is possible that a fraction of the most recent rapid warming since the 1970’s was due to a free variation in climate,” Isaac Held of the National Oceanic and Atmospheric Administration in Princeton, New Jersey wrote in an email to Discovery News. “Suggesting that the warming might possibly slow down or even stagnate for a few years before rapid warming commences again.”
Swanson thinks the trend could continue for up to 30 years. But he warned that it’s just a hiccup, and that humans’ penchant for spewing greenhouse gases will certainly come back to haunt us.
What has become obvious is that there are strong physical processes (natural variations) which are not yet understood, and are not yet adequately accounted for in the GCMs. The models did not predict the current cooling. There has been lots of speculation about what is causing the present pattern – changes in solar activity, changes in ocean circulation, etc. But whatever it is, it is not adequately factored into any GCMs.
One of the most fundamental rules of computer modeling is that if you don’t understand something and you can’t explain it, you can’t model it. A computer model is a mathematical description of a physical process, written in a human readable programming language, which a compiler can translate to a computer readable language. If you can not describe a process in English (or your native tongue) you certainly can not describe it mathematically in Fortran. The Holy Grail of climate models would be the following function, which of course does not exist.
FUNCTION FREEVARIATION(ALLOTHERFACTORS)
C Calculate the sum of all other natural factors influencing the temperature
…..
RETURN
END
Current measured long term warming rates range from 1.2-1.6 C/century. Some climatologists claim 6+C for the remainder century, based on climate models. One might think that these estimates are suspect, due to the empirically observed limitations of the current GCMs.
As one small example, during the past winter NOAA’s Climate Prediction Center (CPC) forecast that the upper midwest would be above normal temperatures. Instead the temperatures were well below normal.
http://www.cpc.ncep.noaa.gov/products/archives/long_lead/gifs/2008/200810temp.gif
http://www.hprcc.unl.edu/products/maps/acis/mrcc/Last3mTDeptMRCC.png
Another much larger example is that the GCMs would be unable to explain the causes of ice ages. Clearly the models need more work, and more funding. The BBC printed an article last year titled “Climate prediction: No model for success .”
And Julia Slingo from Reading University (Now the UK Met Office’s Chief Scientist) admitted it would not get much better until they had supercomputers 1,000 times more powerful than at present.
“We’ve reached the end of the road of being able to improve models significantly so we can provide the sort of information that policymakers and business require,” she told BBC News.
“In terms of computing power, it’s proving totally inadequate. With climate models we know how to make them much better to provide much more information at the local level… we know how to do that, but we don’t have the computing power to deliver it.“
……
One trouble is that as some climate uncertainties are resolved, new uncertainties are uncovered.
Some modellers are now warning that feedback mechanisms in the natural environment which either accelerate or mitigate warming may be even more difficult to predict than previously assumed.
Research suggests the feedbacks may be very different on different timescales and in response to different drivers of climate change
…….
“If we ask models the questions they are capable of answering, they answer them reliably,” counters Professor Jim Kinter from the Center for Ocean-Land-Atmosphere Studies near Washington DC, who is attending the Reading meeting.
“If we ask the questions they’re not capable of answering, we get unreliable answers.“
I am not denigrating the outstanding work of the climate modelers – rather I am pointing out why GCMs may not be quite ready yet for forecasting temperatures 100 years out, and that politicians and the press should not attempt to make unsupportable claims of Armageddon based on them. I would appreciate it if readers would keep this in mind when commenting on the work of scientists, who for the most part are highly competent and ethical people, as is evident from this UK Met Office press release.
Stop misleading climate claims
11 February 2009
Dr Vicky Pope
Dr Vicky Pope, Met Office Head of Climate Change, calls on scientists and the media to ‘rein in’ some of their assertions about climate change.
She says: “News headlines vie for attention and it is easy for scientists to grab this attention by linking climate change to the latest extreme weather event or apocalyptic prediction. But in doing so, the public perception of climate change can be distorted. The reality is that extreme events arise when natural variations in the weather and climate combine with long-term climate change. This message is more difficult to get heard. Scientists and journalists need to find ways to help to make this clear without the wider audience switching off.
