From: userDHAL@mts.ucs.UAlberta.CA (David Halliwell)
Subject: Re: global warming/global cooling/global climate change
Keywords: global warming cooling climate change
Organization: University Of Alberta, Edmonton Canada
Date: Wed, 14 Oct 1992 22:51:04 GMT

gordon@tramp.Colorado.EDU (GORDON ALLEN R) writes:

>I'm confused.  I've heard a lot about global warming as a result of CO2 and 
>other greenhouse gases.  I've also been hearing about this CO2 triggering an
>ice age and global cooling.

    *Sigh*   We really do need a FAQ to deal with a number of these points.
Don't take that as a flame for asking, but the number of times this sort
of thing has been hashed out in sci.environment over the last year or so
is rapidly approaching the point where the time invested in a FAQ would
have been a time-saver!

>A very persuasive paper by Ken Watt of UC Davis was written in '86 for the 
>earth regeration society (Watt also has other papers in refereed journals, but
>this one is very disturbing).  I'll excerpt it here and if I can get it scanned,
>I'll post it here. 

>Basically he's saying that "...there isn't a shred of evidence that the world
>is warming...all available evidence suggests that every part of the greenhouse
>warming theory is incorrect or incomplete and that the world is cooling 
>rapidly." 

   As Michale Tobis has stated a number of times, the greenhouse effect
*does exist*. It is the reason why our global mean surface temperature is
about 15C, instead of the -18C that we would expect if the earth had no
atmosphere. This is a natural effect. This is a "fact" that readily
observed.

   Human activities which are expected to *enhance* the natural greenhouse
effect and lead to warming over the next half century are more debatable,
but there is broad agreement that increasing CO2 will lead to radiative
changes which can only be offset by increasing the global mean surface
temperature. The big question then becomes "How much warming can we
expect?", and this is where uncertainties creep in.


>       He also states that the evidence for cooling comes from "esoteric
>highly technical data such as computer tapes of weather records stored in 
>government bureaus and statistical analyses of climate trends locked up in 
>scientists` file cabinets" but also from newpapers and television.

   "Esoteric and highly technical" sounds like someone saying "I don't
really understand this myself, so I'm going to try to fool you into
thinking that it is too complicated to explain to you" so that you
can't question them about the details of the data. One published set of
results that you can look up yourself is:

   Jones et al (1986) "Northern hemisphere surface air temperature variations
1851-1984", J. Climate and Applied Meteorology 25, 161-179.

   The data from this study shows slight cooling from 1850-1880, warming
from 1880-1940, cooling from 1940-1970, and warming since then. Overall,
there is over half a degree of warming from 1880-1980. The warmest period
is 1980, followed closely by the 1930s.

>      He states 
>that the media are full of news stories about phenomena caused by cooling.  For
>example, headlines have been: "Record lows hit 46 communities (11/14/86), and 
>in many cities low temperature records or 130 years had been broken.  He claims
>that such stories have been occuring more and more in the last 5 years.  He 
>goes on to cite more examples and also include stories of travellers.

   As in sports, we can say that "records are meant to be broken". Records
represent the extremes, not the average. There have also been many instances
where record highs have been broken. Given any time period, there is a good
probability that existing data doesn't include all the extreme values, and
when those extreme values occur you set a new record. This does *not*
necessarily mean that that either the mean or the variance of the distribution
has changed.

   One of the suggested possibilities of "greenhouse warming" is that
weather will become more variable. This could explain *both* high and low
records, and is not inconsistent with the observations you cite. Also,
we have to consider the possibility that "this year's" weather has been
affected by a short-term event. In 1982, a volcano called El Chichon
erupted in Mexico. This was much larger than Mt. St. Helen's in 1980, and
could explain a temporary cooling in the period 1982-1983. 1982 was also
a severe El Nino year, and the atmospheric circulation changes could easily
lead to unusually cold temperatures in some regions. These possibilities
say nothing about the validity of human-enhanced greenhouse warming (other
than making it harder to detect).

>He also cites data collected from 7 rural US climate stations (away from the 
>warmer cities) that show a consistant 2.1 - 4.2 degress F fall in the avg 
>annual temperature over the last 43 years.  Watt states that only 270 of the
>11,600 thermometers feeding climate data of the National weather service are 
>free of urban heat island effects due to waste heat from air conditioning, 
>vehicles, manufacturing plants, space heating etc.

    What do the other 263 rural stations show? Seven selected stations
hardly give a good indication of *global* trends! As I mentioned above,
the Jones et al paper showed northern hemisphere cooling from 1940-1970.
Thus, these seven stations are not unusual in that instance. To comment
further would require knowing which 7 stations he is talking about, and
just how consistent the cooling is, and why the other 263 "acceptable"
stations were excluded from the analysis.

