My guess is that we should let it warm up by one or two degrees and
see how we like it. If we don't like it, we can cool it again. If
any permanent change is beneficial to most of humanity, there will
surely be some who lose. The losers should be compensated by the
John McCarthy, Computer Science Department, Stanford, CA 94305
He who refuses to do arithmetic is doomed to talk nonsense.
> Science for May 12 has an article entitled "Study unveils climate
> cooling caused by pollutant haze." This, combined with CO2 warming,
> indicates that humanity can control the average temperature of the
> earth and adjust it to suit us. Probably there are cheaper ways of
> doing it than CO2 and haze, e.g. by controlling cloud cover and icecap
> My guess is that we should let it warm up by one or two degrees and
> see how we like it. If we don't like it, we can cool it again. If
> any permanent change is beneficial to most of humanity, there will
> surely be some who lose. The losers should be compensated by the
Not in my back yard, thanks. I don't have any objection to large-scale
engineering projects, just do them somewhere else. Take a look at "Red
Mars," by Kim Stanley Robinson. He goes into terraforming Mars in
Earth, as I believe I noted here some weeks ago, is already terraformed
for our comfort (actually, it's the other way around, but the end
result is the same), and is not a suitable experimentation platform due
to the large percentage of the human population to which it is home.
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Tom Gray <tg...@igc.apc.org>
In the first category, for instance, there is the question of how to
calibrate a global response in the absence of a global authority. In particular,
what mechanisms for evaluating and implementing appropriate compensation
to "losers" would be plausible. This is another in a class of problems to
which there is no *technical* barrier, but which is not obviously feasible
due to social and political constraints. I am as much a technical optimist
as McCarthy - I am confident that every forseeable problem has a response
which is benign to both short term (economic) and long term (environmental)
interests. Alas, I am far more pessimistic on whether such responses, which
may involve significant departures from established practice, are politically
feasible. This idea of a system of global compensations and a global climate
target is an example. I can't imagine how such a thing would be put in
As for the proposed climate trajectory, I am pleased to see McCarthy choosing
to limit the warming to one or two degrees. The numbers show that global
carbon emissions must be constrained to be, roughly, no larger than
contemporary emissions to have a chance of limiting warming to that amount,
at least in the absence of large scale geoengineering.
As Len pointed out, the cancellation in the global average due to aerosols
does not amount to a cancellation in other measures of the climate forcing,
so that an exponential growth in greenhouse gas concentrations cannot
be indefinitely cancelled out by an exponential growth in aerosol emissions.
(Someone (Dean?) likened this to increasing amounts of coffee to wake up
and increasing amounts of barbiturates to fall asleep... not a good long-term
Also, note that the lifetime of aerosol is a couple of years, so the plan
of aerosol cooling represents an ongoing expense even after some hypothetical
equilibration of greenhouse gases in the century-scale future.
So I think there's an interesting cost-benefit calculation to be made here,
even accepting that global mean temperature is the only significant dimension
of climate change. On what grounds is it believed that a commitment to
ongoing aerosol releases into the indefinite future has smaller cost than
an equivalent constraint on contemporary emissions?
>>cooling caused by pollutant haze." This, combined with CO2
>>warming, indicates that humanity can control the average
>>temperature of the ^^^^^^^^^^^^^^^^^^^^
It is a "typical human" misinterpretation that we are able to
"control" anything on the worldwide scale. We can not. Just take
a look at the discussions around energy efficiency in your
country, then at the discussions about speed limits in my country
and then at the politics of international bodies at the climate
conference in Berlin. Is there any indication of control based on
common agreements? Nope, nothing.
World is complex system and the presence of thinking (?) humans
makes is more complex. Control in your sense is something for the
children's playground - real winners are thiose who do not rely
on "control" but on self-sustainability and the synergetic powers
* Thomas Rother 73728 ESSLINGEN *
Blithely suggesting that an important issue with potentially disastrous
consequences can be easily solved 'tomorrow' using predicted engineering
advances plays on a number of human foibles, hence it's an effective
Friesel's Conjecture (one realization): the probability of an underlying
strategy P = 1 - exp[-k(n-1)], n = number of apparent coincidences, k =
>Blithely suggesting that an important issue with potentially disastrous
>consequences can be easily solved 'tomorrow' using predicted engineering
>advances plays on a number of human foibles, hence it's an effective
One of the reasons economists and biologists disagree about global human
population growth (biologists generally recognize it as a problem;
economists generally do not) is that economists actually factor in
"unforeseen scientific advances" and ignore absolute nutritional intake
requirements and productivity limits (declining soil fertility, etc.).
