And similarly, if global surface temperatures rise significantly less than what one would expect from a particular degree of sensitivity, the smart money is that climate is less sensitive than that degree. Agreed?
Well in that case, increases in humidity do not offer any additional confirmation of the hypothesis that recent warming is because of CO2. Agreed?
Yes, and I think it’s clear that most of the models have overestimated the rate of warming. I expect IPCC 5 to revise the sensitivity range downward somewhat, but we shall see.
Sorta. Fundamentally, measured increases in humidity simply confirm that the water-vapour amplification is occuring. If you recall:
Measured increases in specific humidity are confirmation that one of the assumed amplifying mechanisms (more water vapour in the air, increasing the water-vapour contribution to the greenhouse effect) is taking place. The exact strength of this mechanism isn’t well established IMO but it’s definitely happening to some degree. Amplifying mechanisms make CO2-induced warming plausible as an explanation of the late 20th Century temperature rise. Without amplifiers, the effect isn’t strong enough.
I’m happy to continue this conversation but I’m probably going to average a little less than one post per day. Training courses and stuff. Apologies for that.
It seems to me that this is weak confirmation at best. Consider an alternative hypothesis that much of recent warming is the result of some factor besides CO2; that CO2 did cause a little warming which caused specific humidity to increase but neither of these factors makes a big difference in the scheme of things.
In that case one would expect to see exactly the same evidence which you have shown me.
So that on the attribution question, the argument basically boils down to (1) we believe that CO2 causes warming but we do not know how much; (2) it has warmed recently; (3) we don’t know what else might have caused the warming; so (4) we conclude that the warming was due to CO2.
Of course the problem is with step (3).
True. At least some of the steep rise observed from 1970 onwards has to have been due to the rising AMO over the same period, for example. I don’t think climate science has really nailed down the contributions of natural and anthrogenic factors that tightly.
I don’t particularly disagree with this, in principle. Note that the uncertainty implicit in your point (1) is inherent in the range of estimates for climate sensitivity. We don’t know exactly how much of the observed warming is due to CO2 but we have a likely range. Also note that the calculated warming effect of CO2 with water vapour amplification is in the right ballpark to explain the warming observed so far. (3) is therefore an unnecessary hypothesis from my point of view, and (4) is entirely reasonable. From your point of view, (3) is necessary because:
You assume that the effect of CO2 will be less than even the no-feedbacks figure. I don’t really understand on what basis that assumption is justified however.
If that range is calculated on the basis of predicting interactions among many different factors in the climate, then it’s basically just a guess.
“right ballpark” is basically a polite way to say “wrong, but not really far off”
If you believe that CO2 should cause X degrees of warming, and instead there are Y degrees of warming, it’s pretty much just self-serving speculation to say “ok, then CO2 caused Y degrees of warming.”
Well also because there is very good reason to believe that there are other forces at work. The warmists are asking us to believe that whatever force caused global surface temperatures to rise in the first half of the 20th century switched off around 1950 and after that it was CO2.
For the same reason that outside of Roadrunner cartoons, you normally don’t see big rocks balanced precariously in high places.
Now a question for you: On what basis is your apparent assumption of “no unknown warming factors” justified?
This is quite a pathetic circle jerk you fellas have going here… I hope you’re enjoying it because after a quick scan of some of the nonsense I see here, you can’t possibly have time to function like normal people.
The fact that any of you actually believe that a beneficial trace gas that occupies less than half of 1% of the atmosphere plays a bigger role in determining our climate than the sun is absolutely amazing. CO2 levels don’t drive temperature change, it’s the other way around. When the sun is in an active period, it warms the oceans which decreases the solubility of CO2 present in them. As a result of warming, CO2 levels increase. When the sun goes into a dormant cycle, it gets cooler causing CO2 to be absorbed back into the oceans. All the other natural sources of CO2 are minor by comparison to the oceans. Rotting vegetation produces far more CO2 than man does, with or without the use of hydrocarbon based fuels.
