"Roger Coppock"  wrote in message
news:1192120210.545576.26760@o80g2000hse.googlegroups.com...
> On Oct 11, 6:12 am, Fran  wrote:
> [ . . .]
> > The deniers used to make a song and dance about water vapour
being a
> > greenhouse gas, but now that elevated water vapour is also
being cited
> > as a corollary and possitve feedback components in AGW, I
wonder what
> > they'll say.
>
> There's nothing new about it, Fran.
> The water vapor feedback mechanism
> was described in the 19th century.
>

Sorry comrade Popcock, there is no positive feedback mechanism.
Nothing new about your lies either.
No matter how much you repeat your lies, you can't fool the
rational amongst us, only the blind sheep!


http://www.junkscience.com/Greenhouse/index.html



While it is intuitively reasonable that the most prolific and
important greenhouse gas could act as a magnifier there is no
evidence that it does. In fact water vapor is self limiting
because it precipitates out as rain and snow and its effect also
varies as cloud, with more bright low cloud acting as a cooling
effect.



If positive feedback from water vapor was really a dominant
climatic effect then it should be very easy to find, firstly by
looking at an unusual event.



Depicted in the adjacent graphic is Earth's response to the
1997/98 El Niño event. These are anomalies and several of the
datasets produce anomalies with reference to different base
periods but that is of no particular interest here -- only the
synchronous warming and subsequent cooling depicted in the
atmospheric series (UAH and RSS satellite, HadAT radiosonde
balloon) and near-surface land and sea surface datasets (NCDC,
GISS and HadCRUT3) of ~0.9 and ~0.5 K respectively.



This warming and subsequent cooling is in addition to the normal
seasonal global variation (plotted as variation from the expected
monthly mean temperature in each case) and thus provides
precisely the situation in which we are interested.



Since the world cooled almost as abruptly as it warmed we can
only assume no positive feedback mechanism was invoked and thus
Earth is not perilously perched upon some critical temperature
threshold beyond which new physics takes over and runaway
enhanced greenhouse warming becomes a self-perpetuating
nightmare. That test for a multiplier effect surely failed.



Secondly, we know there's an annual warming, quite a severe one,
in fact and that's the seasonal heating of the hemispheres. Since
the Northern Hemisphere contains the greatest proportion of
landmass and land heats more than oceans the Northern Hemisphere
summer season causes significant increase in the global mean
temperature:



This is as reported by the National Climatic Data Center, the
means 1961-1990 (commonly used as a reference period) work out
the same globally but do differ slightly on a regional basis:



Combined Mean Surface Temp.

 JAN

 FEB

 MAR

 APR

 MAY

 JUN

 JUL

 AUG

 SEP

 OCT

 NOV

 DEC

 Annual



1880 to 2004 (°C)

 12.0

 12.1

 12.7

 13.7

 14.8

 15.5

 15.8

 15.6

 15.0

 14.0

 12.9

 12.2

 13.9



1880 to 2004 (°F)

 53.6

 53.9

 54.9

 56.7

 58.6

 59.9

 60.4

 60.1

 59.0

 57.1

 55.2

 54.0

 57.0





There is always the possibility this temperature effect is a
seasonal artifact of near-surface measurement so we should check
atmospheric measures. UAH MSU data tells us the lower troposphere
global mean varies somewhat less than near-surface temperature
with monthly averages rising and falling approximately 2.3 °C
through the year (there's no significant difference between UAH
and RSS lower tropospheric data).



The Northern Hemisphere (where most people live) cycles an
impressive 9.76 °C through the monthly averages as far as lower
tropospheric measures are concerned and a whopping 11.6 °C
according to land-based near-surface measures.



With global and hemispheric variation to this extent each and
every year it is somewhat difficult to view an estimated change
of 0.6 ± 0.2 °C over 120 years as being dangerous but it does
seem to be the cause of considerable angst.



Nonetheless, the global troposphere warms at least 2 K from
January to July every year without triggering any
self-perpetuating water vapor-driven positive feedback. Surely a
positive feedback should manifest under the influence of a 10 K
hemispheric warming and this should be sufficient to overwhelm
lack of insolation in the Southern Hemisphere winter inducing
global warming and yet this doesn't happen. So much for 'positive
feedback.


-- 

Regards

Bonzo

"There is now no doubt that the UN's International Panel on
Climate
Change (IPCC), has a history of sacrificing science for political
agendas. This conclusion is based upon the IPCC being found
revising
the writings of contributing scientists (without their consent),
accepting as valid the findings of the "hockeystick" graph, and
completely unreceptive to valid scientific criticism. Michaels
also
documents a number of other errors and misleading statements by
the
IPCC. This is the stuff of political agendas, not of sound
science." Michael R. Fox Ph.D