I would like to coin a new word – “weathersuckers” – anyone who thinks they can predict weather or climate beyond a few days into the future. It has a nice ring to it don’t you think?
Then of course there are the “coolweathersuckers” (CWS) and the “warmweathersuckers” (WWS). You know who you are 🙂
“The only way that the different models (with respect to their sensitivity to changes in greenhouse gasses) all can reproduce the 20th century temperature record is by assuming different 20th century data series for the unknown factors. In essence, the unknown factors in the 20th century used to drive the IPCC climate simulations were chosen to fit the observed temperature trend. This is a classical example of curve fitting or tuning. ”
http://www.climate4you.com/ClimateModels.htm#The ability of computer models to reproduce known temperature series
I model that this statement sums things up quite succinctly
Roger Sowell (18:58:49) :
The theory and practice of Artificial Intelligence holds that there exists several classes of problems in Camp Two for which there are no known solutions, some are so large that even a computer the size of a galaxy would require millions of years to solve.
Reminds me of Hitch hikers guide to the Galaxy. The question posed was “What is the meaning of life” 🙂
SemiChemE — Unfortunately, most people don’t grasp the fundamental value of the modeling exercise in expanding our understanding of a phenomenon. Because of this, there is tremendous pressure on modelers to produce predictive models.
Of course people understand this. On the other hand, a model created to understand air flow characteristics over wing shapes isn’t very useful unless the underlying intent is related to better wings. Maybe you’re designing a new wing. Maybe you supply aircraft paint and you want to see if the paint surface messes with airflow at different speeds. And so on. Models are created from the bottom up with the express purpose of understanding and prediction (implied or otherwise.) It is therefore not unreasonable to suggest that a working model ought to be predictive.
Furthermore, the situation becomes exacerbated when the media or government officials take modeling results out of context and try to formulate policy based on a hypothetical prediction.
This begs the question of how politicians etc become aware of models in the first place. Politicians become aware of these models only when they are used as a presentation to make a prediction which impacts policy.
If you have a computer model of X I have no idea it exists. But one day your boss goes to congress and says there’s a public problem (Z) and we know this because of our model of X. Now I know the model exists, and since the model was used to claim (Z) I think it’s not unreasonable to suggest that the working model ought to be predictive.
You’re correct to say that models are more complex than they are sometimes presented to be. Gore simplified the message to highlight the importance of carbon emissions, but the truth is that increasing anthropogenic CO2 and natural cyclicity of insolation each affect year-to-year variations in climate and the weather we experience.
That’s pretty simple to understand. The addition of a steadily rising curve with a lower amplitude sinusoidal signal produces a stepped but broadly rising profile — in other words, a general warming trend with broadly predictable (but lesser scale) oscillations around that.
Here are a couple of references which amply illustrate that point:
http://www.realclimate.org/index.php/archives/2004/12/just-what-is-this-consensus-anyway/
http://greenfyre.wordpress.com/2008/12/03/global-warming-is-over-once-every-decade-or-so/
The truth is that the cold weather which you highlight so assiduously and correctly on this site is entirely on schedule and as predicted by any scientific model which takes account of those two processes.
I’d warmly congratulate you for reminding us that insolation effects must also be considered in climate modelling, but I’d advise strongly against any kind of hubris that a few recent and impressive spells of cold weather contradict a general warming trend. Because they really don’t.
Kind regards from London.
Sorry — that first link was misplaced. Here’s the correct one:
http://solar-center.stanford.edu/sun-on-earth/600px-Temp-sunspot-co2.svg.png
Kind regards from London.
SemiChemE (00:12:18) :
I think many climate scientists are doing a great job in developing their models. However, it seems to me that some experts in the field are a bit too confident, especially when we all know there are severe limitations for modeling so many incredibly important phenomena, such as cloud formation, humidity, aerosols, etc….
I think you are being too kind in a situation that requires as much ruthlessness as that shown by the politicized AGW crowd as regards the repercussions of denying energy to billions of people mainly in the third world.
Climate scientists who do not speak up at the misuse of modeling are equally guilty as the ones that are pushing modeling as modern day prophecy, so why treat them with gloves? It is not the models that are at fault, but the use made of the outputs.
