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 | | From: | Edward Green | | Subject: | Re: Global dimming masking greenhouse effect | | Date: | 18 Jan 2005 01:35:04 -0800 |
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 | Franz Heymann wrote:
> wrote in message
> news:csc2g7$80j$1@mail.specsol.com...
> > The major factor in evaporation is the local humidity.
>
> No. Roderick did the calculation. You did not. You are therefore
> not empowered to waffle about it.
> An individual photon absorbed by an individual molecule might well
> give it sufficient kinetic energy to allow it to escape from the
> surface before thermal equilibrium conditions under which evaporation
> in the dark has been re-established
Oh. That's what Roderick showed. I thought later you saying he had
done work on the spontaneous combustion of wood. Sorry.
As for the former point, Jim Pennino can, and does, continue to waffle
by in effect allowing that this is a factor, but not the major factor.
The language "major factor" or "the major factor" is vague enough so it
may be that no truth value can be assigned to this claim either way,
but "totally swamped" sounds more hopeful, sugguesting we wonder
whether variation in solar irradiance is a significant factor in
evaporation rates compared to variation in temperature and humidity.
There are cooperative effects: in still air extra molecules kicked into
the layer of humid air directly over the water may be more likely to be
immediately reabsorbed rather than diffusing away, whereas with
efficient wind mixing any process which enhances the rate of transfer
out of the surface will directly add to transfer rate out of the fluid.
I see no reason a priori why switching on sunlight may not
signficiantly increase evaporation: a possibility not to be ruled out
by the persistance of evaporation in the dark. Of course water can
evaporate in the dark! Jeez. Straw dog city in this thread: lack of
combustion of wood in 45C kiln rules out spontaneous combustion of
large sample of untreated whole trees and deadwood cooked in sun at
same air temperature (so we are told), evaporation of water in the dark
rules out higher rate of evaporation given illumination (so we are
asked to believe).
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| | From: | habshi | | Subject: | Re: Global dimming masking greenhouse effect | | Date: | Tue, 18 Jan 2005 14:59:55 GMT |
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| The program said that the rate of pan water evaporation has fallen in the last 30 odd years
, a surprise since temps have gone up , and the reason is less sunny days due to global dimming.
Also the cloud belts are shifting south , increasing the Sahara and in the future the monsoons may
shift south as well
He3 on our moon can be mined for fusion reactors
excerpts
bbc
NARRATOR: So Liepert and Stanhill's work was widely dismissed. But Global Dimming was not the only
phenomenon that didn't seem to fit with Global Warming. In Australia two more biologists, Michael
Roderick and Graham Farquhar were intrigued by another paradoxical result - the world-wide decline
in something called the pan evaporation rate.
PROF GRAHAM FARQUHAR (Australian National University): It's called pan evaporation rate because it's
evaporation rate from a pan. Every day all over the world people come out in the morning and see how
much water they've got to add to a pan to bring it back to the level it was the same time the
morning before. It's that simple.
http://www.mindfully.org/Air/2002/Decreased-Pan-Evaporation1nov02.htm
The cause of decreased pan evaporation over the last 50 Years
RODERICK & FARQUHAR / Science v.298, 1nov02
Cooperative Research Centre for Greenhouse Accounting, Research School of Biological Sciences,
Institute of Advanced Studies, Australian National University, Canberra ACT 0200, Australia.
*To whom correspondence should be sent. E-mail: farquhar@rsbs.anu.edu.au
--------------------------------------------------------------------------------
It is now well established that the surface of Earth has, on average, warmed ~0.15°C decade-1 over
the past 50 years (1). One expected consequence of this warming is that the air near the surface
should be drier, which should result in an increase in the rate of evaporation from terrestrial open
water bodies. However, despite the observed increases in average temperature, observations from the
Northern Hemisphere show that the rate of evaporation from open pans of water has been steadily
decreasing over the past 50 years (2). This trend is general (3, 4) but not universal (5). The
contrast between expectation and observation is called the pan evaporation paradox. It is important
to understand why pan evaporation has decreased despite the increases in average temperature in
order to make more robust predictions about future changes in the hydrological cycle.
