Global Warming for Dummies (Part 3)
Posted by jennifer, June 30th, 2008 - under Uncategorized.
Tags: Climate & Climate Change
The prediction of how much manmade global warming we will see in the future (as well as how much past warming was manmade) depends upon something called “climate sensitivity”.
For many years, climate researchers have struggled to diagnose the Earth’s climate sensitivity from measurements of the real climate system. It’s almost a “holy grail” kind of search, because if we could discover the true value of the climate sensitivity, then we would basically know whether future global warming will be benign, catastrophic, or somewhere in between.
Here I present a new method of satellite data analysis which I believe reveals the climate sensitivity, and I also show why it has been so hard to diagnose from observations.
When the Earth warms, it emits more infrared radiation to outer space. This natural cooling mechanism is the same effect you feel at a distance from a hot stove. The hotter anything gets the more infrared energy it loses to its surroundings.
For the Earth, this natural cooling effect amounts to an average of 3.3 Watts per square meter for every 1 deg C that the Earth warms. There is no scientific disagreement on this value.
Climate sensitivity is how clouds and water vapor will change with warming to make that 3.3 Watts a bigger number (stronger natural cooling, called “negative feedback”), or smaller (weaker natural cooling, called “positive feedback”).
While there are other sources of change in the climate system, cloud and water vapor changes are likely to dominate climate sensitivity. The greater the sensitivity, the more the Earth will warm from increasing atmospheric greenhouse gas concentrations being produced by humans through the burning of fossil fuels.
There are three possibilities for climate sensitivity:
1. If clouds and water vapor don’t change as we add CO2 to the atmosphere, then the expected warming by 2100 would only be about 1 deg. C, which would not be a very big concern for most people. This is called the “zero-feedback” case.
2. If low clouds decrease, high (cirrus) clouds increase, or water vapor increases, then warming will be magnified. Most, if not all, climate models predict that clouds and water vapor will change like this, resulting in an amplification of the CO2-only warming of 1 deg C to as much as 4.5 deg. C or more. This is called the “positive-feedback” case, and the greater the positive feedback, the greater the warming. (NOTE: If the sum of all positive feedbacks more than cancel out the 3.3 Watt natural cooling, then the climate system is inherently unstable…this is why you sometimes hear of climate change “tipping points”.)
3. If the climate modelers are wrong — and low clouds increase, high clouds decrease or water vapor decreases with warming — then the effect will be to reduce the warming to less than 1 deg. C. For instance, if that 3.3 Watts of natural cooling mentioned earlier increased to as much as 8 Watts from cloud changes, the warming would be reduced to about 0.5 deg C by 2100. This is called the “negative feedback” case.
Read more from Roy Spencer here: http://www.weatherquestions.com/Climate-Sensitivity-Holy-Grail.htm
In this simplied version of a paper entitled ‘Chaotic Radiative Forcing, Feedback Stripes, and the Overestimation of Climate Sensitiviy’ submitted on June 25, 2008 to the Bulletin of the American Meteorological Society Dr Spencer goes on to conclude that:
1. Current satellite estimates of climate sensitivity have a spurious bias in the direction of high sensitivity.
2. This bias is probably due to small, natural fluctuations in cloud cover.
3. The true climate sensitivity only shows up during those shorter periods of time when non-radiative forcing (e.g. evaporation) is causing a relatively large source of temperature variability compared to that from cloud variability.
—————-
Read Global Warming for Dummies Part 1 here: http://www.jennifermarohasy.com/blog/archives/000959.html
And Global Warming for Dummies Part 2 here: http://www.jennifermarohasy.com/blog/archives/002844.html
eli, prof, josh?; there are more secret identities on this site than at Gotham City. With all this talk about BB’s and GB’s and sensitivity, I’m wondering why nobody has referred to Arthur Smith’s ‘rebuttal’ of the Gerlich paper, and obstensible reinstatement of the ‘greenhouse’ concept? Smith deals with all the issues, albedo, radiative exchange, emissivity and absorbtion, or lack thereof; one of the problems I have with Smith is that he only allows for minute internal energy contribution from radiactive decay and gravitational tidal forces; I would have thought tectonic activity and ocean recycling generated and used some energy; but most of all he ignores the energy storage capacity of the oceans; this is apparent when Smith states “While the variability in infrared emissivity is relatively small across the surface of a realistic planet, the albedo can be significantly different from place to place.” As luke’s great maps show this is not right; and anyway, as a matter of logic, if albedo varies, then so must emissisivity because the albedo variation determines what sw gets through to be converted to LW; Smith cleverly overcomes this by asserting that regional differences in albedo can be treated as the same as uniform albedo (33); this is unreasonable! Finally, Smith assumes that re-emission is randomly directed, “half the radiation from this atmospheric layer will go up, and half down”; as you explained to me prof – can I just call you Batman? – the up/down configuration is not that simple because of the different things that happen from ‘layer’ to ‘layer’ and lateral movement, and most importantly LW windows, as, once again, luke’s wonderful maps show.