The total joke is, that the climate scientist do not only try to model the climate so they can predict a climate in the future! They even try to “prove” AGW with their models. They always say our models only simulate the strong warming in the last years when they include in their models a strong warming by CO2.
It is ridiculous to “prove” a mechanism with a model
Funny irony:
“Edward Lorenz continued to be active in his work well into his seventies, winning the Kyoto Prize for basic sciences, in the field of earth and planetary sciences, in 1991.”
http://en.wikipedia.org/wiki/Edward_Norton_Lorenz
Steve:
It’s easy to model. Just draw a line out 5 – 10 years that continues the current trend (and maybe nudge it up a little bit if the trend is flat or down) and then just sharply veer the trend upwards. Viola! A climate model that shows run-away warming.
roads — That’s pretty simple to understand. The addition of a steadily rising curve with a lower amplitude sinusoidal signal produces a stepped but broadly rising profile — in other words, a general warming trend with broadly predictable (but lesser scale) oscillations around that.
Common M.O. of the AGW adherent is to show a graph just like this. I don’t think you understand what skeptics are saying.
The graph doesn’t show anything more than correlation. Chances are you can plot temps against land use and population growth and get the same curve. But does this imply that people are raising the temps via spewing gases or are the temps a proxy for land use changes and the CO2 isn’t part of that equation?
Also, how much of that rise is natural vs the work of man? Much is made of the ability to detect the fossil fuel signal in that CO2 plot via analysis of isotopes. And yet this isn’t trumpeted far and wide. Why? because it’s 3%.
The graph may not be telling you what you think it is.
Remember that scientists in Copenhagen saying that global warming has gotten much worse since the last IPCC meeting, as indicated by flat sea level, declining temperatures, increasing Arctic ice, and the end of glacial retreat in Greenland.
And Al Gore says the poles will melt in 5 years.
Roads (04:10:24) :
The truth is that the cold weather which you highlight so assiduously and correctly on this site is entirely on schedule and as predicted by any scientific model which takes account of those two processes.
I’d warmly congratulate you for reminding us that insolation effects must also be considered in climate modelling, but I’d advise strongly against any kind of hubris that a few recent and impressive spells of cold weather contradict a general warming trend. Because they really don’t.
There is no one contributing to this blog that would refuse the warming since 1850 or so. Nobody. What people are refuting are the Anthropogenic as in AGW. Even if Gaia had not had a sense of joke, or irritation at the hubris of AGW, and had not sent a negative PDO, the A in the IPCC models is nonsense.
1)The trends in the tropical troposphere did not warm more than the surface during the years of warming.
2) CO2 lags temperature by 800 years long term and 6 to nine months short term, again even during the warming years.
3)The humidity did not play ball as the models predicted, even during the years of warming.
In addition during the years of stasis CO2 is merrily climbing and is unable to budge the PDO, let alone stop the next ice age as Hansen had the hubris to suggest a while ago.
So we do have a good PR from PDO, as AGW had one when the PDO was warm. So?
have a look at the real prophecy:
http://en.wikipedia.org/wiki/File:Vostok-ice-core-petit.png
and look at the clockwork precision of ice ages, every 100.000 years recently. We are at a flat top that is lasting much longer than other transitions, which is oscillating within 1C from a stable temperature. This will not last. That is the true prophecy, that there will be another ice age. In a few years, a thousand or more, but that is the real danger for humanity where thought and resources should be focused. The flat top shows that we will be playing with tolerable temperatures, until the grand slide starts.
Steven, your post’s title, “If You Can’t Explain It, You Can’t Model It”, is illogical (blind modeling has led to many useful scientific insights) and you first sentence misidentifies “Global Circulation Models” as Global Climate Models. Your “one small example” of the failure of a climate modeling is, unsurprisingly, a rehash of weather as isolated “counter-proof” of climate change.
I’m heartened to see you start referring to climate modelers as “competent and ethical people” though. Perhaps you’re coming to recognize how hard the modelers are working on the sophistication of their models and their predictive value? It’s one thing to say that a particular model is lousy, another thing altogether to offer an improvement…
P.S. Please provide a link to the “fundamental rules of computer modeling” you reference in your post.