Biologists know that scientific advances can't be engineered; they're not
available upon politicians' demand. That's why those on this side of the
debate express concern about economists' claims that population growth is
not only unharmful but necessary for healthy "markets." At some point,
abstract markets' health depends upon the well-being of the component
The notion that climate scientists have stampeded as a herd from
global cooling to global warming is one of the arrant bits of nonsense
that just doesn't seem to die. While a few climatologists (based
on some reasonable conjectures from the Earth's orbital parameters,
and position in the ice age cycle) may have written a bit about
global cooling, there was never a level of interest and concern
of the like of that accorded global warming today. For that matter,
global cooling in the long run is perfectly compatible with
a warm pulse in the short (i.e. two century) run.
By 1980, concern over global warming was already in full swing. Jule
Charney, who was on my thesis committee, said to me at the time that
"I think that doubling CO2 will lead to significant global warming,
and that it will be the biggest climate change since the last Ice
Age." For that matter, the physical basis for concern over warming
was already firmly in place in the 1970's when Manabe and Wetherald
discovered the strong amplifying effect of the water vapor feedback.
> Perhaps there was a herd of one climatologist stampeding from global
> cooling to global warming, i.e. Stephen Schneider. But he did his
> stampeding before Congressional Committees and this made his hooves
> sound louder.
Or perhaps he was the one who was careless with his words, and has
thereby become a rallying point for those who wish for reasons
of ideology or profit to take no action to reduce CO2 emissions.
Would you please give some explicit examples of just what you mean
by this? And how it is relevant to anything under disscussion.
> In 1980, global cooling was the most popular theory. Presently,
>global warming is "the answer".
There has been quite a bit of discussion in sci.enviroment
about this issue. It is certainly true that some climatologists
in the 70s and afterwards were concerned about our entering a new
ice age. However, I believe that the time scale for this was
quite different from that involved in current concerns about global
warming. People also cite one paper by Stephen Schneider in which
he suggested that aerosol cooling might be more important than
enhanced greenhouse gas warming. That paper also debunked (correctly) the
suggestion that there might be `runaway greenhouse warming'.
Aside from these instances, can you cite
other evidence for your claim that `global cooling was the most
popular theory'? Enhanced greenhouse warming was suggested as
something to be concerned about in the 19th century. People,
some of whom are still active in this area, were discussing it
in the 60s, 70s, and 80s.
> Actually, since climate is a rather elusive concept, is is rather
>strange to hear so much about climate change without any true
>understanding of what climate is.
Climate is not that elusive a concept. We certainly know what we
mean by the difference between climate in the Us and climate in
the Sahara or the Antarctic. Moreover, we can distinguish between
the climate during the last glacial period and the climate now.
> Please, don't tell me that climate is average weather. That
>definition is about as useful as defining hamburger as average cow :-)
No, it is like describing cattle as a general classification.
The above "guess" sounds to me like John McCarthy is having a
lapse of good thinking! I say this because we can't control
those factors he believes we can; and climate cooling or warming
is not a simple matter of overall temperature being a little warmer
or cooler. If that were the case, there would be no problem. It
means changes in ecosystems, ferocity of storms, disease vectors,
etc. Science is not nature. In nature there is neither right nor
wrong; only consequences. And nature is far more complex than your
Claire Gilbert, bla...@crl.com
Claire Gilbert, bla...@crl.com
One climatologist and one Science Journalist, John Gribbin, who seems to
jump on every bandwagon that comes down the pike.
>> In 1980, global cooling was the most popular theory. Presently,
>>global warming is "the answer".
>The notion that climate scientists have stampeded as a herd from
>global cooling to global warming is one of the arrant bits of nonsense
>that just doesn't seem to die. While a few climatologists (based
>on some reasonable conjectures from the Earth's orbital parameters,
>and position in the ice age cycle) may have written a bit about
>global cooling, there was never a level of interest and concern
>of the like of that accorded global warming today. For that matter,
>global cooling in the long run is perfectly compatible with
>a warm pulse in the short (i.e. two century) run.
