# Need proof of Global Warming **URL:** \ **Category:** Great Debates\ **Created:** [April 4, 2008, 2:39am UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879 "2008-04-04T02:39:53Z")\ **Posts on this page:** 20\ **Page:** 16
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [May 5, 2008, 10:58pm UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/301 "2008-05-05T22:58:38Z")
[QUOTE=brazil84] So what? If it’s a lousy estimate, it’s a lousy estimate. I bet if you took the study its based on, and did a simple range sensitivity analsys, you’d end up with a huge honking range. [/QUOTE] It’s based on several studies…and indeed I think if you looked at the studies you see that there is a pretty big range but they all have a best estimate of less than 0.12% of GDP growth per year. ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [May 6, 2008, 12:04am UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/302 "2008-05-06T00:04:56Z")
[QUOTE=jshore] Well, the rule on using significant figures is sort of fuzzy, but as I understand it, it argues roughly that the number of significant figures you used should be determined by the fact that the last one you quote might be wrong…but the next digit is very likely correct…or at least wrong by at most one digit (e.g., so if you say “0.19”, the correct result could be “0.21”, say). Let’s just arbitrarily simplify this by saying that we imagine the last digit quoted can be off by at most 3. Then, “0.12” corresponds to 0.12 ± 0.03 and so it is implying knowledge to ±25% variation in the value. However, “0.92” corresponds to 0.92 ± 0.03 and thus implies knowledge to ±3% variation in the value. That’s all I meant…namely the observation that if you have a number quoted to 2 digits and the leftmost digit is a 1, then being off by one in the right digit is an error on the order of ten percent ,whereas if you have a 2-digit number and the leftmost digit is a 9 then being off by 1 in the right digit is only an error of order one percent. [/QUOTE] Most interesting, I’d never considered that quirk. Consider my ignorance fought … much appreciated. w. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [May 6, 2008, 1:39am UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/303 "2008-05-06T01:39:14Z")
**intention** : Thanks for your thoughtful reply (and glad I could clear up that significant figures issue). > [@intention](#): > > 1. The sun is thought to have warmed some 30% in the last three billion years or so. This is a change of about 80 w/m2. To counterbalance this, CO2 would have to double, not increase but double, about 80/3.7 = 21 times. Minor problem - 21 doublings of the current 380 ppmv yields an atmosphere with more than 100% CO2. This means that methane must have been involved as well … but then we have to assume two greenhouse gases in delicate balance with temperature, not just one. Well, there are lots of assumptions in this argument that I am not too confident about…e.g., over what sort of range the dependence of radiative forcing on concentration is approximately logarithmic, and over what sort of range the climate sensitivity is relatively constant. In particular, we know that for an earth in the absence of greenhouse gases, the climate sensitivity is a lot less. E.g., assuming a constant albedo and in the absence of greenhouse gases, the temperature of the earth would be 255 K with the sun at its current luminosity but only drop about 22 K to 233 K for the sun at 70% of it current luminosity. This is because of the dependence of radiative energy on the 4th power of the temperature. > [@](#): > > 1. Since the sun has warmed gradually over this period, in order for this plan to work, the CO2/methane have to very gradually decrease, from a proposed high some three billion years ago, to the present much lower state. There is no evidence that this has happened. I thought that there was in fact evidence that CO2 levels were generally quite a bit higher in the past and are relatively low, by historical standards, over the last several million years than they generally were before that. > [@](#): > > 1. In order for this plan to work, as the temperature slowly increases, the CO2/methane levels would have to decrease. I know of no evidence, either observational or theoretical, which shows a long-term negative correlation between temperature changes and GHG changes. That Wikipedia site explains why methane levels might have been higher a few billion years ago before there was significant oxygen in the atmosphere. And, they propose a theoretical explanation for a negative feedback whereby colder temperatures would tend to eventually lead to a rise in CO2 levels. > [@](#): > > 1. In order for this plan to work, the CO2/methane could not decrease linearly. Since the forcing is logarithmic, this would require a very exact exponential decay of the GHGs to stay in line with the increasing forcing. This is only if you need to keep things exactly in balance. But, in fact what we know is that there has been considerable variation in the earth’s climate, just that it has remained in some not-that-broad (but not that narrow either) range. And, if there is a negative feedback effect, it will tend to keep things in some sort of rough balance…or at least within certain ranges. > [@](#): > > In the words of the