By Roy W. Spencer, Ph. D., October 11th, 2009
It is claimed by the IPCC that there are ‘fingerprints’ associated with global warming which can be tied to humanity’s greenhouse gas emissions, as if the signatures were somehow unique like real fingerprints.
But I have never been convinced that there is ANY fingerprint of anthropogenic warming. And the reason is that any sufficiently strong radiative warming influence – for instance, a small (even unmeasurable) decrease in cloud cover letting in slightly more sunlight starting back in the late 1970’s or 1980’s– would have had the same effect.
The intent of the following figure from Chapter 9 in the latest (AR4) version IPCC report is to convince the reader that greenhouse gas emissions have been tested against all other sources of warming, and that GHGs are the only agent that can cause substantial warming. (The snarky reference to “proof” is my addition.)
But all the figure demonstrates is that the warming influence of GHGs is stronger than that from a couple of other known external forcing mechanisms, specifically a very small increase in the sun’s output, and a change in ozone. It says absolutely nothing about the possibility that warming might have been simply part of a natural, internal fluctuation (cycle, if you wish) in the climate system.
For instance, the famous “hot spot” seen in the figure has become a hot topic in recent years since at least two satellite temperature datasets (including our UAH dataset), and most radiosonde data analyses suggest the tropical hotspot does not exist. Some have claimed that this somehow invalidates the hypothesis that anthropogenic greenhouse gas emissions are responsible for global warming.
But the hotspot is not a unique signature of manmade greenhouse gases. It simply reflects anomalous heating of the troposphere — no matter what its source. Anomalous heating gets spread throughout the depth of the troposphere by convection, and greater temperature rise in the upper troposphere than in the lower troposphere is because of latent heat release (rainfall formation) there.
For instance, a natural decrease in cloud cover would have had the same effect. It would lead to increased solar warming of the ocean, followed by warming and humidifying of the global atmosphere and an acceleration of the hydrologic cycle.
Thus, while possibly significant from the standpoint of indicating problems with feedbacks in climate models, the lack of a hotspot no more disproves manmade global warming than the existence of the hotspot would have proved manmade global warming. At most, it would be evidence that the warming influence of increasing GHGs in the models has been exaggerated, probably due to exaggerated positive feedback from water vapor.
The same is true of the supposed fingerprint of greater warming over land than over the ocean, of which there is some observational evidence. But this would also be caused by a slight decrease in cloud cover…even if that decrease only occurred over the ocean (Compo, G.P., and P. D. Sardeshmukh, 2009).
What you find in the AR4 report is artfully constructed prose about how patterns of warming are “consistent with” that expected from manmade greenhouse gases. But “consistent with” is not “proof of”.
The AR4 authors are careful to refer to “natural external factors” that have been ruled out as potential causes, like those seen in the above figure. I can only assume this is was deliberate attempt to cover themselves just in case most warming eventually gets traced to natural internal changes in the climate system, rather than to that exceedingly scarce atmospheric constituent that is necessary for life of Earth – carbon dioxide.
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Joel Shore (08:45:00) : I have studied it and you are wrong! Will answer you after work.
As is Chris Colose’s argument (Scott A. Mandia (05:24:21))
“Scott A. Mandia (05:24:21) :
@ur momisugly kurt (16:13:39) :
Just open your eyes to what is happening in the past few decades and what has happened in the past 2,000 years. What you will see today has not happened in the past 2,000 years.”
There are two problems with this argument. First, everything I said in my last post applies in spades to climate reconstructions. The procedures may well be theoretically valid, but there is no way to confirm that the results are accurate. More specifically, to determine the rate at which climate changes on a decadal time scale, you need a climate reconstruction that preserves temperature samples at a time resolution of five year intervals (twice the frequency of that of the signal you want to preserve). A good tree may be able to give you yearly measurements, with a lot of assumptions, but I find it hard to believe that, on a global scale that includes bare earth, oceans, ice, etc. you can preserve this sampling frequency at enough of a spatial resolution and a sufficiently small error metric to really be confident that your average annual temperature samples preserve temperature fluctuations at a frequency of a decade or two for times earelier than say 1800. Essentially, there may well have been steep changes in average global temperature over the last 2000 years, but the sampling that we can do would not preserve them.
