Update: It seems that the UNFCCC background page referred to below has changed and the link no longer works – see table of contents.
A response from Justin Wood, writing to me from Australia after my previous post (cited with permission below), has prompted me to write a follow-up on the story of the greenhouse effect (GHE).
I wonder if you’ve seen this terrible description of the greenhouse effect on a UNFCCC background page? http://unfccc.int/essential_background/feeling_the_heat/items/2903.php
It actually says that incoming solar energy is ‘reflected’ by the planet’s surface ‘in the form of a calmer, more slow-moving type of energy called infrared radiation. … Infrared radiation is carried slowly aloft by air currents, and its eventual escape into space is delayed by greenhouse gases’ (emphasis added).Given your recent excellent explanation of the real physics on RC, I thought you might be interested! It’s downright disturbing that this silliness comes from such an important source; and I’ve found it repeated all over the place. (On that RC post, I would humbly suggest that the section on stratospheric cooling could helpfully be expanded to make that clearer?)
I won’t discuss the stratospheric cooling now, but rather try to place recent events (including floods in Niger), which involve the hydrological cycle and atmospheric circulation, into the framework from my previous post ‘A simple recipe for GHE‘.
Again, it can be useful to stop and contemplate whether a simple conceptual framework can provide greater understanding of climate model predictions and the observations we make on the climate system. I think that there are not too many simple descriptions, as Wood pointed out, that are convincing in terms of physics.
Can we use such simple conceptual explanations for events such as the recent spate of extreme rainfall and heat waves then? I want to stress, as we did when discussing tropical cyclones, that single events do not constitute evidence of a climate change. Since climate can be defined as ‘typical weather pattern’ (or weather statistics), then climate change can be that extremes become more or less typical, and such change must start with a few events. This touches the difference between weather and climate, and each of these events can be considered as weather. But there is a connection between these weather events and results obtained from climate models.
There are fascinating as well as disconcerting sides to the fact that global climate models reported in the IPCC AR4 suggest warming in the upper troposphere in the tropics (Figure 1 below). I regard these traits as important clues that may help unveil the secrets of the troposphere; The key into this mystery involves energy conservation, planetary energy balance, and the planetary energy input taking place at its surface while its heat loss mainly occurs at higher levels, as discussed in ‘A simple recipe for GHE‘.
This story is about surface fluxes, a fuzzy connection between energy flow and circulation of water, and physical constraints pin-pointing the solutions. In other words, the hydrological cycle associated with moisture transport is tied to the energy flow associated with moist convection.
Another simple mental picture
I will yet again try to present a simplified physical picture: Our climate includes energy transport both from the equatorial region to the poles as well as a vertical flow from the surface to the height from which it can escape freely into outer space. The story behind mid-to-upper tropospheric warming strongly involves the vertical energy flow, which will be the focus of the discussion. In very simple terms, the laws of physics say there has to be a flow of energy from the planet’s surface, where energy is deposited, to the heights from where the heat loss takes place (see schematic below).
The vertical energy flow can take several forms: radiative, latent, and sensible heat. The radiative energy transfer has a character of diffusion (photon diffusion), and the more opaque the atmosphere, due to increased GHG concentrations, the slower the effective radiative energy transfer. A similar situation is believed to take place in the outer layer of the Sun, in the opaque convective zone, where convection is the main mode of energy transfer (which by the way subsequently play a role in solar activity).
If this were the whole story, then an increase in GHG concentrations would imply a deficit between the rate of energy gained at the surface and heat loss from the upper atmosphere due to hypothetically lowered energy transfer between the two levels: The emission temperature would decline as a result of net heat loss high up, and surface temperature would increase as a result of net gain in energy on the ground.
One consequence of a deficit in the vertical energy flow would be different heating and cooling rates at different heights that subsequently would alter the atmosphere’s vertical structure (lapse rate). The planetary heat loss would drop if the emission temperature were to drop, and the planet would no longer be in energy balance, resulting in energy accumulation. However, planets will eventually reach new equilibrium states where the heat-loss balances the energy input.
Other forms for heat flow between the two levels are expected to compensate for the reduction in radiative energy transfer (despite greater temperature differences) if the planetary energy input and heat loss are to balance. One such candidate is convection, carrying both latent and sensible heat and where the energy transfer takes place in form of heat-carrying vertical motion. Indeed, warming below and cooling aloft give rise to more unstable conditions that favours convection.
Higher temperatures near the surface also cause increased evaporation according to a physical law known as ‘the Clapeyron-Clausius equation‘. Evaporation requires energy so that heat, which otherwise would go to increase temperatures, is instead used to transform water to water vapour (phase change). Differences in the molecular weights of N2 and H2O means that moist air is lighter than dry air. Thus, increased evaporation favours convection, which transports both energy – as sensible (higher temperature) and latent (vapour) heat – and moisture. This is seen occurring naturally, especially in association with warm ocean surface in connection with the El Nino Southern Oscillation. Convection can therefore compensate for reduced radiative transfer if its mean vertical extent reaches the height of the planetary heat loss. Convection also is one of the factors that determines the thickness of the tropopause (Wikipedia on Troposphere: “The word troposphere derives from the Greek: tropos for “turning” or “mixing,” reflecting the fact that turbulent mixing plays an important role in the troposphere’s structure and behavior.”).
Moist convection results in cloud formation: water vapour condenses and form cloud drops. The condensation releases heat and hence increase the temperatures, which subsequently has an effect on the black body radiation. Hence, cloud formation plays a crucial role for the planetary heat loss – in addition to affecting the planetary albedo.
The reason why Figure 9.1 in IPCC AR4 is disconcerting is that the temperature anomaly in the upper tropical atmosphere bears the signature of increased moist convective activity, which means that the hydrological cycle probably gets perturbed by increased GHG forcings, hence affecting rainfall patterns.
