Too many variables like clouds to model future climate with precision
Guest essay by Rolf Westgard
A new United Nations report suggests an imminent danger from global warming. It states that without drastic action we may have “to develop the ability to suck greenhouse gases out of the atmosphere and store them underground”.
Minnesota already has millions of devices which do that. They are called trees and plants. They take in carbon dioxide(CO2), store the carbon(C), and return the oxygen(O) for us to breath.
It is actually not clear that our fossil fuel burning CO2 emissions are a serious global warming threat. There are many poorly understood ocean temperature variables which have a bigger impact on earth temperatures. These include the El Nino cycle and the Pacific Decade Oscillation. Confusion over how those work helps to cause the UN’s Intergovernmental Panel on Climate Change(IPCC) to regularly over estimate temperature warming trends.
Undeterred, federal and state legislatures are spending billions in response to guesses about our climate future. In addition to ocean cycles, there are several other poorly understood natural climate feedbacks. These act as natural thermostats, keeping the earth’s average temperature during inter glacial periods within a fairly narrow range. One of the most important is the action of clouds. Clouds are water vapor, a green house gas which warms us. Clouds reflect the sun’s light, cooling us. Clouds produce rain which removes CO2 from the atmosphere, etc.
A few lines from a popular song about clouds, “Both Sides Now”, pretty much sums up where we are with clouds and other climate variables:
“But now they only block the sun, they rain and snow on everyone.
So many things I would have done but clouds got in my way.
I’ve looked at clouds from both sides now, from up and down, and still somehow
It’s cloud illusions I recall.
I really don’t know clouds at all.”
At this point, no one knows how to accurately plug the impact of clouds or other climate variables into climate forecasting models.
(Westgard is guest faculty on energy subjects for the U of MN Lifelong Learning
program. He recently taught class #17016 “America’s Climate and Energy Future: the Next 25 Years”)
We know clouds here in the UK. They’re full of water. For a while.
(BTW, breath is a noun, breathe is the verb.)
More clouds, less energy into the oceans to drive the climate system.
Less clouds, more energy into the oceans to drive the climate system.
Solar variations appear to change global cloudiness by expanding and contracting the polar vortices thereby making the polar air masses change the extent to which they encroach across middle latitudes.
A quiet sun gives more equatorward / meridional jets and more clouds whereas an active sun gives more poleward / zonal jets and less clouds.
The mechanism appears to involve changes in stratosphere temperatures via changes in the net ozone creation / destruction balance which cause tropopause heights to rise or fall in higher latitudes relative to the heights above the equator.
The effect is to greatly amplify the scale of the initial solar variations by altering Earth’s albedo to affect energy amounts taken up by the oceans.
That mechanism is not proved yet but looking more likely as more data comes in.
Earth’s average cloud cover has changed by multiple percent over recent decades*, let alone compared to further back, and the impact of the corresponding albedo change is large in context (when, for perspective, all of global warming over the past century was merely <=~ 0.6 K or thus <=~ a 0.2% change in an average absolute temperature near 298 K).
* (As illustrated along with much else in http://img213.imagevenue.com/img.php?image=62356_expanded_overview3_122_1094lo.jpg )
Not only total cloud cover can have an influence on global climate – change in latitudinal distribution of clouds will have an influence, even at constant average cloud cover.
I have been informed by a doctor that they will not take there medication please take it for they no not what they a doing
Edim: Yes, and also variation in average cloud altitude.
I would have thought the radiation from a cloud depends on its height. The higher a cloud is the colder it is. The colder it is the less the energy it is radiating down. So if CO2 warms the atmosphere the clouds will warm, rise higher, get even colder and radiate back less energy.
NASA states clouds on average cause cooling.
There is no empirical data showing that CO2 causes temperature increases. In fact empirical data shows the exact opposite.
Clouds, well we do not understand them. 90% are caused by convection which disproves IPCC claims that latent heat is not an important sink for heat. Convective cloud is full of heat that is lost to space. That is where Trenberth,s missing heat is not the oceans.
“So if CO2 warms the atmosphere the clouds will warm, rise higher, get even colder and radiate back less energy.”
I would go further and say that if GHGs do have a net warming effect within an atmosphere then that simply causes more and larger parcels of air to rise higher, become colder and radiate less energy back to the surface.
Thus does a change in the vigour of convection apply an equal and opposite thermal response to any GHG effect.
The presence of water vapour low down and condensate higher up simply lubricates the process by converting KE near the surface to latent form and releasing it from the condensate higher up for radiation to space from that greater, colder height thereby accelerating radiative loss to help offset any net warming from GHGs that would have occurred in the absence of increased convection.
Note that increased convection does not need a warmer surface, merely warmer parcels of air within the vertical column.
However such an effect on convection from GHGs appears to pale into insignificance compared to the changes in convection caused by solar and oceanic variability.
The thermostatic response of global convection (and the clouds generated by it) is simply a global expression of the tropical thunderstorm hypothesis promulgated by Willis Eschenbach and others but carried to the logical conclusion in a global context.
The physical purpose of convection (lubricated by the water cycle) is in providing a mechanism whereby conduction and radiation within the Earth system are balanced as necessary to ensure the long term maintenance of radiative balance with space.
Clouds are NOT water vapour. Water vapour is an invisible gas. You can see clouds, so they are NOT water vapour.
In a field where there is so much misunderstanding already, I think it is important to avoid adding to the confusion by using loose, inaccurate or incorrect statements [where possible].
Fossil fuels already are trapped and stored underground carbon.. So why do they want to re-bury it along with our oxygen this time?
I have the answer.. TO TAKE MONEY OFF THE SCHMUCKS!
Seriously, anyone and everyone who proposes or implements this [snip].
[OTT – mod]
in line with the “underground” theme, what to make of this?
30 Jan: UK Independent: Jamie Merrill: Growing Underground: Michel Roux Jr reveals plans for subterranean farm in the depths of empty south London tunnels
Thanks to advancement in LED lighting technology, the plant-friendly temperature found 100ft below ground and some support from celebrity chef Michel Roux Jr, the damp Second World War air raid shelter is being transformed into the capital’s first underground farm.
The brainchild of foodie entrepreneurs Richard Ballard and Steven Dring, and their firm Zero Carbon Foods, the project, which covers 2.5 acres has already harvested some of its first crop of peashoots, micro radish and mustard redleaf.
Mr Roux, the two-star Michelin chef behind Le Gavroche and one of the stars of “Masterchef: The Professionals”, was an early fan and is now a director of the company…
The site has been leased by Zero Carbon Foods from its owner Transport for London for 25 years but trials have been running for 18 months already. Now the firm is expand production and is seeking £1m in crowd-sourced funding to bring its subterranean herbs, shoots, miniature vegetables, edible flowers and other delicacies to Britain’s high-end restaurants and food stores…
Ballard: “The advancements in LED lighting technology mean we can do this more affordably and efficiently and because we’re underground at a constant temperature we don’t need to add a lot of heat, which they often have to do in conventional farming.”….