Second, even supposing that the current rise in temperatures is a unique event over the last 2000 years, the linkage to CO2 is still based on coincidence, or correlation rather than causation. Random cancer clusters, earthquakes, volcanic eruptions, and a whole host of other events have severites measured by 100 year events, 500 year events, millenia events etc. The fact that something unusual is happening is not an actual demonstration of a causal link to something only hypothesized to be related to cancer, etc. Moreover, you still have the quantification issue. How can you determine how much is due to CO2 and how much is due to natural variations? What if 90% of the temperature rise we saw from 1988 to 1998 was only a 400 year event in the climate reconstructions; can you then conclude that CO2 is rersponsible for 10% or less and assume the rest is nature? Of course not.
“It is easy to criticize the models but they represent the best knowledge that scientists have to date and they predict many aspects of climate change quite well.
Because we cannot create a new planet and test climate change on it, we must use models. They are far from perfect but they are much, much better than chance.”
There may well be legitimate excuses as to why data is inconclusive, but that doesn’t change your basic facts. My criticism isn’t in using models per se, it is in relying upon them well before sufficient time has elapsed to judge their accuracy. Also, climate models may be tweaked to simulate current, and what we presume to be past climate, but again, saying that they have been shown to accurately “predict” any given aspect of climate change is simply untrue given that it takes too long to verify that their predictions were borne out
“BTW, there have been measurements of the greenhouse effect and they do match models fairly well. See:
http://go2.wordpress.com/?id=725X1342&site=wattsupwiththat.wordpress.com&url=http%3A%2F%2Fwww2.sunysuffolk.edu%2Fmandias%2Fglobal_warming%2Fgreenhouse_gases.html”
Color me unimpressed by the impact this study. At best it shows that qualitatively, models are able to reproduce the CO2 absorbtion of LW radiation that are inferred by satellite instrumentation. Although there are some who argue that the atmosphere is already saturated and that added CO2 won’t trap any more outgoing radiation, these were never very good arguments. It is inconceivable that the models weren’t designed and tweaked using the satellite data measuring outgoing longwave radiation, hence I really doubt the model’s output is truly predictive. Also, this study does nothing to either quantify the effect on temperature or quantify feedbacks.
The primary issue I have with the global warming hype isn’t the qualitative science behind the theory, it’s the quantitative science. The case that added CO2 will delay more outbound radiation, and that the earth must respond by increasing temperature is a sound one. It’s basic radiative physics. But the climate system is just that – a system, and an extraordinarily complicated one as well. The idea that after only a few decades (only one and a half to two measurment cycles) of crude study (we can’t control any inputs to the system but have to wait for nature to provide input changes in it’s own increments) we are nonetheless able to accurately quantify the response of one of a multitude of variables to changes in another is a monstrously silly proposition.
kurt says:
Could you please put this in a bold large font and tell it to P Wilson. It is rather painful having to constantly revisit arguments that were settled in the scientific literature half a century ago!
I don’t understand what you mean here. Certainly, the radiative properties of CO2 were understood; however, I think the 2001 Nature paper by Harris et al. really was the first paper to us satellite data to look at how the absorption lines for the trace gases had changed over time. So, yes, I think it was a prediction. True, it was a prediction that there was not really much controversy about in the scientific community (although there still seems to be around here), but it is still always nice to see things work out as one has predicted they must.
True that it is complicated and may hold some surprises in store for us. However, the assumption amongst most around here seems to be that the surprises will be pleasant ones, that the feedbacks will miraculously be negative, the climate will prove to be extremely insensitive to radiative perturbations, and that the increase in temperatures that we have seen in the last several decades will just turn out to have been some combination of a coincidence due to internal variability and bad data.
Unfortunately, we know that this notion of net negative feedbacks goes against our current understanding of the various feedbacks and for the case of the water vapor feedback, we now have some pretty good evidence from satellites that the upper tropospheric humidity is behaving as the models predict with this feedback and definitely not how they predict if we turn the feedback off in the models; cloud feedbacks are admittedly more difficult to verify. However, we do understand from the paleoclimate record that the earth’s climate has been quite sensitive to what appear to have been quite small perturbations…In fact, the best single-source estimate of climate sensitivity probably comes from looking at the difference between the Last Glacial Maximum and now. Other estimates derive from the climate response to the Mt. Pinatubo (which Jim Hansen actually predicted quite well in a paper written immediately after said eruption had occurred) and the rise in temperatures over the instrumental record (although this last piece of empirical data turns out to constrain the sensitivity only weakly mainly because of the large uncertainties in regards to the aerosol forcing).
All in all, it seems to me that there is a lot of evidence you are betting against when you conclude that the increases in CO2 are unlikely to have much of an impact on climate.