There have been some misunderstanding regarding the enhanced warming in the upper troposphere – mistakenly taken as being inconsistent with the climate models, or taken as the “finger print” of GHE, rather than as a plausible consequence predicted for an enhanced GHE due to the perturbation of the hydrological cycle (the “finger print”-misconception assumes that the models are perfect).
Changes in the convective activity also have other repercussions. Air just doesn’t pile up, but if is rises in some places, it means that there is sinking air elsewhere. A typical example of this is the Hadley cell, where the circulation involves rising air near equator associated with low sea level pressure and downward motion poleward of this region – an arid region known as the subtropics with high sea level pressure. A change in convection on a planetary scale, due to compensating a reduction in the vertical radiative energy transport, hence may have a bearing on drought and flooding events – and this is what the global climate models seem to suggest. If a shift in the hydrological cycle were to lower the response in the global mean temperature, there may be a poisonous sting in such a negative feedback: changes in the precipitation patterns.
When GHG concentrations change, there is also a disruption in the vertical energy flow so that the planetary energy balance is perturbed. This is the frequently cited extra forcing estimated at the top of the atmosphere (TOA), and this is where some of the assumptions made above don’t quite hold (the picture is correct for a planet in equilibrium, but during a transition the planet is no longer in an equilibrium) and extra energy is taken up by warming of the oceans and surface.
As a physicist, the key to understanding the relationship between GHE and the hydrological cycle – and indeed the troposphere – is in embedded in the question of what happens with the energy flow between the two levels where the planet receives its energy and where it leaves the planet. For more numbers and details, I’d recommend a number of posts previously published here on RC (here, here, here, here, and here).
Re 98 (and 97) Hank Roberts – Thanks. (Of course by ‘generally’ I was refering to the basic pattern of large-scale mechanically wind-driven gyres. As with effects of spatially-varying ocean bathymetry/geometry, I’d expect different longitudinal variations in atmospheric circulation if the prevailing westerlies shifted sufficiently that they interacted with different mountain ranges, etc…) (PS did you get my climate sensitivity reference in my question about Captcha?)
Hank Roberts 98
Hi.
Wallace Broecker, father of the thermohaline conveyor circulation and author of a recent book chronicling these events (review at http://www.amazon.com/Great-Ocean-Conveyor-Discovering-Trigger/product-reviews/0691143544/ref=dp_top_cm_cr_acr_txt?ie=UTF8&showViewpoints=1) has a long term interest in abrupt climate change, its triggers, etc.
In 1997 Wallace published a description of some of the ideas in science (at http://www.amazon.com/Great-Ocean-Conveyor-Discovering-Trigger/product-reviews/0691143544/ref=dp_top_cm_cr_acr_txt?ie=UTF8&showViewpoints=1). The paper now has over 650 cites. Although Wallace’s studies were of Younger Dryas and other D&O events, ISTM that they might be applicable to some of the current Arctic activity.
You may recall a 2005 RC discussion on Anomalous Recent Warmth in Europe (found at https://www.realclimate.org/index.php/archives/2005/01/anomalous-recent-warmth/) which I believe touches on the same topic (with the usual trollish diversions, of course).
Hank, these refs may have little or no bearing on your request for references and even if they do, you are probably well aware of them. Should this not be the case however, you might find them interesting reading. [If I’m still just mixing the wrong things together, please forgive me – as you know, that’s my style.]
I was hoping Urs Neu might give us an update on how Wallace’s THC shut-off hypothesis was viewed today since 1997 was over 13 years ago…
David Benson 85
Thanks but no thanks. AFAIAC Gerry North (NAS) quashed the “Hockey Stick” controversy in 2006. At worst, MM was prescient.
Mike’s current research on synchronization of NH and SH wrt stuff like MWP, or MCA if you prefer, is spot on. (What else would you expect me to say, we are both products of the same physics department [8<)]. )
Your reference was worth a look to me; thank you, I found it entertaining. OTOH, I have little time or interest in a rerun.
DeNihilist@100 – Not out in left field, quite … apple trees [and less so, pear trees] have a hormonally controlled biennial tendency, if they have a heavy crop one year they put all their energy into growing that seasons fruit so can’t put much into growing next years buds at the same time, hence a light crop the following year. Doubt the ENSO would follow that pattern, it appears instead that El Ninos will become more frequent with increasing temperatures.
87 Surfer Dave: We are studying the troposphere because those heat sources are irrelevant. Heat comes from the sun and gets dumped into the 2.7 degree Kelvin [almost 500 below F] of deep space. The temperature is determined by the rate of heat dumping into deep space. Without the sun, the atmosphere freezes in 2 months. The troposphere and the stratosphere control our temperature.
99 (Rod B),
Please support this statement with specific quotes from my posts to John Peter. Be clear and precise as to how any such statement fits your characterization.
On the other hand, if something I’ve said is, you think, simply incorrect, then point it out and point to the contraindicating facts.
Or you could just label people that don’t agree with you as “religious” zealots guilty of “demon casting” (which is exactly the behavior that you’re currently engaged in).
Surfer Dave 87,
The mean global flux absorbed by the climate system from sunlight is 237 watts per square meter. The mean global flux of geothermal heat is 0.087 watts per square meter. Divide A by B. Discuss.
Re : post 78
“It is not enough to know what should be done, it is necessary to also know how to do it.”
John Peter – If you’d read the literature (like I have) you’d know not only what the costs, and human implications, of not doing something are, but also what the costs, and implications, of “doing it” are. The costs are surprisingly small. The co-benefits are large and, disappointingly, unquanitifed (this is not a oxymoronic statement. The impacts of poor air quality on Asian agriculure and health are vast, but poorly quanitified).
Indeed, I’m struggling to understand what literature it is you read. Perhaps you should get away from physics for a little while and consider economics, health studies and engineering.