But when Al Gore shows video of ice breaking off the edges of the arctic ice sheet and falling into the sea (which happens every year as we go from winter to spring) you children get all hysterical, as if something ominous is happening.
Nobody has ever produced one iota of valid evidence to support the theory that man’s industrialization over the last 200 years is having an adverse effect on the earth’s climate. If it was, why did the earth get steadily cooler during the decades after the end of WWII, which is when industrial use of fossil fuels really began to skyrocket. If there was any truth to this absurd theory, then we would have seen a steady rise in temperatures, rather than what actually happened.
I’ll look in on you from time to time, just for hit and giggles. In the meantime try something new… It’s bad enough that you’ve all been brainwashed… If you don’t find a new hobby, you’re going to go blind as well!
Nite all!
Well, that depends on what you mean by “guess”! I can guess with 100% certainty and without performing any measurements at all, that your weight lies between zero and 800 kg. It’s not a very well-constrained range and it’s absolutely useless for e.g. tailoring a suit, but it could be used to choose an appropriate helicopter for you. If I decided to do a little work I could look at the bell curve of weight for white males (which I’m presuming you are) and choose the 95% confidence range centred on the mean. A guess again, but a good one and I could probably choose an appropriate chair or car for you based on it. A range is not the same thing as “wrong”.
Maybe, but so what? All real-word measurements are made to an arbitary precision - the fact that greater precision is achievable doesn’t invalidate the lower-precision measurement or calculation.
It rather depends on how big the discrepancy is between X and Y, wouldn’t you say? If you guesstimate that changing your air filters will give you 10% better mileage and you only measure a 6% improvement after changing them, would it be self-serving to say that 6% was caused by changing the air filters? (Yes, I acknowledge that it becomes rather more questionable if a whole lot of other things are changing at the same time and your milage fluctuates anyway.)
The early 20th century warming receives a pretty weak treatment by the IPCC in my opinion, with vague blather about solar forcing and a lull in vulcanism. On the other hand, it isn’t entirely true that the IPCC claims the early 20th century warming was all natural and the late 20th century warming all man made. The usual argument presented involves these sorts of figures: http://www.ipcc.ch/ipccreports/tar/wg1/figspm-4.htm. While I take the model output with a BIG pinch of salt, note that neither the all-natural nor all-anthropogenic models fit the early or late warming periods very well. If we get away from the models, we can see that the AMO was trending up from around 1900 to 1940 (and also from 1970 to 2000), giving a big “natural variation” contribution to both of those rises. Note that the AMO is a long-term oscillation - it doesn’t give a net temperature change long term. http://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch3s3-6-6.html We can also see that there most certainly was a jull in volcanic activity, see figure 1 B of this paper: http://www.cgd.ucar.edu/ccr/publications/ammann.pdf So we do see some natural effects that we know about, and we can take them into account.
Weren’t you the one telling me that “positive feedbacks” don’t lead to instability? I’m not saying the climate doesn’t push back against change - it does. It pushes back whether the sensitivity is low or high, the same way that a spring opposes being stretched. You’re basically saying that the spring has to be stiffer than calculated because a weak spring is equivalent to a precarious rock, and it isn’t. It just stretches further for a given load.
I don’t rule out unknown factors, in fact I’m certain there’s several complicating factors that we don’t know about. However, from the outside, the system is quite simple: the Sun shines energy onto the Earth and the Earth radiates energy into space while turning like a pig on a spit. The temperature of the surface under the thin blanket of the atmosphere is rather more complicated due to all the circulations and weather and stuff, but the basic system is simple and we don’t see evidence of unknown factors, nor do we need them to explain what we’ve seen. That’s the whole of it.
Plus he’s obviously never been hiking in a shale gully in upstate New York. Or a Rock City in upstate New York or Georgia. Or Arches National Park. Or…
A range might very well be the same thing as “wrong” in the sense of “worthless.”
For example, suppose I sell you a special puppy food which I assert will cause your dog to gain between 1 and 150 pounds as it grows up based on my carefully constructed computer model of dog maturation. Lo and behold, the dog gains 35 pounds. Is it reasonable to treat this as confirmation that my computer model is correct? Of course not.