Paul Vaughn (13:30:20):
Basic physical processes are much too often overlooked in the AGWers’ IR-radiation-dominated view of the climate system and attendant energy (or power) budgets. With uneven thermalization of insolation on the globe, an appreciable fraction of available power goes into creating and maintaining mechanical pressure gradients, which drive the geostrophic wind. A conservative estimate for a global annual average would be ~30W/m^2.
I’m not acquainted with Barkin’s work. Perhaps you can characterize it briefly and point to a handy reference.
Joel Shore (17:44:11):
I don’t have time for a prolonged debate, but there’s nothing “miraculous” about negative feedback. Such is par for the course in actual physical systems that exhibit true feeback, as opposed to mere recirculation. What is utterly fantastic is the notion that any positive feedback is to be found in the Earth’s climate system. It would would have gone ballistic billions of years ago.
Cheers!
“John S. (18:09:58) :
I don’t have time for a prolonged debate, but there’s nothing “miraculous” about negative feedback. Such is par for the course in actual physical systems that exhibit true feeback, as opposed to mere recirculation. What is utterly fantastic is the notion that any positive feedback is to be found in the Earth’s climate system. It would would have gone ballistic billions of years ago.”
I largely agree with this except for the last couple sentences. As long as positive feedback is less than 1, you have a stable system. Having said that, feedback is not a constant function and in the real world is subject to a limited source of the feedback. In a cold climate, e.g. an ice age, there are lots of sources for positive feedback to warm the climate, but not cool it. Take albedo for example. If 45% of the earth is covered with ice, that’s a huge source of potential warming feedback as the ice slowly melts and exposes all that bare earth or water underneath it. But ice isn’t infinite. As you move into the interglacial and most of the ice has melted, the warming feedback from that mechanism slows down considerably. When the earth moves back into an ice age, all that bare earth is now a source of positive feedback to reinforce a cooling signal until the ice age is in full swing at which point there isn’t much more bare earth that can change to reflective ice. My own personal opinion is that since we are well into an interglacial, whatever positive feedback might exists to reinforce further warming should have mostly depleted itself already. But again, while that’s just an opinion I don’t think that it would be surprising at all if at the end of an interglacial the balance had shifted to net negative feedback.
Back to Joel Shore’s point, however, I was never counting on a “miracle” that all feedbacks were negative, my point was that we don’t really have much information to assess whether the net feedback is positive or negative, much less quantify the net feedback effect. Proving that mechanisms for positive feedback still exist (and I do think there are positive feedbacks still around), but without quantifying them, gains little ground in what is essentially the ultimate question.
Last, let’s also mention the speculative nature of all the catastrphic impacts of global warming. I could easily make a case that a warmer world will be a boon for mankind, causing a decrease in hurricane intensity, less drought, more food, and less energy consumption. And this is coming from someone who actually prefers colder climates to warmer ones.
“What’s the use of having developed a science well enough to make predictions if, in the end, all we’re willing to do is stand around and wait for them to come true?”
— Nobel Laureate Sherwood Rowland (referring then to ozone depletion)
I do not believe we can afford to “gamble” that the science and the models are incorrect.
I suggest you watch the lengthy video series by Greg Craven which is pure common sense:
http://manpollo.org/education/videos/videos.html
Scott Mandia:
Greg Craven’s video logic is nothing more than a reframed Pascal’s Wager.
If you concur with his logic, then I also expect to find you in Church every Sunday for the rest of your life.
“Scott Mandia (20:42:45) :
I do not believe we can afford to “gamble” that the science and the models are incorrect.
I suggest you watch the lengthy video series by Greg Craven which is pure common sense.”
I’m assuming your referring to the Oregon science teacher who laid out a case for the precautionary principal. I did watch that, and it was so full of logical holes that I cringed that this guy was teaching our children. Basically, his point was that the nightmare scenarios of global warming were so, so awful that we just had to take action against it because no matter how small the risk, the consequences of being wrong were just, well, so so awful.
The first logical flaw in that is that if you can’t asses the risk of the consequence occurring in the first place, you can’t rationally act on it. By his logic, the only rational choice of all mankind is to fervently believe in God, because the ultimate risk of not doing so is spending an etermity in purgatory, if not hell, which is well, too, too awful to take a chance on. That drive we all take to go out to eat rather than have the food in the refrigerator -stupid move given that the consequences of dying in a car wreck is simply not worth the transitory and insignificant satisfaction of having the food you crave at the moment. When making these kinds of decisions you simply cannot ignore the step of assessing the risk of a consequence occurring.
Second, he failed to evaluate the nightmare consequences of curbing CO2 emissions. Burning energy does have its benefits in economic growth, standards of living etc. Preventing the third world from economic development using cheap, abundant fossil fuels is essentially condemning them to a perpetual existence of disease, etc. Using the same logic of ignoring risks and just looking at the worst imaginable scenarios, anyone could come up with some pretty good nightmares on the other side.