Re 80 (John Peter):
The Younger Dryas and the possible THC shut off took place in an environment that was characterized by the end of the last ice age and thus by the melting of huge ice masses that were much larger than the ice that has remained until today. The effect of huge melt water input on the THC is plausible for the YD. However, an event like this today is unlikely, because the ice masses around the North Atlantic are much smaller and thus also the probability of huge meltwater pulses. The only remaining ice mass that could deliver meltwater in a comparable order of magnitude is Greenland. This ice sheet is almost completely grounded on land with the underground deepest in the middle and only small outlet glaciers. Therefore it is unlikely that this ice mass will melt down in a relatively short time, although we cannot exclude unknown processes which might speed up melting considerably. There are more plausible physical processes for rapid collapse of the West Antarctic Ice Sheet, since it is grounded below sea level with large borders to open sea. This would not affect North Atlantic THC but might influence ocean currents and deep water formation in the southern hemisphere. Today’s model projections do not point to a shut down of the NA THC but to a slow down which would reduce warming, but not induce cooling, in the region around the North Atlantic
Re 86/88 (patrick027):
There are a huge number of possible processes/influences etc. that might be induced by the shift of the polar front, you mention a couple of them. The problem is, that many of them are interconnected, some of them inducing changes of opposite sign. An assessement of these processes should include an estimate of the strength of the influence compared to other processes and random variability and a consideration of possible counter-acting processes (e.g. has the stronger coriolis force due to a poleward shift of the polar front a noticeable effect on the formation of the circulation structures, compared to other effects?). Such effects could (at least theoretically) be investigated in models, but also for these questions we will face the problem of the description and analysis of wave formation and patterns.
I’ll take out one other example, that of the speed of westerlies. Changes are likely to be influenced by opposing influences. While a decrease of the meridional temperature gradient in general decreases the pressure gradient and thus wind speed, a decrease of the wave amplitude will possibly lead to an increase of high wind speeds, because the highest wind speeds occur in flow sections with very low wave amplitudes. The overall effect on average and extrem wind speed is not easy to estimate.
A partial analogy for the greenhouse effect.
Here is my suggestion.
The Fraunhofer lines discovered about 200 years ago and later used thoughout astrophysics. They are only a partial analogy because they do not involve two quite different forms of energy transport, short and long wave in predominantly opposite directions.But unlike the glasshouse, they do involve something similar to the lapse rate i.e that the outer surface of a star is relatively cold. The actual warming would of course be small relative to the total stellar output.
One aspect of this analogy is that that someone observing the Earth from outer space would be able to use these nineteenth century ideas to identify the presence of CO2 and water vapour in our atmosphere and to illustrate the terrestrial greehouse effect.
The “GW is a religion” line has been around for a few years. My guess is that it is preemptive. Obviously, dinialists who assume that all the science and scientists are wrong are in danger of being accused of simply clinging to their beliefs in a religious manner. But if they use the term of those who accurately present the threats of global warming, it will look to outsiders that both are just calling each other names.
It is a clever trick, but highly ironic, given the religious views of many of those denying climate science.
Back to that science, I’m not sure I can follow all that is being said here, but it certainly strikes me that a much warmer Arctic could play a big role in changing the strength or quality of the basic patterns of circulation in the Northern hemisphere. How far toward the equator would these changes reach in their effects?
to DeNi #100. IMHO the answer is no. Though I certainly expect and hope next year will be cooler than this year, the trend of warmer temps will continue. I expect 2011 will be warmer than 1999. Though the pendulum swings some scoundrel keeps lifting the clock and putting blocks under the feet.
urs neu 109
Thank you for another clear, concise, comprehensive right to the point answer to my query. It really helps with my education.
John Peter – Assuming you are being straightforward, and not sarcastic, I’d suggest the following bits of literature are of interest.
IPCC Working Group Three Report (www.ipcc.ch)
International Energy Agency World Energy Outlook, and Energy Technology Perspectives
David Mackay’s book “Sustainable energy without the hot air”
The Stern Review
This is all definitely OT now, so I’ll shut up.
I’m the last person in the world to suggest how to simply anything but I had an idea and I’ll share it with you all.
If you want explanations that are easier for people to understand, forget “energy” and use “heat”. This should remove a level of indirection since people can sense heat directly. “Energy” is a (slightly) more complex notion and requires that “temperature” must also be addressed. Also everyone is familiar with “heat” which is all that we really sense and feel.
We should lose no technical integrity with descriptions of climate change in terms of heat. Scientifically “heat” is merely “energy” in transit. Any tight description of a process in terms of “heat” should be easily translatable by scientific types into the language of “energy” which is what we climate scientists, being more sophisticated and educated, have been dealing with all along.
Beginning with Archimedes earth, air, fire and water were the four universal elements of nature. In the seventeenth century, Becher added a fifth element to assist the chemists of that day to better describe their experiments and processes.Until recently scientists, mostly chemists, dealt with such a substance, named “phlogiston”.
“”*** Becher suggested a hypothetical substance, which he called “inflammable earth” which every flammable substance contains. Stahl called this mysterious, unknown substance “phlogiston” (pronounced flow-JISS-tunn). During combustion, phlogiston is given off into the air:
wood —> calx (ash) + phlogiston (to the air)
iron —> calx (rust) + phlogiston (to the air)
You and I know that this is not true, that instead various substances combine with oxygen during combustion. But, please suspend your righteous contempt for this phlogiston theory, and try to ignore your inside information, and look at the theory as a somewhat skeptical 18th century chemist would. I will continue to use some 18th century terminology, to keep your mind from leaping ahead to 20th century chemistry.***” http://www.jimloy.com/physics/phlogstn.htm
As with “ether”, phlogiston was a substance and was easier for people, even the early scientists, to deal with. Astronomers employed the concept to describe various properties of the planets. It served pretty well through Maxwell’s electro-magnetic wave radiation formalization until Plank or Einstein, I don’t remember which, moved us into the world of dual particle/wave physics.