Jan you are an obscurantist.
Jan there is one thing we learn from you now mate. You never answer the question. You never expound. You never explain. All you do is quip. Dodge and weave with half answers. So are we any the wiser – nope.
Well Eli was satisfying and comprehensive in his responses which you guys never are.
Jan I’ve asked you a really basic question on shortwave and you’ve ducked it. I know why.
Well Cohenite – you are the pinnacle of hypocrisy – someone named after a meteorite? Is that your first or last name? Dr Rock? Mr Rock. Wouldn’t be involved in research down Newcastle way yourself perhaps? Who cares if you name is really Bush or Gandhi – the issue is content and what you have to say (unless you’re using your fame as some barometer of standing).
It’s hilarious how many on here ack “warmers” who may prefer to use non de plumes while ignoring their own mates and even themselves in the process. Yea Gods !
What is a good barometer though is that when the ID issue comes up you know the opponent is worthy – it’s great index of opponent quality.
All the maps do is (1) bring you guys back to some ACTUAL numeric measurements (assuming the satellite is right) (2) a view of spatial reality – what’s a bright surface, where clouds are often, the equator gets a lot of sunshine, and the Earth’s climate has seasons?
luke; don’t be snarky; I rather enjoy sobriquets and I hope my suggestion to the prof is taken in the spirit is was offered, since from my vantage point he is a bit of a “Dark Knight”; my own has a rather dull history to do with a social commentator called Nic Cohen; I’m afraid I missed the meteorite connection completely, but I’ll gladly claim it.
As to your maps; they, apart from the odd thing over the ME, really work against you for the reasons I’ve offered; there is no question that low-level clouds cool, even if the mechanism is a bit unclear; here are 2 links which establish that;
http://www.agu.org/pubs/crossref/2004/2003GL018765.shtml
http://www.jennifermarohasy.com/blog/archives/002914.html
The first is your good friend Philipona; not only does the study show, by inductive reverse logic, that clouds cool, but that the heating has only a small ghg effect.
Jan – “Now if the emissivity was about the same as absorptivity i.e. .7 the same emission would be achieved with a planetary temperature of
So how does the emissivity get to 0.7 instead of 1?
I can’t see how the emissivity magically gets to 0.7. I can if you accept the actions of greenhouse gases and that they play a part in getting the emissivity down to this value.
So perhaps you can explain yourself and suggest, with references, another mechanism.
So far the accepted theory, that of greenhouse gases is passing all the tests of matching predictions with observations and measurements.
Ender: “So how does the emissivity get to 0.7 instead of 1?”
Same way albedo gets to ~.3 – clouds. They stop IR radiation. It might not be exactly .7 but but then neither is albedo and it certainly isn’t 1.
Cohenite – drat – you know me too well. Anyway – I say again it would be great to get a fullsome guest post from yourself on this whole issue of the details of greenhouse physics from quantum level to radiation budgets.
Wish Eli would do the same for us. I learnt more from him in 2 paras than in the last 2 months.
There is a whole mess of physics arguments here which are frustrating the hell out of me. And we never get a proper story laid out. Just quips and bit n’ pieces.
And for some more – different types of clouds do different things in terms of radiative forcing and changes in cloud trends are not uniform. http://meteora.ucsd.edu/~jnorris/presentations/cloud-aerosol_files/v3_document.htm
Luke: “So are we any the wiser – nope.”
Then you should check between your ears for the problem.
obscurantist
Luke: “obscurantist”
Only to the terminally thick.
Says the unpublished nurses aid.
Luke: “Says the unpublished nurses aid.”
More display of Luke’s arrogant ignorance.
Luke: I reckoned wayback cohenite was salvageable, more so now as he seems to have also missed that nic connection to a certain hard faced Liberal position. Jan on the other hand is destined to melt away like the unfortunate lad Icarus.
Jan – “Same way albedo gets to ~.3 – clouds. They stop IR radiation. It might not be exactly .7 but but then neither is albedo and it certainly isn’t 1.”
So clouds are the only things that trap IR? What about the places where there are no clouds for most of the time? So what you are saying if there were no clouds then the Earth’s global average temperature would be approx 254K?