According to the farm’s creators the project will be carbon neutral and use low-energy LED bulbs and an integrated hydroponics system…
http://www.independent.co.uk/life-style/food-and-drink/news/growing-underground-michel-roux-jr-reveals-plans-for-subterranean-farm-in-the-depths-of-empty-south-london-tunnels-9096184.html
VIDEO: 31 Jan: UK Telegraph: Growing Underground: London’s subterranean farm
Harry Wallop visits a futuristic market garden that lies a full 100 feet under the streets of central London
http://www.telegraph.co.uk/news/uknews/10607635/Growing-Underground-Londons-subterranean-farm.html
…30 Jan: UK Independent: Jamie Merrill: Growing Underground: Michel Roux Jr reveals plans for subterranean farm in the depths of empty south London tunnels…
Presumably using similar technology to that used by the drug gangs to grow cannabis plants in basements and attics…
What do I make of the underground farm? This is what I think of the underground farm :
http://metronews.ca/news/vancouver/921946/vancouvers-first-vertical-urban-farm-goes-bankrupt/
Pretty poor form to quote the song without creditting the writer.
steveta_uk says:
February 11, 2014 at 4:33 am
>> A few lines from a popular song about clouds, “Both Sides Now”
> Pretty poor form to quote the song without creditting the writer.
Joni Mitchell, best sung by Judy Collins.
Its about time someone looks at climate science from both sides, now.
Oh what the heck, this isn’t a major post, I can go off on a tangent and not feel apologetic.
Heinlein wrote the best SF novel that should be a movie, The Moon is a Harsh Mistress. Judy Collins sang a song of the same title that would be a wonderful opening scene. Between the CGI in Titanic and the vomit comet in Apollo 13, would someone please make the movie?
“garymount says:
February 11, 2014 at 4:04 am
What do I make of the underground farm? This is what I think of the und11erground farm :
http://metronews.ca/news/vancouver/921946/vancouvers-first-vertical-urban-farm-goes-bankrupt/”
garymount could have missed the point.
“Now the firm is expand production and is seeking £1m in crowd-sourced funding to bring its subterranean herbs, shoots, miniature vegetables, edible flowers and other delicacies to Britain’s high-end restaurants and food stores…”
The point is that production costs are not likely to be an issue here.
l don’t think its so much that clouds are a big game changer in climate. But rather the size and the movement of the weather patterns that help to cause them. Because l think that a cause of ice age was that the weather patterns became larger in surface area and so became much slower moving and stable, so as to let cold winter weather bed in year after year. Because a waving jet stream will not form a ice age because it makes the weather to changeable for that to happen. What’s needed for a ice age to form is for the jet stream to push south and go zonal over a large area of the globe so as to allow huge area’s of high pressure to form in the NH and set up huge pools of cold air. Because of this growth in the size of the area’s high pressure it means the area’s of low pressure also become larger and much slower moving, and because of this the whole weather patterns in the NH starts to grind to a halt and become stable. Which is just what is needed for a ice age to form.
Apology on breath vs breathe. I’m a geologist, not an English major. Rolf
John Peter says:
February 11, 2014 at 4:58 am
– – –
If you read my link, you would see that the technologies are similar.
The problem is that what we do know about clouds is not incorporated into IPPC models. If the processes that occur in clouds were included in those models, there would very likely be no CO2 “sensitivity”. From what I have observed, clouds are controlling both the atmospheric concentration and distribution of CO2. CO2 concentration changes lag temperature changes.
I’m sorry, guys…
I couldn’t resist; it’s such a beautiful song by Joni:
http://youtu.be/bcrEqIpi6sg
Cheers!
Distribution of atmospheric water is uneven, fractal like, in a scale invariant manner. Therefore, even under clear sky conditions, average optical depth in a water vapor absorption band is pretty independent of average specific humidity, the latter providing only an upper bound. Higher moments of distribution, necessary to calculate radiative properties, are neither measured nor represented in computational models.
Clouds are roughly defined by regions, where relative humidity exceeds 100%, this is why they are fractals as well.
Atmospheric lifetime of moisture is restricted, it is 9 days on average. Absolute humidity of an air parcel depends on its history, that is, on its temperature the last time it got saturated, not on its immediate surroundings. Shape of this parcel gets distorted with time into a fine mesh due to turbulent flows, described by mathematically intractable Navier-Stokes equations. Unfortunately neither Reynolds averaging nor large eddy simulation can offer help in this case, because in the real atmosphere the parameter regime needed for closure is never covered with experimental data. With a submillimeter mixing length scale, the 100 km resolution of general circulation models is somewhat ridiculous.
As none of the water vapor feedback effects can be modelled computationally using first principles, neither experimental control is possible in the atmosphere, only unverified &. unverifiable guesses are available to incorporate them into models by parametrization. Still, with no large positive “water vapor feedback” all dire predictions (projections!) evaporate.
[snip – chemtrails junk, policy violation -mod]
Taxed said:
“What’s needed for a ice age to form is for the jet stream to push south and go zonal over a large area of the globe so as to allow huge areas of high pressure to form in the NH and set up huge pools of cold air.”
There is truth in that. For a full on ice age one would need both equatoward jets and a greater degree of low latitude zonality than we currently observe.
I think that, during periods of transition, meridionality increases first then as cooling digs in the expansion of the polar air masses pushing outwards begins to reintroduce zonality but at a lower latitude.
During an interglacial, one mostly sees changes in zonality / meridionality rather than poleward / equatorward shifting though the latter still occurs to some degree but is less obvious on short time scales.
Look now folks – kenin’s comment will soon be disappeared (as it should be).
Why do we need to understand clouds; it is not as if they have anything to do with the weather, is it? After all, we know that the science is settled. Therefore, since we already know everything about climate change, anything that we don’t know must be irrelevant.
Stephen Wilde says: @ February 11, 2014 at 1:26 am
…..That mechanism is not proved yet but looking more likely as more data comes in.
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I do not know if you have seen these papersthat have to do with the sun, ocean and possible cloud cover.: (I adjusted the links so WordPress would not kick me into the nearest snowdrift)
“Atmospheric Ionization and Clouds as links between solar activiy and climate”
(wwwDOT)agu.org/books/gm/v141/141GM22.pdf (Note: American Geophysical Union killed my old link so this might not work either ) or try – onlinelibrary(DOT)wiley.com/doi/10.1029/141GM22/summary
Solar forcing of the Indian summer monsoon variability during the Ållerød period(wwwDOT)nature.com/srep/2013/130925/srep02753/full/srep02753.html
Possible Solar Forcing of Late Holocene Mega-Droughts in India lasp{DOT}colorado.edu/sorce/news/2005ScienceMeeting/presentations/thur_am/Sinha_India_Droughts.pdf
There are several other papers on the India Monsoon – solar connection. Monsoons are too critical to India, southeast Asia and China for the politics to get in the way of science so it is a “Dig Here” area.
