# Climatologist Dr. Michael Mann completely vindicated...again. **URL:** \ **Category:** Great Debates\ **Created:** [August 23, 2011, 12:17am UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724 "2011-08-23T00:17:11Z")\ **Posts on this page:** 20\ **Page:** 21
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [September 9, 2011, 5:08am UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/401 "2011-09-09T05:08:06Z")
> [@Magiver](#): > > The car is a environmental waste of time because nobody wants it. It’s a failure on many levels and I’ve discussed this in length before. And the truth was that GM has, so far, not intended it to be a car sold on a wide release. At the levels it is being sold it is really a gross exaggeration to claim that nobody wants it. I still can see that it will not be a big hit, but it is doing good in it’s niche, what I will expect is to see new cars models with improved technology, and if not the Volt, then we will see others. As I see it the issue is still the nonsense of not putting the real costs of releasing so much CO2 in the atmosphere into the value of things like coal and other fossil fuels. [http://www.energyboom.com/policy/danish-author-bjorn-lomborg-advocates-carbon-tax-and-clean-energy-investments](http://www.energyboom.com/policy/danish-author-bjorn-lomborg-advocates-carbon-tax-and-clean-energy-investments) > [@](#): > > Danish author and statistician Bjorn Lomborg this week reversed his previous position that humans can do little to combat climate change, now acknowledging that climate change is “a challenge humanity must confront” and calling for global investment in clean energy solutions like wind, wave and solar power. > > In an interview with The Guardian, Lomborg confirms that his forthcoming book will argue that a carbon tax and a $100 billion annual global investment in clean energy technologies are necessary solutions to safeguard humans from the worst impacts of climate change. Of course Lomborg makes also the point that a carbon tax will do little, unless we do invest the revenue on improving green technologies. ---
**Author:** ![Magiver](https://avatars.discourse-cdn.com/v4/letter/m/4491bb/32.png) [@Magiver](https://boards.straightdope.com/u/Magiver)\ **Post date:** [September 9, 2011, 8:06pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/402 "2011-09-09T20:06:56Z")
> [@GIGObuster](#): > > And the truth was that GM has, so far, not intended it to be a car sold on a wide release. At the levels it is being sold it is really a gross exaggeration to claim that nobody wants it. At the levels it is being sold it’s a gross exaggeration to claim that anybody wants it. The definition of not selling cars is… wait for it… not selling cars. > [@GIGObuster](#): > > I still can see that it will not be a big hit, but it is doing good in it’s niche, what I will expect is to see new cars models with improved technology, and if not the Volt, then we will see others. absolutely. We’ll be drowning in electric cars when the battery technology catches up to the utility value expected of cars. I’ve said this many times but you can’t stand to see anything green berated because of your obsession with global warming. > [@GIGObuster](#): > > As I see it the issue is still the nonsense of not putting the real costs of releasing so much CO2 in the atmosphere into the value of things like coal and other fossil fuels. And as I see it, the real world can’t afford to destroy what little is left of the global economy because by doing so we will NEVER see green technology advance. Have you ever looked at pictures of cities during the great depression? Not a lot of trees around. Guess where they went when people couldn’t afford to heat their homes? The law of unintended consequences will add more co2 to the air then reduce it if we continue on the financial path you suggest. ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [September 9, 2011, 9:05pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/403 "2011-09-09T21:05:39Z")
> [@Magiver](#): > > At the levels it is being sold it’s a gross exaggeration to claim that anybody wants it. The definition of not selling cars is… wait for it… not selling cars. If that was the case then we would not see GM taking it to other markets: [http://www.theglobeandmail.com/globe-drive/new-cars/auto-news/chevy-volts-arrive-at-canadian-dealers/article2156560/](http://www.theglobeandmail.com/globe-drive/new-cars/auto-news/chevy-volts-arrive-at-canadian-dealers/article2156560/) > [@Magiver](#): > > absolutely. We’ll be drowning in electric cars when the battery technology catches up to the utility value expected of cars. I’ve said this many times but you can’t stand to see anything green berated because of your obsession with global warming. Piffle, once again you are reaching for a contradiction, you are indeed implying that there \*\*is \*\*a problem. Your obsession is clearly with finding contradictions on others were there are not, while you are happy to keep yours. > [@Magiver](#): > > And as I see it, the real world can’t afford to destroy what little is left of the global economy because by doing so we will NEVER see green technology advance. Have you ever looked at pictures of cities during the great depression? Not a lot of trees around. Guess where they went when people couldn’t afford to heat their homes? The law of unintended consequences will add more co2 to the air then reduce it if we continue on the financial path you suggest. Alarmist! 