Finally, about every nightmare scenario of global warming has an opposite possibility. Hurricane intensity could decrease in a warmer world due to the reduction in the temperature differential between the sea surface and the air aloft. Increased evapration could speed up the hydrogeological cycle and reduce droughts, and let us feed the world. By counteracting global warming, we could be preventing all these so, so wonderful things from happening. Again, under Craven’s logic, assesment of the probability of global warming lessening the occurrence of natural disasters is a no-no. We just look at the consequences and ask whether it is worth the gamble.
But, of course this just proves how silly it all is because the analysis just boils down to how creative you can get in stringing together a sequence of events without regard to their plausibility.
Joel Shore (08:45:00)
Richard says: “This is very important as it points to a negative feedback – something that the warmists say doesnt exist and are very uncomfortable with, as it may nullify any dangerous warming claimed due to CO2”.
Joel Shore – “As I have pointed out, the most direct implication of the “hot spot” not being there would in fact be that a negative feedback that is currently included in the models, the lapse rate feedback, should not be there. The lapse rate feedback occurs because, under the assumption that the warming is larger in the upper troposphere than at the surface, the earth’s surface doesn’t have to warm as much as the effective radiating level in the upper troposphere does in order to restore radiative balance. If the assumption is wrong, the models have a negative feedback in them that should not be there.”
You may have pointed this out, but respectfully you are not the oracle at Delphi, and in this case have got the issue completely by the tail.
The “negative feedback” that I am referring to is NOT the negative feedback that you are suggesting, which suggests that the scientific experts of the IPCC have got the science wrong on this.
Nor am I arguing that the lack of the “hot spot” show that the models are wrong about the water vapour feedback.
Of the 6 graphs shown above the only one that shows a cooling rather than warming is the effect of aerosols. If anthropogenic GHG’s cause tropospheric warming and this warming is not there then, if we assume that the “forcings” shown in the models are correct, the effect of Anthropogenic Aerosols correspondingly generated have been grossly underestimated. These very aerosols also would offset any warming effects of GHG’s and provide some of the missing negative feedback that must be there, which has caused the Earth not to warm despite rising CO2 levels.
There must be other negative feedback mechanisms fundamental to the warming caused by any means.
Me – “Real Climate may claim (to the hear hears, amens and head noddings of RW, Joel Shore and Scott Mandia) that the tropospheric “hot spot” is simply a signature of any warming, but the IPCC AR4 report says that that this hotspot is a SPECIFIC signature of Anthropogenic Global Warming.”
Joel Shore – ”I don’t think that is correct. You can tell me where you think that they say that but I seem to recall that this claim involves considerable interpretation of what they actually say. I agree that the IPCC should have been clearer in explaining how the hot spot arises but I don’t think they said anything directly incorrect about it.”
You may not think so but this is what the IPCC says “The simulated responses to natural forcing are distinct from those due to the anthropogenic forcings..” I don’t think they could be clearer than that.
Me – “The graphs shown above are from the IPCC AR4 report which SPECIFICALLY show this.”
Joel Shore – This is absolutely incorrect. …The graphs that the IPCC shows are simply not sufficient to resolve the spatial pattern of the warming for the mechanisms that are not believed to have contributed very much to the 20th century warming. For example, … …. Blah blah blah … absolute mumbo jumbo and irrelevant stuff involving the Great Gavin etc…
The 6 graphs are temperature changes due to (a) solar, (b) volcanoes, (c) GHGs, (d) ozone changes, (e) aerosols and (f) the sum of all the forcings.
These are all from the IPCC AR4 report. They are well labeled and perfectly clear. Does the GHG graph look like any of the other 4 “forcings”?
The sum is obviously wrong but that is probably due to wrongly estimating the relative influences of the various forcings.
Joel Shore – “People are using that figure from the IPCC AR4 report to try to determine something that it simply was not designed to distinguish…and are getting confused because they don’t understand the subtleties of contour plots.”
Excuse me there is nothing “subtle” about those contour plots, and they are perfectly clear, despite your efforts to mystify and obfuscate the matter.
Scott Mandia (20:42:45):
I do not believe we can afford to “gamble” that the science and the models are incorrect.
India and China are doing exactly that, wagering that the greater disaster will be for them to not modernize, using fossil fuel energy sources.
The ipcc actully made the same “gamble” by not requiring countries containing ~5 billion of the Earth’s ~6.5 billion people to adhere to its own Kyoto Protocols.
