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Hi Bruce & All, Nov 23, 2006
Thanks for the comments and I hope more will follow.
Perhaps you are able to address somewhat my questions re recent
departures from the astronomical model [pasted below in case you don't
still have a copy]. Also, having first heard of the hockey stick model
via Naturens today, some time after it apparently became defunct, I am
wondering what sequence of climatic change since 1000 AD is now
considered to be valid ? Does conventional wisdom now say that the
"Little Ice Age" didn't happen ?
Yours truly, Dave Webster, Kentville
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Since this 1975 article was written (I think) these or similar
fluctuations in temperature have been explained to a major extent by
periodic astronomical fluctuations (orbital distance, axis tilt and (?)
sun output). Does anyone know how temperature fluctuations of the last
several centuries compare with fluctuations that would be expected on
the basis of this astronomical model ? Is the current positive residual
exceptional as compared with residuals over the last 15,000 years ? Was
this astronomical model constructed from independently established
astronomical constants or were the astronomical fluctuations derived by
being fitted to the temperature curves ?
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Bruce Stevens wrote:
> All:
>
>
>
> As a student of climate change, paleoclimate and climate modelling, I
> feel I should chime in after reading posts from Dave, Steve and Chris.
> I would like to present the following points:
>
>
>
> 1) The term "global warming" is too specific a term to use when
> discussing anthropogenic (man-made) influence on the global climate
> system. "Climate change" is a more appropriate title as it encompasses
> the entire array of issues which includes global warming, sea-level
> increase, polar ice melt, and an increase in the severity and
> frequency of atmospheric events to name a few.
>
>
>
> 2) Peer-reviewed journals are currently the best way to contribute to
> any field of science. When an article is submitted to a journal, the
> editor generally makes a summary decision about whether or not the
> article is of appropriate scope and merit for their readers, then
> passes it to 2 or more reviewers or rejects it outright. These
> reviewers are generally anonymous, and have enormous impact on the
> success of the article. If an article survives to be published, it has
> undoubtedly gone through several revisions.
>
>
>
> 3) Top tier peer-reviewed journals are generally not available for
> free access. This makes it difficult for the public to assimilate
> first-hand knowledge from these journals. Instead, popular media
> outlets such as television, books and magazines present distilled
> versions of these findings. Very often these come with spin.
>
>
>
> 4) The pereceived battle between the media and the scientific
> community has happened on countless occasions. If there is consensus
> among scientists (never unanimity!) over a certain issue that goes
> against some political status quo, it is sufficient to create the
> illusion of debate to cast doubt on the facts. A perfect example of
> this is the acid rain "debate". John Smol is a
> Canadian paleolymnologist (a scientist who uses sediment deposits from
> lake bottoms to infer past climatic events). His repeated findings
> showed that pH levels in lakes were increasing in acidity, and this
> acidity was due to precipitation that contained sulfur compounds
> produced by industry. In one study, Smol showed that of all the lakes
> surveyed (in Vermont of New Hampshire I believe) only one lake did not
> show elevated and increasing concentrations of acidity. A media story
> was created illustrating that there was no acid rain problem, because
> John Smol and his team found no increase in pH in that one lake. The
> Reagan administration employed media tactics that very much resemble
> the pattern of denial seen in climate change.
>
>
>
> 5) The "hockey stick" that brought Michael Mann to the forefront of
> climate change is a multiproxy reconstruction of past temperature [1].
> Since there are hardly any direct, instrumental meterological data
> before 1900, indirect means of inferring past climate, or proxy
> data, must be used. There are many types of proxy record, including
> ice cores, boreholes, tree-rings and lake sediments to name a few. The
> hockey stick gets its name from its gradual cooling from year 1000 to
> 1700 (the "shaft"), and abrupt warming from 1700 to 2000 (the
> "blade"). This multiproxy reconstruction has been all but completely
> discredited, but not by those who deny climate change. There were
> fundamental problems with their reconstruction method that rendered
> their results unreliable.
>
>
>
> [1] Mann, M. E., R. S. Bradley and M. K. Hughes (1999), Northern
> Hemisphere temperatures during the last millennium: inferrences,
> uncertainties, and limitations, Geophysical Research Letters, 26 ,
> 759-762.
>
>
>
> 6) I urge caution at taking anything said at www.realclimate.org
> <http://www.realclimate.org> at face value. This is a completely
> unmoderated forum of climate change discussion in which anybody can
> state their opinions as gospel. Many of the top scientists worldwide
> (as well as non-scientists!) involved in various aspects of climate
> change frequent this forum and express opinions that may be
> unsubstantiated and unproven.
>
>
>
> 7) There IS debate within the scientific community about climate
> change. However, this debate is almost entirely restricted to how
> climate change is manifesting itself, what causes climate change, to
> what degree climate will change, where change will occur first, etc.
> The problem with viewing climate change as a "future" problem that
> "may" cause problems down the road, is that we may already have
> started down the road. One of the most important tasks is to establish
> a precedent for historical levels of temperature and greenhouse gas
> concentrations so we have a baseline for what is normal. This
> understanding is far from complete.
>
>
>
> 8) If anyone is interested in reading about bridging the gap between
> scientific investigation of climate change and actually implementing
> policy, the Intergovernmental Panel on Climate Change (IPCC) was
> created to address this issue. Their information is available online
> at http://www.ipcc.ch/ .
>
>
>
> I hope this didn't sound too much like a rant. It is important that we
> all form our own ideas about climate change from legitimate sources.
>
>
>
> Bruce Stevens
>
>
>
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