To better serve Rasmus’s need for simple descriptions, global energy balance, could be described as a redistribution of heat received from the sun to the oceans, land surfaces, atmosphere and (partially) back to space.
Heat could be stored in the ocean, absorbed by the glaciers, etc., etc.
I could go on and on (ugh), but instead let me throw out a challenge. Someone come up with a process that Rasmus needs to cover, and I’ll try to come up with an heat substance description of that process, with energy replaced by heat and temperature as something that people could sense (hypothetically, of course).
Patrick,
Your reference in 96 above, to the forcings chart reminded me of a few CO2 questions. For reference, I have no science background.
In the article below:
http://www.pik-potsdam.de/~stefan/Publications/Book_chapters/Rahmstorf_Zedillo_2008.pdf
Rahmstorf says:
“Without any feedbacks, a doubling of CO2 (which amounts to a forcing of 3.7 W/m2) would result in 1°C global warming, which is easy to calculate and is undisputed.”
“This consensus holds that a doubling of CO2 anthropogenic climate change
causes a radiative forcing of 3.7 W/m2, which in equilibrium would cause 3°C ± 1.5°C of global warming.”
Although I know that this is not the case, there appears to be a discrepancy in temperature change/watt. How is the 1C figure, (CO2 doubling temp effect,sans feedback) calculated? From the total 3C effect back; or from infrared line? analysis, line broadening calculations? Or both or others? Are there multiple methods of calculating the number? Are the methods independent of each other?
So the calculation of the feedback radiative effect resides in the forcing number, 3.7 Wm2, and the 3C + – temperature increase?
Now, back to the forcings chart. The Total Net Anthropogenic # of 1.6wm2 includes the CO2 forcing with feedback radiative effects from wv and albedo?
Next, when considering contributions to the greenhouse effect, water vapor 50%, clouds 25%, CO2 20%, other 5%, are confidence levels in those contribution estimates similar? Or, for example, is a lower confidence associated with the cloud estimate? Are there multiple methods to calculate these estimates?
Finally, I recall from Ray P’s book, during the writing phase, sentiment akin to the following:
All aspects of the essential chemistry, radiative physics and thermodynamics underlying the prediction of human-caused global warming have been verified in numerous laboratory experiments or observations of the Earth and other planets.
Are you able to flesh out, from an evidential point of view, verification of the science, or examples of it, in lab. experiments and Earth/planet obs. What are examples of intersections between chemistry, radiative physics, thermodynamics, and lab experiments, Earth/planet obs. I am looking for examples of evidence of CO2 forced warming that I can communicate to others.
Thank you, Patrick.
I think it’s very, very important that simple explanations of these processes exist, and I thank you for this valiant attempt. As science communicator, I’d like to offer some tips:
– People who read the web tend to want a clear overview right at the start. Because there was a long introductory discussion before you began answering the question, it was difficult for me to follow your train of thought from the question to the answer. I suggest waiting until the end to discuss whether simple conceptual frameworks are valuable – especially when the post itself is aimed at people who need these conceptual frameworks!
– Don’t use the word “simple” so much. It comes across as patronizing, and if a reader cannot understand the text, he or she might feel stupid. How about something like a “nonspeci4list’s overview”?
– Hyperlinks within the text are nowhere near as valuable as clear explanations. It’s time-consuming and confusing to click on a word, read a new page, and then return to the context of the word and read the rest of the sentence. Just do without the term, or quickly define it.
– Your drawing is almost impossible to understand. I know we’re not all artistically trained, but it’s getting easier and easier to whip up something in PowerPoint or some other graphics program.
– Simplify your language. Many of your larger words could be replaced with simpler ones, while still retaining the character and credibility of the post. Your sentences are often absolutely packed with information — the resulting reduced word count isn’t worth sacrificing clarity.
– Have a nonspeci4list read your post and give you feedback before you post it. You’ll be surprised by what you missed.
I very much appreciate these attempts, and they’re sorely needed. But adhering to just a few quick communication rules would make these “simple” posts more accessible. I predict that the number of readers who object to the basic nature of the post will be overwhelmed by the number of new readers who now longer find these types of posts so intimidating.
(Sorry about the ‘4’s for ‘a’s — your site blocks comments with the word ‘speci4list’, but I don’t think there’s a better word.)
Re: #112
http://en.wikipedia.org/wiki/Psychological_projection
That covers it and lots more besides, except that in a propaganda campaign its not all unconscious.
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Silk 115
Not the least sarcastic, because I truly respect your analysis and articulation. Web accessible literature is easiest for me but I can try to get some books from our local library. Looking at your list however I am curious as to what you thought I meant in 78 where I said
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“…FWIW, I believe globally we are very short of resources for our world’s population. With this in mind we must certainly try to adjust our behaviors wrt CC.
As one example, I believe we have waited much too long to try to find alternatives for fossil fuels. One result is that developing nations like China, trying to improve the quality of life of their citizens by following centuries old models that developed nations used have little choice but to continue to pollute…”
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I was trying to show Bob some sensitivity to sociology, resource depletion and global asset economics. What went wrong?
burt says: 17 August 2010 at 4:47 PM
Not to butt in, but in the nature of offering a perspective on the utility of what you’re asking of Patrick…
Imagine you meet a person who does not believe an internal combustion engine functions in the way most of us understand to be the case. If you could supply the level of detail you’re referring to in the case of climate forcing, do you think such a person would be swayed?
In other words, what’s the point? Why bother constructing a case designed to reach the utter fringe of the population, those who have such an unusual perspective?