🙂 ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://boards.straightdope.com/u/matt)\ **Post date:** [September 16, 2011, 4:28pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/404 "2011-09-16T16:28:28Z")
> [@brazil84](#): > > I would be surprised. Feel free to make arguments to the contrary, but I’m pretty confident that you take a complex system which has been reasonably stable for a long time and push on it, the smart money is that it will push back. You are not the first to make this argument. Lindzen made it with his postulated “iris effect” and Eschenbach has made it with his temperature “governor”. Neither of them argue against water vapour feedback however - instead they argue for a large negative cloud feedback. Cloud feedback is still uncertain and might just turn out to be a net negative, but it is unlikely to be large. It is perfectly true that the Earth’s temperature has been remarkably stable over a wide range of conditions including a much weaker Sun and different arrangements of continents. However, note that this limited temperature variation has still included both ice-ages and ice-free poles. It isn’t stable enough for us to bet that it will take anything we can throw at it. > [@me](#): > > The prediction is basically a long-term warming trend, about 0.2 deg C per decade on average…(snip)I’m fairly sure this prediction will turn out to be pessimistic but that won’t disprove global warming - it would only show that the IPCC has overestimated climate sensitivity, which I personally believe is the case. > [@brazil84](#): > > I would say that for all practical purposes, “global warming” – as the phrase is commonly understood – will have been disproved. Keep in mind the fundamental issue is whether mankind needs to go through the trouble of dramatically cutting CO2 emissions Well, “not as bad as we thought” is a fairly unusual definition of “disproved”, in my opinion! I do agree that the fundamental issue is how the science informs policy. > [@GIGObuster](#): > > [http://www.aip.org/history/climate/co2.htm#SCM](http://www.aip.org/history/climate/co2.htm#SCM) > Quote: > Yet amid all the uncertainties about how carbon cycles operated, how much could we trust the computer models to work under circumstances different from the present? Scientists are more likely to believe something if they can confirm it with entirely independent lines of evidence, preferably from somewhere nobody had looked before. Just such new evidence came up in the 1990s, thanks to an unexpected alliance of paleontology and plant physiology. Studies of plant species that had changed little since the rise of the dinosaurs (magnolia for one) showed that if you exposed them to a higher level of CO2, the structure of their leaves changed. Ancient fossil leaves showed just such changes. Several kinds of chemical studies of ancient rocks and soils helped pin down how the level of the gas had swung widely over geological ages, and the temperature too. Eventually geochemists and their allies managed to get numbers for the “climate sensitivity” in past eras, that is, the response of temperature to a rise in the CO2 level. Over hundreds of millions of years, a doubled level of the gas had always gone along with a temperature rise of three degrees, give or take a degree or two. That was in startling agreement with the range of numbers coming from many computer studies. Evidently the computer modelers had not missed something huge. It’s a nice cite, but you realise a climate sensitivity range of 1-5 degrees (“three degrees, give or take a degree or two”) has very different policy implications between the top and bottom of those ranges? I gave my view on policy in post 302: I consider that economic growth cannot and should not be opposed in the developing and third world (not so important for us) as it is the only way that global quality of life can be improved. Learning how to grow sustainably is therefore paramount and carbon-neutral energy should be a mainstay of that. BUT, if I may throw in a hypothetical, suppose GLORY hadn’t crashed and the next ten years of GLORY and ARGO data led the IPCC to narrow down that sensitivity range to, say, 1 - 1.8 degrees, most likely value 1.4 degrees per doubling. Then I would be okay with doing away with cap-and-trade and carbon taxes, pumping the oil and gas till it runs out, and just putting a small tax on coal burning. OTOH if the sensitivity range was narrowed to say, 4.6 - 5.4 degrees, most likely value 5 per doubling, then I would be okay with going to a wartime-like economy in order to solve the problem. Rationing, conscription of scientists and engineers, building nuclear power plants like they were Liberty ships, the works. The thing is, we don’t have a well-constrained estimate of climate sensitivity at the moment and the resulting policies are frankly the worst of all worlds - they cost a lot and don’t do much. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [September 16, 2011, 5:09pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/405 "2011-09-16T17:09:34Z")
> [@matt](#): > > You are not the first to make this argument. Yes, I know. > [@](#): > > Neither of them argue against water vapour feedback however It depends what you mean by “argue against water vapour feedback.” Presumably they believe that the net result of all factors is negative feedback. The warmists presumably maintain that the net result of all factors is positive feedback, i.e. that any water vapor feedback loop dominates other interactions. > [@](#): > > It isn’t stable enough for us to bet that it will take anything we can throw at it. Perhaps, but it is stable enough to presume that net feedback will be neutral or negative absent solid evidence to the contrary. > [@](#): > > Well, “not as bad as we thought” is a fairly unusual definition of “disproved”, in my opinion! It depends what you mean by “not as bad as we thought.” If the IPCC predicts disaster and all we get is the same level of warming we got over the last 100 years, i.e. about a degree, would you agree that the warmist case has been disproved? ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://boards.straightdope.com/u/matt)\ **Post date:** [September 17, 2011, 12:53am UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/406 "2011-09-17T00:53:13Z")
> [@brazil84](#): > > It depends what you mean by “argue against water vapour feedback.” Presumably they believe that the net result of all factors is negative feedback. The net result of everything _has_ to be negative feedback, or else the Earth’s climate is analogous to a pencil balanced on its point - give it a nudge and it’ll tip right over. The big “feedback” everybody neglects, because it is trivially obvious, is that hotter things lose heat faster. That’s why a lightbulb filament reaches a new constant temperature when you turn up the dimmer switch. There is a fraction of a second of transition during which the electrical energy going into the filament exceeds the energy being radiated from it. During that transition, the temperature goes up. That transition is supposedly where we are at now, with a calculated (not measured) Top-of-Atmosphere (TOA) energy imbalance. At some new elevated temperature, the rate of radiative loss will have increased to match the incoming energy and the TOA imbalance will disappear. Problem is, continuing to elevate the CO2 level is equivalent to continuously nudging the dimmer switch upwards. We must have net negative feedback, but it simply governs how far the temperature shifts for a given change in forcing. But all this is an aside. The phrase “water vapour feedback” is usually applied only to the expected increase in atmospheric water vapour from rising temperature, with a consequent increase in the water vapour contribution to the greenhouse effect. Expecting a positive water vapour feedback in this sense is like expecting a bowling ball to roll downhill - a no brainer. The cloud response is generally considered seperately since nobody knows what cloud coverage changes will occur and what their overall effect will be. Both Lindzen and Eschenbach propose mechanisms for negative cloud feedbacks. Eschenbach goes even further and proposes a mechanism beyond negative feedback, acting more like cruise control in a car and making the climate very stable. (Eschenbach is basically just an amateur on the Internet but I find him quite interesting to read.) Observational data on clouds is surprisingly poor and the theoretical understanding of them is even worse. Many models simply assume they don’t have a net effect either way. > [@brazil84](#): > > The warmists presumably maintain that the net result of all factors is positive feedback, i.e. that any water vapor feedback loop dominates other interactions. Some (not all) “warmists” appear to like any evidence supporting positive feedback contributions, high climate sensitivity, “tipping points” etc. because they believe the best way to implement change is to ramp up the percieved urgency and scare