immortal IPCC, I find it “highly unlikely” (\<5% chance) that all of those conditions have obtained over the entire period of the last three billion years. This part confuses me. When there is a very speculative negative feedback proposed on short time scales involving clouds, you embrace it even though the evidence from the geologically recent past, which is the best evidence available, seems to be against such strongly stabilizing effects However, when the talk turns to negative feedbacks that might have operated over longer timescales to keep the temperature from varying too far afield, you are skeptical and seem to believe that such a feedback requires some sort of miraculous balancing rather than the same sort of principles that apply to any negative feedback. > [@](#): > > This question, of whether the world has an equilibrium temperature, is to my mind the great unanswered question in the field. Unfortunately, it cannot be answered with GCMs, at least in their present form. To do that, we need models like Wu’s model in my citation above. The problem that I have with your solution to the faint-sun paradox is it seems to be rejecting the current theories that best fit the available evidence that we have in favor of a new hypothesis that explains just this one piece of evidence. It seems to me that you still have to show that it can explain all of the other paleoclimate evidence…including the more recent past, for which we have much better and accurately time-resolved experimental evidence. What we know from the more recent past is that the climate has varied quite considerably in response to what appear to be pretty small forcings, and that it has been both considerably colder and considerably warmer than it is today. (There is even some evidence for a [“snowball earth”](http://en.wikipedia.org/wiki/Snowball_earth) and a [“hothouse earth”](http://adsabs.harvard.edu/abs/2004AGUFMPP33B0944M) in the more distance past.) So, it does not seem like we are particularly close to a point in either direction where a strong negative feedback might kick in (and, at any rate, the negative feedbacks that seem likely to apply would tend to operate on much longer timescales than the timescale over which we are causing the current perturbation in forcing). ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [May 6, 2008, 3:41am UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/304 "2008-05-06T03:41:19Z")
jshore, a very interesting post. A quick question, more to come. You say: [QUOTE=jshore] E.g., assuming a constant albedo and in the absence of greenhouse gases, the temperature of the earth would be 255 K with the sun at its current luminosity but only drop about 22 K to 233 K for the sun at 70% of it current luminosity. This is because of the dependence of radiative energy on the 4th power of the temperature. [/QUOTE] I thought the luminosity was a measure of the radiative energy … not so? w. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [May 6, 2008, 5:38am UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/305 "2008-05-06T05:38:53Z")
[QUOTE=jshore] It’s based on several studies… [/quote] Depends what you mean by “based on.” Looks to me as though the 0.12 figure comes from a number that comes from ONE scenario in ONE study. Looks to me as thought there was essentially no real meta-analysis. Nor was their any uncertainty analsysis as far as I can tell. > [@](#): > > a best estimate of less than 0.12% of GDP growth per year. Oh really? Would you like to guess where the following quote comes from? > [@](#): > > The scenarios in this report are **not predictions or best-judgment forecasts** from the modeling groups. (emphasis added) ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [May 6, 2008, 3:46pm UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/306 "2008-05-06T15:46:44Z")
[QUOTE=intention] I thought the luminosity was a measure of the radiative energy … not so? w. [/QUOTE] Yeah…I meant to be using them basically synonomously. What I am saying is that in the straight graybody calculation (so, in the absence of any feedbacks…or really any greenhouse gases at all), the fact that the radiative energy goes as the 4th power of the temperature means that a 30% decrease in radiative energy would correspond to about an 8.5% decrease in the absolute temperature [0.085 being is 1-(0.7)^(1/4)]. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [May 6, 2008, 3:59pm UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/307 "2008-05-06T15:59:23Z")
By the way, [here](http://earthobservatory.nasa.gov/Newsroom/MediaAlerts/2007/2007020524276.html) is a paper showing what they claim to be the first direct evidence supporting the hypothesis that atmospheric CO2 levels were much higher during the early Earth’s history. There also seems to still be some debate in the astrophysics community regarding whether the sun really was that much fainter back then. So, in summary, while this “faint young sun paradox” is interesting, the observational and theoretical constraints do not seem strong enough to elevate solution of it above understanding the much more recent paleoclimate events that we have much better data for. ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [May 7, 2008, 8:38am UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/308 "2008-05-07T08:38:20Z")