Regional atmospheric circulation shifts induced by a grand solar minimum (wwwDOT)nature.com/ngeo/journal/v5/n6/abs/ngeo1460.html
Variations in solar magnetic activity during the last 200 000 years: is there a Sun–climate connection? (wwwDOT)sciencedirect.com/science/article/pii/S0012821X02005162
Two solar cycles of nonincreasing magnetic flux onlinelibrarywiley(DOT)com/doi/10.1029/2001JA000503/abstract
Multidecadal Covariability of North Atlantic Sea Surface Temperature, African Dust, Sahel Rainfall, and Atlantic Hurricanes journals(DOT)ametsoc.org/doi/abs/10.1175/JCLI-D-11-00413.1
Persistent influence of the North Atlantic hydrography on central European winter temperature during the last 9000 years onlinelibrary.wiley(DOT)com/doi/10.1029/2006GL028600/abstract
Multidecadal variability and late medieval cooling of near-coastal sea surface temperatures in the eastern tropical North Atlantic onlinelibrary(DOT)wiley.com/doi/10.1029/2011PA002130/abstract
Trends in sunspots and North Atlantic sea level pressure onlinelibrary(DOT)wiley.com/doi/10.1029/2012JD017502/abstract
Given the recent increase to record ice in the Antarctic these papers may also be of interest. Please note this map showing a tongue of the Antarctic Circumpolar Current headed up the side of South America to the place where El Niño and La Niña starts. Bob Tisdale and Willis have connected clouds to changes in ocean and atmospheric temperature, so again a possibly good “Dig Here’ place.
Orbitally paced shifts in the particle size of Antarctic continental shelf sediments in response to ice dynamics during the Miocene climatic optimum geosphere(DOT)gsapubs.org/content/9/1/54.abstract
On the meridional extent and fronts of the Antarctic Circumpolar Current (wwwDOT)sciencedirect.com/science/article/pii/096706379500021W
Intrinsic variability of the Antarctic Circumpolar Current system: low- and high-frequency fluctuations of the Argentine Basin flow (wwwDOT)ocean-sci-discuss.net/10/1933/2013/osd-10-1933-2013.html
New Source Found For Cold, Deep Antarctic Currents (wwwDOT)livescience.com/27390-antarctic-bottom-water-current-found.html
Willis would say that doesn’t matter, since English isn’t logical. So feel free to orange water given bucket of plaster.
Thanks, Gail.
I’m mainly waiting on new data for the post 2007 period as regards ozone and temperature changes in the stratosphere above and below 45km.
can someone please explain why my last comment about geo-engineering
was cut?
MikeB says:
February 11, 2014 at 3:18 am
Clouds are water vapor, a green house gas which warms us.
“Clouds are NOT water vapour. Water vapour is an invisible gas. You can see clouds, so they are NOT water vapour.
In a field where there is so much misunderstanding already, I think it is important to avoid adding to the confusion by using loose, inaccurate or incorrect statements [where possible].”
Yes, it is very important to stick to the facts. Clouds reflect visible light. Water vapor does not reflect visible light. Determining Earth’s albedo is crucial for any science of global warming. We cannot know what Earth’s albedo is if we are unwilling to research clouds as reflectors of visible light.
The following was taken from section two of the Weather Modification Act of The government of Canada:
“weather modification activity” includes any action designed or intended to produce, by physical or chemical means, changes in the composition or dynamics of the atmosphere for the purpose of increasing, decreasing or redistributing precipitation, decreasing or suppressing hail or lightning or dissipating fog or cloud.
It is not JUST the clouds it is ALL of H2O. I have never seen any paper that talks about all of the different phases of H2O ascribed to their affects on the atmosphere and “Global Warming.” All I ever get when I ask about it is “the water vapor leaves the atmosphere in a few days and has no effect.” Well the “water” that is in a river leaves the position it is in, in the river, in a few seconds – AND YOU CAN STILL DROWN IN THAT SPOT IN THE RIVER. The fact that the percent of water in the atmosphere remains fairly constant and at a level that means it is about 20 – 100 times as effective at controlling the temperature of the earth means a lot more that “it leaves the atmosphere in a few days.”
First off you have the latent heat of fusion (melting) and latent heat of vaporization (boiling). [Latent heat – enthalpy] When this happens there is a flow of energy when changing from one phase to the next: from solid to liquid, and liquid to gas. Melting and boiling are endothermic, meaning that the system absorbs energy when going from solid to liquid to gas. However the change is exothermic (the process releases energy) for the opposite direction – gas to liquid, liquid to solid. When a water molecule evaporates from the surface of any body of water, energy is absorbed by the water molecule and results in a lower temperature of the a few molecules of the air in the immediate vicinity of this transformation. It does not have to “boil” like a pot of water on a stove to get this energy. A few rays of sunlight striking the surface of the water can get it close and then the rest comes from the air. This water vapor is now a gas, like O2, and is carried in rivers in the atmosphere that carry more water vapor than the Amazon River carries water. When it rains, that water vapor, will, has to, MUST, release that energy, enthalpy, back into the surrounding air, making that area warmer, transporting that energy miles high into the atmosphere. Now you have to throw in the fact that this temperature (of fusion or vaporization) changes with pressure.
Similarly when that water vapor freezes, energy will be released and the air temperature will increase in the immediate vicinity.
Some of the various atmospheric currents can cause the water vapor that has turned into water droplets (clouds) again reabsorb that energy. Or the rain that is falling to “evaporate” – absorb energy and make it cooler, and never hit the ground. Other currents and conditions can cause the vapor to turn into snow and release that stored energy. Or the snowflakes that are on their way down to melt and cool the air in that area. Just like the old fashioned ice-cream maker worked – the salt started the melting which required more energy which was taken from the cream.
Then we have sublimation and that energy transfer and it also works both ways Solid to Gas and Gas to Solid. If there are rivers of water larger than the Amazon, and many of them I am told, then there are actually transmission line of energy larger than any power transmission lines man has built on Earth. AND NO ONE IS TALKING ABOUT WHERE ALL OF THAT ENERGY IS GOING OR WHAT IT DOING.
All of this makes even a model of just this one concept of the atmosphere (near) impossible.