On the other hand, if my computer model had predicted that the dog would gain between 34 and 36 pounds, then I might have something.
Are you saying that it’s simply a matter of measurement error? That increases in global surface temperatures may very well be in line with IPCC sensitivity estimates?
Yes, and I would say it also depends on what other factors – known or unknown – are in play.
Absolutely if there were numerous other factors which may have caused the mileage increase.
Ok, so you concede the point it seems.
Not entirely true, but close enough for purposes of discussion. Clearly the IPCC is claiming that the temperature increases in the first half of the 20th century were largely natural in cause.
Are you asserting that it is in fact known with some degree of certainty what caused warming in the early 20th century? Or are you just speculating?
No, I don’t think so. What I said was that “positive feedback” doesn’t necessarily lead to a runaway process.
Not at all. A weak spring is a negative feedback system. For example, if you push a block which is attached to a weak spring, the block will not travel as far as if it were attached to no spring at all. Warmists assert that there is no spring at all – that if you push the climate the push will be amplified.
Then what caused the Little Ice Age? What caused the Medieval Warm Period?
Actually, the “balanced rock” formation in Arches National Park is a good example of my point. These types of formations are unusual enough in nature that when they occur, they attract a lot of interest.
And here’s a quote from the Wiki page:
What causes climate change in general? Especially “what causes the glacier periods?”.
Okay, but why not then call it worthless rather than wrong? The IPCC TAR gave a likely range of climate sensitivity of 1.5-4.5 deg. C per doubling. That range may well be correct but it is certainly problematic when it comes to deciding policy and I wouldn’t argue very much if you described it as worthless. 'Wrong" has a somewhat different connotation - it implies that you think the true value lies outside the range, at least to my way of thinking.
Yes. I am convinced that the sensitivity lies in the range 1.5 - 2 deg. C per doubling, at the low end of the IPCC estimates.
Not really. I was responding to your statement “If you believe that CO2 should cause X degrees of warming, and instead there are Y degrees of warming, it’s pretty much just self-serving speculation to say “ok, then CO2 caused Y degrees of warming””. I regard that as too absolute and too prejudicial. It’s a matter of degree. If you have sufficient milage data with and without clean air filters, you can average out the noise and extract a result.
I am speculating. I gave cites showing that both an upswing in the AMO cycle and a lull in volcanic activity (resulting in a decreased optical depth) coincided with the early warming, but it is not known exactly what caused that warming and the IPCC has avoided admitting that explicitly.
I thought I’d discussed this, but I guess I failed to communicate my point. Overall, the climate IS a negative feedback system in the sense of a weak spring! A spring extends according to Hooke’s law - a particular load gives a particular extension, governed by the spring constant. Equlibrium climate sensitivity is analogous - a particular increase in CO2 gives a particular temperature rise, governed by the climate sensitivity. This is why I dislike the amplifying mechanisms being referred to as “positive feedbacks” and the net feedback being described as positive, since the final result is a weakening of the climate’s spring, not an absence of a spring! If you push a block that’s attached to no spring at all it never stops moving - never comes to a new equiibrium, and there would be no equilibrium climate sensitivity.
I was sloppy in my phrasing. There are certainly plenty of gaps in our knowledge and understanding. We don’t even know what causes the now-familiar short term ENSO oscillation and there’s plenty of controversy over the longer term PDO and AMO. However, in response to your question "On what basis is your apparent assumption of “no unknown warming factors” justified? " it’s because we don’t NEED an unknown warming factor to account for the twentieth century warming in terms of energy budget. The extra joules accumulated by the Earth can be accounted for in terms of the extra heat flux from CO2 increases, with water vapour amplification. That doesn’t rule out unknown factors or prove that CO2 plus amplification actually did it all, but it’s a demonstration of plausibility.
For purposes of the attribution question, it doesn’t make a difference. Either way, there is no reasonable basis for attribution.
And what is the uncertainty in measurements of global surface temperatures, in your view?