It is true that weather and climate patterns, like patterns of movement in complex economies, have so many variables that computer models to predict future trends do not work for long periods of time.
On the other hand, from what I have read, we have some strong indications that global warming is real. Sea level is slowly rising, and the melting of arctic ice is making life harder for polar bears. They may be in danger of imminent extinction. I have also read that whales are starting to starve to death because of the death of organisms at the bottom of their food chain.
Since I live in a coastal city (Long Beach, California), I am particularly concerned about the rise in mean sea level. From what I have read, glaciers in Switzerland and the Andes are receding, threatening hydroelectric-generation systems in Switzerland and fresh-water supplies in South America. (Changing patterns of rainfall are also threatening fresh-water supplies in Southern California.) And the rise in sea level also is threatening to flood small, low-lying island nations in the Pacific.
While we know that mean sea level is rising, we don’t know whether it will rise by one foot by 2100 or two or three yards (this apparently depends on the how fast the glaciers of Greenland and Antarctica melt).
Any rise at all threatens the continued viability of New Orleans, for example, parts of which lie below current sea level. Right now, it seems to me that it is foolish to try to rebuild New Orleans because it is highly likely that the city will be flooded before the beginning of the next century.
Harleigh Kyson Jr.
Didn’t have a chance to check other posts to see if this has been referenced:
…a new study by the University of Wisconsin-Milwaukee could turn the climate change world upside down.
Scientists at the university used a math application known as synchronized chaos and applied it to climate data taken over the past 100 years.Now the question is how has warming slowed and how much influence does human activity have?
“But if we don’t understand what is natural, I don’t think we can say much about what the humans are doing. So our interest is to understand — first the natural variability of climate — and then take it from there.
Didn’t have a chance to check other posts to see if this has been referenced:
…a new study by the University of Wisconsin-Milwaukee could turn the climate change world upside down.
Scientists at the university used a math application known as synchronized chaos and applied it to climate data taken over the past 100 years….Now the question is how has warming slowed and how much influence does human activity have?
“But if we don’t understand what is natural, I don’t think we can say much about what the humans are doing. So our interest is to understand — first the natural variability of climate — and then take it from there.
Excellent post. I spent something like 20 years ( before I retired) trying to model demand for penicillin based antibiotics with similar lack of success except where it was possible to apply the central limits theorem when I could get quite close to the next years requirements.
It seems to me that climate modelling is full of difficulties such as not having a clear set of independent parameters that define what the climate’s state is at any one time and what represents an appropriate time bucket to model what is a continuous process that is probably chaotic. It seems that climate modellers place great score on temperature measurements which, of course, is not independent variable but dependent on many other parameters which themselves are not independent and relationships that are purely empirical. That’s not to say that empirical relationships cannot be useful but they usually, in real science, represent a starting point for study not he conclusion. Correlation is not causality! Without establishing causality climate models are not worth the paper they are written on nor the number of trees used in preparing them!
@ur momisugly G Alston (18:16:52) :
Exactly! I have often posited that these models produce warming because that’s exactly what they are programmed to do. The models don’t test the AGW hypothesis, they just illustrate how it might work, given various scenarios.
In the cited quotation it says:
From this, it sounds like they’re saying that they understand more than they can calculate. That is, the explanatory grasp exceeds the computational reach. This is the opposite of the point you make, no?
It is of course true (not to mention trivial) that climate models have improved (and are improving with continuing observation) in providing a complete accounting of all forcings and feedbacks, anthropogenic and otherwise. We’ve known for a long time that there’s a natural anthropogenic positive forcing, as predicted by basic physics. That isn’t in doubt at all, and the researchers you yourself cite on the “30 year pause” story have said that continuing to accelerate the anthropogenic forcing will finally result in “aggressive” and “explosive” warming. To repeat, it’s one of the experts you’ve cited that has chosen the alarmist term “explosive warming”.
Here laid plain is your gambit: Cartesian skepticism. Your standard is this: if there is any doubt about anything then we know nothing. However, you fail or refuse to acknowledge that uncertainty cuts both ways. A good illustration of this is recent research indicating that Greenland and Antarctic ice sheets may increase sea level rise above the more conservative IPCC predictions. The IPCC refused to make alarmist assumptions about rates of melting, but some recent observations have been alarming.