MikeB
That water vapor and cloud equivalence statement caught might eye also. I am generally skeptical of AGW but it and a few things made me skeptical about this post.
Clouds and water vapor have distinctly different effects on heat absorption and reflection.
There was much concern among the climate change community when at the Hadron collider
at Cern it was shown that the possibility of variations in solar emissions could cause vapor to coalesce into larger water particles (clouds)
In general high clouds and vapor in the atmosphere tend to cool the earth and Roy Spencer has indicated that only a 1 or 2% change in the higher atmosphere could account for all the changes we see. The higher clouds cool because on average they reflect more solar irradiance back into space. Incidently, Spencer used that ‘I have looked at clouds from both sides now’ in his book.
Low clouds tend to warm the atmosphere because of their back radiation of IR (Heat) frequencies
coming from the earth. It was known a hundred years ago that CO2 was saturated with respect to the IR frequencies it could absorb. Then came quantum mechanics and the idea that the feedback from the CO2 could cause more water vapor/ and clouds to form.
So the idea of not knowing about clouds and water vapor is generally at the core of the uncertainty and what could be. Water Vapor is the only gas in the atmosphere which is not homogeneous.
Assumptions have simply been made about historical quantities at various altitudes because until recently there is no record.
And look at where that’s gotten them: http://blogs.mprnews.org/updraft/2014/02/coldest-winter-in-30-years-so-far-warmer-pattern-shift-next-week/?from=weather
It’s so cold there that people beat each other with sticks to stay warm.
http://www.teamusa.org/Road-to-Sochi-2014/Features/2013/June/24/USA-Hockey-Announces-Roster-For-US-Womens-National-Team
What’s needed in Minnesota is fewer trees and more teeth.
taxed says: @ February 11, 2014 at 5:05 am
…. Because a waving jet stream will not form a ice age because it makes the weather to changeable for that to happen. What’s needed for a ice age to form is for the jet stream to push south and go zonal over a large area of the globe so as to allow huge area’s of high pressure to form in the NH and set up huge pools of cold air….
>>>>>>>>>>>>>>>>>>>>
The shape of the Laurentide Ice Sheet from the Wisconsin Ice Age suggests different. link The cold weather from the ‘polar vortex’ link
The Rocky Mtns help funnel the cold air towards the plains while the oceans act as giant modifiers for the east and west coast.
“Edim says:
February 11, 2014 at 1:51 am
Not only total cloud cover can have an influence on global climate – change in latitudinal distribution of clouds will have an influence, even at constant average cloud cover.”
Also the day/night ratio of cloud cover- as anyone who steps outside on a winter clear night versis a winter overcast night will notice immediately,
Speaking of clouds, I thought this post by Michael Hammer on Jennifer Marohasy’s website was interesting. Check the figures- most of earth’s greenhouse effect is due to CLOUDS
http://jennifermarohasy.com/2009/03/radical-new-hypothesis-on-the-effect-of-greenhouse-gases/
As soon as the word “clouds” gets mentioned, people forget that the issue is CLIMATE and not LAST NIGHT’S WEATHER !!
So if talking about CHANGES in cloud cover, we have to talk of changes that PERSIST for climatically significant periods of time; like 30 or 60 years or so; not here tonight and gone tomorrow.
Clouds (liquid and solid H2O) react differently to Solar spectrum energy (0.2 to 4.0) micron wavelength (for 98% of the total), and LWIR Radiant energy; either surface or atmospheric emitted thermal radiation, or GHG emitted band spectra radiation.
Incoming solar spectrum radiation; particularly visible wavelengths shorter than about one micron, get highly scattered by multiple refractions by water droplets and ice crystals. It is NOT reflection; well maybe 3-5% is reflection. Water droplets of suspendable size, refract a highly collimated (0.5 deg. divergence) solar beam, into a very wide angle (approaches 90 deg.) exit distribution, so just three or so sequential refractions, renders the suns rays almost totally isotropic. Even very small droplets that become diffraction limited, result in wide angle scattering. The result is as much as 80% isotropic scattering that looks like diffuse reflection to the eye (from a plane). The important thing is that it is solar spectrum radiant energy; that is largely directed out into space..
Well, of course, tall cumulous type structures, will scatter plenty of oblique solar energy down to the surface. That radiation might have simply gone right on by, in the absence of the cloud, so it adds to the surface energy. But such clouds, will also scatter solar energy that would have totally missed the surface, back to space; so it’s a debatable point. The tops of course should be a net energy loss to the surface.
With the surface emitted LWIR radiation that is somewhat black body like (thermal radiation) , at the purported mean surface Temperature of 288 K, is centered at 10.1 microns, and should have most of its energy between 5 microns, and 80 microns. CO2 in the atmosphere will alter the spectrum, in the 15 micron band, perhaps 13 to 17 microns.
A good part of this spectrum, is highly absorbed by water, with of course the atmospheric window in the 10 micron region, where the ozone GHG hole resides at 9.6 microns.
But the surface of the earth is anything but 288 K. Large portions of the surface area is ocean, much of which is warmer than 15 deg. C. And on land, the tropical deserts, are radiating at much higher Temperatures and shorter wavelengths, peaking nearer 8 microns, than 10.1.
In any case, water and ice in clouds, is highly absorbing at these wavelengths, and droplets around 50 microns or larger, absorb almost all of the radiation in the water bands. The true reflectance of water and ice in the long infra-red is not very different from the visible, so clouds do not really REFLECT the upward LWIR radiant energy. They absorb it, and then re-emit it largely as a thermal spectrum characteristic of the cloud Temperature, but also with an H2O band spectrum signature.
The portion of this in the CO2 15 micron band, now has to face re-absorption in the atmosphere on the way to the surface, so CO2 would inhibit that portion of the thermal spectrum, from reaching the surface.
Well this would then be expected to warm the atmosphere, just as the upward LWIR does, but it does not seem to be much of a surface warmer. Certainly the cloud downward LWIR energy, is not likely to get stored in the deep oceans.
Even small increases (for climate time scales) of the global amount of cloud cover can have a large effect on the total solar energy reaching the deep ocean storage.
How anyone can make positive feedback warming out of cloud increases over multi-decadal time scales, is beyond me.
But I’m always happy to learn.
I’ve noticed that folks focus on the big, white fluffy Cumulonimbus when it comes to radiative forcings, albedo etc. However, as we’ve discussed in the past, noctilucent clouds exist…what is their effect upon climate?
http://wattsupwiththat.com/2011/04/20/nasa-takes-aim-on-noctilucent-clouds/
usurbrain says: @ February 11, 2014 at 8:41 am
…. All I ever get when I ask about it is “the water vapor leaves the atmosphere in a few days and has no effect.”….