Well then lets go back to your analogy: Let’s suppose someone predicts that with new air filters your car’s gas mileage will increase by 10%. There are also numerous other factors which may affect mileage; and mileage is also constantly changing. If the car’s gas mileage is observed to increase by 6% over the next 40 miles, is it reasonable to attribute essentially all of the change to the air filter?
Sure, and with the climate we do not have this kind of data.
If you are speculating about that, then you are necessarily speculating about the causes of late 20th century warming too.
I’m not sure what your point is. Do you understand that according to warmists, anything which causes a temperature increase in the climate will ultimately cause an increase substantially greater than what would be expected from first order effects?
Do you understand that, in effect, this means that the climate will add to any push towards a greater temperature (according to warmists)?
You might not NEED such a factor, but so what? You are trying to RULE OUT such a factor.
Well this is a matter of language use and we’ll have to agree to disagree there. “Worthless” and “wrong” are substantially different in my view.
Now you’re getting into areas of measurement and data analysis that are above my pay grade - I’m no statistician! I’m happy with the notion that a car’s gas milage will average out to a particular figure if you collect data long enough. That the milage plotted against time will wander around, but over enough time it will demonstate a constant level plus a variance that averages out to zero. If you then change the air filters and collect data long enough, you then find that the constant level has jumped 6% but you have to collect data for long enough to average out the variance before you can determine this. I’m okay with that in principle. I doubt that 40 miles would be long enough to make the assessment though.
I partially agree, but we also have physics. To return to the car analogy, we know that a clean air filter will improve the milage by some degree, because the engine has to work less hard to suck air in. We can probably calculate a ballpark figure. You seem to be saying that because the data is noisy and needs a lot of processing, you can dismiss the effect altogether.
Not quite! Look, I’m no warmist. I accept that it’s entirely possible for Nature to produce a temperature upswing of the kind we’ve seen ALL ON HER OWN. But I also think it’s incredibly blinkered to dismiss the increase in CO2 and the prediction that physics gives us. To return to the car analogy and beat it to death a bit: - we know it was driven with the windows fully closed a lot of the time in the early 20th C, and so I speculate that that is the reason fror the improved milage noted back then, even though we lack the data to say for sure. We have better data today and we know the air filter has been changed, but you seem to be arguing against the air filter change having done anything.
I don’t want to put words in your mouth here, but I gained the impression that a big part of your argument is that the climate must “push back” against climate forcings. You recognise that a load on a spring is a negative feedback system, and if I understand you correctly, you think the warmist position is that the climate is NOT a negative feedback system.
My understanding of the warmist position is different. I recognise that black body radiation is also a negative feedback system analagous to a loaded spring. Increase the load on a spring and it extends a little, the spring force increases to match the new load, and you have a new equilibrium. Increase the energy going into a radiating black body (say a bulb filament) and its temperature increases a little, the outgoing radiative flux increases to match the new energy input, and you have a new equilibrium. It’s a negative feedback. The thing is though, climate scientists don’t include the black body response in the feedback scheme - the black-body response is sometimes referred to as the “no feedback” situation. So when warmists talk about the net feedbacks being positive, they are talking net positive feedbacks plus the black body response which is a great big negative feedback. That’s why I say that the climate always DOES push back - the overall situation is negative feedback. The only real argument is about the stiffness of the spring.
The “no-feedback” blackbody response (in reality a negative feedback) is about 1.1 deg. C per doubling of CO2. You seem to be arguing that the true sensitivity must be lower because the climate should “push back” - I claim that the value already incorporates some “pushing back”!
I accept that some water vapour amplification is inevitable, and believe that the ice-albedo feedback is plausible, and so the true sensitivity is likely higher than 1.1. The lower level given in the IPCC TAR was 1.5 deg. C and this is in line with most of the empirical derivations of sensitivity. The models tend to come in somewhat higher, and the paleo derivations higher than that, but I don’t have much confidence in either of them.
I am not. There may be such a factor. I just think it’s dangerous to count on there being such a factor.