Apparently, the alleged cure to GW is taken to be worse than the alleged disease – the Precautionary Principle must also be applied to the “precautions”.
The idea that GW, regardless of cause, will be a net disease has not been established: no one has spent billions of dollars having scientists “prove” the likely and wildly optimistic benefits of GW.
The planetary experiment which the Models suggested to prove AGW resulted in the failure of the Models – the predicted “hot spot” did not materialize.
For help in spotting, here is an official link to radiosonde data:
http://www.climatescience.gov/Library/sap/sap1-1/finalreport/sap1-1-final-chap5.pdf
figure 5.7 E should actually be included under the IPCC figure above.
It is the IPCC report that is being waved as a bible to stampede the hoi polloi, and it should be clear it is wrong.
After the fact, that reality does not have a hot spot, models and modelers can scramble and play with their numerous parameters ( five parameters can fit an elephant) to fit the data, but that is all they are doing. And, BTW, when they are doing that they should give us for THE SAME RUNS the temperature projections to 2100. I strongly suspect that when they fit the measured hot spot, temperatures are rolling along reasonably.
********
kurt (18:39:49) :
I largely agree with this except for the last couple sentences. As long as positive feedback is less than 1, you have a stable system. Having said that, feedback is not a constant function and in the real world is subject to a limited source of the feedback. In a cold climate, e.g. an ice age, there are lots of sources for positive feedback to warm the climate, but not cool it. Take albedo for example. If 45% of the earth is covered with ice, that’s a huge source of potential warming feedback as the ice slowly melts and exposes all that bare earth or water underneath it. But ice isn’t infinite. As you move into the interglacial and most of the ice has melted, the warming feedback from that mechanism slows down considerably. When the earth moves back into an ice age, all that bare earth is now a source of positive feedback to reinforce a cooling signal until the ice age is in full swing at which point there isn’t much more bare earth that can change to reflective ice. My own personal opinion is that since we are well into an interglacial, whatever positive feedback might exists to reinforce further warming should have mostly depleted itself already. But again, while that’s just an opinion I don’t think that it would be surprising at all if at the end of an interglacial the balance had shifted to net negative feedback.
Kurt, your thoughts are similar to mine. The dominate positive feedback is the ice/albedo effect — especially in the temperature “mid-range” of the glacial periods. Right now there’s practically no ice except at the highest latitudes where the effect is minimal due to low solar input in those areas, so the positive feedback is mostly absent. This shows up in the ice-cores as our relatively “stable” interglacials. Once glacial conditions return & snow/ice advances into lower latitudes, temp swings are much greater (the drastic temp swings of 1500 yr period in Greenland’s cores). What causes the apparent “cap” at the bottom like the LGM (last glacial max)? This is unclear to me, but conditions could reach a point where summer snow/ice cannot survive into lower latitudes no matter how much winter snow/ice occurs — too much sun. But the essence should be the same — running out of positive feedback.
This raises a point — tho negative feedback dominates overall, especially at the high and low “caps”, positive feedback dominates in the middle temp ranges during glacials. Some positive water-vapor feedback seems to add to the ice/albedo feedback — glacial periods are also much drier than interglacials & even tropical rainforests recede to mere localized patches compared to today. During the LGM conditions were exceedingly dry & dusty.
As to what triggers transitions to/from glacial periods, the only thing I can think of to cause such rapid, global changes are ocean-current changes (atmospheric changes follow that). Milanchovich forcings are just too slow and gradual to do it by themselves. I don’t think we’ve seen in modern history the range of possible ocean-current changes — they could be dramatic.
Richard says:
Aerosols are not a feedback but a forcing. And, yes, aerosols are offsetting part of the warming. Unfortunately, the more that they offset, the higher the climate sensitivity likely is to CO2 on the basis of the instrumental temperature record. (And note that the aerosols won’t keep offsetting the warming forever since CO2 accumulates in the atmosphere whereas aerosols in the troposphere wash out quickly so their concentration is basically just proportional to the current emissions. For obvious reasons, we don’t want to keep increasing these emissions.
Well, apparently it wasn’t clear enough because you have misinterpreted what they said. Let me give you a fuller quote of what they say and then explain it to you:
So, in other words, the way the natural forcing of solar is distinct from the anthropogenic forcings is that the former warms the whole atmosphere while the latter warms the troposphere but cools the stratosphere (as is seen in the real world). There is no discussion there of whether or not tropical tropospheric amplification is expected to be different for each.
