BBO Discussion Forums: Climate change - BBO Discussion Forums

Daniel1960, on 2012-May-17, 12:24, said:

This is false. As I laid out in more detail, most of the sun's energy is in the visible spectrum. Look up Wien's law for the maximum energy out put of a black body per unit frequency. The higher the temperature, the shorter the wavelength where it peaks. The earth is cooler than the sun, and emits in the IR wavelengths.

McIntyre's work in this area has specifically not been aimed at suggesting that there is no global warming occurring. His stance has, to my knowledge, always been that the world is warming but that there is little evidence that this warming is exceptional, in particular in relation to the Little Ice Age (LIA). He has been extremely successful in pointing out various statistical failings used in the modelling that produces the "hockey stick" graphs. As a mathematician, the most fundamental thing wrong with these models is that they fail the statistical test usually used for models of this type. In fact the climate models have a correlation on this statistic of close to zero. On the other hand the modellers use a different statistic which has a confidence level of over 90%. It is still unclear what these differing statistics mean but the whole process has not been without criticism from some statisticians.

What is clear is that the process used is extremely sensitive to a single dataset becoming dominant in the final numbers. The reason for this is that the whole methiod depends on weightings for different datasets representing regions. Some datasets have only a small number of data points which means that each data point has a very high weighting. If such a dataset is used in combination with other datasets with a comparatively weak signal the result is that the final graph will look very much like the "dominant" dataset. This is the reason why Yamals, and bristlecone pines before that, are so important. Without these datasets containing such a dominant signal the hockey-stick shape of the graph disappears. This is the major problem with these graphs - they are not really very resilient to different data sets being used. This may well be a remnant of the zero correlation I mentioned in the first paragraph.

Meanwhile, there are continuing fears about the ice sheets. The good news here is that the Antarctic may be gaining ice. It is certainly gaining ice in some places and losing it in others. On the other hand the Arctic has certainly lost a significant area of ice. I say area because the ice sheet covers less land but is thicker. Overall there is less ice though and (afaik) noone is disputing this. This is where we come back to the LIA. During this period the records indicate that there was less ice in, for example, Greenland than there is now. The models do not show a LIA because the modellers say the Southern Hemisphere was cold enough to offset the LIA effect, which their records indicate was localised to Northern Europe (despite some records suggesting there were abnormally warm years during this period in many other countries). If this is the case then it might well be that the world was (much) cooler during the LIA despite having less Arctic ice. It does not suggest that the lack of ice alone should be taken as an indicator of catastrophic warming though.

There are several other aspects which have been effectively debunked despite newspaper claims that like to suggest them from time to time. One obvious one refers to "serious wether events". When this was first mentioned a (pro-AGW) Norwegian group investigated the numbers of SWEs and found that there had been no change over time. There was a slight increase in the Northern hemisphere and a slight decrease in the Southern. This came as a surprise. You can, of course, change the criteria and create statistics on both sides of this. Nonetheless I believe this original study is still valid.

Now to the computer models. The most compelling evidence for AGW comes from these. It surprises a lot of people that the amount of warming that greenhouse gases, especially CO2, cause directly is tiny. You can measure this in the lab and the effect is that beyond a certain point the increased warming would not increase temperatures to anything like dangerous levels, pretty much ever. However, this does not tell the whole story because increasing greenhouse gases does a lot more than the direct effect would suggest. There are a number of feedbacks that occur which amplify the effects. These feedbacks are complicated and every computer model has different values for them. The most controvercial feedback is currently clouds. Clouds are just incredibly complicated; it depends on what type of cloud you get as to whether clouds are a positive feedback (warmer) or a negative feedback (colder). There are several scientists who believe clouds will turn out to be an overall negative feedback. However, all of the major models currently have clouds with a positive feedback.