As it is even clear, not even skeptics can ignore what the instrumental and natural thermometers are saying, but it is funny to see brazil84 jumping from doubts about water vapor feedback to a complete denial of the whole thing without missing a beat.
But, besides the good info from matt in the recent posts, there are still some squickitems still popping up.
Once again, using the term warmist does betray where are you are getting your information too, just beware that no serious groups involved on this resort to that term, and it leads to getting burned in discussions, so for example, lets be more clear on the AMO (Atlantic Multidecadal Oscillation), even Tamino sees it as a red herring.
Call it whatever you want, it makes no difference.
So you are unable to answer the questions? They really are very simple. The first question simply calls for a number; the second question calls for a yes or no.
If you do not know what the range of uncertainty is for surface temperature measurements, I’m not sure how you can assert that anything is within that range.
If you are unable to answer the second question, then surely you are unable to answer the basic attribution question.
Not really. Warmist predictions about the climate are based on physics in the same sense that Sunny Delight is “made with real juice” and the same way that the board game Risk is based on geographic principles. It’s technically true but fundamentally the predictions are based on computer simulations which have not been adequately tested or validated.
It’s not necessary for me to dismiss anything – I don’t bear the burden of proof here. You are the one who is (apparently) dismissing something – the possibility that something besides CO2 is responsible for a significant part of the late 20th century warming.
So your answers to the questions are “no”?
I’m a little confused. Are you reasonably confident that the increase in global surface temperatures in the second half of the 20th century was caused primarily by CO2?
You’re right. Call me naive, but I’ve always assumed if uncertainty in the temperature records was an issue, one of the more technical skeptics such as McIntyre or Watts would have publicised it by now, but you’re right - I should know the uncertainty. For NASA’s Gistemp, it is apparently 0.05 deg. C for a 95% confidence interval, see e.g. Data.GISS: GISS Surface Temperature Analysis: News, Updates, and Features So now we both know. The uncertainty is an order of magnitude smaller than the sensitivity range.
Well the second question was: “Well then lets go back to your analogy: Let’s suppose someone predicts that with new air filters your car’s gas mileage will increase by 10%. There are also numerous other factors which may affect mileage; and mileage is also constantly changing. If the car’s gas mileage is observed to increase by 6% over the next 40 miles, is it reasonable to attribute essentially all of the change to the air filter?” There is insuficient information to answer that question. By what percentage has mileage been “constantly changing” in the past? What do we know about the “numerous other factors” and can we reasonably compensate for their effects over the 40 mile trial? The second question could be reasonably answered “yes” or “no” depending on the details.
I reject your analogies here. The fundamental predictions are not based on computer predictions - many of them were made before computers existed! The 3.7 watt/ sq. metre per doubling is a simple radiative transfer calc. The 1.1-1.2 deg. C per doubling is a simple black-body radiation calc based on the 3.7 watt figure. Those are clean calcs, no computers required. The prediction of increasing specific humidity with temperature, and therefore some water vapour amplification, is a physics-based no brainer. The assumption of fixed relative humidity and a consequent estimate of the water vapour amplification was first done by Moller in 1963 AFAIK, again without computers. (That estimate is still being disputed today of course.) Additionally there have been several attempts to evaluate the climate sensitivity empircally from the known forcing history and the temperature record, an approach I have more faith in. Schwartz’s 2007 paper was probably the first attempt published and gave a figure of 1.1 deg. C per doubling - basically the same as the black body response with no net additional feedbacks. Scarfetta pointed out some problems with Schwartz’s method and calculated his own value of 1.7. Schwartz accepted Scarfetta’s work and published again in 2008 with a figure 0f 1.9 and uncertainty +/- 1, in line with Scarfetta. I trust the empirical work rather more than the computer models, which is one reason why I think the sensitivity will turn out to be at the lower end of the IPCC range.
