Skip to comments.Polar Ice Sheets and Global Sea Level: How Well Can We Predict the Future?
Posted on 07/24/2002 8:55:25 PM PDT by PeaceBeWithYou
Volume 5, Number 30: 24 July 2002
After lengthy analyses of various topics related to these objectives, van der Veen arrives at some important conclusions that the general public has not only a right, but a need, to know. In this regard, for example, the polar scientist notes that with "greater societal relevance comes increased responsibility for geophysical modelers to demonstrate convincingly the veracity of their models to accurately predict future evolution of the earth's natural system or particular components thereof." In stepping forward to perform this task for glaciological modelers, however, he is forced to conclude that "the validity of the parameterizations used by [various] glaciological modeling studies to estimate changes in surface accumulation and ablation under changing climate conditions has not been convincingly demonstrated."
Some of the problems associated with model testing, of course, are observational, i.e., there must be a documented history capable of being simulated. With respect to the mass balance of the Greenland Ice Sheet, for example, van der Veen notes that "it is currently not well known whether or not the ice sheet is growing or shrinking, although most studies agree that the whole of Greenland is not far out of balance in either direction." Hence, if what is "known" is really not all that certain, there is little opportunity to assess model performance. Furthermore, even if a model prediction turns out to be consistent with present or past observations, van der Veen notes that "there is no guarantee that the model will perform equally well when used to predict the future," especially if one of the model parameters extends into a range that is beyond the range within which the model was tested.
Admittedly, these observations appear to suggest that it is essentially impossible for a model to ever be "proven" to be a valid tool for assessing the likelihood of future events; and that perspective is correct. At best, says van der Veen, models can only be confirmed "by matching observational data that were not used to calibrate model parameters." But even then, considering the observations of the preceding paragraph, it really becomes a matter of faith as to how well one believes a model that has successfully replicated the past will predict the future.
Laying these considerations aside - but remembering they imply that whatever follows may be even less well defined than what is suggested by the numbers - van der Veen calculates that within the context of greenhouse-warming-induced sea level change, uncertainties in model parameters are sufficiently great to yield a 95% confidence range of projected contributions from Greenland and Antarctica that encompass global sea-level lowering as well as rise by 2100 A.D. for low, middle and high warming scenarios based on surface mass balance calculations. Hence, even for the worst of the global warming projections - which could well be way off base itself, as we personally believe it is - there could be little to no change in mean global sea level due to the ongoing rise in the air's CO2 content.
In view of these findings, van der Veen concludes that the confidence level that can be placed in current ice sheet mass balance models "is quite low." Paraphrasing an earlier assessment of the subject, in fact, he says that today's best models "currently reside on the lower rungs of the ladder of excellence." Hence, it is not surprising that he states that "considerable improvements are needed before accurate assessments of future sea-level change can be made."
Clearly, the results of van der Veen's eye-opening study should be trumpeted in the ears of the public at large, as well as those of all world leaders. Via this small essay, we are doing our part. It is now up to you to do yours.
|Dr. Sherwood B. Idso
|Dr. Keith E. Idso
van der Veen, C.J. 2002. Polar ice sheets and global sea level: how well can we predict the future? Global and Planetary Change 32: 165-194.
If I find the C.J. van der Veen paper I will post it or a link to it in the thread.
If you can't show at least a 1 foot increase in sea levels the world over, who cares? A millimeter increase is too close to the margin of error. And just because it changes does not mean that's a bad thing. If global warming produces more plant life and rain and the added warmth saves lives, shouldn't we want it?
"Why did the polar bear go to the south pole?"
To see his Aunt Artica!...splash
Remind me to tell you the one about the "Czech is in the male."
Because "I don't know" is the hardest phrase for a PHD to say, but I suspect that he said "we don't know" in his paper of 32 pages, which is the second hardest phrase for a PHD to utter.
Global Warming Hoax :
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Technically it's CO2 Science Magazine but for some reason the post filter told me it was too long for the field, so I shortened it to CO2 Magazine. In hindsight CO2 Science Mag. would have been better.
Check it out, it's a great resource.
I think that is what it is.
and why couldn't warming be a natural cause?
Lots of places that are devoid of the heat island effect are recording colder temps. It could be that once we are out of the current solar maxium, that it becomes apparent that Global Cooling should be our concern, as we are much less able to cope with colder temps than with warmer temps.