Two proposals for the decline in pan evaporation have been advanced: the first invokes changes in
the humidity regime over the pans (6), whereas the second invokes reductions in solar irradiance
resulting from more clouds and/or aerosols (5, 7) and is generally consistent with the independent
suggestion that increased pollution would weaken the hydrological cycle (8). The first proposal is
that pan evaporation has decreased because evaporation from the environment surrounding the pan has
increased (6). The explanation is that in water-limited
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| | From: | jimp at specsol-spam-sux.com | | Subject: | Re: Global dimming masking greenhouse effect | | Date: | Tue, 18 Jan 2005 15:35:02 +0000 (UTC) |
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| In sci.physics habshi wrote:
> He3 on our moon can be mined for fusion reactors
There is no such thing as a working, man made, fusion reactor.
--
Jim Pennino
Remove -spam-sux to reply.
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| | From: | Steve Schulin | | Subject: | Re: Global dimming masking greenhouse effect | | Date: | Tue, 18 Jan 2005 11:09:28 -0500 |
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| In article <41ed2457.1358253@news.clara.net>, habshi@anony.net (habshi)
wrote, in part:
> The program said that the rate of pan water evaporation has fallen in the
> last 30 odd years
> , a surprise since temps have gone up , and the reason is less sunny days due
> to global dimming...
After noting the dimming and pan evaporation findings, Dai et al [J.
Hydrometeorology 5:1117, Dec 2004] discuss how and why evaporation can
increase, and probably has increased, even though pan evapoation has
decreased:
"Pan evaporation (Epa) and actual evapotranspiration (E), however,
exhibit complementary rather than proportional behavior such that, for
regions with less than adequate moisture, E increases with potential
evapotranspiration (consistent with the Palmer model) but decreases with
Epa (Brutsaert and Parlange 1998). For example, over the Mississippi
River basin during the last 50 yr, increased cloudiness has decreased
solar heating and thus pan evaporation, while actual evapotranspiration
has increased because of increased precipitation and soil moisture
(Milly and Dunne 2001). A recent reassessment of the evaporation data
from the United States and the former Soviet Union (Golubev et al. 2001)
suggests increasing trends in actual evaporation over southern Russia
and most of the United States during the last 40 yr."
"Our PDSI results, which are based on atmospheric moisture supply and
demand near the surface, are consistent with increased evaporation under
greenhouse gas-induced warming, as predicted by comprehensive coupled
climate models (Cubasch et al. 2001; Dai et al. 2001). Global
temperature increases have become pronounced after the 1970s (Folland et
al. 2001) and have been attributed to human-induced climate changes
arising primarily from increased greenhosue gases (Mitchell et al. 2001;
Dai et al. 2001; Karl and Trenberth 2003). Higher temperatures increase
the water-holding capacity of the atmosphere and thus increase potential
evapotranspiration. Hence global warming not only raises temperatures,
but also enhances drying near the surface, as is captured by the PDSI.
The increased risk of drought duration, severity, and extent is a direct
consequence (Trenberth et al. 2003), and the theoretical expectations
are being realized, as shown here and discussed by Nicholls (2004)."
Here are the citations for the references in this section:
(Brutsaert and Parlange 1998) - Brutsaert, W., and M. B. Parlange, 1998:
Hydrologic cycle explains the evaporation paradox. Nature, 396, 30.
(Milly and Dunne 2001) - Milly, P. C. D., and K. A. Dunne, 2001: Trends
in evaporation and surface cooling in the Mississippi River basin.
Geophys. Res. Lett., 28, 12191222.
(Golubev et al. 2001) - Golubev, V. S., and Coauthors, 2001: Evaporation
changes over the contiguous United States and the former USSR: A
reassessment. Geophys. Res. Lett., 28, 26652668.
(Cubasch et al. 2001) - Cubasch, U., and Coauthors, 2001: Projections of
future climate change. Climate Change 2001: The Scientific Basis: The
IPCC WG1 Third Assessment Report, J. T. Houghton et al., Eds., Cambridge
University Press, 525582.
(Dai et al. 2001) - Dai, A. G., T. M. L. Wigley, B. A. Boville, J. T.
Kiehl, and L. E. Buja, 2001: Climates of the twentieth and twenty-first
centuries simulated by the NCAR Climate System Model. J. Climate, 14,
485519.
(Folland et al. 2001) - Folland, C. K., and Coauthors, 2001: Observed
climate variability and change. Climate Change 2001: The Scientific
Basis, J. T. Houghton et al., Eds., Cambridge University Press, 99181.
(Mitchell et al. 2001) - Mitchell, J. F. B., and Coauthors, 2001:
Detection of climate change and attribution of causes. Climate Change
2001: The Scientific Basis, J. T. Houghton et al., Eds., Cambridge
University Press, 695738.