Well, I didn’t think the point was that subtle personally, but since so many people including you seem confused by it, it is apparently more subtle than I had realized. You can’t tell from looking at the graph how similar the pattern is because the pattern is not very well-resolved for the forcings like solar that don’t contribute very much. It is as simple as that. If they replotted the solar forcing with a spacing between contour levels of, say, 0.04 C instead of 0.2 C, I expect it to look very much like the one for GHGs except without the cooling in the stratosphere. And, in fact, Gavin made this sort of plot here http://www.realclimate.org/index.php/archives/2007/12/tropical-troposphere-trends/ , except instead of changing the contour levels between the two, he adjusted the two forcings so the magnitude of the temperature effects are about the same. (This may in fact be better for detecting the spatial structure due to a forcing since I am not sure how small you can have a forcing by before noise tends to overwhelm the spatial structure.)
Even Roy Spencer says in this post, “the hotspot is not a unique signature of manmade greenhouse gases. It simply reflects anomalous heating of the troposphere — no matter what its source.” If you don’t want to believe me, maybe you can believe him.
J. Peden says:
(1) The models did not suggest this as an experiment to prove AGW since it does not distinguish between warming due to greenhouse gases and other warming mechanisms.
(2) It is still unclear whether tropical tropospheric amplification (what people loosely call the “hot spot”) occurs or not. For temperature fluctuations such as that which occur due to El Nino, where the satellite data is reliable, this amplification is clearly there. For the multidecadal temperature trends, it has been more difficult to detect; however, given the difficulty in the datasets due to contamination of these trends by artifacts (plus the fact that the prediction itself has errorbars associated with it for trends over such a time interval), one cannot really make a conclusion one way or the other at this point.
(3) The cooling of the stratosphere that is a specific prediction of the effect of greenhouse gases (and also decreases in stratospheric ozone, although the pattern of the cooling due to these two effects is somewhat different) has been seen and this cooling is so large that the signal-to-noise issues that plague the tropospheric multidecadal trends are not a problem.
kurt says:
Yeah, this might be so…However, the problem is, as James Hansen has pointed out, the calculation that gives you a climate sensitivity of ~0.75 C / (W/m^2), which translates to a sensitivity of ~3 C per CO2 doubling, considers the land ice and vegetation changes to be a forcing and not a feedback. What this means is that essentially the 3 C sensitivity in fact assumes no changes in land ice or vegetation that further lower the albedo.
True enough…but that’s what looking at the climate’s response to different events and also that numerically modeling the feedbacks (and testing those models in various ways, such as against satellite data for upper tropospheric humidity in the case of the water vapor feedback) helps us to determine.
There could be some winners, especially for small changes. However, as a general rule, change…especially quite rapid change…tends to be bad because both we and the other species that inhabit the planet are adapted to the current climate and especially the current sea levels. Also, the other species have stresses on them and limitations on them from us (due to habit fragmentation, for example) that will likely limit their abilities to adapt.
Finally, the modeling suggests that you are not correct, for example, on your hopes for less drought. In fact, drought is expected to increase in many places (especially the American Southwest). This is true due both to changes in weather patterns and due to increasing drying out from the higher temperatures. At the same time, there is also expected to be increasing in the highest magnitude precipitation events, which can lead to more flooding too.
http://www.nsstc.uah.edu/data/msu/t4/tlsglhmam_5.1
take the data and form a graph plot and see the gradient of stratospheric trend. At best, its a flat line, save for several perturbations eitherway notably Mt Pinatubo 1991
P Wilson: Every time I think you can never say anything sillier than what you have already said, you prove me wrong. You don’t even have to plot that data to see that there has been a strong cooling trend. And, any least-squares fit through the data would confirm it.
I would say that you can’t just eliminate data that you don’t like but what you are doing is actually much worse than that. In fact, if you just eliminated data around 1991 and didn’t include it in the fit, you would still get a significant negative trend. What you are doing is presumably eliminating the whole drop by shifting the data up after 1991 or down before 1991 or something like that.
In fact, if you don’t want to believe me, just look at the “decadal trend” kindly put into that file by the Spencer and Christy UAH team themselves.
kurt (18:39:49):
My last two sentences point to the quintessential features of bona fide feedback: the need for an INDEPENDENT source of of power for physical implementation and the RUNAWAY instability of positive feesback in all cases. It appears that both of you (and you are not alone) harbor the analytically unsupported notion that finite accumulation of energy, such as a capacitor acquiring a charge, or some step-wise process expressed by the sum of the binomial series, constitutes “feedback” in a system. This is simply a vague misappropriation of the term from rigorous system analysis.