Also how are you going to reconcile this, assuming it it true, with the cosmic ray theory that postulates that more sun activity -> less cosmic rays -> less clouds -> warming?
Eli: This appears to have displeased some.
James: Not so much. I have a general residual disdain for James Hansen’s small cadre of online minions in my personal climate pipeline. Consider it a PDO which will never shift. You should have some experience with that. Heh
June is in the books. Eli, don’t you have some temperature readings to fudge???
Gavin: “Jan on the other hand is destined to melt away like the unfortunate lad Icarus.”
Not likely because unlike you I had sense enough to keep away from the doors when they opened them on the open hearth furnaces. Never tried to use my body as a thermometer.
Ender: “So clouds are the only things that trap IR?”
It’s the only thing relevant when taking into account that they are the source of albedo. That is to say one should not be worrying about the one without the other i.e. one must take into account the entire radiative effect of the clouds not just half of it.
You seem to have some difficulty with this.
“So what you are saying if there were no clouds then the Earth’s global average temperature would be approx 254K?”
No clouds, no water AND no GHG at all (O2 and N2) do have some collision induced absorption in the Far IR so they must go too then we have the same conditions as the moon which sits at 254.
Obviously if there is no water there will be no water vapour and hence no clouds so the cosmic rays won’t have anything to work on – just like the moon.
Ender – funny this doesn’t happen on Earth.
http://www.lunarpedia.org/index.php?title=Lunar_Temperature
For a surface with the sun directly overhead, for example a horizontal region near the equator at lunar noon, I is the solar constant in Earth’s neighborhood, about 1366 W/m^2, minus the portion reflected. Since the emissivity is close to 1 minus the reflectance, those two terms cancel out, and inverting the equation gives the maximum day-time high on the Moon: 394 K or about 120 degrees C.
During the night the surface temperature drops further as the rocks radiate away the energy they’ve absorbed during the day time, with regions near the lunar equator dropping to about 120 K or -150 degrees C by the end of the night.
The temperature drop is limited by conduction of heat from layers several meters below the surface, which maintain a roughly steady average temperature that can also be determined from the Stefan-Boltzmann law. In this case ‘I’ represents the incoming solar energy averaged over a full day-night cycle
Iave = 1366cos(θ) / πW / m2
so at the equator T is about 296 K, or a comfortable 23 degrees C if you bury yourself sufficiently. At 60 degrees that drops to 249 K or -24 degrees C. The average subsurface temperature near the poles (85 degrees and higher) would be below 160 K or -110 degrees C
Jan – “It’s the only thing relevant when taking into account that they are the source of albedo. That is to say one should not be worrying about the one without the other i.e. one must take into account the entire radiative effect of the clouds not just half of it.”
So the water vapour in clouds also traps IR? What about the water vapour we cannot see – does that trap IR also?
Also I am pretty certain that the albedo effect is what Luke is saying and is mainly the reflection of SW radiation straight back into space. If you want to advance the cosmic ray theory then this is more consistent with its assumptions than yours that clouds do all the IR trapping.
“Obviously if there is no water there will be no water vapour and hence no clouds so the cosmic rays won’t have anything to work on – just like the moon.”
However what you are saying, that clouds do all the IR trapping, is diametrically opposed to the cosmic ray theory. So how do you reconcile this?
gavin; thank you for your kind words, but I’m afraid I’m already gone; at the end of the day I’m still a lawyer.
Jan; may I call you Icarus? That reminds me of the tale about Hathaway who wanted to find out why the sun was fading, but he had to be back before sunrise. Anyhow, I’m glad you raised N2 and O2, which between them constitute 99% of the atmosphere; it seems to me they pick up some heat through conduction with the planet’s surface; I wonder what happens to that heat?
Ender: So the water vapour in clouds also traps IR? What about the water vapour we cannot see – does that trap IR also?
Yes and no. It absorbs IR and shares the energy with other species while some people call this trapping I think it creates a wrong impression because it radiates it as well and once the atmosphere is in thermal equilibrium at the same rate it receives it in all directions. Hence it only “traps” it until thermal equilibrium is achieved then it just hands it off to the next layer and so on.
Clouds reflect (and scatter and absorb some) infrared just like they do with SW incoming so the overall effect is that they raise albedo AND reduce absorbance AND reduce emissivity.
I’m not interested is cosmic ray theory I think it’s still far from proved even though there is some persuasive data about any suggestion that I’m about advancing cosmic ray theory amounts to a strawman red herring. Forget it.
Jan – “Hence it only “traps” it until thermal equilibrium is achieved then it just hands it off to the next layer and so on.”
However that is exactly what we have been saying. If the greenhouse gases trap the IR then it does not make it back out to space as it is transferred to other molecules as you said.