    The Jones et al paper also discusses how problems of urban effects,
inhomgeneities in station distributions, changes in station location,
time of observation, and method of calculation of means affect their results.
(Or how they were eliminated from the analysis.)

>Watt argues against the evidence that tree mortality thought to be due to acid
>rain in favor of evidence showing that the mortality is due to cooling effects.
 
   Can't comment unless I see the evidence and the hypothesis being
examined.


>One of the most astounding (to me) arguments  concerned the sources of CO2:

>"...was that combustion of fossil fuels was the principal source of increased
>concentrations of CO2 in the atmosphere.  This idea also proved false:  CO2 
>kept increasing after '79 when release of carbon from combustion of fossil 
>fuels was declining.  Further, some scientists are now beginning to point out
  
   Wait a minute. I'm filling a sink with water from a tap. I reduce the 
amount of water coming out of the tap. This is supposed to *lower* the
level in the sink? Maybe it won't rise as quickly, but....?

>that the increase in CO2 concentration of the global atmosphere began too early
>in the 19th century, if combustion of fossil fuel was the source.  Rather, the
>buildup of atmospheric carbon coincided with the massive destruction of the
>north temperate forests in Europe and North America in the 19th century..."

   ...and that 19th century deforestation is still causing the ever-increasing
atmospheric CO2 rise that has been well-documented since the 1950s?
How about "deforestation in the early 19th century initiated an increase
in atmospheric CO2, which is now principally the result of fossil fuel
combustion"?


>Finally, the effect of CO2 in the atmosphere would warm the planet is a correct
>idea, however, it, Watt claims is incomplete.    The surface warming causes 
>increased evaporation of water from the ocean surfaces which forms clouds that
>the prevailing westerly winds move to high latitudes, increasing polar snow 
>fall.

    This is entirely speculative. Clouds are the result of condensation,
not evaporation. A warmer surface should evaporate more water, and a 
warmer atmosphere will be able to hold more water vapour. This doesn't
automagically lead to more cloud. Globally, evaporation equals
precipitation, and there is no concensus that this balance will require
more cloud in a warmer climate. (There is also no concensus that it won't.)
The primarly effect of cloud would be the albedo (reflection of solar
radiation) of the cloud itself, rather than effects of snow cover.
Generally, warmier temperatures should mean that stuff that used to be
snow will now be rain, and snow and ice cover would decrease. This albedo
change would amplify the warming.
 
   There are a number of consideration needed regarding cloud in addition
to just cloud amount: height, thickness, type, location, time, etc.


>  He states that October snow cover in the Canadian arctic is now 
>spreading.  He also indicates that the models for global warming left out the
>effects of clouds.

   The exception to the global trend of warming--->less snow is likely
to be in areas that are currently too cold for much precipitation. Warming
could enhance snowfall without getting warm enough for rain. This is also
central to your initial point about ice ages: warming could lead to glacier
growth in locations where winter snow accumulation is increased more than
summer melting. (Note that this does *not* mean that the increased ice
will be coincident with global cooling.)
 
   Given the nature of some of the other anecdotal evidence, I'd hesitate
to accept the statement that snow cover is increasing in the Canadian
arctic without more background information.

    Many of the earlier global climate models did keep clouds fixed.
Newer models include "interactive cloud" which can vary as the climate
changes. These models still indicate 2-4C warming for doubled CO2. Clouds
do represent an uncertainty in our current understanding of climate, but
"uncertainty" != "will reduce the warming".

>He points out that the major source of funds for scientists supporting the 
>warming theory has been the US Dept of energy, who represents the nuclear 
>power and nuclear weapons industry.  These industries have a vested interest in
>promoting nuclear power and so would support the notion that fossil fuels 
>cause increased atmospheric CO2 and lead to gobal warming.

   Gee. And I thought it was the oil and coal companies that had a vested
interest in *disproving* the CO2-induced warming scenario, so that they
can continue to sell large quantities of gas to motorists. This is much
better for them than releasing their "miracle-100mpg-carburetors" that
they are keeping under wraps. :-) Conspiracy theories and $1.00 will buy
you a cup of coffee. (Please no flames about coffee prices. I don't drink
the stuff.)


>Finally, the way out, Watt claims, is to cease the destruction of forests, and 
>to revitalize existing ones in order to stem the rise in atmospheric CO2.
 
   There are other reasons to limit deforestation, but doing so *won't*
stop the increase in CO2. (Note that deforestation only leads to increased
atmospheric CO2 if the carbon in the wood is oxidized. Burn it or let it
rot.)


>I'd be interested in reading your comments about this.

   You're welcome.



Dave Halliwell
Department of Geography
University of Alberta
Edmonton, Alberta