>>>>>>>>>>>>>>
The smart aleck answer to that is “water droplets absorb CO2 molecules and wash the CO2 out of the atmosphere so CO2 should also have no effect.”
I sense the coming of a very detailed dicussion on clouds and water vapor here on WUWT in the near future. When that occurs I don’t now what or who will be right but I will be right there.
george e. smith says: @ February 11, 2014 at 9:33 am
As soon as the word “clouds” gets mentioned, people forget that the issue is CLIMATE and not LAST NIGHT’S WEATHER !!
So if talking about CHANGES in cloud cover, we have to talk of changes that PERSIST for climatically significant periods of time….
>>>>>>>>>>>>>>>>>>>>>
It has changed over time if you consider changes to albedo as a good approximation to changes in cloud cover: GRAPH from the Earthshine Project. WUWT discussion HERE
Sort of looks like the inverse of the temperature over the same period of time. http://www.drroyspencer.com/wp-content/uploads/UAH_LT_1979_thru_January_2014_v5.61.png
per darylb,
“””””…..In general high clouds and vapor in the atmosphere tend to cool the earth and Roy Spencer has indicated that only a 1 or 2% change in the higher atmosphere could account for all the changes we see. The higher clouds cool because on average they reflect more solar irradiance back into space. Incidently, Spencer used that ‘I have looked at clouds from both sides now’ in his book.
Low clouds tend to warm the atmosphere because of their back radiation of IR (Heat) frequencies…..””””””
Actually, the usual weatherman wisdom, is exactly the reverse. The standard weather text books claim that high clouds warm, and the higher the warmer., while low clouds cool.
The graphs I have seen seem to show that at one particular cloud altitude, the Surface Temperature does not change from zero cloud to 100% cloud. If the clouds are higher than that altitude, then more cloud cover gives more surface warming. If the clouds are lower than the critical altitude, then more cloud cover means more surface cooling.
Those observations may in fact be true; but their interpretation is not..
Those higher warming clouds, are usually high cirrus clouds such as one sees developing in the late afternoon and early evening, after a warm or hot and likely humid day.
It was that hot steamy day that CAUSED those high cirrus clouds; not verse vicea.
On such hot days, lots of water evaporates giving humid days, and as the sun gets lower, and the warm moist air rises; it eventually reaches the dew point, and something or other results in nucleation of water droplets. The hotter it was during the day, for a given humidity, the dew point will be at a higher altitude so the clouds will form higher up. And the night time temperatures will be warmer BECAUSE OF THE HOTTER DAY, but it will still COOL at night, and be decidedly cooler at dawn.
Lower clouds are usually of the heavy moisture laden kind, that precipitate, and they block a whole lot of solar radiation from the surface; which results in cooling.
Nobody seriously thinks that dark low clouds warm anything.
Bill Parsons Hey, from inside (Minnesota) and looking out, yeah it has been cold, but I would like a few more trees. The reason: I like trees—-and marshes—-and creeks and rivers—and lakes and we have about 15,000 of those (10,000 was just a nice rounded number).
So go CO2 we need you to help everything GREEN to grow.—-but I will be glad when spring gets here.
george e. smith says:
February 11, 2014 at 9:33 am
===============
Thank you. That was an explaination I have been looking for.
One other question, please explain the vapor state of H2O (that which is not visable) in the same context as your explaination above.
Thanks in advance.
@ darrylb says:
February 11, 2014 at 10:15 am
; – )
I absolutely agree. I was there in Rochester for two few weeks in December. To counterfeit a phrase by Mark Twain, it was the coldest winter I ever spent.
“Solar variations appear to change global cloudiness by expanding and contracting the polar vortices thereby making the polar air masses change the extent to which they encroach across middle latitudes.”
Look at the active region count of sunspots at the begining of 2003
Look at the active region count of sunspots in 2009.
is that a solar variation?
If so, then your hypothesis is that it will change global cloudiness.
Predict: how will the global cloudiness change at various pressure levels
what will it do to cloud fraction at 1000hPa? 925? 850? 700? 600? 500?.. 400, 300? 250? 150?
Go ahead, lets test your theory. make a testable prediction and I’ll plot the data.
How much will it increase or decrease cloud fraction at each of these levels
What a great thread! GC and SW and many of the usual suspects with their best work. I’ll digress a bit to say that the major problem in climate science is not atmospheric clouds, but cranial clouds, the cumulonimrod thinking of wannabe scientists.
I’m certain the climate modeling problem will never be solved. When making a GCM, well-understood first principles will only take you so far, then you have to add in empirical phenomena that are NOT well-understood. This can be done in token fashion by using statistics to create a mathy emulation of those climate features. But the result is NOT a true simulation; it merely has climate-like properties.
Weather produces more weather in a cause-and-effect way. But there are random processes that keep us from showing the exact relationship mathematically. Over time, the randomness takes our emulation farther and farther away from reality and its underlying cause-effect processes. Therefore, no climate model will give a valid prediction of climate for more than a few years–by luck. Adding up a bunch (“ensemble,” in science-feller-speak) of flawed climate models will just create another failure-in-progress.
There’s an ancient Greek term that describes the AGW climate scientist mind-set: hubris,. Hubris is overbearing pride or presumption; arrogance. (American Heritage® Dictionary). In Greek tragedy, hubris always results in the sinner’s ruin. We are living out a Greek tragedy, currently in the front seats, soon to be dragged on-stage by He-Who-Must-Not-Be-Named. Whom the gods would destroy they first drive mad.
george e. smith says: @ February 11, 2014 at 9:33 am
“As soon as the word “clouds” gets mentioned, people forget that the issue is CLIMATE and not LAST NIGHT’S WEATHER !!
So if talking about CHANGES in cloud cover, we have to talk of changes that PERSIST for climatically significant periods of time.”
A decline in 4/5% in global cloud cover from the 1980s to early 2000s is significant and adjusting for this change removes the warming period during it.
.
“Clouds are water vapor, …”
No. Clouds are water droplets.
“Clouds are water vapor, a green house gas …”
No. Clouds are near gray-bodies and radiate in a full spectrum manner unlike greenhouse gases which have areas in the spectrum where they do not radiate little or at all. This is especially true for carbon dioxide which only affects a very narrow band of wavelengths. Between 13 μm and 17 μm co2 at most affects 18.8% of the spectral radiance if totally opaque and if you adjust for the partial sidebands, which you must to get closer, this is but about 12% out of the 391 W/m² at 288.15 K with 5.5% being already totally opaque and immune to any further radiative affects. That central band’s effect has moved into the thermodynamic realm of effect except at and above the TOA (about 14.33 to 15.5 μm).
But just like the clouds slow or stop the cooling underneath the cloud cover because the clouds are near the same temperature as the surface, above the clouds they radiate more easily to space due to a decrease in the pressure broadening as the pressure drops with altitude.