This is quite true, Raymond. I was in oceanography graduate school in
the mid-70s, and there was considerable discussion of the possibility
of global warming and how it could be ameliorated or prevented. There
was always an awareness, based on knowledge of orbital parameters and
feedback processes, that there might be another ice age someday
(in several thousand or ten thousands of years), but that was obviously
only a very long term consideration. There was considerable
nonsense about ice ages in the popular press when there was a large
blizzard one winter, especially in Buffalo, NY, and I think this is
what some lay people remember. The claim that earth scientists have
been stampeding back and forth is nonsense, as any even cursory look
at the literature will reveal.
This claim is purely a propaganda ploy: "How can we believe you on
warming, when just a few years ago you were all claiming we were about
to have an ice age!"
not an official spokesman
"It was a great piece of meat."
Mexican truck driver who shot and
ate one of the last two Imperial
Woodpeckers on earth.
Does anyone remember or have a reference to the conference?
John McCarthy, Computer Science Department, Stanford, CA 94305
> There was considerable
> nonsense about ice ages in the popular press when there was a large
> blizzard one winter, especially in Buffalo, NY, and I think this is
> what some lay people remember. The claim that earth scientists have
> been stampeding back and forth is nonsense, as any even cursory look
> at the literature will reveal.
A little more info: my recollection is that it was the winter of
1977-1978, and it *was* startlingly cold. I was in Washington, DC, for
part of the winter, and the Potomac froze solid for several weeks,
something I don't think has happened since. I was in Detroit May 1, and
the temperature at 6 am (when I went jogging) was 28.
> This claim is purely a propaganda ploy: "How can we believe you on
> warming, when just a few years ago you were all claiming we were about
> to have an ice age!"
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Interested in energy and the environment? The free electronic
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I don't understand the first sentence of the posting. What
imminent ice age flap?
I don't know the date of such a conference, but it seems a quite
reasonable thing for earth scientists to be interested in as a
scientific matter. After all, to all appearences, we are indeed
in an interglacial period. There have been long periods in
the earth's history without extensive glaciation, so it is possible
no more glaciations are in the works, but it doesn't seem too plausible
on the basis of what we currently know. Hence, on a geologic
time scale, it is not unreasonable to expect this interglacial
to end. (Note however that this is entirely different from
the question of how increased greenhouse gas levels---as an
unintended consequence of human activities---will affect climate
in the next few centuries. The time scales are entirely
As to the question of why the conference didn't address measures
to prevent it, I can't really say since I don't know what was
discussed, but that won't stop me from speculating :-)
The idea that humanity can effect global phenomena is a very
new idea, and many people still find it hard to accept. It
underlies at least part of the skepticism about ozone depletion
and global warming. The traditional pattern of thought was,
even among scientists, that the world is so large that humanity
can't really make much difference to the global environment, no
matter what it does. The first real change in this
attitude was brought about
by the realization that CFCs, a human product, were having a significant
effect on the ozone layer in a relatively short period of time.
So it is not surprising that in a conference discussing
interglacial climatology, no one would suggest global engineering
projects to avert cooling. In this respect, John McCarthy
is a visionary way ahead of virtually everyone else. I should
also add that he seems to be far ahead of the science. Thus,
one could envision, adjusting CO_2 levels or taking other measures
to avert an ice age. However, our understanding of what
controls the beginning and end of interglacials is so rudimentary
that there is little hope such fine tuning could be done in a
way that would make any difference. In any case, the way
things appear to be going in terms of greenhouse gas emissions,
we probably don't have to worry about global cooling for several
centuries at least.
: Does anyone remember or have a reference to the conference?
What do you mean by "blame for the imminent ice age flap"? I've only
read up a few papers on paleoclimate data relating to past ice ages,
but the clearest message I got out of it was that ice ages happen all
the time, and the current interglacial period we are in right now
has been one of the longer ones. So, it common sense would tell you
that if ice ages happened plenty in the past, why not the future? and
if we've had a rather long interglacial, shouldn't it be ending soon?
Just because some scientists are busy talking about anthropogenic
global warming, and others are talking about natural climate cooling,
does not mean that atmospheric scientists are a bunch of confused
fellows who don't know what is going to happen.
I'm not sure about 'several weeks', but the Potomac did freeze over
in winter of '94. The local electric companies having the brains of
gnats, this caused serious problems for power generation and distribution.
(Hint: What weather conditions will cause record demand for electricity
in winter? What happens if your fuel supply comes up the Potomac?)