You could simply point to NCDC’s Climate Indicators page as well as Spencer Weart’s book “The History of Global Warming and achieve the same effect as you would with exhaustive personal effort. If the person is tractable, can be reached with reasoned arguments, you’re done. If not forget about it because for reasons we can only speculate about they’re beyond reach.
107 – thank you – in winter, what is the rate of insolation on the Antartic? is it different to that of summer? is it 237 W m2 at all times of the year? if is not, is that insolation more sensitive to the output of the sun, ie do variations of TSI have more impact on polar regions than perhaps on the equatorial? niave questions from me.
does the geothermal rate vary with the season? i’m sure it would vary geographically, but can we assume it is generally evenly distributed over the planet’s surface? if i divide the winter polar insolation rate (A) by the (invarying?) geothermal (B) don’t I get zero? ie, at that time geothermal energy has infinitely more influence than insolation for that region?
but my niave question was more about sensible heat directly injected into the atmosphere as convection currents from all our mechanical heat pumps (cooling towers, car radiators, etc). I understand that it is small, 10TW per annum and I am better educated for that fact thank you.
btw, neither of these tiny factors (geothermal, human sensible heat) seem to appear in the IPCC diagram that one kind reader linked to. i guess the supporting text to the diagram discusses them as being too small to include.
Re 116 burt –
1. The approx. 1 K warming is the warming of the surface and troposphere that is necessary to cause an approximately 3.7 W/m2 increase in upward net LW flux at the tropopause (global time average). A doubling of CO2 reduces the net upward LW flux at the tropopause by approximately 3.7 W/m2 (global time average); that reduction causes an imbalance – heat builds up, changing the temperature, until the balance is restored.
(Note that the 3.7 W/m2 forcing at the tropopause level is with stratospheric adjustment. Doubling CO2 causes a larger direct (instantaneous) forcing at the tropopause level, but it causes stratospheric cooling; this cooling reduces the downward LW flux at the tropopause level, thus bringing the net effect at the tropopause level to a 3.7 W/m2 forcing. The stratosphere will actually warm up a bit in response to surface+tropospheric warming, which will feed back on the surface+troposphere via downward stratospheric emission; however, I don’t think this is very large for Earthly conditions (because the stratosphere doesn’t absorb much of the upward radiation from below – see also some of the comments at https://www.realclimate.org/index.php/archives/2010/07/a-simple-recipe-for-ghe/ (and the approx. 1 K warming may include that effect )
The forcings listed in that IPCC graphic are externally imposed forcings (in the sense that they are changes that have been caused by something other than climate change); they do not include climate change feedbacks.
Optical properties that change as a function of climate will cause radiative feedbacks, and the temperature responds to those as it would externally imposed radiative forcing. (For a stable climate, the warming that results from feedback is less than the warming that causes the same magnitude of feedback; in order to sustain that same amount of feedback, some additional warmth must be supported by external forcing).
Re: 119
Not at all, Doug. I appreciate your posts, and I recall a number of them on the topic of climate science communication. In this case, you may well be right, but influence of others is also a factor.
Prior to hitting submit,I muttered “This is embarrassing,” and then I hit submit anyway.
I trust that Patrick will act in his own interest.
Thank you, Patrick.
… in case that last part wasn’t clear
For example, consider a feedback of 3.7 W/m2 per 2 K warming, where a 1 K warming would change the net outgoing flux by 3.7 W/m2. Then a 2 K perturbation would produce a feedback that could only support 1 K of that warmth; cooling would result, and as the feedback responds to that cooling, even less of the temperature perturbation can be supported – thus the perturbation eventually decays to zero. Now starting from zero temperature perturbation, an imposed forcing of 3.7 W/m2 would cause heat to build up, eventually raising the temperature 1 K – there is an initial imbalance of 3.7 W/m2, and the imbalance decays as the temperature approaches the new equilibrium. But the feedback adds 1.85 W/m2 per 1 K warming to the imbalance, so the imbalance only decays half as quickly, and the heat builds up more. When the temperature has risen 2 K, the imbalance has decayed to zero and the system is again at equilibrium, with 1 K of warming supported directly by the imposed forcing and the other 1 K supported by the feedback that is supported by the full warming.
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Regarding the apportionment of the total greenhouse effect, see discussion and links here:
https://www.realclimate.org/index.php/archives/2010/07/a-simple-recipe-for-ghe/comment-page-8/#comment-181122
(which is the first of a series of comments I made, the first few being more relevant to the meaning of the total greenhouse effect):
391
404,405,409,
—
413, 414, 420, 421,
426, 427,
428 – 431, 433, 436
(PS some other comments I made pp 7-9:
stratospheric cooling:
340, 344, 348, 356, 368, 370, 372 – 377 (but see also 388), 387,
my better comments: 437 – 441, 443 – 446
(see also Andy Lacis 341 and 366, Chris Colose 343 and 359, Hank Roberts 347)
other stuff 395,396, 398, 400, 401
thermodynamics and radiation
350,351,353
390,399
411,419,424
412 internal variability )
burt says: 17 August 2010 at 9:45 PM
Prior to hitting submit,I muttered “This is embarrassing,” and then I hit submit anyway.
Well, as the saying goes, “the only dumb question is the one not asked” so don’t feel embarrassed. Me, I’m jaded. :-)
Re 121 Surfer Dave
10TW per annum – that’s an order of magnitude statement, it might actually be 12 or 14 TW, I don’t remember offhand but it’s in that ballpark and certainly much less than the geothermal flux. TW is a unit of power; 10 TW per annum is the wrong unit for this quantity.
There would be some seasonal and diurnal cycles in heat coming out of the ground (or ocean), but that is from solar heating variations and storage of that energy in the ocean or uppermost layer of the land surface; the geothermal flux from deeper within the crust and below won’t have any such cycle – of course there will be local fluctuations associated with hydrothermal and volcanic activity; but generally the geothermal flux is relatively steady except on much longer timescales. There will be some pulsation of tidal energy dissipation, of course (most obviously, besides the diurnal and semidiurnal tides themselves, the cycle through the spring and neap tides).