I think most of the eastern U.S. now knows what it’s like with three weeks of mostly cloud cover in the dead of winter! So yes, clouds cool or stop or slow any warming warming that would have occurred without the cloud cover.
“Clouds are water vapor, a green house gas which warms us.”
No. Clouds do not “warm” us which means raising temperatures as clouds move in… no… clouds slow and sometime completely stop the cooling underneath the cloud cover but you have an opposite affect above the cloud cover.
My goodness, seems so many misconceptions, or at best misstatements.
Some may disagree with me above but that is how I see clouds, winter clouds at least, while awaiting just a few days above freezing, but the sun’s out today, it will start to “warm” without the clouds, literally.
Ric Werme says:
February 11, 2014 at 4:48 am
Heinlein wrote the best SF novel that should be a movie, The Moon is a Harsh Mistress. Judy Collins sang a song of the same title that would be a wonderful opening scene. Between the CGI in Titanic and the vomit comet in Apollo 13, would someone please make the movie?
Heinlein was one of the best.
Here is Joan Collins.
“A decline in 4/5% in global cloud cover from the 1980s to early 2000s is significant and adjusting for this change removes the warming period during it.”
except low clouds ( those supposedly effected by GCR) did not decrease from 2002 to 2009.
george e. smith says:
February 11, 2014 at 10:03 am
“Low clouds tend to warm the atmosphere because of their back radiation of IR (Heat) frequencies…..””””””
Lower clouds are usually of the heavy moisture laden kind, that precipitate, and they block a whole lot of solar radiation from the surface; which results in cooling.”
This is not the true picture though because both warming and cooling occur with high and low clouds depending on whether long wave, short wave, day, night, above or below. The overall energy change is what dictates the clouds behavior.
Low clouds only seem to warm by preventing more energy escaping for the time being. Overall the energy balance is a loss due to solar energy prevented reaching the surface, easily outweighs the energy trapped below the cloud. Scientific evidence for this is by observing low clouds usually only warm the atmosphere below the cloud when during night. During daylight low clouds cool the atmosphere below the cloud because the warming from solar energy is much greater. The one exception is in regions where solar energy is very weak in winter and therefore during daylight low clouds may actually increase the temperature of the atmosphere below the cloud. Finally satellites show that a increasing trend in global low clouds cause overall cooling when compared to HADCRUT surface temperatures..
http://climate4you.com/images/TotalCloudCoverVersusGlobalSurfaceAirTemperature.gif
High clouds still allow significant solar energy to filter through because they are very thin compared with low based clouds. High clouds do cause a little cooling compared with clear sky during the day. Solar radiation sensors back these up with the scientific evidence and temperatures very slightly cool with their presence on a hot summers day.. The thin high cloud though is still effective at preventing LWR from escaping through it and the result is slight warming at night. The problem being the little loss of solar energy compared with slightly less effective LWR makes the overall energy balance very difficult to call. Knowing that solar energy is significant even with a little loss, then it maybe possible that high clouds cause cooling too, but being less insignificant compared with low clouds.
“but being less insignificant compared with low clouds.”
Sorry, should read more not less.
Ric Werme says:
February 11, 2014 at 4:48 am
Second your Moon is a Harsh Mistress idea.
Ric Werme says:
February 11, 2014 at 4:48 am
“Joni Mitchell, best sung by Judy Collins.”
Heretic! Joni Mitchell, best sung by Joni Mitchell.
And if you ‘extract’ those pesky CO2 molecules at the source, you can grab them before they make their remarkable voyage to the upper atmosphere and become gg simple really
“The point is that production costs are not likely to be an issue here.” (john Peter 4:58am – re: underground grow-ops).
Really. How is that possible? Is the socialist U. K. government (who style themselves “conservatives”) going to pay part of those costs with confiscatory taxes (thereby preventing jobs in the private sector from coming into being)?
OR
Are there enough “who cares what it costs” restaurant patrons willing to pay a high enough price to break even (much less make a profit)?
There are ALWAYS production costs.
Somebody must pay them.
*************************************************************
Well, if your answer is that it is completely privately funded, then… GO, HIPPIES!
I hope it is a success. I wouldn’t waste my money on their high-priced vegies (no matter how wealthy I were), but, if they can find enough Enviro-guilt (based on the flim flam science re: human CO2/”carbon”) customers, more power to them… .
And that power had better not be from windmills — plants don’t recover well from sudden drops in temperature and light. GO BIG COAL! (until nuclear can replace it, I mean)
#(:))
**********************************
Re: clouds — Thank you, Mr. Westgard, for running the gauntlet of the commenters and posting a useful article on WUWT. You make a good, basic, point. Such things need to be said over and over given the constant barrage of Envirostalinist propaganda. You shored up the bulwarks of truth in science. Nice job! (and don’t sweat the nitpickers — it is not important that you spell correctly, not at all — you communicated your message just fine)
Mr. Westgard, I must apologize, on reading Janice’s comment I realized I left one HUGE statement… sir, that was not to pick on your words per se. You didn’t say anything I don’t hear so very regularly and it points to just how far the proponents of AGW have warped the language about the science involved. It was more a statement against those who have made it perfectly normal for you an others to say the same thing, clouds are greenhouse gases, they warm, they are water vapor… which they then pick up to extend to — just as bad as CO2, no, even worse, fed back by CO2 and on and on. that was what I was railing against.
Other than that point, good post! I look forward for more of your thoughts.
I have an IR thermometer and if I point to a clear sky it is normally very very cold, outside it’s range. If I point it at clouds I get the temperature of that clouds surface. Usually close to the same temperature one will find at the same heights in that atmosphere.
Dear Wayne,
I hope that you didn’t think I considered you one of the nitpickers, for I did not. Your post wasn’t nitpicking at all. Hope all that flooring and the hole in the yard, etc… are all taken care of SOON!
You are one of the more conscientiously diligent commenters and always (unlike me!) polite.
Keep warm out there!
(and get a dog — it will keep you company until the cat makes another emergent appearance; and it will be friendly, too)
Your WUWT pal,
Janice
Clouds are not water vapour. Water vapour is a gas and clouds are suspended droplets of water.
A gas emits/absorbs in specific bands and does not act like a blackbody. Water droplets will act as blackbody emitters. The radiation dynamics are totally different.
No, no, Janice, no worries, I didn’t take it that way at all, but the word base ‘nitpick’ did queued me to think of what I had just written and oh no, without those words I added later, and should have been my very first sentence, it does seem like I am nitpicking the author himself! That is even if you didn’t pick up on it. It needed some quick clarification of who exactly I was criticizing!