January/February '94 saw the first time that Lake Superior is recorded
to have frozen over all the way across. (The 76-79 winters got it
most of the way, but not all.)
Both of which are reasons that anecdotes about individual events,
such as a cold winter here or there, floods here or there, a record
warm spell here or there, ... are not taken to mean a great deal in
the professional community, even if the media do so.
Bob Grumbine rm...@access.digex.net
Sagredo (Galileo Galilei) "You present these recondite matters with too much
evidence and ease; this great facility makes them less appreciated than they
would be had they been presented in a more abstruse manner." Two New Sciences
Well, they have to sell papers and attract viewers, after all.
But gee, you're absolutely right, wonder why no one else has made this
point before in this newsgroup. Stephen Schneider was indeed involved
with the global cooling question, but it was not an environmental
issue, to the best of my recollection, at all.
: But gee, you're absolutely right, wonder why no one else has made this
: point before in this newsgroup. Stephen Schneider was indeed involved
: with the global cooling question, but it was not an environmental
: issue, to the best of my recollection, at all.
I am baffled. It seems that you are using "environmental" in the same
peculiar sense that Moore & McCarthy did when they asserted that many
of their fellow Hooverites were "uninterested in the environment". Defining
"environment" as "that which is of interest to environmentalists" seems to
me a singularly unhelpful way of thinking about the world.
Be that as it may, it is not correct to assert either that 1) few scientists
were worried about imminent ice age onset twenty years ago nor that 2) few
persons concerned about human impact on the environment were worried about
FULL DISPLAY ITEM 1 (of 1)
AUTHOR Ponte, Lowell, 1946-
TITLE The cooling / by Lowell Ponte. -- Englewood Cliffs, N.J. :
with an introduction by our own (I mean the meteorology department at
the University of Wisconsin's own) professor (now emeritus) Reid Bryson.
Bryson coined the term "human volcano" to designate the human output of
particulates, which he feared might contribute to triggerring the then
plausible scenario of a sudden onset ice age. (Contrary to Niven and
Pournelle's ridiculous botch in their science fiction novel _Fallen Angels_,
this is no longer considered plausible. See Crowley & North, _Paleoclimatology_,
Oxford U press, 1991, pp 121-122.)
Bryson, by the way, remains a greenhouse skeptic, and is frequently
embarassed by invitations to speak to ultraconservative groups.
It is important to note exactly who made those predictions, (or more
properly, who expressed those worries) about an imminent ice age, and
who is now predicting rapid global warming. By and large these are not
the same people. The first group was essentially the observational
paleoclimatologists. Bryson still claims that "the proper tool of the
climatologist is the shovel". The compendium by Lamb which Tom Moore
takes as his primary reference was essentially the pinnacle of achievement
in that field.
With all due respect (I mean this quite seriously - the erudition and
breadth of knowledge of these people, Lamb in particular - is enormously
impressive) to that group, their grasp of mathematics and statistics
was weak, and of physics weaker still.
For instance, Lamb's prediction in particular of imminent and rapid
cooling was based on, essentially, a crude Fourier analysis (best fits
of sinusoidal curves to his record). Since one of the dominant features
was a rapid rise over the last century, the *presumption* of a cyclical
nature of the record forced a prediction of a rapid cooling *precisely
because there had been a recent rapid warming*. And although the niceties
of periodograms had all been worked out by that time, Lamb seemed blissfully
ignorant of the need to take particular care when fitting sinusoids to
a record with significant information at its termination.
In the 1970s, a separate discipline of physical climatology was just
emerging from an infancy at the peripheries of mathematics and astrophysics.
Since the 1890s, physical climatologists or their precursors have always
asserted that the anthropogenic cooling of the human volcano was
counterbalanced and probably outweighed by anthropogenic warming of
the human greenhouse.
The groups making the assertions were essentially distinct, the group
asserting warming was making far more specific and testable predictions,
and the reasoning behind the assertions was far more clearly based in
established and demonstrated results in physical science.
However, it is completely false to say that no scientists or no
"environmentalists" were concerned about global cooling or human effects
on such hypothetical cooling.
Science, vol 193 pp 447 ff, Aug 6, 1976, has an article specifically
addressing the then widely held perception of global cooling and presenting
arguments that to the contrary, predict warming. (The article is entitled
"Global Cooling?") Interestingly, in this article Stephen Schneider
is mentioned as being firmly in the camp that expected warming. I wonder
on what basis he has been accused of ever having been in the cooling camp
- perhaps on the basis of a statement cynically removed from its context?