Solar TSI variations will have their bigger direct impact where solar energy is absorbed more; in the annual average that is at low latitudes (because the tilt of the Earth’s axis is not much larger), though at TOA the largest incident solar fluxes are near summer solstices at the highest latitudes (because the tilt of the Earth is large enough for this) – the amount of solar radiation actually absorbed may still be small at high latitudes because of remaining summer snow/ice (and the angle of the sun affects scattering in the air and by clouds as well as off the surface, but I don’t know all the details of that) – but this won’t have as much effect on the UV absorption by ozone; and the solar variability is relatively greater for UV than it is for the whole spectrum in total. Of course, then we have to consider the distribution of ozone…
But the effect of the spatial distribution of solar heating can be smeared out (horizontally as well as vertically) by convection and (essentially only vertically) by LW responses, and might be small relative to the effect of the spatial distribution of feedbacks (there is a characteristic spatial and seasonal pattern to the changes in climate in response to a generalized warming provided the external forcing that drives it is not too idiosyncratic.)
Solar heating drops to essentially zero at each poles for about half the year.
Re Justin Woods’s comment:
“I wonder if you’ve seen this terrible description of the greenhouse effect on a UNFCCC background page”?
Readers of RealClimate might be interested in a more terrible statement that appears in the Sunday NY Times which suggests that the theory of global warming might be “revived” after the recent Russian heat wave, floods in Pakistan, and in Tennessee.
In Weather Chaos, a Case for Global Warming
http://www.nytimes.com/2010/08/15/science/earth/15climate.html?_r=1&scp=2&sq=global%20warming&st=cse
To suggest that the theory of global warming has been discredited but may demand a second look is outrageous. How will the editors of the NY Times be able to look at themselves in the mirror in the next several years as the effects of climate change become more and more extreme? The Times has truly become a second-rate newspaper.
Re 109 Urs neu – Thank you (and if you knew of any books specifically on the topic, I would enjoy reading it)
– with the speed of the westerlies affect quasistationary Rossby wave behavior (as well as PV gradients affecing baroclinic instability), I was wondering (based on the dependence on winds throughout the atmosphere and not just the surface) about the effect of the increasing meridional temperature gradient at higher levels combined with (particularly at some latitudes/seasons) the opposite change near the surface – neither of which actually directly determines the surface wind, only the geostrophic wind shear.
Regarding waste heat, Skeptical Science has a nice little post on the matter here, followed by a ~200 comment adventure touching on such topics as Schrödinger’s cat, Romans, magnetrons, dead horses, engine blocks, buckets of water, the Sahara Desert, billiard tables, Al Gore, the Apollo program, light bulbs, mirrors, lizards, boulders, Philadelphia, thunderstorms, Chuck Yeager, Phoenicians and much, much more.
All this to avoid grappling with the ratio of anthropogenic waste heat to greenhouse warming, ~1:100, ~0.028 versus ~2.9 watts/m^2. A breathtaking display of agile, elliptical evasion of the very finest kind.
The real gag is “RSVP.” Us clowns should know better.
Burt 116,
The radiative equilibrium temperature of the Earth can be found by inverting the Stefan-Boltzmann law:
T = (F / σ)0.25 [1]
where F is the flux density absorbed by the planet. For Earth F is about 237 watts per square meter.
If we define
k = (1 / σ)0.25 [2]
Then, substituting and differentiating [1],
dT/dF = 0.25 k F-0.75 [3a]
And
dT = dF (k / 4) F-0.75
For σ = 5.6704 x 10-8, k/4 works out to about 16.2, so given dF = 3.7 W m-2 for doubled carbon dioxide, dT = 0.99 K.
The greenhouse effect makes the Earth about 13% warmer, at 288 K, than its radiative equilibrium temperature of 254 K. So at the surface this would correspond to about a 1.1 K increase in temperature.
With no feedbacks.
John Peter – Re: 119
No problem with that at all. Looks sane to be.
However, was riled by your suggestions that uncertainty (in either the magnitude of warming, the magnitude of the impact, or the cost of alternatives) precluded dealing with the problem.
The magnitude is will understood, within (for a phyicist) fairly large error margins. i.e. climate sensitivity is around 3 degrees, plus or minus 1.5 degrees
Impacts is not my area, but plenty of published material on this. IPCC WG2 is a good starting point. Even from my limited knowledge, I would suggest a 5% chance of a 4.5 degree C increase in global mean temperature (at 550ppm CO2e, which we will exceed on a BAU profile sometime before 2050 according to the International Energy Agency) is absolutely terrifying
The cost of dealing with the problem (a problem that needs to be dealt with in any case, as you noted) is large, but not so large as one might expect. The documents I listed provide more details on this.
Re: #128
You need some supporting argument. Apparent mismatch here between comment and linked article?
#128–But that’s not what the story says.
It is not “the theory of AGW” that is (allegedly) revived, but rather “the question of whether global warming causes more weather extremes.”
I’d agree that “revive” is not the best choice of verb, but the Times story is pretty good overall, IMO.
Len @ 128,
I understood the term “revived” in the sense that the opinion polls showed a drop in concern after the extremely cold northern winter, but now that there has been an extremely hot northern summer, the OP’s may be “revived”.
re128 and following – I like that the article was pretty dismissive of denialists …. AND included good quotes from Schmidt and Trenberth, as well as providing references – I don’t see any suggestion “global warming has been discredited”, overall I’d say it is foward looking.
119 (John Peter),
Let’s start from scratch.
I have two issues with your posts (outside of their patronizing I-know-more-than-you tone).