I even find myself often using AGWese and I hit myself on the head every time do so, and always just after hitting the “Post Comment” button! Cra*, too late, can’t believe I just posted that! Why I always think over what I write after the Submit and not before I’ll never know, many years and I still can’t break myself of that habit.
🙂
[Right the correction note. As soon as you see it. We will see it. No writing, no righting. Mod]
Gail Combs
Hi there
What makes me think the jet stream move south and went zonal is the the sheer extent of the ice sheets. Yes you are right a waving jet pushing down south across the USA does give the USA a cold winter. But as the jet has moved into the Atlantic it has pushed back northwards again and has given Europe a mostly mild and wet winter. Which shows that a waving jet limits the area where the cold winter weather can set in. But as you know during the ice age not only was there ice sheets in the USA but also in Europe as well. So for the cold weather to extend to such a large area the jet must of moved south and went mostly zonal over a large part of the globe.
Thanks, Wayne. Glad to know it. Re: impulsive posting… I do it all the time, too. I think it is because…. we are delightfully humble* (prideful people are SUPER careful) and honest, thus, we merrily write away knowing we aren’t going to be caught in a l1e if we aren’t very careful and with blithe disregard for whether or not we crossed all the t’s and dotted all the i’s. I like us!
I do admire those who are more self-disciplined, but not if pride is what motivates them. I would rather make mistakes!
#(:))
*Vain (speaking for myself only), yes, lol, but not full of hubris
Oceans are recharged, to a greater or lesser amount, in the equatorial band by solar shortwave infrared light. These recharged waters then meander the globe and affect small and large scale atmospheric weather pattern systems, which in turn affect the equatorial weather band, which in turn allows recharge, to a greater or lesser amount. A case in point, I have a hunch that equatorial cloud measurements may be the only measure needed to eventually predict what will happen to the weather pattern variations marching across the US. Could we have predicted the arrival of that large anamolous warm pool sitting off the coast of Alaska and its ability to move the Jet stream based just on some previous “season” of clouds around the equatorial band?
Steven Mosher says:
February 11, 2014 at 10:51 am
There are so many internal system variables that it would not be possible to predict cloudiness changes at individual levels.
Gail Combs makes my point at Gail Combs says:
February 11, 2014 at 9:56 am
“Jon says:
February 11, 2014 at 3:14 pm
I have an IR thermometer and if I point to a clear sky it is normally very very cold, outside it’s range. If I point it at clouds I get the temperature of that clouds surface. Usually close to the same temperature one will find at the same heights in that atmosphere.”
That is a point I made about IR sensors previously.
Rather than measuring the downward radiation from the sky they measure the temperature along the lapse rate at the height where they focus and that height depends on the optical depth of the atmosphere.
Thus, for a perfectly transparent or non existent atmosphere they measure the temperature of space and for a non transparent atmosphere they measure the temperature of the gases just above or in front of them.
When a cloud passes over they switch from measuring the temperature higher up to measuring the temperature at the height of the cloud because the optical depth in front of them has changed.
For that reason I think their output has been incorrectly interpreted as measuring downward IR when in fact that is not the case.
Instead, they measure the temperature at the height where the optical depth is sufficient for them to focus.
They have been grossly misused in my opinion.
Pamela Gray says:
February 11, 2014 at 8:18 pm
Yes, Pamela, you have it right for the bottom up oceanic effect but to produce events such as the MWP and LIA and all the other longer term historical variability you need the top down solar effect too.
Natural climate change is a result of the interaction between top down solar and bottom up oceanic processes moving the jets and climate zones to and fro latitudinally.
That is way, way bigger than anything that our emissions can achieve.
IR thermometers can be tricky beasts. If you use it outside what it’s designed for, you can get unusual results. The heart of it is a semiconductor, the actual sensor. You need to know who manufactures it and the technical specifications of it ie. the sensitivity values for wavelengths. In actuality , that is a relatively narrow band. You should then compare it to a Wein’s displacement graph for a particular temperature. You will find that you are dealing with a low percentage of available energy. There will then be a ROM which incorporates an algorithm to ‘adjust’ the output to accommodate sensitivity etc.. There will then be an ‘albedo’ control of some sort , which will essentially be an opamp to adjust signal strength.
Now for the optics. Designed to take a large area of emission and focus on a point like a cone with the pointy end on the sensor. There is a possibility of IR filters as well.
I now take this outside and start pointing at the sky. I live in NE China at the moment. Tonight it will be -14 C. My apartment is around 20 C. I am going to get condensation on the lens and components (visible or not). How much energy am I picking up from outside as compared to the blackbody radiation from inside the equipment? How much diffuse radiation is outside?
I wouldn’t bet any part of my anatomy on the accuracy of the reading. It would be just a basic litmus test ie. blue or red. I would just determine that it is cooler on a cloud free night. I could do that without any equipment.
ADDENDUM:
If you want a low tech alternative to an IR thermometer to measure sky temperatures then try this, probably more accurate.
U need a reflective parabolic dish. An old satellite dish with aluminium foil as reflector would do. Place an accurate temperature sensor at the focus. A quick response time would be useful. Without calibration the figures would not be accurate but comparative. A quick calibration method would be to point at a wall of known temperature. Morning and afternoon would give 2 points to decide the offset. The reflective dish would practically eliminate any blackbody radiation from the ground. Being parabolic would also mean that energy gathered would be in a narrow beam.
I came across a paper http://enso.larc.nasa.gov/manuscripts/pdffiles/Harrison.etal.JGR.90.pdf
“Overall, clouds cool the Earth atmosphere by 17 W/m^2. The global mean cooling varied from 14 to 21 W/m^2 between April 85 and Jan 86.”
So just within that little snippet of time, (it could vary much more over a longer period then right?) they detected a cloud induced variation of cloud cooling capacity three times greater than CO2’s warming? Or am I missing something?
In response to George E Smith at 10:03
I stand corrected—- completely.
Not sure Of what I was thinking at the time. That has to do with thickness of the clouds and relative temp difference on the top of the cloud.
In reading g smith, I have to say that I am in complete agreement.
“”””””……….QUOTATION…..Matt G says:
February 11, 2014 at 1:08 pm
george e. smith says:
February 11, 2014 at 10:03 am
“Low clouds tend to warm the atmosphere because of their back radiation of IR (Heat) frequencies…..””””””
Lower clouds are usually of the heavy moisture laden kind, that precipitate, and they block a whole lot of solar radiation from the surface; which results in cooling.”…..END QUOTATION.
Matt please don’t post statements made by others and allege that I said them.
I take great pains to delineate items that are direct excerptions from other people’s posts.