Mr. McCarthy and I have been over this in e-mail a time or two
before. Still he has not answered the question of _why_ scientists
meeting to discuss ice ages (physics, paleoclimate, ...) (even
assuming that the conference was actually held) should devote time
to how humanity might prevent an ice age. And, more relevantly,
why it is any more incumbent on them to carry out such a discussion
than, say, a group of computer scientists who collect to discuss
the LISP programming language should have to discuss the fabrication
process of CPU's. Nor do I see what the absence of a particular
line of (irrelevant) discussion at a single (putative) conference
20 years ago says about the field.
A related point we've discussed in e-mail is the matter of
earth scientists (oceanographers, meteorologists, climatologists,
glaciologists, ...) considering large scale engineering responses
to climate change. As I've pointed Mr. McCarthy to in our e-mails,
there is in fact a body of literature on the subject already. And
off the top of my head I added in another dozen or so schemes. The
engineering is not difficult if you don't care much about side
Somewhere about this point, Mr. McCarthy complained about the
absence of a journal dedicated to climate engineering. I invited
him to start up an electronic journal on the subject, and volunteered
(legal requirements related to my employer permitting) to be the
or an editor.
Since he hasn't modified his complaints about the field, I get
the feeling that he hasn't read any of the papers I directed him
to. Nor does the absence of a climate engineering journal seem a
truly serious problem, since he's not so far willing to do anything
about the absence.
Still he has not answered the question of _why_ scientists
meeting to discuss ice ages (physics, paleoclimate, ...)
(even assuming that the conference was actually held) should
devote time to how humanity might prevent an ice age.
It seems like an obvious question to me, so I don't see how to carry
the discussion further.
Grumbine suggests that I start an electronic journal of climate
engineering and volunteers to be an editor or the editor. It would be
great if someone would take him up on that, but I am not the person.
Edward Teller once said to me apropos of a quite different matter,
"John if you want to do any good you will have to specialize." I try
to take his advice, but I confess that I am distractable.
I think that McCarthy has fooled us all. He is actually debugging
his artificial intelligence program. I refuse to believe that a
genuine human is responding to the posts.
I remember that when Cicerone's ideas were discussed in the local media
(he was at NCAR at the time; he has since moved to UC Irvine) there was
a certain amount of knee-jerk reaction from environmentalists and from
some local scientists as well. While he readily conceded that we don't
know enough about the atmosphere *now* to carry out such proposals,
Cicerone was talking about what we might do ~40 years from now *if*
things turn out to be much worse than we think they will, and suggesting
that now is a good time to start thinking about it. I think that there
is a generation gap of sorts here. Many people who got their scientific
training in the '60's and early '70's imbibed some oversimplified
pop-ecology notions about "the balance of nature" that inhibit clear
thinking about environmental issues. Those of us who got our degrees in
the 1980's tend to take a more sophisticated/cynical (take your pick
I don't have the reference handy, but I did track most of this down
over a year ago and posted the results. I did a search of Science
and found an article by Schneider in which he and a joint author
examined the question of particulates and suggested that they might
play a significant role. They even, if I remember correctly, referred
to a paper which considered a possible imminent ice age and wondered
if increasing particulates could trigger it. They also correctly
deduced that a runaway greenhouse effect, as on Venus, was highly
unlikely. I followed this further and found criticisms of this
paper by others and Schneider's response. By then, he was already
casting doubts as to whether cooling or warming was more significant,
and suggesting the need for more research. The last references of
his I found showed him clearly in the warming camp. I don't know if
he exhibited any other flirtation with cooling during this period.
What I said above is all from memory, and I could easily have gotten
some of it wrong.
It should be added that the relative effects of cooling by particulates
and warming by greenhouse gases are still being analyzed. This
is after all not a political debate between two opposing sides, but
rather an attempt to understand a complex situation in which different
factors play a role. I agree with Michael that the general consensus
is that greenhouse warming is likely to predominate. At least this
seems plausible on physical grounds, if greenhouse gas concentrations
> Tom Gray (tg...@igc.apc.org) wrote:
> : But gee, you're absolutely right, wonder why no one else has made this
> : point before in this newsgroup. Stephen Schneider was indeed involved
> : with the global cooling question, but it was not an environmental
> : issue, to the best of my recollection, at all.