Finally, there is the temperature record itself. You might think it is simple to measure the temperature and for the numbers to be comparable acorss centuries. Unfortunately almost all of the older temperature records are taken in urban areas of wealthy countries. That leaves a huge hole for less welathy countries. Worse than that, these urban areas have generally become major cities which are automatically warmer due to the heat island effect. This is not a trivial problem. There are also some records of the temperature record in less wealthy countries being highly inaccurate due to poor procedure being used. It should not happen but it does.

A more consistent and objective record is available using satellites. This has the disadvantage of being compartaively new but ought to be comparable acorss the entire timeframe. The problem with the satellite records is that the instruments have changed over time, both in terms of their sensitivity (age) and because new instruments needed to be fitted as replacements. This means that the satellite records are continually adjusted. These adjustments are often derided by those opposed to AGW since they are almost always positive (except for the earliest years where they are negative). I am not ebtirely sure why this is so. However, we can be fairly sure that the satellite temperature record showing an increase is true since a prominent scientist on the anti-AGW side also keeps a satellite record and this also shows warming (or did last time I looked). Therefore the main argument is not whether there is warming but rather by how much (and for some from what cause).

A few years back I got interested in this subject quite a lot and did a fair amount of research on it. I came in as a sceptic, open to the evidence. What I found is that it is clear that there is AGW. What is less clear is how much and whether our models have the feedbacks set to the right levels. Equally clear is that the maths behind the hockey-stick graph should come with a warning and are not 100% reliable. It is also obvious (to me) that we have the technology now to fix the problem, however serious it really is. We can extract the CO2 directly and store it in containers, artifical trees as some call them although I prefer the term aeroforming. Naturally noone wants to be the one paying.

The most important thing here at the end of the day is to understand "tipping points". Tipping points are where the levels change in a sudden, usually catastrophic, way. These are what produce the doomsday scenarios the papers are so fond of printing. They sound perhaps impossible and yet the world has gone through this before. So it is important to make sure that we take out insurance against these points. The good news is that they are some way off so we have a bit of time yet. The bad news is that we do not know exactly how long.

Overall, I personally do not think either side is right. The world will warm somewhat through AGW but I doubt we will ever see the levels predicted in the more extreme IPCC scenarios. The answers are available through technology. I will not be changing my lifestyle to "make a difference" and neither will the Chinese. I just hope that when we finally get around to implementing the technology that Europe gets its share of the pie too and it is not just shared out between America and China.

phil,

I am not sure where got the impression that the sun does not emit radiation in the IR spectrum. Here is a graph for your information:

http://www.physics.o...lar-energy.html

While solar radiation certainly peaks in the visible region, there is considerable incoming IR (otherwise, we would be darn cold). Integration would yield more totla energy in the IR region than visible. The cooler Earth emits radiation at much higher IR wavelengths.

Zelandakh,

Nice summary. Let me add that the assumed reason that there was less ice in Greenland during the LIA, was the large melting attributed to the MWP. Eventually, the glacial ice expanded to reach the maximum extent in the 19th century, and started receding again in the 20th century.

I agree that much of the AGW evidence comes from computer models. Most modelers will tell you that clouds constitute a positive temperature feedback, but some incorporate a positive feedback associated with increased cloud coverage, others a positive feedback associated with a decrease in cloud coverage. None have a negative feedback attributed to clouds, even though there is much speculation that increased clouds will act to decrease temperatures due to blockage of incoming radiation.

I definitely agree with your last paragraph, and find it heartening that at least one person shares a similar view to my own.

Daniel1960, on 2012-May-18, 11:03, said:

I am sure that I have never been under that impression. My assertion was that your argument that CO2 in the atmosphere would lead to a cooling effect by reflecting/absorbing solar radiation. This is completely wrong. For lots of reasons:

(1) when we say "CO2 absorbs in the infrar red" it does not mean that all of the infrared spectrum, equally. CO2's primary absorption band is at about 1500nm from memory, and then a bunch more at higher wavelengths. This is almost off the end of the spectrum for solar energy you linked to. The atmosphere is almost totally transparent in the near infrared.