Now here is where you got that:
QUOTATION……””””””……george e. smith says:
February 11, 2014 at 10:03 am
per darylb,
“””””…..In general high clouds and vapor in the atmosphere tend to cool the earth and Roy Spencer has indicated that only a 1 or 2% change in the higher atmosphere could account for all the changes we see. The higher clouds cool because on average they reflect more solar irradiance back into space. Incidently, Spencer used that ‘I have looked at clouds from both sides now’ in his book.
Low clouds tend to warm the atmosphere because of their back radiation of IR (Heat) frequencies…..””””””
Actually, the usual weatherman wisdom, is exactly the reverse. The standard weather text books claim that high clouds warm, and the higher the warmer., while low clouds cool…….”””””””……END OF QUOTATION.
Now note Matt that I was directly quoting a post by ……darylb……. NOT ME.
Did you not then see this part…….QUOTATION……””””””……Actually, the usual weatherman wisdom, is exactly the reverse. The standard weather text books claim that high clouds warm, and the higher the warmer., while low clouds cool…….”””””””……END OF QUOTATION.
I quoted ……. darylb, ……. and then pointed out that this (his statement) was contrary to the common belief.
Now if ….darylb…. did not say that himself, but was quoting some other source, he made no indication of that.
Well Matt, we crossed posts in the atmosphere; no harm ; no foul, play on.
George
Stephen, you still must admit the null hypothesis, that it is all intrinsic oscillations interacting to produce both long and short term weather pattern variations. You must. And I think you know why. Scientifically, your idea is speculation. There is plenty of evidence that Earth’s own variability has been the source of interglacial and glacial weather pattern variations (climate shifts). So it must hold for the present, at least, as being the null hypothesis that all must not only show is insufficient (and none have as yet), but that alternate theories explain more than the null hypothesis does.
Therefore to be taken seriously, you must state the null hypothesis also, being that your hypothesis has not been verified even the least little bit, which you have admitted to stating you will leave to others the job of calculations and specific physics (chemical as will as physical properties) based plausible and observable teleconnections related to your combo meal of top down and bottom up mechanism.
That would be an improvement on your comments here. As it is, you state your thoughts as if they are fact. Your ideas are clearly not fact. You demonstrate hubris, which detracts from your desire to be considered a scientist.
Pamela.
The null hypothesis is that all climate change is natural.
You are trying to exclude the possibility of a top down solar effect from that natural variability.
There is plenty of data and many recent papers suggesting a solar / climate link.
I have pinned my hypothesis very firmly to an easily falsifiable ozone / solar interaction affecting tropopause height differentially between equator and poles.
It is established physics that such differential effects on tropopause height can be caused by temperature variations above the tropopause and that tropopause height can affect the pressure distribution beneath the tropopause.
The sequence of events set out in my New Climate Model matches observations and basic physical principles unless you can produce evidence to the contrary.
If my tone offends your sensibilities then that is your problem.
In the time that I have paid any attention to the weather; the last few decades, and more recently since the age of WUWT, somewhere between a dozen, and a hundred; or more people have posted that high cirrus clouds cause positive feedback warming… The argument is that their small “optical depth” still lets a lot of solar energy through to the ground, compared with low thick clouds, and then they absorb all this upward LWIR and often evaporate letting more solar energy to the ground, and assorted variations on that theme.
So I should state here, Smith’s firs axiom, of Cloudology.
“In the study of the effect of clouds, on weather/climate/skiing/whatever, the default state or condition is…NO CLOUDS… !!
Now Al Gore is the only person who has ever seen the earth from outer space, in its default NO CLOUDS state. He took a picture and published it in “An Inconvenient Truth.” Not a cloud anywhere.
I have seen the earth with NO CLOUDS, many times, but only from the ground side; well it was cloudless from horizon to horizon in all directions, even from a somewhat high (called mountainous) position.
So what is a cloud ?
Well I’ve been as high as 40,000 ft in a plane, and never seen clouds above that, but they might exist. I’ve heard of 45,000 ft tops of thunderheads. Dunno if that’s true.
But I’ll be generous and say clouds exist below 20 km. Yes I know there may be higher ones but not in any amount likely to change the climate, so that’s 20km or 60,000 ft.
The angular diameter of the sun is about 30 arc minutes; let’s call that 1/120 radians. So a 20km cloud needs to be 167 meters or 500 ft in diameter to occult the sun.
Anything smaller than that is an aerosol, but lower clouds can be smaller.
If you are standing in CAVU conditions, in bright sun, and a 500 ft cloud goes in front of the sun at 20 km height, you will be at the center of a 1500 ft diameter penumbral disc, and will see just the bright edge of the sun peering around the cloud. And it WILL register lower solar energy at your location, and it will get colder. I have never experienced it to warm up when a cloud goes in front of the sun; yet all the while that cloud was sitting there returning surface origin LWIR radiation back to me to keep me warm. No it got colder (instantaneously).
Larger clouds, than the minimum, will cast a bigger shadow, that takes longer to pass by, and all that time, the surface is cooling frantically from LWIR emissions, and as it cools, the LWIR returned from the cloud is also diminishing.
I have measured hot blacktop pavement in the late summer afternoon, and by the end of evening twilight, it is quite cool to the touch.
Now notice that my definition of a cloud, as being at least 30 arc minutes diameter favors high clouds for LWIR warming, because they are larger than low clouds, and it is claimed still stop all the LWIR, at least in the water bands. Note also that the higher the cloud, the less LWIR from the surface reaches it because of more CO2 and water vapor between ground and cloud, so this reduces the cloud irradiance from surface LWIR, which in turn reduces the re-emitted LWIR from the cloud’s water/CO2 bands, and the lower Temperature thermal spectrum emission too. That lower down LWIR now has to make it through that thicker layer of GHGs, to get back to the surface.
Richard Courtney, says the bottom 100 meters of atmosphere absorbs all the CO2 band emissions. OK, so at higher altitudes, that 100 meters will have expanded to maybe 1,000 meters to absorb all the CO2 band (coming down). OK, it is still 19 km back to the surface.
You see this claim that high clouds warm, simply doesn’t hold water. Sure they slow down LWIR escape, but the Temperature measurements (in a cloud shadow) show that they block more solar energy than they do LWIR.
I’ve been in mid west Sunday afternoon (4PM) flash thunderstorms, and even inside the house looking out at the fireworks, when the storm cloud passes over the sun, the heating stops even inside my house, standing at the window. So the effect is radiant energy, and not atmospheric Temperature cooling which is a slower effect.
Then as I said, it is CHANGE (cloud anomalies) that persist for climate time scales that we should keep in mind.
Make that a 1,000 foot penumbral disc, with a 500 ft cloud Umbrage in the center.
george e. smith says:
February 12, 2014 at 11:27 am
Sorry, I got mixed up with the quotations and your response was far more accurate.