The first was the implication that there are large areas of doubt in climate science. I accept your overall premise that there is much doubt about individual specifics, but not the basic scenario that CO2 is dangerously warming the world. On those details, you seemed to try to hedge and further impart doubt, while to me (and I think many here) the basic equation of
is beyond denial, while
is looking dangerously likely (not certain, but likely enough to warrant action).
The accusations of being “religious” about this scientifically gained and documented, wide base of knowledge, of course, was an unnecessary side irritation.
My second point of contention is your position that we need to know more before we can do anything about it. You are right in that we need to know more if our strategy is to proactively adapt (i.e. mitigate the dangerous symptoms while leaving the underlying disease untreated). This is, to me, a fatally flawed strategy. That expense will far exceed the cost of true mitigation (i.e. reasonably reducing CO2 emissions ASAP), and may even be impossible to do in many, many cases… not to mention the human suffering involved (see Moscow, 2010, for a possible example, specific attribution always being too difficult to make accurate claims).
So, I’ll leave it to you to clarify your position (without going OT into CC mitigation details) on:
1) What aspects of climate science you feel are in doubt, solely with respect to whether or not warming is occurring, how much can be expected, and what the cause is.
2) What sort of details science does not have nailed down which you feel are required before civilization can begin to take effective action (again, without wandering too far into the actual actions that might be taken).
Please do so in light of the post at hand, i.e. the idea that many people misunderstand the science and so need clear explanations of what we really do and do not know, and what the implications are of each.
Re Patrick027, Hank Roberts, Urs Neu, John Peter, and the discussion about changing tropospheric circulation and its coupling to the Atlantic Meridional Overturning Circulation, I have a rhetorical question and a few thoughts.
Why doesn’t the Atlantic Ocean circulation mirror the Hadley tropospheric circulation, with upwelling and warming at the equator, polar motion at the surface, evaporation/salinity increase+cooling, density driven sinking near both poles, and equatorward motion of deep currents to close north and south loops?
I once read a paper (unfortunately I can’t find a reference to it) that showed mathematically and with easy to grasp diagrams, a simple slab model of the circulation in the Atlantic. They used a rectangular box model, 4000 km wide, 4km deep, extending from 65S to 60N, with notches in the side representing the Drake passage and the region south of the Cape of Good Hope. Flow into this model ocean through the Drake passage(mean transport of 123 Sv and a range of 87 to 148 Sv ) driven by the Antarctic Polar Vortex, without any other wind or thermohaline forcings, is altered by Ekman transport(coriolis effect) into a north surface current and a south deep current(the base AMOC), and mass balance is maintained by net flow eastward south of the Cape of Good Hope.
Equatorial trade winds divert the surface flow westward, and the net Ekman transport symmetrically across the equator is zero; this drives surface circulation of two gyres. They have north currents along the US Coast, south current past Europe, south current along Brazil, and north current near the African coast. Superposition(vector summation) of the AMOC and the gyres enhances the Gulf Stream(30 to 150 Sv, increasing to the north) and the Benguela current(ca 29 Sv), and reducing the Brazil and Azores currents(ca 18 and 10-12 Sv respectively).
Thermohaline sinking in the North Atlantic works with & strengthens the AMOC; thermohaline forcing is working against the AMOC in the South Atlantic. The shape of Brazil diverts most of the equatorial current north into the Caribbean
further increasing Gulf Stream flow.
The width(northward extent) and depth of the passage south of the Cape of Good Hope provides a path for cold Atlantic bottom water to exit into the Indian Ocean/Pacific circulation, and a return path for large quantities of surface water via the Agulhas current, 40-70 Sv. A good discussion of Atlantic Ocean currents can be found at http://oceancurrents.rsmas.miami.edu/atlantic/atlantic-arrows.html, and was the source for the strength of the various currents I gave.
My guess is that even with a catastrophic(in the scientific sense of abrupt and nonlinear dynamics) collapse of the Greenland Ice sheet and fresh water injection into the North Atlantic, the AMOC would not stop, but would slow and the sinking region would move south. There is some evidence that this happened during the Younger Dryas – http://www.sciencemag.org/cgi/content/abstract/280/5364/725. AGW changes in the jet stream, and Hadley circulation, will likely change the details of ocean circulation, and there will be “minor” consequences – like the occasional complete snow coverage of the UK, or flash floods in France – http://www.guardian.co.uk/world/2010/jun/16/flash-floods-france-casualties.
The strengthening of the Antarctic vortex will tend to support the AMOC. “Table 10 shows 30-yr trends in this index calculated independently for each calendar month. Positive trends, indicative of a strengthening of the westerlies at subpolar latitudes, are evident in all but one month. They exceed the 90% significance threshold during six calendar months, and no clear seasonality is evident.”
http://journals.ametsoc.org/doi/full/10.1175/1520-0442%282000%29013%3C1018%3AAMITEC%3E2.0.CO%3B2#s5
Len Conly17 August 2010 at 11:0 PM
The NYT article isn’t as bad as you describe. Apart from the tendentious title, in fact I think it was pretty good.
You said about the article that it suggests that the theory of global warming might be “revived”…
But in reality it said this:
…these far-flung disasters are reviving the question of whether global warming is causing more weather extremes…
That is something completely different. The theory of global warming itself is never in doubt throughout the article.
Furthermore, both Gavin Schmidt and Kevin Trenberth were quoted and no contrarian bloggers. That is refreshing.
128 Len Conly: Thank you. The bad news is that the NYT is representative of people in general. Nobody ever went broke by underestimating the average intelligence. THAT is our problem. Is Homo Sap worthy of survival?
Silk 132
Nice job!
In the past, I claimed good familiarity with IPCC, and even some TAR. I’ve been all over WG1 (use it as an index to the science papers). Until your posts, did not realize I’d hadn’t even looked at WG-2.
I’ll fix that problem.