The more you say, the more you are confirming the greenhouse gas idea of warming.
To summerise, you agree thatthe Earths emissivity is lowered by clouds and greenhouse gases such as water vapour. So theoretically, to maintain its radiation balance, the Earth must be then warmer to emit sufficient energy through the layers of clouds and greenhouse gases so that the incoming energy balances the outgoing. Scientists have indeed confirmed by direct observation that that global average temperatures are warmer than then black body temperature by an amount consistent with the measured and observed energy flows. So the prediction is confirmed by observation.
You have to agree with this as it is a summary of your recent comments.
Ender: “The more you say, the more you are confirming the greenhouse gas idea of warming.”
Don’t mistake for some who thinks the presence of CO2 has no effect this is not the case I don’t think the effect is as great as that put about IPCC and the like. CO2 (and water vapour) in the atmosphere makes the air a lot more comfortable than it would be without it but I expect that the effect on the solid surface temperatures will be minimal <1K/2xCO2 is as low and high as I’m prepared to go for the reasons mentioned above.
ender; I have just the paper for you; it is by Peter Dietze; in it he compares clear sky and cloudy sky forcing, and looks at the effect of vapor and the Svensmark factor and cosmic rays;
http://www.john-daly.com/forcing/moderr.htm
Try not to go the ad hom with Dietze who has a masters in engineering.
ender; your fascination with clouds is addressed in this paper which compares CO2 forcing in clear-sky and cloudy-sky conditions, and also looks at the crucial role of vapor, and for good measure the Svensmark factor and cosmic rays;
http://www.john-daly.com/forcing/moderr.htm
cohenite: Dietze, based on the Daly site can hardly be neutral. Let’s say some other engineering types don’t bother with it.
Folks: If I had to catch up again, the first place to look is here -
http://www.johnwiley.com.au/trade/engine.jsp?page=browseTitles_l3&pt_banner$acecode=CHXXXX&acecode4$acecode=CHXXXX&all$sacecode=CH0300
Then -
http://www.johnwiley.com.au/trade/engine.jsp?page=browseTitles_l3&pt_banner$acecode=CHXXXX&acecode4$acecode=CHXXXX&all$sacecode=CH0600
And so on -
Reckon it would take a while?
Jan said that greenhouse gases only trap until thermal equilibrium is reached and then the radiation is handed off to the next level.
This is not true. You can see that this is the case by looking at emission spectra at various levels, for example in this figure, you see that the blackbody equivalent temperature in the CO2 absorption region is about 220 K, while that in the clearer windows is about 290 K, a leaky trap, but a trap all the same.
“The more you say, the more you are confirming the greenhouse gas idea of warming.”
Only in a very simplistic model. If more CO2 in the atmosphere causes less moisture, then there does not need to be warming. It’s the amount and balance of all greenhouse gases that makes the difference. You cannot treat the addition of CO2 in an isolated manner, and you cannot assume that the addition of CO2 will increase the amount of moisture. It may in fact decrease the amount of moisture.
Eli: “for example in this figure, you see that the blackbody equivalent temperature in the CO2 absorption region is about 220 K, while that in the clearer windows is about 290 K, ”
Which figure was that?
This one?
http://i165.photobucket.com/albums/u43/gplracerx/PettyFig8-2.jpg
these are coincident downward and upward reading in the CO2 band shows BB equivalent temperature 268K and the downward clear areas it’s also 268K indicating the surface layer is in thermal equilibrium with the surface. A certain amount of the energy absorbed is converted to kinetic energy which is heating the atmosphere which causes the warmed parcel of air to rise. Some kinetic energy is thus being converted to potential energy which does NOT contribute to radiation but the KE that remains does. Therefore we will have less radiation the higher we go from CO2 because there is less KE to radiate but nothing is being leaked it is being used.
r
Jan; beautiful; but I assume you mean the surface layer is in thermal equilibrium with the ‘atmosphere’?
“Therefore we will have less radiation the higher we go from CO2 because there is less KE to radiate but nothing is being leaked it is being used”
And you know this how?
And sorry for forgetting you prof;
“You cannot treat the addition of CO2 in an isolated manner, and you cannot assume that the addition of CO2 will increase the amount of moisture. It may in fact decrease the amount of moisture.”
Indeed Minschwaner and Dessler provide the theory for that, while NOAA has provided the detail with relative humidity falling at pressures of 925mb or above; below that, increases in low cloud cover, another Miskolczian -ve feedback, are producing the increase in moisture. So with Kirchhoff put to bed by Jan, and the prof on board with Miskolczi, the stinking corpse of AGW can be entombed in the Erhlich mausoleum of failed doomsday scenarios.
just spat more coffee over a new keyboard. Blogging is expensive.