(2) Here are some graphs of atmospheric transmission:


This includes CO2 and all other atmospheric gases. So you can see that I was correct. I used `visible light' as short hand for wavelengths greater than 1350nm. I am not going to attempt to provide publishable-level rigour on an internet board. Compare this to your graph of solar energy and you will see that there is virtually no solar emission in the bands of significant absorption.

(3) You realise I am a physicist yes?

Daniel1960, on 2012-May-18, 11:16, said:

I feel that there is a disconnect between how science is actually done, and how the public thinks science works. For one thing, the more science one does the more skeptical one becomes about data. There is always a reason why the data is wrong. If you can't think about at least three ways in which a data set may be completely wrong you probably are not trying hard enough. Most scientists don't care too much about actual data for this reason, because we appreciate just how poor lots of it can be. Especially if you use some kind of selection procedure. Narratives based on sound theories actually carry a lot more weight. Normally for every new piece of data there are lots of different interpretations, but there tend to be relatively few theories that are consistent across broad ranges of different types of data.


Ensemble models can generally work around uncertainties in the modelling, the only thing they require to be true is that the relationships between the variables in the past also hold in the future.

So you have two models of cloud formation, and their relationships to temperature: f(T) and g(T), and you don't know which, if any, are dominant, no problem, you put into your model af(T) +bg(T) and choose a, and b randomly as part of your mix of parameters. It might be the case that it doesn't matter too much what you choose for a and b, in which case your sucessful model runs on past history will look like a scatter plot in a and b, which means that your could formation doesnt matter at all. Ideally you might get a really strong condition like a=0.2 b=0.6 or something, which all the models need to be accurate, in which case you are pretty sure that the real atmosphere is a mix. More likely you get some range of conditions which are strongly correlated, with other variables. E.g. you can fit the past either with more cloud formation but less albedo change due to vegetation, or vice versa.

This type of uncertainty is only a problem if it causes your models to become uncorrelated. E.g., suppose g(T) is basically constant, but f(T) grows exponentially, then in the past in the flat part of the exponential it is possible for albedo to off set it, but in the future on the steeper part these two models may diverge wildly in their future estimates. If this happens you need to make theoretical choices about which are more likely, or use more past data to calibrate it.

Essentially you can see where this goes, as long as the ensemble models are reasonably strongly correlated, you are pretty sure that your parameter choices are ok, and that the range of uncertainty does not effect the model too much. The danger of ensemble modelling is that it never has new physics. It might be the case that one of your cloud formation functions changes dramatically in an unpredictable way if you warm the world two degrees, and that no quality of correlation with past data will help predict the future as the new physics is just not there in the old models.

However, I don't think many people believe that is plausible in the next fifty years or so. Most things in science are (or can be reasonably approximated as) power laws (over small changes in parameters). You can get pretty good correlation with the AGW results if you just assume that every physical law is a polynomial and fit every parameter off past data. Even if you restrict yourself to the past 50 years when data is pretty good, you get a strongly correlated set of models that predict warming.

So for cloud feedback, its very unlikely that they had to choose a specific model. More likely they have tried multiple models to see what best fit the past. They are not generally putting their models together based purely on scientific theory. They are a combination of theory and ensemble models. I suspect could formation ensemble modelling has come up with a range of parameters for the feedback, which are mostly positive, so people put the mid point of the ensemble cloud models in as theory when they want to use their models for something else.

On selection procedures:

Came across an interesting thought experient on selection procedures.

Suppose that beauty and acting are uncorrelated, but that hollywood looks for actors who have beauty+acting skill>c

Then when you look at hollywood actors you get a strong negative correlation between acting and beauty. This can also completely negate a positive correlation. This type of selection effect is prevalent in data sets, in fact its close to impossible to avoid. You look for a data set to measure A, and then someone else uses your data set to measure B instead. Suddenly they find a correlation that may be nothing more than the way in which you selected it in order to best measure A.

phil_20686, on 2012-May-18, 12:29, said:

The GCMs all have issues with fitting past data, they ignore ENSO cycles (for the most part) and they certainly haven't been able to predict squat since they came into existence in the last several decades. Might it be possible that their correlation amongst themselves, as good as the theoretical science they use may be, is also a result of parameterization and the matching of their variable "effects"?