Thank again
Fueled by anti-Obama rhetoric and news articles purportedly showing scientists manipulating their own data, Republicans running for the House, Senate and governor’s mansions have gotten bolder in stating their doubts over the well-established link between man-made greenhouse gas emissions and global warming.
Read more: http://www.politico.com/news/stories/0810/41192.html#ixzz0x2Gcj8ul
Bob 137
#70 is my negative review of your six point approach as to how to best describe GHE, this topic of this thread. A negative review, that’s all.
The rest has become very tedious. Let’s stop.
John Peter. Let’s look at a non-physics analogy for a moment.
A medically knowledgeable person enters a community and notices a large number of people exhibiting signs of cretinism and a similar number with ugly goitres disfiguring their necks. Aha! Iodine deficiency, we say. What do we do next?
What we don’t do is delay action while we ascertain the precise details of which particular areas of cropland display more or less iodine deficiency. We don’t wait for elaborate testing of everyone to see all the exact details of thyroid dysfunction in each and every individual. We don’t have an orgy of genetic testing to see which individuals are more susceptible or resilient to iodine deficiency.
We straight away start supplementing everyone’s diet with iodine. In climate terms that would be mitigation, reducing the prime cause of the problem. Then we start checking all the goitre afflicted individuals and prescribing suitable doses of thyroxine to compensate for their depleted thyroid function. In climate terms, that would be mitigation. Like dealing with fire, flood and agricultural problems. And the people born with cretinism? They’re the irretrievable casualties. In climate terms, migration, starvation, drowning, death from heat.
In this community, a couple of generations will see the casualties die off and not recur because pregnant women have adequate thyroid function. The people who needed medication lived longer and healthier and more productive lives before they died. The new generations are born healthy with normal intelligence and stay healthy so long as they keep an eye on their diet and get medication as soon as there are signs it is needed.
For climate, it may take a few more generations to get to the happier final condition.
But getting started is the main requirement.
The finer details, of regional impacts especially, will require much more of the work you’re talking about.
Oh dear. That second “mitigation” should be adaptation.
Geoff Wexler says:
16 August 2010 at 7:34 PM
Re #73 and #71 (not #70)
I can’t see that it’s anything other than a strong analogy.
[i.e. the glass greenhouse]
I can’t discuss this if you do not address the comments I make. But I shall try once more. I know the reference in #70 is tedious and flawed, but you would only have needed to read the part devoted to the well known weakness of the glasshouse analogy.
The glasshouse may be useful as a case study expecially in your hands, when you may be there to point out the contrast between the glasshouse , based on blocking convection, with the greenhouse gas effect based on escaping radiation from cold layers high up.You would be able to contrast the large fall in temperature between the ground and the radiating levels in the atmosphere with the tiny fall in temperature in the first 8 feet to the top of a glasshouse.
You would be there to point out that the analogy might work with a huge sheet of glass placed high up in the troposphere where it would re-radiate weakly at a really low temperature.
You would be there to explain that rock salt is analagous to oxygen and nitrogen in the sense that it is a good transmitter of infra-red, but all the same provides a good alternative to glass in keeping the glasshouse warm (by blocking convection) and is therefore not analagous after all to O2 and N2 in its actual behaviour. You would thus be able to discuss Wood’s old experiment (nearly 100 years ago) and show why this experiment would be irrelevant i.e that his contrarian claim that he had disproved the greenhouse gas mechanism was wrong.
The trouble is that other people , not in your classroom, are reading the Spectator where Wood’s false interpretation of his results,revived by Gerlich and Treuschner has joined the other zombified arguments.
Agree 100% with your last sentence, Wood’s comment that he’d only given it a cursory analysis (and as you correctly point out, inaccurate analysis) is usually ignored. However the analogy isn’t as bad as is commonly stated. The atmosphere does have a convective block (the tropopause) like the greenhouse, additionally the glass provides a filter like the ghg in the atmosphere does, which passes visible and blocks part of the IR.
John Peter,
I am afraid that uncertainty provides no refuge for the inactivist. The empirical evidence makes it unequivocal that the planet is warming, and the science we know about the climate makes it clear that we are the only possible culprit. What the science cannot yet do is bound the risk. We cannot with any degree of confidence say this won´t spell the end of civilization and mass extinction. Probabilistic risk assessment tells us that the only feasible strategy in such circumstances is risk avoidance. Any other choice is irresponsible.
And since the science does not yet allow us to exhaustively assess the feasibility and side effects of mitigations other than reducing cargon emissions,… it doesn´t help your case there either. I´ll keep saying it ´til you get it: Uncertainty is not your friend.
143 (John Peter),
A cop out.
It amounts to the position that you can make unsupported claims (a “review”) about my statements, but you want those claims to stand on their own because you can’t be bothered. But okay, so be it.
You do say that despite your doubts in GHE we do need to take action… some day.
At the same time, you’ve claimed we need far more information before we act, but you now refuse to support that position with details, as well.
Looking back at your posts, I’m finding you have never included a clear statement of the details of your own position. Just “we don’t know enough, let’s wait.” That’s it.
I think you should rectify that. I’ll ask again. You said:
Please explain what sort of details science does not have nailed down, but which you feel are required before civilization can begin to take effective action (again, without wandering too far into the actual actions that might be taken).
Please do so in light of the post at hand, i.e. the idea that many people misunderstand the science and so need clear explanations of what we really do and do not know, how and how strongly, and what the implications are of each.
Ray Ladbury wrote: “We cannot with any degree of confidence say this won´t spell the end of civilization and mass extinction.”
It’s worth noting that a single “extreme weather event” may yet prove sufficient to cause something resembling “the end of civilization” in Pakistan.
> the AMOC would not stop, but would slow and
> the sinking region would move south.
I recall Peter Ward makes the same point; it explains the periods of formation of anoxic deep water (warmer, carries less oxygen)