> I am baffled. It seems that you are using "environmental" in the same
> peculiar sense that Moore & McCarthy did when they asserted that many
> of their fellow Hooverites were "uninterested in the environment". Defining
> "environment" as "that which is of interest to environmentalists" seems to
> me a singularly unhelpful way of thinking about the world.
Hmmmmm. Actually, I am using it in a somewhat different sense. When I
say cooling was not an environmental issue, I mean that
environmentalists were not demonstrating, campaigning, etc., to get
anyone to change their conduct so as to avoid the possibility of global
cooling. The key word is "issue," with its connotation of political
activity. Issue as in species extinction, acid rain, nuclear power, or
the like. Global cooling was viewed as something like an asteroid
strike--an "act of God."
This in turn means it is inappropriate to say, "You environmentalists!
First, you told us the world was going to cool, now you say it is going
to warm. Obviously, you have no credibility."
> Be that as it may, it is not correct to assert either that 1) few
> scientists were worried about imminent ice age onset twenty years ago
> nor that 2) few persons concerned about human impact on the
> environment were worried about it. Witness:
> FULL DISPLAY ITEM 1 (of 1)
> AUTHOR Ponte, Lowell, 1946-
> TITLE The cooling / by Lowell Ponte. -- Englewood Cliffs, N.J. :
> Prentice-Hall, c1976.
> with an introduction by our own (I mean the meteorology department at
> the University of Wisconsin's own) professor (now emeritus) Reid Bryson.
> Bryson coined the term "human volcano" to designate the human output of
> particulates, which he feared might contribute to triggerring the then
> plausible scenario of a sudden onset ice age. (Contrary to Niven and
> Pournelle's ridiculous botch in their science fiction novel _Fallen
> Angels_, this is no longer considered plausible. See Crowley & North,
> _Paleoclimatology_, Oxford U press, 1991, pp 121-122.)
> Bryson, by the way, remains a greenhouse skeptic, and is frequently
> embarassed by invitations to speak to ultraconservative groups.
Well, Pournelle in particular has never been constrained much by
science--he's right up there with Rush as an ideologue. Yes, I was
thinking that I remembered Bryson as a noted skeptic.
> However, it is completely false to say that no scientists or no
> "environmentalists" were concerned about global cooling or human effects
> on such hypothetical cooling.
Agreed. Fortunately, that is not what I said. 8^)
> Science, vol 193 pp 447 ff, Aug 6, 1976, has an article specifically
> addressing the then widely held perception of global cooling and presenting
> arguments that to the contrary, predict warming. (The article is entitled
> "Global Cooling?") Interestingly, in this article Stephen Schneider
> is mentioned as being firmly in the camp that expected warming. I wonder
> on what basis he has been accused of ever having been in the cooling camp
> - perhaps on the basis of a statement cynically removed from its context?
Thanks, that's a great ref. I recall reading or seeing Schneider
quoted at the time, saying that a new ice age was a distinct
possibility or words to that effect.
Actually, the cooling flap demonstrates another phenomenon, which is
the dominance of the Eastern seaboard in media climatology. Donella
Meadows says in her column today that the average temp over the US was
*warmer* than normal during the winter of '77. However, it was
bitterly cold in NYC and Washington, hence global cooling. 8^)
Hmm, now that I think of it, I remember the weather maps that year.
The West was very warm for most of the winter.
: It seems like an obvious question to me, so I don't see how to carry
: the discussion further.
Hmm, I guess that there should be no scientists who aren't also enginneers,
according to McCarthy?
Hint: much more basic science has to do done before global climate change
becomes an enginneering problem. McCarthy might realize this if
he were a scientist.
: Edward Teller once said to me apropos of a quite different matter,
: "John if you want to do any good you will have to specialize." I try
: to take his advice, but I confess that I am distractable.
It figures that McCarthy would be a friend of Teller.
sketched something like two generations of climatologists, those
relying mainly on observations and those adding physics as another
corner stone. Michael outlined some "observationists'" cooling
worries during the 1970s, including
Be that as it may, it is not correct to assert either that
1) few scientists were worried about imminent ice age onset
twenty years ago nor that 2) few persons concerned about
human impact on the environment were worried about it.