Phil,

I am a chemist, so I can relate. Having worked considerably with FTIR, I find your 1350 cutoff rather interesting, but I see you are including some of the near infra-red in the visible spectrum. Still, the sun's radiation tails off slowly, so that significant incoming radiation still exists at wavelenths past 2000 nm, out to the edge of the near IR (2500). While CO2 does absorb a greater percentage of the terrestrial IR, than solar, the solar radiation is significantly higher, such that the absorption by CO2 is non-negligible.

Daniel1960, on 2012-May-18, 12:44, said:

SUre but its just not significant. The earth emits nearly all in the deep infra red, and if you look at the absorption for that you can see it is is really much much more opaque in the deep infrared.






you can look at the whole spectrum in bits here

Compare the two spectra for incoming solar and outgoing terrestrial radiation:

http://scienceofdoom...ropera-2007.png

http://activistteach...-on-global.html

Compare them on a similar axis:

http://robbservation...ion-of-co2.html

Now compare the incoming solar radiation and outgoing terrestrial radiation at the four main absorbance bands for CO2: 1.8, 2.5, 4.2, and 16 microns.

Incoming solar radiation: 150 W/m2, 50 W/m2, ~1 W/m2, and 0 W/m2

Outgoing terrestrial radiations: 0, 0, 2 W/m2, and 17 W/m2.

The incoming solar radiation in the lower CO2 IR absorption areas is ~100 x higher than in tghe outgoing terrestrial area, and about three times higher in the , such that the smaller IR absorption by CO2 at the lower wavelengths are not insignificant.

So the graphs there didnt seem that helpful:




So I am not totally sure what your point is, so i will just repeat those I made above:
(1) The atmosphere is much more transparent at visible wavelengths than it is in the far infra-red where the earth radiates. By about a factor of 4.
(2) Yes H20 is the most important green house gas, accounting for 70% of the greenhouse effect. But that isn't too important, as the quantity of water vapour basically depends on the temperature, it is never a driver of climate change.
(3) All effects of atmospheric composition are easily modelled. I repeat my earlier assertion: if you know the atmospheric composition you know the temperature.
(4) The most important unknown is the precise relationship between the temperature and the density of water vapour, but it is almost certainly well captured by ensemble models. To disbelieve that is to believe that the relationship between water vapour and temperature has some kind of discontinuity. While it is impossible to rule out such things, it does not seem likely that in a small range of temperature change (we are talking 2-5 degrees out of an absolute range of 300k), the behaviour should change dramatically.
(5) There are also uncertainties about albedo and biological feedback, but these are generally assumed to be small. Given that biological feedback is almost wholly controlled by humans, (cutting down rainforest far outweighs any small increase in their metabolic rate), it does not seem plausible to believe that it will change soon.

I believe that the biggest risk of a tipping point is almost certainly in the albedo. The Hadley cycle is fundamentally unstable, at the moment it runs with five channels and generates the trade winds. If it moved to a different number of channels it would significantly alter the distribution of temperature across the globe. In particular it is not impossible that by making the polar cells smaller (in terms of lattitude) there would be a significant drop in polar temperature, with a corresponding rise in tropical temperatures. This could affect the albedo, but such considerations are pure speculation. We have no reason to suppose that a 2- 5 degree warming is enough to cause such a change.

A self-referential comment by Steve McIntyre concerning the "Hockey Stick" and the IPCC methods and manners.

Posted May 27, 2012 at 7:03 AM | Permalink | Reply

In 2005 before ar4, I wrote the following response at Roger Pielke’s to the question about whether the Hockey Stick “mattered”. I didn’t get interested in it because it seemed like a vulnerable topic but because it was presented to the public, at least in Canada, not as an incidental argument, but as one of the major arguments, particularly for action right that instant.