Well you appear to be dismissing some or all of an extra 3.7 watts/ sq. m, based on: “In my view, the natural a priori assumption should be that the system will push back even if we do not know the exact mechanisms at work.” I argue that the black-body response is a negative feedback that already “pushes back” and so there is no need to invoke any extra unknown negative feedback mechanisms. The claim of “net positive feedback” on the “warmist” side results from the truly horrible description of the black-body response as the “no feedback” situation. I agree with your a priori assumption that the system must push back. We know it does, and we know how.
As I thought I’d already said, I don’t dismiss the possibility that there are unknowns that affect the picture - I think it’s virtually certain that there are. I won’t be particularly suprised if the warming we’ve seen turns out to be up to 50% natural.
You mean these questions? "Do you understand that according to warmists, anything which causes a temperature increase in the climate will ultimately cause an increase substantially greater than what would be expected from first order effects? Yes, I understand that. “Do you understand that, in effect, this means that the climate will add to any push towards a greater temperature (according to warmists)?” Yes, I understand that too. What I don’t understand is why you find it so unreasonable. You have a complex system, an input (energy) and a response (temperature). We are effectively progressively increasing the input by progressively elevating CO2. The question is what the temperature response will be. The black-body response is a very simplifed version of the situation. Observation, physics, modelling, paleohistory, all indicate that the system’s temperature response will be somewhat greater than the black body response. So what? It doesn’t mean that anything illogical or counter-intuitive is happening. It doesn’t mean that the climate isn’t “pushing back”, just that the climate’s “spring” is less stiff than that of a black-body.
Yes, I’m confident that CO2 is responsible for at least half of it. That’s my definition of “primarily”.
I’m not sure if that’s aimed at me, but if it is you’re making one hell of a leap. I’m in a conversation here and I’m using vocabulary brought up by others. If I get burned, I’ll get burned because I’m wrong and not because you think I’m getting information from the wrong sort of site, thank you very much.
My only links regarding the AMO have been the IPPC, which is a body of climate scientists last time and checked and not a statistician-blogger like Tamino/Grant Foster. His entire post adds up to - the temperature record is wiggly, therefore global warming is wiggly, therefore the AMO is caused by global warming and not the other way round. Hurray for him, he should publish. His analysis isn’t even supported by Realclimate, not that they say too much about it: “A multidecadal (50-80 year timescale) pattern of North Atlantic ocean-atmosphere variability whose existence has been argued for based on statistical analyses of observational and proxy climate data, and coupled Atmosphere-Ocean General Circulation Model (“AOGCM”) simulations. This pattern is believed to describe some of the observed early 20th century (1920s-1930s) high-latitude Northern Hemisphere warming and some, but not all, of the high-latitude warming observed in the late 20th century. The term was introduced in a summary by Kerr (2000) of a study by Delworth and Mann (2000).” Bolding mine. RealClimate: Atlantic Multidecadal Oscillation (“AMO”)
IMHO they do not say much about it because researchers already took a look and they are more with the position that global warming is influencing AMO more these days.
The reason why I trust Tamino more (and he was pointed by yourself as a good source before) is that, and I also did a search of who in heck is so confident saying that it is the AMO alone and not global warming is what is increasing the temperature, and the results were not encouraging, suffice to say WUWT and other denier sites popped in the search and so, as you try to be fair on this, the unfortunate reality is that you are looking too much at “skeptical” sites that in reality are deniers, and while I do see that overall you doing a good job of identifying the trash, you are still catching some of the crap they throw.
Your cite does not remotely support your point and is only tangentally related to the subject, nor is anyone here claiming that the AMO causes global warming anyway. I have said (repeatedly?) in this very thread that it is an oscillation - it averages out to zero in the long term but causes bumps and dips in the trend.
Italics mine. Show me where I said that, or go to those sites and argue with them about it. I have explicitly said otherwise and I have only cited the IPCC in regards to the AMO - not any of the sites you are so down on. Do me the courtesy of not leaping to conclusions about my sources and then suggesting that I am “still catching some of the crap”. If you disagree with any points I make, bring a technical argument to counter them. (Hint: spurious guesses as to where I’m getting my information from, and then dismissing it based on the assumed source, is not any kind of argument, technical or otherwise.)