Robert,
Roy Spencer is one of the leaders in the denialist camp. His post, to
which you link, discusses only changes in CO2, which misses some other
rather obvious forces which would likely have been at work during the
glacial to interglacial changes.
The most obvious would be increases in methane gas, which is a strong
greenhouse gas.
http://en.wikipedia.org/wiki/File:Vostok_420ky_4curves_insolation.jpg
The second is changes in the plants covering the ground, as warmer
conditions and glacial melting allow the migration of trees from lower
to higher latitudes in the NH. Trees are much darker than snow and
ice, and increased coverage of trees over the land would tend to
absorb much a greater fraction of the incident solar energy. Trees,
especially conifers, can stand high enough above the ground such that
winter snows would fall below them, the result being much lower albedo
during Winter as well as during Summer. We are beginning to see
evidence of a morthward migration of trees in the NH, beginning with
shrubs in tundra areas and more trees replacing areas previously
dominated by low lying shrubs.
Of course, Dr. Spencer should be able to understand this effect.
However, his focus is not that of a scientist and he only presents one
part of the case, apparently hoping that his readers lack sufficient
understanding to see thru his deception. Dr. Spencer is a
Creationist, i.e., someone who chooses to accept the supernatural over
the findings of science. Spencer has never publicly explained the
method which he and John Christy used to create their TLT algorithm,
nor has he explained the obvious problem with the TLT over the
Antarctic. Spencer is not an unbiased scientist, IMHO...
E. S.
---
Robbo wrote:
> There is an essential difference between paleoclimatic co2 and todays
> co2 - in the paleo co2 concentrations were feedbacks.
>
> 'About the only thing that seems like a safe inference from the Vostok
> record is that temperature drives CO2 variations – even Hansen’s
> theory requires that much — but the view that CO2 then caused most of
> the temperature variations seems exceedingly speculative.'
>
> http://www.drroyspencer.com/2009/06/ice-ages-or-20th-century-warming-it-all-comes-down-to-causation/
>
> speculative best describes Alistairs ponderings
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