the crap out of people. Personally I think this is terribly counterproductive but it seems to be the tactic of choice. > [@brazil84](#): > > Perhaps, but it is stable enough to presume that net feedback will be neutral or negative absent solid evidence to the contrary. As I said, net feedback of _everything_ has to be negative. How negative it is, overall, determines how far the temperature will shift for a given change in forcing. It’s analogous to hanging a weight on a spring. The spring’s return force is a negative feedback - add a bit to the hanging weight and the spring force increases to match the weight. The question is how _stiff_ the spring is, how far the spring will extend before the new equilibrium is reached. Our continued emissions are the equivalent of continuously adding weight to the spring - it WILL extend and keep extending! If the spring is sufficiently stiff (low climate sensitivity) we’ll run out of fossil fuels and stop adding weight before the extension becomes a problem. If the spring is weak, we really need to curb emissions. If the spring is somewhere in between, I see no problem with pushing the no-regret emission reductions that are possible - partial vehicle electrification, higher-efficiency IC-engined vehicles, low-energy housing, heat-pump cooling and heating, solar panel hot water (not photovoltaics, yet), combined heat-and-power, phasing out coal power generation for combined-cycle gas, and making sure any coal power uses the higher-efficiency, supercritical technology. These are all win-win, positive-payoff steps if they’re implemented sensibly. > [@brazil84](#): > > It depends what you mean by “not as bad as we thought.” If the IPCC predicts disaster and all we get is the same level of warming we got over the last 100 years, i.e. about a degree, would you agree that the warmist case has been disproved? I’d say “rendered moot” rather than “disproved”, but sure. Whatever happens, it will be interesting to look back on this period through the lens of hindsight! ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [September 17, 2011, 1:32pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/407 "2011-09-17T13:32:17Z")
> [@matt](#): > > The net result of everything _has_ to be negative feedback, or else the Earth’s climate is analogous to a pencil balanced on its point - give it a nudge and it’ll tip right over. > > . . . > > But all this is an aside. The phrase “water vapour feedback” is usually applied only to the expected increase in atmospheric water vapour from rising temperature, with a consequent increase in the water vapour contribution to the greenhouse effect. Expecting a positive water vapour feedback in this sense is like expecting a bowling ball to roll downhill - a no brainer. I’m not sure I understand your point. Let me ask you this: Do you agree that using just basic physics, it’s possible to calculate the expected increase in global surface temperatures from a doubling of CO2 levels from pre-industrial levels assuming that there are no feedbacks or other interactions? Do you agree that generally speaking, people on the “pro” side of the debate hold that the actual sensitivity is greater than this basic amount? i.e. they hold that the effects of CO2 will be amplified? Do you agree that it’s reasonable to characterize such amplification as being the result of net positive feedback? ---
**Author:** ![FXMastermind](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fxmastermind/32/7289_2.png) [@FXMastermind](https://boards.straightdope.com/u/FXMastermind)\ **Post date:** [September 17, 2011, 3:13pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/408 "2011-09-17T15:13:26Z")
> [@AT116](#): > > H. L. Mencken once said: “The whole aim of practical politics is to keep the populace alarmed (and hence clamorous to be led to safety) by menacing it with an endless series of hobgoblins, all of them imaginary.” That certainly does seem to be PART of politics, but it isn’t that simple. > [@AT116](#): > > The AGW (Anthropogenic Global Warming) theory is a perfect example of what Mencken was referring to. It’s 100% bogus. Rising levels of CO2 don’t cause warming, warming causes CO2 levels to rise, because higher temperatures decrease the solubility of CO2 in our oceans. The warmer it gets, the more CO2 enters the atmosphere. It’s as simple as that. Again, while true that the oceans are the largest source of CO2 changes, it isn’t that simple. > [@AT116](#): > > Yes the earth has been warming, ever since the Little Ice Age, but it was a completely natural, and extremely beneficial phenomenon caused primarily by changes in cycles of solar activity. That it happened to coincide, in part, with the industrial revolution when man started to use fossil fuels in huge quantities is mere coincidence. Our use of these fuels had no meaningful effect on temperature change… No, it isn’t that simple. We know a lot about the earth now, but we don’t enough to know that it is “that simple”. Biological factors, weathering, tectonics, solar wind, cosmic rays, dust, circulation of the atmosphere and oceans, it’s very very complicated. ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://boards.straightdope.com/u/matt)\ **Post date:** [September 18, 2011, 2:16pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/409 "2011-09-18T14:16:53Z")