Genuine feedback requires 1) a transducer to sense the system output signal without disturbing it, 2) external power to replicate it (with or without filtering) , and 3) a loop feeding the replicated signal to the system input for algebraic addition to the driving input signal. Nothing in the climate system is capable of doing that. It would lead to violation of energy conservation principles. There simply are no power plants or operational amplifiers in the sky. Only redistribution and/or storage of energy ultimately received from the Sun is possible. Nothing on Earth can change the TSI; thus no genuine feedback (positive or negative) is possible. But the climate system can affect insolation.
What you’re calling “feedback” appears to be little more than a simplified version of the response characteristic of the system. That characteristic is generally frequency dependent, thus not reducible to the simple notion of “sensitivity” or “gain.” It indeed changes with changing albedo due to clouds and snow/ice distributions on the globe. But, if one hopes to analyze the climate system rigorously, using the well-developed mathematics of system analysis, then such changes and their consequences should not be confused with feedback.
Try it. All you need is to plot the graph – do it from 1993 instead
Joel Shore:
Even Roy Spencer says in this post, “the hotspot is not a unique signature of manmade greenhouse gases. It simply reflects anomalous heating of the troposphere — no matter what its source.” If you don’t want to believe me, maybe you can believe him.
What Dr. Spencer says and the ipcc said are two different things.
As Richard directed above: For a more complete discussion/ explanation see here
a link to Lucia’s discussion.
The issue was also discussed at Climate Audit a while back, but I can’t access CA’s search engine right now.
Link to Lucia’s here
Joel Shore (09:49:33) : Aerosols are not a feedback but a forcing.
Joel Shore if the blasted Aerosols are a result of the anthropogenic production process of CO2 then it becomes a feedback. And if that feedback works in opposition to the effect of CO2 it becomes a negative feedback – can you understand this simple concept?
“Our best scientific understanding is that:..Human-induced changes in the atmospheric burdens of sulfate aerosol particles cause regional cooling of the surface and troposphere.”
Besides this I have said there must be other negative feedback mechanisms fundamental to the warming caused by any means, such as cloudiness. You do not like to consider this possibility because it would upset your belief that CO2 will cause unstoppable run-away warming.
The reason why I say this must be so because the Earth’s climate says so. If CO2 goes up and temperatures do not then your hypothesis is wrong – you must discard it – not cling onto it for dear life, fudge the data and argue that white is black.
Me – You may not think so but this is what the IPCC says “The simulated responses to natural forcing are distinct from those due to the anthropogenic forcings..” I don’t think they could be clearer than that.
Joel Shore – Well, apparently it wasn’t clear enough because you have misinterpreted what they said. Let me give you a fuller quote of what they say and then explain it to you:
(Let me tell you how when the IPCC says that the simulated responses to natural forcing are distinct from those due to the anthropogenic forcings they do not mean that they are in fact distinct. They mean instead that they are in fact indistinguishable and this is obvious from the above statement.)
(In fact, dont you understand the IPCC says “Greenhouse gas forcing is expected to produce warming in the troposphere, cooling in the stratosphere, and, for transient simulations, somewhat more warming near the surface in the NH due to its larger land fraction,..”
and only then do they go on to say that “The simulated responses to natural forcing are distinct from those due to the anthropogenic forcings described above. Solar forcing results in a general warming of the atmosphere (Figure 9.1a) with a pattern of surface warming that is similar to that expected from greenhouse gas warming, but in contrast to the response to greenhouse warming, the simulated solar-forced warming extends throughout the atmosphere
So whereas a moron would understand from this that GHG’s would produce a tropospheric “hotspot”, solar “forcing” would not, you, who are not a moron, understands from this that what they in fact mean is solar forcing WILL produce a tropospheric hotspot, indistinguishable from the CO2 “forcing”. How very brilliant you are Joel Shore.
Joel Shore – So, in other words, (other words? they are the same words jumbled up why are you waffling you ……!!!!!?) the way the natural forcing of solar is distinct from the anthropogenic forcings is that the former warms the whole atmosphere while the latter warms the troposphere but cools the stratosphere (as is seen in the real world). There is no discussion there of whether or not tropical tropospheric amplification is expected to be different for each.
Discussion? Maybe not, (I cant be bothered to hunt around) but there are two graphs which are quite distinct from each other. The GHG graph shows a tropospheric hotspot whereas the solar one doesnt. Maybe they think this is clear enough to not warrant further discussion?
Joel Shore – Even Roy Spencer says in this post, “the hotspot is not a unique signature of manmade greenhouse gases. It simply reflects anomalous heating of the troposphere — no matter what its source.” If you don’t want to believe me, maybe you can believe him.
