Dear Eric,
I had unsubscribed from this forum because of a lack of polite
discourse. You at least show a measured response - in possibly the
last update I get - which I appreciate.
I did begin by quoting the IPCC to the effect that past climates do
not provide analogues for the near future. That should be the take
away point.
Just another quick point - I am not sure there is an obvious problem
with the UAH temp record. It is showing about a 0.13 degree C rise in
recent decades similar to the RSS, GISSTEMP and CRUTEM records. Much
of a muchness I would have thought. I am not sure that the
temperature rise in recent decades is all CO2. I have discussed ENSO
dynamics and the relation to cloud cover. On cloud cover and albedo -
see for instance some of the bibliography at the Big Bear Solar
Observatory Project Earthshine site. Kevin Trenberth et al - not a
notorious 'denialist' - discuss in a recent paper some of effects of
cloud change on Earth’s recent radiation balance. Amy Clement and
colleagues suggest that cloud decline between the mid 1970’s and the
end of last century was a global warming feedback but both ISCCP and
Project Earthshine records suggest more cloud since 1999 – about 2.7 W/
m2 less shortwave radiation at the surface since 1999. The direction
of causation is very obscure.
It is agreed generally that CO2 and methane lag temp. This makes
sense biologically and chemically. Warmer water holds less CO2 more
biological activity increases the mass of CO2 being cycled through
organisms and the atmosphere as well as biologically mediated (always)
methogenisis. The reverse is true also. It obviously a positive
biological feedback (in both directions) in a complex system. Peatland
has also been suggested as a vegetative succession positive feedback
in both directions.
So other effects are important in both the initiation and recovery
from glaciation. For instance - collapse of the west Antarctic ice
shelf is implicated in the recovery from the last interglacial.
Cessation of deep water formation in the Artic is implicated in the
initiation of ice ages. Snow accumulates, ice melts and THC slows and
one or other of the poles cools enough to initiate rapid growth in ice
cover. Snow and ice cover is obviously an important factor in Earth
albedo - and this changes signs. Cloud cover and snow accumulation
change significantly - perhaps largely in response to ENSO - on
decadal and longer timescales. Airborne dust may also be important in
cloud dynamics but this also seems to lag temp changes.
It is all speculative but something in the past 1.88 million years
results in recurrent glaciation. It may be a combination of orbital
changes, tectonic uplift and drift and dynamic internal climate
processes. The fall into glaciation is interesting. What could cause
carbon dioxide and methane to decline other than declining temps? The
decline in temperature in the early stages of a glacial also proceeds
the fall in CO2 and methane. This is a point that Roy Spencer made
and it suggests that other factors are involved. Something that would
seem obvious to me. Snow and ice are the essence of glacial
periods.
I had mentioned elsewhere in this forum the Younger Dryas. It seems
from Irish bogs that Europe cooled to near glacial conditions over a
few months and stayed that way for 1300 years. In this case you would
have to think that CO2 was probably not amongst the major
drivers.
There are number of interesting puzzles in climate. One of these
involves changes in UV, ozone warming and cooling and ice cloud
feedbacks. Warming and cooling in the stratosphere above the
Antarctic feeds more or less downwelling air into the polar vortex.
It influences stormtracks in the SH but also ocean surface (Ekmann)
flow up the Antarctic Peninsula to the west coast of South America.
This in turn influences the thermal evolution of ENSO and therefore
global cloud cover, snow accumlulation and precipitation. Solar UV
changes a lot more than radiation in the visible or IR bands. There is
a lot more to understand about climate.
As I say - I think that abrupt climate change is the reality rather
than global warming necessarily.
‘Researchers first became intrigued by abrupt climate change when they
discovered striking evidence of large, abrupt, and widespread changes
preserved in paleoclimatic archives. Interpretation of such proxy
records of climate—for example, using tree rings to judge occurrence
of droughts or gas bubbles in ice cores to study the atmosphere at the
time the bubbles were trapped—is a well-established science that has
grown much in recent years. This chapter summarizes techniques for
studying paleoclimate and highlights research results. The chapter
concludes with examples of modern climate change and techniques for
observing it. Modern climate records include abrupt changes that are
smaller and briefer than in paleoclimate records but show that abrupt
climate change is not restricted to the distant past.’
Abrupt Climate Change: Inevitable Surprises – p19
Committee on Abrupt Climate Change
Ocean Studies Board
Polar Research Board
Board on Atmospheric Sciences and Climate
Division on Earth and Life Studies
National Research Council
I linked to Roy Spencer because I agree with the conclusion about the
speculative nature and partial treatment of factors in abrupt ice age
climate transitions - and not because he is a so called 'denialist'.
I don't know if it is even a useful classification. What is being
denied? That CO2 is a greenhouse gas? I don't think so. That we will
be sent to the saltmines for expressing an opinion? IMHO (I had to
google it) - I think they can go get rooted as we say in Oz.
I have quoted elsewhere in this forum Wally Broecker on climate being
an unpredictable and capricious angry beast which we shouldn't poke
with a stick. But I think that dire predictions of global warming are
an 'all in' ploy that risks complete loss of the policy debate and
potentially does a great disservice to the cause. Indeed, I think it
has already happened.
Cheers
Robert
On Jan 19, 1:09 pm, Eric Swanson <[email protected]> wrote:
> 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-...
>
> > speculative best describes Alistairs ponderings
>
>
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