Stefan Rahmsdorf and others (including Roger Pielke, the proprietor of this site) have taken the position that the Hockey Stick is irrelevant to the great issue of the impact of 2xCO2 on global climate. Even the originator of the Hockey Stick, Michael Mann, who received many awards and honors for its construction, ironically has taken the position that it doesn’t “matter”. (I do not believe that he has not returned any of the honors.) I’m inclined to agree that, for the most part, the Hockey Stick does not matter to the great issue of the impact of 2xCO2. However, I believe that it matters (or should matter) to IPCC, to governments that relied on IPCC and to climate scientists who contributed to and supported IPCC and to people who may wish to rely on IPCC in the future.

The Hockey Stick was not, as sometimes portrayed, an incidental graphic, buried in IPCC TAR. Nor was it an icon resurrected by sceptics purely to torment poor Michael Mann. It could almost characterized as the logo for IPCC TAR. Figure 1 below shows Sir John Houghton, at the press conference releasing IPCC TAR, standing in front of the Hockey Stick. The graphic was used repeatedly in IPCC TAR and was one of the most prominent graphics in the Summary for Policymakers. Some governments (and, the Canadian government in particular) relied upon it in their promotion of Kyoto policy even more than IPCC. In the lead-up to adopting Kyoto policy, Canadians were told by their Minister of the Environment that “1998 was the warmest year of the millennium and 1990s the warmest decade”. So even if the Hockey Stick did not “matter” to the scientific case, it mattered to the promotion of the scientific case. Scientists may want to “move on”, but institutions cannot, if they want to maintain any credibility. If the Hockey Stick was wrong, it would be as embarrassing as the failure to find WMD in Iraq. In both cases, the policy might well be justified on alternative grounds, but the existence of the alternative grounds does not mean that responsible agencies should not try to isolate the causes of intelligence failure and try to avoid similar failures in the future.

The issues surrounding the MBH Hockey Stick are complicated by IPCC TAR statements and decisions, which, in retrospect, seem misguided, although there is little to suggest that IPCC AR4 is taking to steps to avoid similar potential problems. The most questionable IPCC statement about the Hockey Stick is that the MBH98 reconstruction had “significant skill in independent cross-validation tests”. I added bold to highlight the plural—a second level to the misrepresentation contained in this claim. The statement appears to have been written by Michael Mann about his own work. It is now known that the MBH98 reconstruction in the controversial 15th century portion failed the majority of cross-validation tests, including the standard R2 test [McIntyre and McKitrick, 2005a]; the source code provided to the Barton Committee shows that the adverse cross-validation R2 statistics were calculated, but not reported. It is also now known that the MBH98 reconstruction does not live up to its warranty that it is robust to the presence/absence of all dendroclimatic indicators, as the reconstruction depends on the inclusion of bristlecones, a series known to be potentially contaminated as a temperature proxy. Again, this adverse information was known to the authors and not reported.

If I were in Houghton’s shoes, I would be mad as a boil about all this. Since Houghton has a sincere belief that the impact of 2xCO2 is the great issue of our times, then, if I were Houghton, I would be particularly angry at being placed in a position where I used this logo and wasn’t fully informed about adverse information pertaining to it. I also wouldn’t be leaving it up to some probably adversarial committee like the Barton Committee to sort this out. I’d be all over the problem so that my community, the community of climate scientists, was not further embarrassed and so that government institutions would be able to rely confidently on the opinions of IPCC.

If I were Houghton, one line of argument that I would not accept is that the other “independent” studies all say similar things. It was the Mann study that I stood in front of. If there are serious problems in it, which were known ahead of time and I didn’t know about them, I would carve everyone involved a new you-know-what. Now for public purposes, I’d feel a lot happier if I could at least retreat to the safe haven of other studies that showed something at least similar to the Mann study. But I’d be pretty worried about them on a couple of counts and I’d want them torn through from top to bottom. The first thing that would worry me is that the studies were not really “independent”. The coauthors all seem to swap places: you see Mann, Jones, Briffa, Bradley, Cook, Schweingruber – all well-known scientists, but all having coauthored together. I’d be worried about a monoculture and want a fresh set of eyes. The second thing that would worry me is that the same proxies are used over and over – the bristlecones, the Polar Urals etc. I’d be worried about systemic problems. I’d be worried that no one seemed to have gone through these other studies like M&M had gone through the MBH studies. Maybe there are more time-bombs. I wouldn’t just passively wait for them to go off.