> [@brazil84](#): > > I’m not sure I understand your point. Let me ask you this: > > Do you agree that using just basic physics, it’s possible to calculate the expected increase in global surface temperatures from a doubling of CO2 levels from pre-industrial levels assuming that there are no feedbacks or other interactions? Sure. > [@brazil84](#): > > Do you agree that generally speaking, people on the “pro” side of the debate hold that the actual sensitivity is greater than this basic amount? i.e. they hold that the effects of CO2 will be amplified? Absolutely. I also happen to believe that the proposed water-vapour-greenhouse amplification mechanism _on its own_ is entirely reasonable, but unlikely to be the whole story. > [@brazil84](#): > > Do you agree that it’s reasonable to characterize such amplification as being the result of net positive feedback? It is commonly described as such, but to me this is truly horrible terminology because a real net positive feedback has to lead to a runaway situation. I dislike much of the terminology of climate science - “forcings”, “feedbacks”, “greenhouse effect”, even “relative humidity” gives a misleading impression! We’re kind of stuck with it though. I’d prefer the amplification to be talked about in terms of “amplification mechanisms” rather than “feedbacks”, but that’s just me. ---
**Author:** ![FXMastermind](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fxmastermind/32/7289_2.png) [@FXMastermind](https://boards.straightdope.com/u/FXMastermind)\ **Post date:** [September 18, 2011, 4:37pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/410 "2011-09-18T16:37:01Z")
There was no run away greenhouse effect, much less global catastrophic climate change, during the last really warm interglacier period. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [September 18, 2011, 4:49pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/411 "2011-09-18T16:49:36Z")
> [@matt](#): > > It is commonly described as such, but to me this is truly horrible terminology because a real net positive feedback has to lead to a runaway situation. I would say that this is technically incorrect since a positive feedback loop can in theory be increasingly attenuated at each step. So for example, a degree of warming leads to an additional half a degree of warming, which leads to an additional quarter degree of warming, etc. “Deniers” such as myself dispute even this kind of positive feedback. ---
**Author:** ![FXMastermind](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fxmastermind/32/7289_2.png) [@FXMastermind](https://boards.straightdope.com/u/FXMastermind)\ **Post date:** [September 19, 2011, 1:57pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/412 "2011-09-19T13:57:35Z")
I think you got the last word. ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://boards.straightdope.com/u/matt)\ **Post date:** [September 19, 2011, 2:26pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/413 "2011-09-19T14:26:21Z")
> [@brazil84](#): > > I would say that this is technically incorrect since a positive feedback loop can in theory be increasingly attenuated at each step. So for example, a degree of warming leads to an additional half a degree of warming, which leads to an additional quarter degree of warming, etc. Sure. The additive elements form a convergent series so there’s a finite result. In your example, a degree of CO2 warming gains an additional 1/2 + 1/4 + 1/8 +1/16 etc., which converges to an extra 1 degree of warming. So one degree of CO2-induced warming gains an extra degree of amplification. I object to this being described as an extra 1 degree due to “positive feedback” because that’s not what “positive feedback” _means_. Positive feedback is technically an output of an amplifying system that is additive to the input, not simply an additive contribution or amplification of the output. It’s just a terminology nitpick though - let’s not get too hung up on it! > [@brazil84](#): > > “Deniers” such as myself dispute even this kind of positive feedback. That’s easy enough to say, but what is the detail of that disputation? If I understand correctly, you accept that increasing atmospheric CO2 on its own should have have a warming effect. Do you dispute that increasing atmospheric water vapour should also have a warming effect by the same mechanism? Or do you dispute that an increase in temperature should increase atmospheric water vapour? Is it a conviction that the cloud “feedback” is substantial and negative? Or an article of faith based upon the relatively narrow historic range of global temperature; a conviction that global temperature _must_ be insensitive to changes in energy fluxes even if we don’t have a mechanism to explain why? The devil is in the details. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [September 19, 2011, 3:14pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/414 "2011-09-19T15:14:11Z")
