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VK2AAB > AGW 02.12.09 12:03l 159 Lines 10506 Bytes #999 (0) @ WW
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Subj: wHATS TO TALK ABOUT @ COPENHAGEN
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Sent: 091202/0242Z @:VK2WI.#SYD.NSW.AUS.OC #:22790 [Sydney] $:22790_VK2WI
From: VK2AAB@VK2WI.#SYD.NSW.AUS.OC
To : AGW@WW
For a long time I had difficulty getting my head around global warming
being caused by humans. I can accept that there is some warming going on
up until about 1998 but even the *experts* cannot explain the drop in
temperature since then.
The scandal of the record fiddling and computer fiddling that went on at
the University of East Anglia has together with reports like below have
got
me wondering what they are going to talk about at Copenhagen.
Anyway have a read of this, it seems to make sense to me. The writer is a
pre-eminent climatologist I believe from reports I have seen and he has
set the cat omoung the pigeons.
73 Barry VK2AAB
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* NOVEMBER 30, 2009, 7:44 P.M. ET
The Climate Science Isn't Settled
Confident predictions of catastrophe are unwarranted.
By RICHARD S. LINDZEN
Is there a reason to be alarmed by the prospect of global warming? Consider
that the measurement used, the globally averaged temperature anomaly (GATA),
is always changing. Sometimes it goes up, sometimes down, and occasionallysuch
as for the last dozen years or soit does little that can be discerned.
Claims that climate change is accelerating are bizarre. There is general
support for the assertion that GATA has increased about 1.5 degrees Fahrenheit
since the middle of the 19th century. The quality of the data is poor, though,
and because the changes are small, it is easy to nudge such data a few tenths
of a degree in any direction. Several of the emails from the University of
East Anglia's Climate Research Unit (CRU) that have caused such a public
ruckus dealt with how to do this so as to maximize apparent changes.
The general support for warming is based not so much on the quality of the
data, but rather on the fact that there was a little ice age from about the
15th to the 19th century. Thus it is not surprising that temperatures should
increase as we emerged from this episode. At the same time that we were
emerging from the little ice age, the industrial era began, and this was
accompanied by increasing emissions of greenhouse gases such as CO2, methane
and nitrous oxide. CO2 is the most prominent of these, and it is again
generally accepted that it has increased by about 30%.
The defining characteristic of a greenhouse gas is that it is relatively
transparent to visible light from the sun but can absorb portions of thermal
radiation. In general, the earth balances the incoming solar radiation by
emitting thermal radiation, and the presence of greenhouse substances inhibits
cooling by thermal radiation and leads to some warming.
That said, the main greenhouse substances in the earth's atmosphere are water
vapor and high clouds. Let's refer to these as major greenhouse substances to
distinguish them from the anthropogenic minor substances. Even a doubling of
CO2 would only upset the original balance between incoming and outgoing
radiation by about 2%. This is essentially what is called "climate forcing."
There is general agreement on the above findings. At this point there is no
basis for alarm regardless of whether any relation between the observed
warming and the observed increase in minor greenhouse gases can be
established. Nevertheless, the most publicized claims of the U.N.'s
Intergovernmental Panel on Climate Change (IPCC) deal exactly with whether any
relation can be discerned. The failure of the attempts to link the two over
the past 20 years bespeaks the weakness of any case for concern.
The IPCC's Scientific Assessments generally consist of about 1,000 pages of
text. The Summary for Policymakers is 20 pages. It is, of course, impossible
to accurately summarize the 1,000-page assessment in just 20 pages; at the
very least, nuances and caveats have to be omitted. However, it has been my
experience that even the summary is hardly ever looked at. Rather, the whole
report tends to be characterized by a single iconic claim.
The main statement publicized after the last IPCC Scientific Assessment two
years ago was that it was likely that most of the warming since 1957 (a point
of anomalous cold) was due to man. This claim was based on the weak argument
that the current models used by the IPCC couldn't reproduce the warming from
about 1978 to 1998 without some forcing, and that the only forcing that they
could think of was man. Even this argument assumes that these models
adequately deal with natural internal variabilitythat is, such naturally
occurring cycles as El Nino, the Pacific Decadal Oscillation, the Atlantic
Multidecadal Oscillation, etc.
Yet articles from major modeling centers acknowledged that the failure of
these models to anticipate the absence of warming for the past dozen years was
due to the failure of these models to account for this natural internal
variability. Thus even the basis for the weak IPCC argument for anthropogenic
climate change was shown to be false.
