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 Posted: Thu Nov 05, 2009 9:06 am |
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GREENHOUSE CONFUSION RESOLVED
by Stephen Wilde
Fellow of the Royal Meteorological Society since 1968.
article image at (no spam)
http://climaterealists.com/index.php?id=1562
GREENHOUSE CONFUSION RESOLVED -
By Stephen Wilde
Fellow of the Royal Meteorological Society since 1968
A short while ago I published an article on this site attempting to
explain why the so called atmospheric greenhouse effect was
insignificant as a planetary heat store in comparison to the oceans.
The Hot Water Bottle Effect
I received interesting comments from AGW proponents and sceptics alike
which showed an astonishing range of differing interpretations and
understandings of the greenhouse effect none of which bore much
relation to the actuality.
Perhaps those who made no comment were free of such confusion but
somehow I doubt it.
The fact is that unless one can properly appreciate the nature and
scale of the effect that an atmosphere has on planetary surface
temperature then the significance of my article and indeed the entire
underlying debate is impossible to assess meaningfully.
This article will attempt to resolve that confusion.
1) Planets with atmospheres are seen to be warmer at the surface than
they otherwise would be. The Earth and the Moon are on average
equidistant from the sun but have very different surface temperatures.
Mars and Venus follow the same principle in that their huge surface
temperature differences are caused primarily by their different
atmospheres and not by their different distances from the sun. The
atmosphere of Venus is very dense so the surface is much hotter than
it otherwise would be. That of Mars is very thin so the surface is
only a little hotter than it otherwise would be. The Earth is a
special case because I would argue that the oceans should be regarded
as a form of atmosphere in much the same way as the air because both
air and oceans have heat storing properties. In effect Earth’s
‘atmosphere’ is in two parts for heat storing purposes and water is
the primary player in both components.
2) The only significant heat source for the purpose of this article is
solar energy. When solar energy reaches the Earth it is in the form of
radiant energy which travels at the speed of light. When that energy
hits molecules in the atmosphere the energy is absorbed by the
molecules in the atmosphere which then vibrate more quickly. The heat
contained in a molecule is expressed by the speed of vibration. First
the molecules in the atmosphere warm up followed by those on the
surface whether it be land or sea. Part of the total radiant energy is
absorbed by the atmosphere, part by the oceans and part by the land.
3) It is important to distinguish between the effect of solar energy
falling into the air, onto the land and that falling onto and into the
sea. In the case of land the energy hardly penetrates the ground at
all hence the consistent coolness of caves worldwide. In the case of
oceans the energy does penetrate the surface layers and is often
carried away for eventual release elsewhere, depending on the ocean
currents.
4) Once the radiant energy has arrived in the air, on the land and in
the oceans the question arises as to how it then exits Earth back out
to space. According to satellite observations there is always a net
balance between radiant energy coming in and radiant energy going out.
That must be so because the Earth quickly arrives at a thermal
equilibrium by virtue of the fact that radiant energy coming in and
radiant energy going out both travel at the speed of light.
5) A warming effect in the atmosphere arises because between coming in
and going out the radiant energy is ‘processed’ by the molecules in
the atmosphere into heat energy and then back again, often many times
for a single parcel of radiant energy, the number of times being
directly proportionate to the density of the atmosphere. It is the
density, not the composition which gives more or less opportunities
for such collisions between radiant energy and molecules whilst the
incoming and outgoing radiant energy is negotiating the atmosphere.
When an atmospheric molecule absorbs radiant energy it vibrates faster
thereby becoming warmer. It is momentarily warmer than the surrounding
molecules so it releases the radiant energy again almost immediately.
The speed of release is again dictated by overall atmospheric density
because greater density renders it less likely that the neighbouring
molecules are cool enough for a release of radiant energy to occur.
However the time scales remain miniscule on the level of an individual
molecule BUT on a planetary scale they become highly significant and
build up to a measurable delay between arrival of solar radiant energy
and it’s release to space.
It is that interruption in the flow of radiant energy in and out which
gives rise to a warming effect. The warming effect is a single
persistent phenomenon linked to the density of the atmosphere and not
the composition. Once the appropriate planetary temperature increase
has been set by the delay in transmission through the atmosphere then
equilibrium is restored between radiant energy in and radiant energy
out.
There is much confusion over the issue of ‘re-radiation.’ An
environmental activist told me that re-radiation occurs repeatedly
from greenhouse gas molecules with a consequent runaway warming
effect. If that were so then only a handful of greenhouse gas
molecules at the creation of the Earth would have destroyed it by now.
I think that misconception is at the heart of the public’s AGW fears
even though some scientists know better.