If I were Houghton, I would be enraged at the public refusal by IPCC authors to show their data and methods. When I read in the Wall Street Journal that Mann had said that he would not be “intimidated” into showing his algorithm, I’d have taken immediate action; I’d have told Mann to stop acting like a prima donna, to archive every line of code and data used in MBH98 and stop fighting a pointless battle that simply embarrassed IPCC and the entire field of climate science. I’d have done more than that. I’d have notified everyone contributing to IPCC that we did not expect the same kind of nonsense any more, that anyone contributing to IPCC would have to ensure that their archives of data and methodology were complete or else we couldn’t use their articles. I’d have done so before I heard from some redneck Republicans.

I would also review how we were checking studies in IPCC AR4. If our very logo for IPCC TAR blew up on us, then something was wrong with our procedures for review. I wouldn’t go around patting ourselves on the back and telling everyone that this was the most “rigorous” review procedure in the history of science, since we’d goofed on such a prominent issue. I’d want to know why we goofed and how to avoid it in the future, or at least, how to minimize the chances of a recurrence. So when some redneck tried to use the Hockey Stick fiasco against IPCC, I’d at least have an answer.

A final thing that I’d ask myself: if this damn chart is “irrelevant” to the great issue of 2xCO2, why did we use it at all? And why did we rely on it so much in our sales presentations? Why didn’t we just talk about the issues that were important and stay away from little irrelevant stuff? Maybe I’d find out, when I investigated, that someone had decided that this was merely for sales promotion – the climate equivalent of a sexy girl sitting on a car. If that were the case, I wouldn’t necessarily be happy about it, but at least I’d understand it. Then I’d want to make sure that we were also selling steak as well as sizzle. I’d sure want to make sure that we’d really done a good job on the issue which Ramsdorff and others now say was the “real” issue: climate sensitivity to 2xCO2.

Here I’d be bothered by how little guidance we actually gave to policymakers interested in an intermediate-complexity analysis of whether 2xC02 will lead to a temperature increase of 0.6 deg C or 2.6 deg C or 5.6 deg C. When I re-examined the TAR, I’d notice that we’d virtually skipped over these matters. I’d think: it’s not enough just to list all the results of different models; let’s try to figure out why one model differs from another, what are the circumstances under which a model gives a low sensitivity and what are the circumstances that a model has high sensitivity – if that’s the “real issue”. When I saw that we’d barely touched this sort of analysis in IPCC TAR, I’d be pretty embarrassed. I would certainly vow that in AR4, we would not repeat the mistake of ignoring the “real issues” in favor of hood ornaments.

The other thing that I wouldn’t do is simply ignore the problem and hope that it goes away of its own accord. I wouldn’t rely on the assurances of Mann and similar protagonists that the various alleged defects do not “matter”. No corporation would do so in similar circumstances and IPCC shouldn’t either. I would long ago have got some independent statistician to see if there really was a problem that I should be worried about. I wouldn’t have stood still for this water torture. I’d tell Mann to co-operate with the investigator and request McIntyre to cooperate. I’d try to get the parties to sign off on an exact statement of points and issues that everyone agreed on and ones that were in dispute. Once I saw what was in dispute, I’d ask for what would be involved to determine once and for all who was right on specific issues. I would long ago have gotten tired of barrages from both sides, where I couldn’t be sure that they were not at cross-purposes.

So does the Hockey Stick matter? Yes, if you’re a climate scientist that believes that the IPCC is an important institution whose opinions should be valued. Mann now thinks that the Hockey Stick does not matter. As so often, life is full of ironies.