The final appeal to authority? I have pointed out that THE IPCC SAYS THAT THE HOTSPOT SHOULD EXIST DUE TO ANTHROPOGENIC WARMING and ANTHROPOGENIC WARMING ALONE. That is the point – cant you comprehend????? Not whether it is actually so or what RealClimate or the you or the great Gavin or anybody else says.
They have said so in black and white (and red and yellow and blue).
This is my last “discussion” with you Joel Shore. After what you have written I do not have a very great opinion of your logical powers or your ability to understand simple English or an elementary understanding of graphs.
Joel Shore (10:03:46) :
Yeah, this might be so…However, the problem is, as James Hansen has pointed out, the calculation that gives you a climate sensitivity of ~0.75 C / (W/m^2), which translates to a sensitivity of ~3 C per CO2 doubling, considers the land ice and vegetation changes to be a forcing and not a feedback. What this means is that essentially the 3 C sensitivity in fact assumes no changes in land ice or vegetation that further lower the albedo.
Joel, please don’t cite statements by J Hanson. His irrational media statements & other acts make him out to be some kind of pious kook. Please cite other sources — there must be many more.
Do you think global “sensitivity” is constant in time? If it isn’t, extrapolating present interglacial conditions to past glacial won’t work. Something as profound as the presence of continental glaciers and particularly global ocean-current changes will change the inner workings of the global “heat engine”, and the characteristics like sensitivity will change. Models may incorporate some aspects of ice/albedo feedback, but have no clue of large-scale ocean-current changes.
John S. (12:11:46) :
The long-used term “feedback” in control/electrical systems analysis has been usurped by climate modellers to have its own new meaning.
Richard says:
There are several reasons why they should be considered a separate forcing even though many of the same processes that produce CO2 also produce aerosols and vice versa:
(1) The ratio of aerosols to CO2 produced can vary considerably. For example, biomass burning essentially produces no net CO2 (if you grow the biomass that you burn) but can produce a lot of aerosols. And, in Western countries, we have used technologies to significantly cut aerosols but not CO2 so our aerosol emissions have been dropping significantly while our CO2 emissions continue to increase.
(2) Even if the emission of aerosols and the emission of CO2 were directly proportional, the forcing due to each would not remain proportional over time. This is because CO2 accumulates in the atmosphere whereas aerosols wash out quickly, so the forcing due to CO2 depends mainly on the cumulative emissions (with some dependence on how fast they are being emitted) whereas the forcing due to aerosols only depends on total emissions. (The forcing also probably has a different dependence on concentration for aerosols and CO2…For CO2 it is roughly logarithmic in concentration whereas I think for aerosols it is closer to linear.)
The basic point is that, assuming that we want reasonable air quality, we are not going to want to keep increasing our aerosol emissions at the rate necessary to try to counterbalance the warming due to our CO2 emissions. There have been some proposed geo-engineering schemes where we inject aerosols into the stratosphere, where they will remain longer and have much less impact on near-surface air quality; however, there are various difficulties with this as a realistic solution.
They don’t directly say that the tropospheric hotspot for the two will be indistinguishable but they certainly don’t say or imply that it won’t. Their statement is quite clear on what the difference is: “but in contrast to the response to greenhouse warming, the simulated solar-forced warming extends throughout the atmosphere”. So, we have one forcing where the warming extends throughout the atmosphere, i.e., warms both the troposphere and the stratosphere and another where the troposphere warms and the stratosphere cools.
You basically come up with the most convoluted interpretation of what the IPCC says as possible, ignoring all the evidence to the contrary. Maybe the IPCC could have been a little clearer but most people try to interpret statements in the way that seems most sensible; you simply do so in the way that suits you. I have noticed this trend in a lot of “skeptics”…To make the most uncharitable possible interpretation of what some scientific source says, no matter how convoluted, and then attack that statement as you have interpreted it as if no other interpretation…in fact a much better interpretation…exists.
Which part of my previous discussion of this, which I will repeat here, are you having trouble understanding? Which part of Gavin’s figure are you having trouble understanding? I said:
Richard says:
No, what you have shown is that you can come up with an interpretation of what the IPCC says that you think suggests this. The problem with said interpretation is it doesn’t really make sense when you look closely at what they actually said and the context in which they were saying it.
As for the figure, why do you think that Roy Spencer looks at that same IPCC figure and does not seem to think that it shows that the “hotspot” is a unique signature of the GHG mechanism? Could it be that he understands the issue of resolution in contour plots, like I do, but apparently you do not?