There is a kernel of truth in that when a molecule in the atmosphere
re -radiates the radiant energy previously absorbed then it does so in
all directions i.e. half of it goes back down towards the surface
again. However one cannot create heat or energy from nothing so there
is no net heat gain merely a delay until the part sent down is
radiated back up again and has another attempt at leaving the planet.
Even if it hits another molecule on the way up then that second
molecule sends only half of the initial half back down again so
repeated re- radiations decline in size geometrically.
The fundamental point is that the total atmospheric warming arising as
a result of the density of the atmosphere is a once and for all
netting out of all the truly astronomic number of radiant energy/
molecule encounters throughout the atmosphere. The only things that
can change that resultant point of temperature equilibrium are changes
in solar radiance coming in or changes in overall atmospheric density
which affect the radiant energy going out. In the real world the most
obvious and most common reason for a change in atmospheric density
occurs naturally when the oceans are in warming mode and solar
irradiation is high as during the period 1975 to 1998. The increased
warmth allows the atmosphere to hold more water vapour so that total
atmospheric density increases and the atmospheric greenhouse effect
strengthens. This effect is far greater than any CO2 effect. When the
atmosphere cools again water vapour content declines and the
atmospheric greenhouse effect weakens. CO2 and other trace gases are
far too small a proportion of the atmosphere to have any significant
effect in comparison to the water vapour effect. Even the water vapour
effect has never provoked any tipping point in the face of the primary
solar/oceanic driver so CO2 could never do so.
6) Nevertheless a legitimate question is as to whether an increase in
one or more allegedly potent greenhouse gases such as CO2 or methane
can cause a significant difference on a planetary scale.
The fact is that every molecule in an atmosphere contributes to the
greenhouse effect of the entire atmosphere. Some constituents such as
CO2 and methane have a stronger effect than average but their
quantities are so small that even large proportionate increases have
no significant effect on overall atmospheric DENSITY. If as I suggest
one includes the much denser oceans as a component of atmosphere then
increases in CO2 become irredeemably trivial in terms of their power
to alter overall density and thus the global heat retaining process.
Furthermore each constituent of an atmosphere reacts slightly
differently to incoming radiant energy. As a result each constituent
can only operate as a greenhouse gas with certain limited bandwidths
of incoming energy. If there is not enough energy of the right
bandwidth coming in then the greenhouse effect of a particular
constituent stops. That is why it is often said that the greenhouse
effect of CO2 declines logarithmically as the available bandwidth gets
used up. Some say that at the current level of 380 parts per million
we are close to saturation as regards more warming effect from extra
CO2.
That mechanism is quite separate from the matter of density which
overrides the matter of absorption characteristics anyway. The
atmosphere of Venus is mostly CO2 but the atmospheric heat arises as a
result of the density of the Venusian atmosphere (apparently more than
60 times that of the Earth) not just the absorption characteristics of
CO2. On Earth the proportion of CO2 is so small that it cannot affect
overall atmospheric density even if it increases by many multiples of
the current level.
Much of the warming feared by the alarmists relies upon a positive
feedback involving increased water vapour exaggerating any CO2 warming
effect. However that process is unconvincing to my mind because it
ignores the water vapour reducing processes of evaporation,
convection, condensation and rainfall which are all substantial, but
so far unquantified, moderating effects as far as atmospheric warming
from water vapour is concerned. In the past no tipping point has ever
been known to have occurred as a result of runaway warming from extra
water vapour so how have we been persuaded to fear it so much?
I see no scientific grounds for a speculation that increasing CO2 will
have a significant effect on the temperature of Earth when we have the
far more important, long lasting and frankly overwhelming Hot Water
Bottle Effect to consider and here I will go on briefly to link the
contents of this article to my previous one.
7) When land receives radiant energy the surface layer of molecules
becomes warm quickly but penetration is insignificant. The heat is
quickly radiated back into the atmosphere and joins the rest of the
radiant energy in the atmosphere in the process of release to space.
Despite any atmospheric greenhouse effect land gets cold very quickly
at night and in winter. This suggests that if the planet were entirely
land then the speed of heat loss to space would soon make Earth more
like Mars or the Moon than Venus. Without the humidity from the oceans
there would never be enough density from all the other gases in the
atmosphere to achieve a density that could save us from rapid
freezing.
8) Now the important bit.
When solar energy reaches the ocean it penetrates the surface. Some is
reflected into the atmosphere but compared to land, very little. Ocean
currents tuck it away for use another day. Huge amounts of past solar
energy are locked in the oceans and only released to the atmosphere
when solar driven oscillations deign to release it to us.