At the time, I sharply criticized the use of conflicted scientists to carry out controversial assessments – Keith Briffa was about the worst possible choice. This caveat proved out, as one of the worst revelations of the Climategate dossier was Briffa’s surreptitiously allowing Eugene Wahl, a party to the dispute, to insert assessment language in the report that varied from that sent out to external reviewers, to an assessment that more or less endorsed Wahl and Mann’s side of the dispute from the more agnostic assessment that had been sent out to reviewers.

The destruction of emails that Jones later instigated pertained to these review comments. And rather than coming clean, the University has fought disclosure of Wahl’s edits tooth and nail. All of this leaves a very unsavory impression of the people.

The people who should care about policy action of some sort, such as Allen, are the ones who should have been most concerned about getting to the bottom of what Mann, Briffa etc had done and whether there stuff constituted real “science” or was little better than paleophrenology. And should have been the ones that were most resolute in ensuring transparent and thorough inquiries.

The wider climate community took a great risk to their own credibility by idly standing by. The price has been that the credibility of the entire community has been tarnished at a time when their advice is important. That’s too bad.

But instead of blaming others, they should look in the mirror.

Phil,

I agree that the atmosphere is much more transparent in the visible than the far IR. However, the atmosphere does absorb at several bands in the near IR, where the incoming solar energy greatly exceeds the outgoing terrestrial energy; the outgoing energy varies from 14 - 20 W/m^2/micron in the major CO2 absorption region, while the incoming solar radiation is ~150-200 and ~50 W/m^2 in the two CO2 absorption regions. The energy of the incoming solar radiation is up to 100x greater than the outgoing terrestrial, such that even a small increase in absorption of the incoming IR radiation is significant compared to the large (realtive) absorption of the outgoing IR radiation.

I disagree that water vapor is not important. Large quantities of heat are transported through evaporation and precipitation, not to mentioned the previosuly discussed IR absorption.

I disagree that all effects are easily modelled, but then I may just be old school when data reigned and models were just theoretical.

I would be surprised if density changes have any measureable affect.

I am not sure about your last contention, except that we humans have a large control of the biological systems. I feel that both the albedo and biological effects are large, though not as large as atmospheric and oceanic effects, and changes in the land can have profound effects. I fail to see how the drop in polar temps could greatly increase tropical temps, especially since tropical temps appear to be the most stable longterm.

Daniel1960, on 2012-May-29, 11:00, said:

Its not really a good way to think in terms of "absorption" and "transmission" when you are talking about the global temperature. Let me put it to you this way, there are three types of atmospheric process. Absorption, emission, and scattering. In a scattering process, a photon hits a molecule, and is (essentially instantly) remitted at the same wavelength, but in a new (basically random) direction. In an emission process, two molecules bang together, and some of the energy excites one of their internal degrees of freedom and it emits a photon. Absorption is the opposite of emission, a photon is absorbed and the energy is transferred to some internal degree of freedom. Normally vibrational or rotational, but also sometimes kinetic. Sometimes (often) absorption results in the emission of a new photon at a lower energy (longer wavelength).


Absorption is the same process that heats the ground. Extra absorption heats the atmosphere whether the light is going in or out. If this doesn't convince you, consider that if there was no absorption, then the only heating would come from conduction, and since hot air rises the temperature of the atmosphere would fall monotonically with height: instead



so you can infer that only in the troposphere is the energy transfer dominated by conduction/convection. In the rest of the atmosphere it is dominated by radiative balance.

Now scattering is not wholly independent of absorption, it depends on what fraction of the energy gets re-emitted on average etc. It is certainly not correct to say that increases in the absorption in the visible bands automatically leads to enough extra scattering back into space to offset the warming effect of absorption.

My favourite way to think about it is to say that what matters is how long a given quanta will stay in the atmosphere. Scattering/reflection can make the path shorter or longer (shorter if its reflected straight out, longer if it scatters a few times before reaching the surface anyway), but absorption always makes it take longer, so it always warming.