Ender: “And you know this how?”
Law of conservation of energy is well established.
cohenite: “but I assume you mean the surface layer is in thermal equilibrium with the ‘atmosphere’?”
Each layer is in local thermal equilibrium, which is actually an approximation, with the one above and below and that includes the solid surface with the skin layer.
You can even see it in a MODTRAN simulation downward looking at 100m where the BB radiation in the window as at the surface temperature and that in the CO2 absorption band it’s due to emission from CO2 at the same temperature.
http://i229.photobucket.com/albums/ee272/JanPompe/rad29193535.gif
“Law of conservation of energy is well established.”
That doesn’t explain anything that you are talking about.
“Each layer is in local thermal equilibrium, which is actually an approximation, with the one above and below and that includes the solid surface with the skin layer.”
Makes me think you have no idea what you are talking about, you seem to be at some stage of understanding that has not reached to the level of Calculus yet.
Ender: “That doesn’t explain anything that you are talking about.”
Perhaps not to you but I didn’t expect that it would.
for a constant entropy
dQ = dU – dW
dQ is the energy input dU is the change in internal energy dW is the energy required to do work (for example convection) nothing is lost it can’t go anywhere except out. The radiation form the atmosphere is proportional to the 4th power of temperature or if you prefer the 4th power of it’s average kinetic energy now the higher you go the more of this kinetic energy has been converted to potential energy which does not contribute to the radiation this is the “leak” Rabbett is talking about but as you can see it’s not a leak.
As the parcel of air sinks it regains the kinetic energy from potential energy.
Jan, if you are at 20km looking down almost all of the atmosphere (molecules)is below you. You see about the same thing at 100 km looking down.
Rabbet “Jan, if you are at 20km looking down almost all of the atmosphere (molecules)is below you. You see about the same thing at 100 km looking down.”
I know you “see” the same thing at 70 km looking down but is it really the same think you are looking at. At 20 km you are looking at and seeing in the window the surface radiation barely modified and that would be the similar at 70km but wrt 15micron band we are looking at the radiation from CO2 at different heights to a depth of a few metres because of the atmospheric opacity in that band. Strangely enough the temperature at around 70km is very similar to the temperature at 20 km, so perhaps we aren’t really seeing the same thing at all. We can’t even see the thermal radiation due to the higher temperature at the stratopause in the 15 m icron band.
Now that rather boring trivially obvious lot is not really relevant. Looking down from 20 km you see the surface radiation in the window which is at the BB equivalent of 268K the upward one shows the same temperature driven radiation from the CO2 absorption band meaning the temperatures are the same. That the downward looking radiation at 20 km for the CO2 band is ~220K hardly surprising as that is about the temperature of the tropopause where the kinetic energy has been converted to potential energy.
So start at the bottom and work your way up in 1 km increments, look up and down. You might learn something like the radiation from lower levels in the CO2 bands does not get out to space, e.g. it is blocked
Rabbett:So start at the bottom and work your way up in 1 km increments, look up and down. You might learn something like the radiation from lower levels in the CO2 bands does not get out to space, e.g. it is blocked
It doesn’t get blocked it gets diverted some gets used before being radiated off to space e.g. something had to power my sailboat.
What we see in the upward looking chart is that the atmosphere radiates very well in bands where there are polyatomic atmospheric species with resonant vibration modes not so well where there aren’t. Without them the atmosphere will take quite a bit longer to cool but then without them the atmosphere would probably not warm as fast or as much.
Without polyatomic my sailboat would probably never have worked but then we would be here either and would it never have been built in the first place.
Not really. The largest changes are when you look up. For one thing the water vapor concentration and absorptions change radically. There is practically none left at 15 km. That is the lapse rate at work as the saturated vapor pressure of water vapor decreases with temperature. You will notice that there is a lot less emission from CO2 as the altitude increases, and if you look closely you will see that the width of the band decreases.
Looking down you will notice that there is practically no absorption at 100 m, and the CO2 and water bands grow in with altitude. This is because the layers near the surface are practically at the same temperature as the surface so the atmosphere appears transparent with equal amounts of absorption and emission. As one goes higher there is more absorption than emission, so the window closes.
For those who wish, the application to see these things is at
http://geosci.uchicago.edu/~archer/cgimodels/radiation.html
[...] by the IPCC scientists are similar to those often discussed at this blog, including the issue of cloud feedback and climate sensitivity. There have been recent major breakthroughs in this area by Dr Roy Spencer a so-called climate [...]