Posted on 11/16/2001 1:06:32 PM PST by Steve Schulin
[This is from "Current Journal Reviews" in CO2 Science Magazine, v 4 n 46, November 14, 2001]
Uncertainties in Anthropogenic Radiative Forcing of Climate: There's lots of them; and they're big.
Reference: Ghan, S.J., Easter, R.C., Chapman, E.G., Abdul-Razzak, H., Zhang, Y., Leung, L.R., Laulainen, N.S., Saylor, R.D. and Zaveri, R.A. 2001. A physically based estimate of radiative forcing by anthropogenic sulfate aerosol. Journal of Geophysical Research 106:5279-5293.
Background: In setting the stage for their study, the authors state that "present-day radiative forcing by anthropogenic greenhouse gases is estimated to be 2.1 to 2.8 Wm-2; the direct forcing by anthropogenic aerosols is estimated to be -0.3 to -1.5 Wm-2, while the indirect forcing by anthropogenic aerosols is estimated to be 0 to -1.5 Wm-2," so that "estimates of the total global mean present-day anthropogenic forcing range from 3 Wm-2 to -1 Wm-2." Now let's see, that would be somewhere between a warming and a cooling, right? And that would seem to be rather shaky justification for the worldwide institution of draconian measures to fight potential global warming, which could well turn out to be potential global cooling, right? Right; for as the authors themselves say, "clearly" - and we love that word clearly, for it is obviously most appropriate - "clearly, the great uncertainty in the radiative forcing must be reduced if the observed climate record is to be reconciled with model predictions and if estimates of future climate change are to be useful in formulating emission policies." Doing so, however, will, as they say, "require profound reductions in the uncertainties of direct and indirect forcing by anthropogenic aerosol," which is what they thus set out to do, i.e., reduce the uncertainties.
What was done: In the words of the authors, they employed a strategy that consisted of "a combination of process studies designed to improve understanding of the key processes involved in the forcing, closure experiments designed to evaluate that understanding, and integrated models that treat all of the necessary processes together and estimate the forcing." For more details - and there's lots of them - we recommend direct consultation of their paper.
What was learned: At the end of their laborious investigation, Ghan et al. come up with some numbers that considerably reduce the range of uncertainty in the "total global mean present-day anthropogenic forcing," but it still stretches from a small cooling influence to a modest impetus for warming. Hence, they present a long list of other things that must be done in order to obtain a more definitive result, after which they acknowledge that "this list is hardly complete." Indeed, they conclude their treatment of the topic by saying "one could easily add the usual list of uncertainties in the representation of clouds, etc."
What it means: The bottom line, in the words of the authors, is that "much remains to be done before the estimates are reliable enough to base energy policy decisions upon," to which we can only say "Amen!"
Reviewed 14 November 2001
Copyright © 2001. Center for the Study of Carbon Dioxide and Global Change
GLOBAL WARMING: SOUND SCIENCE OR SCIENCE FICTION?
Thursday, November 15th, 2001, 8:30 a.m. to 11:30 a.m.
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The effect of human activity on the atmosphere is significant - and grows more so with increasing population and industrialization - whatever its ultimate consequences.
Therefore caution is strongly advised.
If areas of the world become uninhabitable or more difficult, people will move. Worry about global warming is more reflective of general paranoia than any real 'problem'.
Oil companies profit on production. Climatologists and governments profit on fearmongering. The amount of chatter about climate change is ridiculously out of proportion with the quantity of useful data.
And that is the very first time in the history of the planet that has ever happened! < /sarcasm>
The effect of human activity on the atmosphere is significant - and grows more so with increasing population and industrialization - whatever its ultimate consequences. Therefore caution is strongly advised.
Yes, caution is strongly advised--especially when we are being urged to base public policy on uncertain foundations. Consider just two points:
(1) According to the article, the uncertainty in the "anthropogenic forcing" is about 200%. It is not even clear whether the effect on temperature is positive or negative.
(2) The mean solar irradiance at the outer limits of the earth's atmosphere -- the so-called "solar constant" -- is about 1370 Watts per square meter. Accurate satellite measurements over the past 20 years have shown a variation in the solar constant of about 0.1% or 1.4 Watts/square meter. There is reason to believe that greater changes have occurred over longer periods of time. (An interesting discussion is found here: Constant as the Sun? A Look at Solar Variability
In short, not enough is known about global warming to justify drastic changes in public policy.
As far as drastic or draconian changes based on "assumed" global warming, I agree. But it's definitely in American interests to do everything possible - but not draconian - to wean ourselves from foreign oil and unwanted, useless, and/or poisonous by-products. Who is for toxic emissions?
On a global scale there are other threats - like species extinction - which are equally problematical. All are a consequence of population growth and industrialization. Here again - caution is strongly advised. I am not convinced by those who argue that there's plenty of land and population is - magically - going to decrease in the near future. Conscious effort is required to change habits and awareness.
As far as drastic or draconian changes based on "assumed" global warming, I agree. But it's definitely in American interests to do everything possible - but not draconian - to wean ourselves from foreign oil and unwanted, useless, and/or poisonous by-products. Who is for toxic emissions?
Indeed, who is for toxic emissions? Few would argue that we should poison the air, water, soil, or ourselves with toxic substances. However, most greenhouse gases are not toxic.
I believe that most Americans would prefer that we not be so dependent on foreign oil. I am less sure that most Americans would accept increased domestic oil production, coal mining, or nuclear power.
On a global scale there are other threats - like species extinction - which are equally problematical. All are a consequence of population growth and industrialization. Here again - caution is strongly advised.
Industrialization -- or more properly, economic growth -- may be the solution to environental problems. The rich countries are the ones that can afford to be envrionmentally conscious. Poor people are too busy trying to survive.
I am not convinced by those who argue that there's plenty of land and population is - magically - going to decrease in the near future. Conscious effort is required to change habits and awareness.
I don't know about magic, but it appears that population growth has slowed dramatically, even in the Third World. (There is an interesting article on the subject in the current issue of the American Spectator.) In many developed countries, the concern is that the population growth rates have fallen below replacement.
It just begins to scratch the surface of the problems with trying to predict climate change with any degree of accuracy.
Given that we can never calculate an accurate weather forecast for a specific point on the surface of the earth more than 4 or 5 days in advance, the notion that we can predict with any accuracy what global temperatures will be 100 years from now based on changes today in a few of the variables is absurd.
I was being ironic when I said that fertility was "magically" dropping. The drop is due to changing attitudes about large families (at least partially due to increasing wealth brought about by economic growth) and increasing availability of effective contracteptive measures. Both policies are opposed by those who cite the drop in fertility as evidence that there is no population problem.
I'm not prepared at this time to engage in a real discussion of population and land issues. I'm still reading material recommended to me on other threads. I'll flag you in a few days (I hope. Keeping up is getting harder and harder).
It may be - and almost certainly is - far easier to predict averages than individual variations. If that were not so there would be no mathematical discipline of probability, no quantum statistical mechanics, and no insurance industry.
True, but not relevant to the issue at hand.
One cannot accurately model physical processes for any significant length of time is the processes are non-linear systems sensitive to initial conditions. Whether one is looking for a specific prediction or an average prediction is irrelevant.
True. Generally. But it may not be necessary to model the process in order to predict some average behavior.
This is the problem with not being an expert.
I once watched Linus Pauling calculate accurately to 6 places with a slide rule. I was amazed at the number of different approaches Feynman used when viewing a problem.
I, personally, am limited by my lack of ability. I can only go with the best assessment of a situation as reported to me by those whose knowledge and skill I trust.
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