Re the poles. The warming of the surface depends on the sin of the angle it makes with a surface perpendicular to the sun's radiation. So the warming is much higher at the equator. The atmosphere, aswell as its blanket statues, also shifts heat from the equator to the poles. This temperature difference is what drives the ocean circulations and most of the atmospheric circulations. However, it does not to so linearly, for the atmosphere the primary mechanism is the hadley cells:



and circulation within a hadley cell is much more efficient than from one cell to another. If the number of hadely cells were to change from 6 to 8, it would significantly decrease the efficiency of the this mechanism, and so the poles would not have as much energy transferred to them. Conversely, the equatorial cells would be hotter. Ocean circulation is similar, but complication by the geography of the ocean floors.

Phil,

I have no disagreement with your last post, and understand fully. I would like to add that increased absorption of IR by the atmosphere will increase warming of the atmosphere (from both soalr and terrestrial radiation). This will lead to a decrease in the surface absorption, due to a reduction in incoming solar radiation. Indeed, the increase in atmospheric sulphates has been postulated as a cause of the cooling trends in the 1960s-1970s and the past decade. The Earth's surface will heat/cool based on the total of the incoming solar radiation and reflected terrestrial radiation. Interestingly a recent paper about the ozone reduction of the 1980s and 1990s has been postulated as another cause of surface heating by reduction of incoming solar radiation.

http://www.sciencedi...364682612000867

An increase in Hadley cells from 6 to 8 should results in less heat flow. I have read about movement of the Hadley cells affecting local weather patterns, but not about an increase in their number. By what mechanism could this occur, and how likely is it?

Daniel1960, on 2012-May-30, 07:22, said:

I know that more intense heating normally leads to more. Its not an effect that can be analytically modelled, because it depends on turbulence. In the first instance it depends on the fact that you are heating the fluid, and so it rises, but there is a limit on how high it can rise, so eventually it has to move sideways, and it is cooling while it does that, then it falls down. It falls down basically due to energy considerations, when it falling (as its cooler and denser) has a high enough energy gradient to overcome the fact that it is pushing on a column of rising air. So how fair it goes aught to depend only on the temperature gradient at the surface. On the earth the temperature decreases away from the centre, and since the pressur relation is fairly linear it will depend on the absolute temperature change not the erlative temperature change. Warming will increase the absolute temperature gradient, so it will eventually increase the number of cells.

You can see this in a pan of liquid (try adding some die), on a very low heat it will not form cells, on a higher heat it will form only one cell, but if you heat it more fiercely it will form several cells. The process is an example of emergence of order, and of symmetry breaking, as for a pan heated evenly there is no reason why it should form a cell in one place rather than another. The exact criteria are difficult to understand, and exhibits hysteresis. It depends non trivially on how smoothly the liquids flow and that kind of thing.

Thanks Phil,

I believe that the hysteresis may be the key here. Overriding the current system may be more difficult than imagined. On the other hand, I feel that if a change in the number of Hadley cells occurred, the effects would be sudden and dramatic. Agreed?

Daniel1960, on 2012-May-30, 09:25, said:

Yes. This type of dramatic change is impossible to capture in modelling essentially, as we won't really know the criteria for a change until we see one.

hrothgar, on 2011-December-17, 19:19, said:

I would be interested in technical commentary on the statistical methods used in paleo-reconstructions using proxies.
Principle component analysis and selection criteria that produce hockey stick graphs from red noise seem to be the major complaint about the data analysis of past temperatures. It seems that "Team" climatologists are not only reluctant to divulge the data used, they don't want to provide what data was excluded or why.
My stats experience was limited to experimental design in a production environment. The maths were daunting but I did catch on that methods etc. were critically dependent on not being subjected to selection criteria, if biased by response expectations rather than technical considerations.
Are the current methods used by alarmists viable and valuable?
Should they be more rigorous given the stakes?