So, there is uncertainty, but also some important knowledge. Furthermore, uncertainty goes both ways. Maybe ocean currents cause a periodic negative forcing that will pause things before explosive warming resumes, as the research you cite indicates. Or maybe a positive feedback like methane release will be worse than anticipated. Maybe the ice sheets will melt slower, maybe faster. I am not willing to subject billions of human beings to a dangerous experiment just to find out if things will be not-quite-as-bad, about-exactly, or somewhat-worse than the best predictions of the world’s top researchers.
G Alston:
“The anthropogenic contribution of CO2 is 3%.”
No, it’s not. The additional flux of anthropogenic CO2 is 3% per year. That’s not at all the same thing.
Think of an account paying 3% interest. After 1 year, the proportion of interest to capital in the account is close to 3%. After 10 years, the additional flux of interest to capital is still 3%, but is the proportion of interest to capital in the account still 3%?
No. Absolutely not.
anna v: The Earth experiences cyclical climate change from natural effects.
Yes, that is true — however it’s critical to note that the timescales of the changes in CO2 concentration implicit in the geological record and those which have been recorded since 1850 are of a completely different magnitude.
Under ‘normal’ (pre-anthropogenic) conditions, there is a significant lag between CO2 and temperature. The balance between organic productivity and changing temperature equilibrates over considerable time, all other things being equal.
As for your arguments about ‘the years of stasis’ — I’m not quite clear what you mean here, since CO2 has been climbing more or less continuously. Temperature is subject to superimposed and lower magnitude insolation effects, which can give the appearance of temporary stasis or even a modest and temporary fall in the global temperature curve, but the overall trend is upwards.
All other things are not presently equal. Anthropogenic carbon emissions are increasing by 3% per year. CO2 concentrations are rising by around 2 ppm per year. CO2 concentrations have risen from c.280 to c.390 ppm precisely because the additional flux is greater than the amount which can be accommodated by natural sinks.
If CO2 were falling consistently over time, we might predict a new ice age in a few tens of thousands of years. But on the timescale we are considering, it isn’t — quite the converse is currently true, as above — and so we most certainly can’t.
Ben Lawson,
Maybe this will help you out.
The EdGCM Project develops and distributes a research-quality global climate model (GCM)
http://edgcm.columbia.edu/
Obviously you can’t model a physical process which you can’t describe mathematically. Have you ever looked at a GCM to see how they work? Each physical process is broken down into a mathematical model of it’s behaviour, based on physics. Another fundamental rule is that magic is not permitted in modeling.
Perhaps someone needs to publish the fundamental rules of common sense.
A convenient model for a convenient lie: Global Warming equals Global Cooling. In any case “The Unconvenient” wins. “Laugh and grow fat” That´s “his” philosophy…and its growing!
Roads (08:19:26)
If CO2 were falling consistently over time, we might predict a new ice age in a few tens of thousands of years. But on the timescale we are considering, it isn’t — quite the converse is currently true, as above — and so we most certainly can’t.:
Again, look at this plot: http://en.wikipedia.org/wiki/File:Vostok-ice-core-petit.png
CO2 does not change the temperature. The temperatures change CO2 with a lag of 800 years, no matter what Gore told you in that movie.
If CO2 falls bellow 150ppm , most plant life will wilt and disappear, so maybe Gaia let us dig up the coal and burn it so that the CO2 that was trapped there could be released and the green stuff can keep flourishing. Green houses, the real ones, flourish with 1000ppm CO2. The alveoli in our lungs work with something like 8000 ppm, saying something about when lungs evolved: when CO2 was much more abundant. ( unless you do not believe in evolution).
In contrast to this, all estimates of CO2 doubling give a small rise in temperature, except the IPCC scaremongering with fictitious water vapor feebacks, that have been disproved by data. A 1C warmer temperature per century is within the flat top of the warm time we are enjoying before the next ice age, and it will be mostly at night time, so whats the problem with having -3C instead of -4C in winter nighttime?
Nothing will melt because of this small rise in night temperatures more than it has been melting ever since the little ice age..