jshore, you raise some interesting points. Let me see if I can elucidate them. On a moment to moment basis, the tropical cloud albedo regulates the energy entering the peta-watt scale heat engine we call the climate. Suppose something changed with the cloud cover, so that instead of that albedo being about 30%, it changed to 33%, a mere 10% change. What would happen? According to orthodox theory, it would heat the planet by around 10 degrees C (eighteen degrees F) or so. And if it changed to 27%, it would cool the earth by 10°C or so. In the last half billion years, there’s no record of an excursion like that, 10° C. A freaking great asteroid hit the planet, for goodness sake, wiped out whole lineages of species, and the planet just went back to the same temperature. So clearly, some combination of physical processes is keeping the cloud albedo in the tropics in balance with the temperature. As I said, I see it on a daily basis. Rising humidity makes clouds and thunderstorms that cool the surface down. If that cooling system failed for a couple weeks, the town I live in (on a Pacific island at 9° S Latitude) would be unbearably hot. Hasn’t happened in recorded history. The question isn’t whether that effect exists. The question is how strong that effect is, how tightly it constrains the range of possible temperatures. Whether or not this explains the “Faint Early Sun” paradox is not very important to me. I’m more interested in how it works on a daily/monthly/annual/decadal/century basis. It is noteworthy, however, that Ou’s results (in the equilibrium study I cited above) showed that with a 50% change in solar constant from todays values, the surface temperature only varied by 10°C … this does not show, or prove, or establish, that this is the solution to the paradox. It does, however, establish it as a contender. w. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [May 8, 2008, 9:11am UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/309 "2008-05-08T09:11:11Z")
[QUOTE=brazil84] Would you like to guess where the following quote comes from? [/QUOTE] Since you apparently don’t want to guess I’ll tell you. As far as I can tell, it comes from the paper that was the basis for the 0.12 figure you have been bandying about. Turning back to the IPCC Report, it’s clear that the IPCC never actually says something like the following: > [@](#): > > Our best forecast for the worst-case cost of stabilizing CO2 levels between 445 ppm and 710 ppm is 5.5% of GDP by 2050, which is equivalent to a reduction of GDP growth rate by 0.12% per year. But that’s what’s implied and that’s what you took away from it, no? ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [May 8, 2008, 9:21am UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/310 "2008-05-08T09:21:55Z")
[QUOTE=brazil84] Since you apparently don’t want to guess I’ll tell you. [/quote] BTW that was addressed to **jshore** ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [May 8, 2008, 7:28pm UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/311 "2008-05-08T19:28:40Z")
[QUOTE=brazil84] Since you apparently don’t want to guess I’ll tell you. As far as I can tell, it comes from the paper that was the basis for the 0.12 figure you have been bandying about. [/QUOTE] Without the context from which that quote appears, it seems like you have just engaged in a meaningless quote-mining exercise to me. (And, we saw how you took that “case-by-case basis” quote out of context previously.) ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [May 8, 2008, 7:36pm UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/312 "2008-05-08T19:36:40Z")
**intention** : Thanks for your response. I understand your desire to use paleoclimate evidence to try to estimate the climate sensitivity, but why is it that the scientists who actually do this come to [the conclusion](http://www.sciencemag.org/cgi/content/summary/sci;306/5697/821) that “the climate system is very sensitive to small perturbations and that the climate sensitivity may be even higher than suggested by models” while you, in what is frankly a very hand-waving way, come to a different conclusion? > [@](#): > > If that cooling system failed for a couple weeks, the town I live in (on a Pacific island at 9° S Latitude) would be unbearably hot. Hasn’t happened in recorded history. So, are you saying that the current climate models estimate the temperature on your Pacific island to be considerably hotter than it actually is? > [@](#): > > It is noteworthy, however, that Ou’s results (in the equilibrium study I cited above) showed that with a 50% change in solar constant from todays values, the surface temperature only varied by 10°C … this does not show, or prove, or establish, that this is the solution to the paradox. It does, however, establish it as a contender. The more interesting question is whether Ou’s results can predict the ice age - interglacial cycles and the other recent climate changes that we have the best data for. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [May 8, 2008, 7:48pm UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/313 "2008-05-08T19:48:50Z")
[QUOTE=jshore] Without the context from which that quote appears, it seems like you have just engaged in a meaningless quote-mining exercise to me. [/quote] Lol. You gotta be kidding me. Anyway, here’s the full section: > [@](#): > > This report presents research from Synthesis and Assessment Product 2.1a of the Climate Change Science Program, Scenarios of Greenhouse Gas Emissions and Atmospheric Concentrations. The scenarios in this research product are designed to stabilize the influence of a suite of greenhouse gases (GHGs)–carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulfur hexafluoride (SF6)—on the Earth’s radiation balance, measured in terms of radiative forcing. Four radiative forcing stabilization levels are considered. The resulting atmospheric concentrations of the largest single contributor, CO2, are roughly 450, 550, 650 and 750 ppmv. In response to the Prospectus for this research product, this report presents scenarios with an emphasis on (1) GHG emissions trajectories, (2) global and U.S. energy system implications, and (3) economic implications of stabilization. > > This research was conducted using computer-based research tools known as integrated assessment models. Three modeling groups each independently developed a reference scenario, in which all climate policies were assumed to expire in 2012, and then developed four stabilization scenarios as departures from their respective reference scenarios. Idealized emissions-reduction measures – designed to achieve emissions reductions wherever, whenever, and using whichever GHG was most cost-effective – were imposed to limit GHG emissions and meet the four radiative forcing limits. Evidence from previous literature suggests that if less idealized measures were employed to stabilize radiative forcing, costs could be substantially higher. Further, this research considers only the costs of stabilization; it does not consider the benefits of potential climate change avoided or of possible ancillary benefits of emissions reduction (e.g., less air pollution). > > **The scenarios in this report are not predictions or best-judgment forecasts from the modeling groups.** Rather, they constitute new research intended to advance understanding of the forces that lead to GHG emissions and that shape opportunities to stabilize GHG 6 concentrations and radiative forcing. Although the future is uncertain and the scenarios are strongly dependent on many underlying assumptions, this research provides useful insights for those engaged in climate-related decision making. (my bolding) > [@jshore](#): > > (And, we saw how you took that “case-by-case basis” quote out of context previously.) Nonsense. ---
**Author:** ![intention](https://avatars.discourse-cdn.com/v4/letter/i/e95f7d/32.png) [@intention](https://boards.straightdope.com/u/intention)\ **Post date:** [May 9, 2008, 3:45am UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/314 "2008-05-09T03:45:37Z")
[QUOTE=jshore] intention: Thanks for your response. I understand your desire to use paleoclimate evidence to try to estimate the climate sensitivity, but why is it that the scientists who actually do this come to the conclusion that “the climate system is very sensitive to small perturbations and that the climate sensitivity may be even higher than suggested by models” while you, in what is frankly a very hand-waving way, come to a different conclusion? [QUOTE=intention] If that cooling system failed for a couple weeks, the town I live in (on a Pacific island at 9° S Latitude) would be unbearably hot. Hasn’t happened in recorded history. [/QUOTE] So, are you saying that the current climate models estimate the temperature on your Pacific island to be considerably hotter than it actually is? [/QUOTE] First, please dial back on the accusations of hand-waving. I have provided a citation for my claim that the Earth has an equilibrium temperature. I have provided a citation for the idea that the earth is running at a condition of maximum power production/dissipation. I have also discussed the mechanism in detail. Your insults do not strengthen your case. In addition, your pretended shock that other scientists might come to different conclusions does not become you. The article you cited is not peer-reviewed, it is a “Perspective”. Science Magazine, where it was published, says Perspectives "are meant to express a personal viewpoint ". Why haven’t you accused the author of “hand-waving”? In any case, from the personal viewpoint you cited: [QUOTE=Schrag] Likewise, warm episodes in Earth’s history reveal a similar cautionary lesson. During the Eocene, 50 million years ago, palm trees grew in Wyoming (8) and deep ocean temperatures were more than 10ºC warmer than present (9). Because we do not know exactly how high the atmospheric CO2 concentration was at that time, we cannot use it as a direct measure of climate sensitivity. However, the extreme warmth at high latitudes–especially during the winter in continental interiors–cannot be simulated by climate models purely through elevating greenhouse gas concentrations (10). Special cloud feedbacks must be included that are not present in the models used to predict future climate change (10, 11). This observation suggests that feedbacks may be missing from current models and that future climate change may be underestimated in these models, particularly at high latitudes. [/QUOTE] This is indeed a “cautionary lesson” … but about the climate models, not the