The New York Times yesterday published a short piece on a new book by coastal geologist (and InterActivist alum) Orrin H. Pilkey and his daughter Linda Pilkey-Jarvis, also a geologist. The book, Useless Arithmetic: Why Environmental Scientists Can't Predict the Future, argues that nature's unruliness -- conditions are highly variable and uncertainties inevitable -- makes mathematical modeling ineffective. (Here's an excerpt with more on the book's underlying premise.)
For example, Pilkey suggests that dredging up a pile of sand and dumping it on an eroded beach willy-nilly might be just as effective as utilizing complex computer programs to predict exactly how much sand is needed and where to maximize the beach's longevity during storms and erosion.
From the NYT article:
Nature is too complex, they say, and depends on too many processes that are poorly understood or little monitored -- whether the process is the feedback effects of cloud cover on global warming or the movement of grains of sand on a beach.
Their book ... originated in a seminar Dr. Pilkey organized at Duke to look into the performance of mathematical models used in coastal geology. Among other things, participants concluded that beach modelers applied too many fixed values to phenomena that actually change quite a lot. For example, "assumed average wave height," a variable crucial for many models, assumes that all waves hit the beach in the same way, that they are all the same height and that their patterns will not change over time. But, the authors say, that's not the way things work.
With so much of climate-change science based on complex models and computer-generated predictions, the book brings up some interesting issues -- like, for example, whether environmental scientists can make predictions about our future climate with any kind of certainty at all.
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Comments
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Kit Stolz Posted 11:43 am
21 Feb 2007
Climate science is beyond doubt a complex endeavor, but in the last twenty years we have learned a lot. Climatologists not only have much more confidence in their predictions, they also have a much better understanding of what they can predict and what they cannot. (For example, they're just beginning to work on the problem of how long it will take for ice sheets to melt, which is why that field is so contentious.)
Kelly Redmond, a highly respected and articulate leader in the field of climatology, discussed this in an interview with Grist a few months ago.
http://gristmill.grist.org/story/2006/9/9/154714/4417
Note especially the difference between predicting average temperatures, which climatologists can do with real confidence, even on a decadal level and a regional basis, and predicting precipitation, which is much more difficult and less certain.
But there's more. If you ask James Hansen, on whose work much of climatology is based, he will tell you that his energy balance calculations have nothing to do with General Circulation Models. He will point out that for the last 450,000 years globally averaged temps correspond remarkably closely to concentrations of greenhouse gases. And he will add that we can't explain the temps we've been notching over the last twenty years without including the "human signal" -- global warming.
Don't be misled. Here's what Dr. Trenberth, who heads up climate analysis for the National Center of Atmospheric Research, told Congress in testimony a couple of weeks ago:
"The IPCC Fourth Assessment finds that the Earth is warming, and that major components of the Earth's climate system are already responding to the warming. This wide variety of observations gives a very high degree of confidence to the overall findings. Moreover these changes are now simulated in climate models for the last 100 years to a reasonable degree, adding confidence to future projections."
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Daniel Collins Posted 2:28 pm
21 Feb 2007
The point that resonates most with me is that over-reliance on model predictions can leave you worse off than having no predictions at all. This largely stems from a difference in understanding by scientists and non-scientists about what a prediction is. To us scientists, it's not what will happen, just the average of all possible scenarios. It seems that this probabilistic aspect is often dropped outside science, so that the public feels they now know what will happen.
The clarification that I feel needs to be made is that the modeling I think the authors are largely talking about are models currently en vogue to inform standard management and policy decisions (there are many other models that do not fall into this category, and I'd say climate models are one such subset). The standard management models are certainly fraught with simplifications and assumptions. They are used because they have been vetted and used for some time. But many of them are old models - models being developed by researchers are for more advanced (fewer, if any, "fudge factors").
Some models are not even used for prediction at all. They are used in scientific circles in order to better understand how things behave. They are imaginary lab experiments that can be used to test how our integrated set of theories work, and to help generate new hypotheses to test in the real world. No policies will be based on these predictions.
I'm sure this is much more than many wanted, but you got it anyway.
Blog: Down to Earth
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Zarkov Posted 5:43 pm
21 Feb 2007
Oh it is so complex oh dear!!! the main parameter for world climate disaster has been completely hidden from view !
Overlooked you say... LOL, no it is in the basement 1000 km below the surface of Alpha Centauri.
Wonder why something known since 1930 and reported very often in every marine micro-layer study has been entirely neglected...
Oh way to complex... or way too sinister and unbelievably expensive, and the liability way to damning.
One simple parameter other than solar heat drives this planet's climate cycle and that is water evaporation.
The heart and soul of our climate cycle has been ripped out by the oil companies and their legacy of world wide marine oil pollution..
Better address the problem, NOW
No use ignoring my posts... that won't solve the problem
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