Of course, none of the articles stressed this. Rather they emphasized that
according to models modified to account for the natural internal variability,
warming would resumein 2009, 2013 and 2030, respectively.
But even if the IPCC's iconic statement were correct, it still would not be
cause for alarm. After all we are still talking about tenths of a degree for
over 75% of the climate forcing associated with a doubling of CO2. The
potential (and only the potential) for alarm enters with the issue of climate
sensitivitywhich refers to the change that a doubling of CO2 will produce in
GATA. It is generally accepted that a doubling of CO2 will only produce a
change of about two degrees Fahrenheit if all else is held constant. This is
unlikely to be much to worry about.
Yet current climate models predict much higher sensitivities. They do so
because in these models, the main greenhouse substances (water vapor and
clouds) act to amplify anything that CO2 does. This is referred to as positive
feedback. But as the IPCC notes, clouds continue to be a source of major
uncertainty in current models. Since clouds and water vapor are intimately
related, the IPCC claim that they are more confident about water vapor is
quite implausible.
There is some evidence of a positive feedback effect for water vapor in cloud-
free regions, but a major part of any water-vapor feedback would have to
acknowledge that cloud-free areas are always changing, and this remains an
unknown. At this point, few scientists would argue that the science is
settled. In particular, the question remains as to whether water vapor and
clouds have positive or negative feedbacks.
The notion that the earth's climate is dominated by positive feedbacks is
intuitively implausible, and the history of the earth's climate offers some
guidance on this matter. About 2.5 billion years ago, the sun was 20%-30% less
bright than now (compare this with the 2% perturbation that a doubling of CO2
would produce), and yet the evidence is that the oceans were unfrozen at the
time, and that temperatures might not have been very different from today's.
Carl Sagan in the 1970s referred to this as the "Early Faint Sun Paradox."
For more than 30 years there have been attempts to resolve the paradox with
greenhouse gases. Some have suggested CO2but the amount needed was thousands
of times greater than present levels and incompatible with geological
evidence. Methane also proved unlikely. It turns out that increased thin
cirrus cloud coverage in the tropics readily resolves the paradoxbut only if
the clouds constitute a negative feedback. In present terms this means that
they would diminish rather than enhance the impact of CO2.
There are quite a few papers in the literature that also point to the absence
of positive feedbacks. The implied low sensitivity is entirely compatible with
the small warming that has been observed. So how do models with high
sensitivity manage to simulate the currently small response to a forcing that
is almost as large as a doubling of CO2? Jeff Kiehl notes in a 2007 article
from the National Center for Atmospheric Research, the models use another
quantity that the IPCC lists as poorly known (namely aerosols) to arbitrarily
cancel as much greenhouse warming as needed to match the data, with each model
choosing a different degree of cancellation according to the sensitivity of
that model.
What does all this have to do with climate catastrophe? The answer brings us
to a scandal that is, in my opinion, considerably greater than that implied in
the hacked emails from the Climate Research Unit (though perhaps not as bad as
their destruction of raw data): namely the suggestion that the very existence
of warming or of the greenhouse effect is tantamount to catastrophe. This is
the grossest of "bait and switch" scams. It is only such a scam that lends
importance to the machinations in the emails designed to nudge temperatures a
few tenths of a degree.
The notion that complex climate "catastrophes" are simply a matter of the
response of a single number, GATA, to a single forcing, CO2 (or solar forcing
for that matter), represents a gigantic step backward in the science of
climate. Many disasters associated with warming are simply normal occurrences
whose existence is falsely claimed to be evidence of warming. And all these
examples involve phenomena that are dependent on the confluence of many
factors.
Our perceptions of nature are similarly dragged back centuries so that the
normal occasional occurrences of open water in summer over the North Pole,
droughts, floods, hurricanes, sea-level variations, etc. are all taken as
omens, portending doom due to our sinful ways (as epitomized by our carbon
footprint). All of these phenomena depend on the confluence of multiple
factors as well.
Consider the following example. Suppose that I leave a box on the floor, and
my wife trips on it, falling against my son, who is carrying a carton of eggs,
which then fall and break. Our present approach to emissions would be
analogous to deciding that the best way to prevent the breakage of eggs would
be to outlaw leaving boxes on the floor. The chief difference is that in the
case of atmospheric CO2 and climate catastrophe, the chain of inference is
longer and less plausible than in my example.
Dr. Lindzen is professor of meteorology at the Massachusetts Institute of
Technology.
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