> [@matt](#): > > Or an article of faith based upon the relatively narrow historic range of global temperature; a conviction that global temperature _must_ be insensitive to changes in energy fluxes even if we don’t have a mechanism to explain why? The devil is in the details. “Must” is a bit of a strong word. 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. By “push back” I mean that the net warming as a result of all forcings and interactions should be assumed to be LESS than that expected from the simple calculation I described a few posts back. Thus, in my view, the warmists bear the burden of proving that amplification is likely to take place. But yes, I have no idea if the negative feedback I assume is the result of an “iris effect” or something else. Does that answer your question? ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://boards.straightdope.com/u/matt)\ **Post date:** [September 20, 2011, 12:30pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/415 "2011-09-20T12:30:52Z")
> [@brazil84](#): > > “Must” is a bit of a strong word. 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. By “push back” I mean that the net warming as a result of all forcings and interactions should be assumed to be LESS than that expected from the simple calculation I described a few posts back. Okay. So you believe in a compensating subtractive mechanism. While I don’t rule that out, there are a couple of difficulties with it. First, we know of quite a few additive amplifying mechanisms (although the magnitude of their effects are basically WAGS) but clouds are the only _possibly_ subtractive mechanism that we know about. Second, the observed warming so far is consistent with the warming expected from the simple calculation, plus a little bit more. Most models predict rather more warming than that observed, almost certainly because they overestimate the effects of the amplifying mechanisms. The climate sensitivity due to CO2 alone is around 1 deg. C per doubling IIRC, and the IPCC estimated range is 1.5 - 4.5 deg. C. I suspect it’ll turn out to be in the low end of that range rather than the high, but at the moment what we’ve seen is consistent with _some_ amplification. ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://boards.straightdope.com/u/matt)\ **Post date:** [September 20, 2011, 1:26pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/416 "2011-09-20T13:26:56Z")
Amplifying mechanisms include: warmer temperatures causing the oceans to outgas CO2 (a mechanism actually proposed by some sceptics to claim that the increasing CO2 isn’t due to human activity); warmer temperatures causing winter snow cover to establish later and melt earlier, decreasing albedo; and of course, warmer temperatures increasing the atmospheric water vapour and the consequent water vapour contribution to the greenhouse effect, to name a few. While all of these mechanisms are highly plausible, actually evaluating their effect is another matter. The water vapour “feedback” for example has generally been modelled by assuming a constant relative humidity, but satellite measurements show that the real story is a lot more complicated - [http://www.sciencedaily.com/releases/2010/01/100131145840.htm](http://www.sciencedaily.com/releases/2010/01/100131145840.htm). This is one of the reasons I have my doubts about the climate sensitivities derived from the models. ---
**Author:** ![FXMastermind](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fxmastermind/32/7289_2.png) [@FXMastermind](https://boards.straightdope.com/u/FXMastermind)\ **Post date:** [September 20, 2011, 1:57pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/417 "2011-09-20T13:57:38Z")
Thanks Matt. ---