This brought an old article by Robert Parson to my mind. It outlines
some of the fledgling "physicalists'" (?) thoughts on cooling versus
warming at about the same time. It is appended below, I think it is
worth a repost. Apologies to the author, in case you disagree ;-)
Jan Schloerer schl...@rzmain.rz.uni-ulm.de
Uni Ulm Klinische Dokumentation D-89070 Ulm Germany
---- begin repost
Subject: Cooling vs. Warming
From: rpa...@rintintin.Colorado.EDU (Robert Parson)
Organization: University of Colorado, Boulder
Date: Mon, 18 Oct 1993 01:21:39 GMT
One way to get a sense of what scientists thought was important 20 years
ago is to look up conference proceedings.
In our library I found the proceedings of a December 1968 AAAS
Symposium, _Global Effects of Environmental Pollution_, ed. by
S. Fred Singer (who was at the Interior Dept. at that time), Springer,
N.Y. 1970. I also found what appears to be a followup volume, also
edited by Singer and published by Springer, _The Changing Global
Environment_, pub. 1975. Actually the later book seems to be a sort
of expanded edition of the former; revised versions of the papers from
the first book are reproduced and newer ones added. Incidentally,
Singer's editorial remarks in these books are well worth reading,
he was a lot less irritating back then ;-).
Part III of the second book is entitled "Effects of Atmospheric
Pollution on Climate". It contains papers by:
Reid Bryson and Wayne Wedland
J. Murray Mitchell
H. E. Landsberg
The first 4 were in the earlier volume as well.
Singer's introduction to this section summarizes it nicely:
"Human activities are not only increasing the content of carbon dioxide
in the atmosphere (see Part I), but also the particle content...
"The effects are not at all well understood; even the immediate effects
are difficult to predict and our confidence in predicting long-term
effects is not high...
"Bryson and Wendland attempt to delineate the current thinking and
review available scientific studies. They opt for a downward trend in
planetary temperatures, over the long run, because of increased albedo
effects of atmospheric particulate material...
"Mitchell uses a different, but complementary approach, but with
differing results. He concludes that the carbon dioxide increase is more
effective in raising planetary temperatures than is the human-derived
particulate loading in reducing temperatures. Natural dust loads
dominate at present; in the future, however, anthropogenic dust effects
could eventually have an important effect on climate.
"On the other hand, Ellsaesser concludes...that the human-related
particle loading is only 13% of the natural loading, and that the
anthropogenic contribution is growing slowly, if at all.
"Manabe examines some of the fundamental assumptions in a critical
manner. The induced temperature changes depend on the optical properties
of the particles. Under certain circumstances. the increased particulate
loading could even raise planetary temperatures.
"Schaefer describes more local effects on the weather due to air
"Many of the foregoing discussions are tied together in the review by
Landsberg which deals with climactic change on global, regional, and
local scales. It concentrates on the last five centuries and on future
changes produced by CO2 and dust..."
I have looked briefly over these papers. They all seem to agree that
there are two major anthropogenic impacts on global climate: CO2 and
aerosols/particulates. The one causes warming, the other cooling. They
disagree substantially about how these stack up against each other.
It is clear that Keeling's Mauna Loa and South Pole results were
starting to make people think very hard about greenhouse warming;
however much less was known about earlier CO2 levels (the ice core data
hadn't been collected yet) and it was not known that the CO2 increase
was unprecedented in human history. Everyone notes the warming trend
before 1940 and the cooling trend since 1940. Some (e.g. Bryson) argue
that the cooling could be due to anthropogenic particulates, others that
it is more likely due to increased volcanic activity. Nobody has a very
good idea of what the anthropogenic contribution to particulates is, or
whether it is increasing.
Mitchell mentions the Rasool and Schneider study, but he argues that it
represents an upper bound to the possible cooling effects. As Singer
says above, he thinks that CO2 warming is more important, but he hedges
his statements very carefully. Mitchell seems to be closest to the
positions that are generally adopted today.
The impression that I get from all this is that everyone agreed that CO2
emissions could produce warming and that particle emissions could
produce cooling, but that lack of information precluded any definite
conclusions about which was more important. By making different
assumptions, different researchers came to radically different
conclusions. All contributors readily admitted the enormous
uncertainties that they were faced with. Nothing remotely resembling
the claim that "they were preaching global cooling" is evident in this
volume. Some suggest cooling, some suggest warming, some suggest
neither, some are not willing to draw any conclusions, and nobody is
---- end repost