The average near surface temperature of Earth’s atmosphere is much the
same as the average surface temperature of the oceans. That will
always be so for as long as we have big enough oceans. Consequently to
be able to affect us any extra atmospheric warming effect of CO2 would
need to be able to warm up the oceans in order to make any difference
to global atmospheric temperature. Due to the huge volume of sea water
and the density differentials between air and ocean that would be
impossible or would require such huge amounts of atmospheric heating
and such huge lengths of time that for practical purposes it should be
ignored. To be convinced of that one only needs to consider the
impracticality of heating the air in a bathroom in order to raise cold
tap water to the temperature of a warm bath. It just doesn’t happen.
Where air and water are involved the air temperature is always
dictated by the water and never vice versa. Stored solar energy built
up in the oceans over past millennia dictates the temperature of the
oceans which then dictate the temperature of the atmosphere. The
atmospheric greenhouse effect is an irrelevance in the face of The Hot
Water Bottle Effect. Any extra warmth generated in the atmosphere by
CO2 or any other trace gas will quickly be neutralised by the hugely
greater effect of the oceans in so far as it has not already been
dispersed by increased radiation to space, evaporation, convection,
condensation and rainfall.
Warming activists have tried to deal with this problem for their
theory by asserting that over time a warmer atmosphere will have a
warming effect on the oceans. However they suggest merely a couple of
decades. They are ignoring the issue of scale and erroneously believe
that the greenhouse effect and not the oceans sets the global
atmospheric temperature. Before any measurable warming effect on the
oceans can occur the following problems must be overcome:
i) CO2 and other trace gases are too small a proportion of the
atmosphere to make a significant difference to overall atmospheric
density even if their volumes were to be multiplied many times over.
This problem for warmists is greatly enhanced if one considers the
much more dense oceans as part of the planetary atmosphere for heat
storage purposes.
ii) The respective absorption bands for each trace gas will be
exhausted long before the volumes of those gases in the atmosphere
become big enough to make a measurable difference to the overall
density of the atmosphere and the size of the greenhouse effect which
is density dependent.
iii) Any increase in temperature differential between atmosphere and
space will increase the outward flow of radiant energy and reduce the
overall temperature change if any
iv) Any increase in temperature differential between the surface of
the Earth and the top of the atmosphere will increase evaporation,
convection, cloud formation and rainfall and so further enhance the
flow of radiant energy to space thereby further reducing any
temperature change
v) After all that, only a residual greenhouse warming effect (and it
may be zero) will be left to have any effect on the oceans. In the
unlikely event that it is still large enough to have any effect at all
it may well take millennia for any warming of the oceans to become
apparent by which time it would be dwarfed by natural changes anyway.
Without a warming of the oceans we cannot see a warming of the
atmosphere, both are fixed in lockstep with the oceans as the leader.
Summary
The Greenhouse Effect is only a tiny part of the global temperature
control mechanism. In addition there is The Hot Water Bottle Effect
whereby the oceans release stored heat intermittently at variable
rates depending on the average state of the various oceanic
oscillations at any particular time. The current assumption that the
oceanic oscillations are ‘just’ a mechanism for redistributing heat
already available to the atmosphere must be wrong. The oceanic heat
store should be regarded as an additional heat source that adds or
subtracts the effect of earlier solar irradiance (or lack of it) to or
from the present day effect of current solar irradiance.
The total heat store available in the oceans is so large that it is
capable of rendering changes in any Greenhouse Effect an irrelevance
for all practical purposes.
Oceanic oscillations are sufficient to cancel out or enhance the
effects of natural variations in solar irradiance or other forms of
solar input to the heat budget of the Earth for variable periods of
time. A range of a mere 4 Watts per square metre or less in Total
Solar Irradiance is sufficient to explain changes in Earth’s
atmospheric temperature for the past 400 years. Outside that narrow
band of apparent solar normality we would have more to worry about
than any Greenhouse Effect.
The global temperature switches from cooling to warming mode
frequently as a result of the ever changing interplay between
variations in solar influence and intermittent heat flows from the
oceanic Hot Water Bottle. The mechanism by which the oceanic effect is
transferred to the atmosphere involves evaporation, convection, clouds
and rainfall the significance of which has to date been almost
entirely ignored due to the absence of any relevant figures.
The atmospheric Greenhouse Effect merely sets a theoretical background
atmospheric temperature level that is continually overridden as a
result of the size of the constant interlinked changes in both the
solar and oceanic heat inputs. It is wholly swamped by the far more
powerful oceanic Hot Water Bottle Effect.
The atmospheric greenhouse effect is a flea on the back of an oceanic
elephant and the influence of CO2 but a microbe on the back of the
flea and the influence of anthropogenic CO2 but a molecule on the back
of the microbe.
Copyright © 2008 Stephen Wilde |
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