**Author:** ![GIGObuster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gigobuster/32/421_2.png) [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)\ **Post date:** [September 20, 2011, 2:09pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/418 "2011-09-20T14:09:27Z")
Not so sure about that, and as I already noticed, there is still a little bit of squick on the implication that models are not good tools to use > **[What is the role of stratospheric water vapor in global warming?](https://skepticalscience.com/water-vapor-stratosphere-global-warming.htm)** > > The effect from stratospheric water vapor contributes a fraction of the temperature change imposed from man-made greenhouse gases. Also, it's not yet clear whether changes in stratospheric water vapor are caused by a climate feedback or internal... > [@](#): > > The effect from stratospheric water vapor contributes a fraction of the temperature change imposed from man-made greenhouse gases. Also, it’s not yet clear whether changes in stratospheric water vapor are caused by a climate feedback or internal variability (eg - linked to El Nino Southern Oscillation). However, the long term warming trend seems to speak against the possibility of a negative feedback. Water vapor feedbacks under the stratosphere are still there. [http://www.nasa.gov/topics/earth/features/vapor\_warming.html](http://www.nasa.gov/topics/earth/features/vapor_warming.html) > [@](#): > > Specifically, the team found that if Earth warms 1.8 degrees Fahrenheit, the associated increase in water vapor will trap an extra 2 Watts of energy per square meter (about 11 square feet). > > “That number may not sound like much, but add up all of that energy over the entire Earth surface and you find that water vapor is trapping a lot of energy,” Dessler said. “We now think the water vapor feedback is extraordinarily strong, capable of doubling the warming due to carbon dioxide alone.” > > Because the new precise observations agree with existing assessments of water vapor’s impact, researchers are more confident than ever in model predictions that Earth’s leading greenhouse gas will contribute to a temperature rise of a few degrees by the end of the century. > > “This study confirms that what was predicted by the models is really happening in the atmosphere,” said Eric Fetzer, an atmospheric scientist who works with AIRS data at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Water vapor is the big player in the atmosphere as far as climate is concerned.” ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [September 20, 2011, 3:28pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/419 "2011-09-20T15:28:33Z")
> [@matt](#): > > Okay. So you believe in a compensating subtractive mechanism. While I don’t rule that out, there are a couple of difficulties with it. First, we know of quite a few additive amplifying mechanisms (although the magnitude of their effects are basically WAGS) but clouds are the only _possibly_ subtractive mechanism that we know about. I disagree. For example, one possible subtractive mechanism is higher humidity –\> greater precipitation in Antarctica —\> more snow and ice coverage in Antarctica —\> higher albedo. Perhaps more importantly, one needs to consider that there are likely to be unknown unknowns. For example, what caused the Little Ice Age? Nobody knows. So it’s reasonably likely that there are important forcings and interactions which are simply unknown. > [@](#): > > Second, the observed warming so far is consistent with the warming expected from the simple calculation, plus a little bit more. This is only a problem if there is a solid a priori reason to believe that recent excess warming is largely the result of CO2 levels. I am not aware of any such reason. Indeed, global surface temperatures increased significantly in the first half of the 20th century and according to the IPCC reports, this increase was NOT due to CO2. How do we know that the same force which caused this increase has not been in play more recently? The answer is that we do not know. ---
**Author:** ![FXMastermind](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fxmastermind/32/7289_2.png) [@FXMastermind](https://boards.straightdope.com/u/FXMastermind)\ **Post date:** [September 20, 2011, 3:37pm UTC](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724/420 "2011-09-20T15:37:55Z")
The giant elephant in the climate room is solar activity. Perhaps due to the political nature of the doom and gloom global warming/climate change/alarmists view of the future, real science is often ignored in the “climate debate”, which resembles a mudfight of politics rather than a quest for the truth [http://www.climatescienceinternational.org/index.php?option=com\_content&view=article&id=31:vanishing-sunspots-prelude-to-global-cooling&catid=1:latest](http://www.climatescienceinternational.org/index.php?option=com_content&view=article&id=31:vanishing-sunspots-prelude-to-global-cooling&catid=1:latest) The ardent alarmists probably won’t even read the link, or already knows why it can’t be true, in any case, an honest debate is almost impossible to come by online. Or it seems anywhere else. [Previous page](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724.md?page=20) [Next page](https://boards.straightdope.com/t/climatologist-dr-michael-mann-completely-vindicated-again/593724.md?page=22)