(Karl and Trenberth 2003) - Karl, T. R. and K. E. Trenberth, 2003:
Modern global climate change. Science, 302, 17191723.
(Trenberth et al. 2003) - Trenberth, K. E., A. Dai, R. M. Rasmussen, and
D. B. Parsons, 2003: The changing character of precipitation. Bull.
Amer. Meteor. Soc., 84, 12051217.
(Nicholls 2004) - Nicholls, N., 2004: The changing nature of Australian
droughts. Climatic Change, 63, 323336.
--- END OF EXCERPT FROM DAI ET AL ---
The full citation for Dai et al (2004) is:
Aiguo Dai, Kevin E. Trenberth, and Taotao Qian. A Global Dataset of
Palmer Drought Severity Index for 18702002: Relationship with Soil
Moisture and Effects of Surface Warming. Journal of Hydrometeorology
5:1117-1130, December 2004.
The affiliation listed for all three authors is NCAR-Boulder.
I don't pretend to know the truth of the matter. I have long been
concerned with the results of any endeavor where Dr. Trenberth has a
guiding hand, but that doesn't mean he's wrong on this specific point.
[Have you guys and gals seen the stunning open letter released yesterday
which highlights Dr. Trenberth's recent mischaracterizations as seen by
a leader of the hurricane research community? It's available at
http://sciencepolicy.colorado.edu/prometheus/archives/science_policy_gene
ral/000318chris_landsea_leaves.html
and is discussed in sci.environment thread titled "IPCC process
'motivated by pre-conceived agendas' and 'scientifically unsound', sez
veteran IPCC author".]
Very truly,
Steve Schulin
http://www.nuclear.com
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| | From: | jimp at specsol-spam-sux.com | | Subject: | Re: Global dimming masking greenhouse effect | | Date: | Tue, 18 Jan 2005 16:28:42 +0000 (UTC) |
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| In sci.physics Edward Green wrote:
> Franz Heymann wrote:
> > wrote in message
> > news:csc2g7$80j$1@mail.specsol.com...
> > > The major factor in evaporation is the local humidity.
> >
> > No. Roderick did the calculation. You did not. You are therefore
> > not empowered to waffle about it.
> > An individual photon absorbed by an individual molecule might well
> > give it sufficient kinetic energy to allow it to escape from the
> > surface before thermal equilibrium conditions under which evaporation
> > in the dark has been re-established
> Oh. That's what Roderick showed. I thought later you saying he had
> done work on the spontaneous combustion of wood. Sorry.
> As for the former point, Jim Pennino can, and does, continue to waffle
> by in effect allowing that this is a factor, but not the major factor.
> The language "major factor" or "the major factor" is vague enough so it
> may be that no truth value can be assigned to this claim either way,
> but "totally swamped" sounds more hopeful, sugguesting we wonder
> whether variation in solar irradiance is a significant factor in
> evaporation rates compared to variation in temperature and humidity.
> There are cooperative effects: in still air extra molecules kicked into
> the layer of humid air directly over the water may be more likely to be
> immediately reabsorbed rather than diffusing away, whereas with
> efficient wind mixing any process which enhances the rate of transfer
> out of the surface will directly add to transfer rate out of the fluid.
> I see no reason a priori why switching on sunlight may not
> signficiantly increase evaporation: a possibility not to be ruled out
> by the persistance of evaporation in the dark. Of course water can
> evaporate in the dark! Jeez. Straw dog city in this thread: lack of
> combustion of wood in 45C kiln rules out spontaneous combustion of
> large sample of untreated whole trees and deadwood cooked in sun at
> same air temperature (so we are told), evaporation of water in the dark
> rules out higher rate of evaporation given illumination (so we are
> asked to believe).
Waffle?
OK, how's this?
The dominant factors in water evaporation is the local humidity and
water temperature.
Local humidty is a function of the air temperature and air movement which
replaces the local high humidity air with lower humidity air.
Any photon effects, other than heating, if they do in fact exist, are at
best trivial in comparison.
Get two clear, plastic, 2 liter soda bottles.
Cut the bottom off one such that you are left with a saucer.
Put equal amounts of water in both of them and put them side by side
in the noon day sun. Having an Englishman to watch is optional, but
noting the temperature of the water is mandatory.
Note the time required for each to go dry.
Unscrew your oven light and get the oven to the noon day temperature of
the water and repeat with the bottles in the oven.
For extra credit, repeat having the water at different initial temperatures.
--
Jim Pennino
Remove -spam-sux to reply.
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