climate sensitivity. This shows that current models don’t understand the basic fundamentals of the climate, since they cannot explain the Eocene without including … hey, guess what, cloud feedback. Which is what I have been talking about, the fact that the models don’t properly represent the cloud feedback. However, his claim that including the proper cloud feedback in the models will increase estimates of future climate change is un-cited, un-referenced, and without any basis in fact. Which is OK, after all, this is his personal viewpoint … but I hope you don’t think it is more than that, I hope you don’t mistake his viewpoint for established science. Also, his estimates of past sensitivity to small perturbations is based on these very same climate models that can’t successfully model the Eocene … which doesn’t exactly inspire confidence. Do “the current climate models estimate the temperature on your Pacific island to be considerably hotter than it actually is?” Haven’t you been following the discussion? The problem is not that the models don’t get the rough numbers right, they’re tuned to do just that, so of course they do. How many times do we have to go over that? THE MODELS ARE TUNED TO THE PRESENT CLIMATE, SO THEY FACT THEY GET IT RIGHT PROVES NOTHING. The problem is that they don’t get the feedbacks right, which has much larger implications. You seem to think that the models calculate the feedbacks … not so. The feedbacks in the model are set by the modelers based on their particular beliefs. They are _inputs_ to the models, not _outputs_. [QUOTE=jshore] [QUOTE=intention] It is noteworthy, however, that Ou’s results (in the equilibrium study I cited above) showed that with a 50% change in solar constant from todays values, the surface temperature only varied by 10°C … this does not show, or prove, or establish, that this is the solution to the paradox. It does, however, establish it as a contender. [/QUOTE] The more interesting question is whether Ou’s results can predict the ice age - interglacial cycles and the other recent climate changes that we have the best data for. [/QUOTE] That is indeed an interesting question … however, as I’ve said before, there are many interesting and unanswered questions in the study of climate, it is a newcomer to the sciences. To date, for example, I have not found a good explanation for the ~100,000 year cycles of the glaciations. Might be one, but I haven’t seen it. It is a puzzle because this frequency is not among the Milankovic cycles. Nor is there a theory about why the previous interglacial was warmer than the current one, nor why it was shorter. Heck, we don’t have an explanation as to why we’re not in an ice age right now … w. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [May 10, 2008, 2:14am UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/315 "2008-05-10T02:14:15Z")
[QUOTE=intention] First, please dial back on the accusations of hand-waving. I have provided a citation for my claim that the Earth has an equilibrium temperature. I have provided a citation for the idea that the earth is running at a condition of maximum power production/dissipation. I have also discussed the mechanism in detail. Your insults do not strengthen your case. [/quote] **intention** , thanks for your response. Your citations just present a very speculative hypothesis about the climate system. (One does not even seem to address the issue of how the speculative hypothesis would affect climate sensitivity, at least from what I could see on skimming it, while the other does propose in general terms that it would tend to lead to low sensitivities.) Neither address the point that I was saying you are “hand-waving” which is the claim that a study of paleoclimate data favors the idea of a low climate sensitivity (other than Ou’s vague speculations, similar to yours, along the lines of the faint sun paradox). > [@](#): > > In addition, your pretended shock that other scientists might come to different conclusions does not become you. The article you cited is not peer-reviewed, it is a “Perspective”. Science Magazine, where it was published, says Perspectives "are meant to express a personal viewpoint ". Well, it is not clear to me exactly what the review process is for Perspectives but you have quoted what they say about them rather selectively. [Here](http://www.sciencemag.org/about/authors/prep/gen_info.dtl) is the full description from which you presumably took your quote: > [@](#): > > Perspectives (up to 1000 words plus 1 figure) highlight recent exciting research, but do not primarily discuss the author’s own work. They may provide context for the findings within a field or explain potential interdisciplinary significance. Perspectives commenting on papers in Science should add a dimension to the research and not merely be a summary of the experiments done in the paper. Although many of the Perspectives that comment on research published in Science are solicited, we welcome inquiries regarding new advances and fresh insights. As these are meant to express a personal viewpoint, with rare exceptions, Perspectives should have no more than two authors > [@intention](#): > > Why haven’t you accused the author of “hand-waving”? Because they have discussed specific paleoclimate events and what the study and modeling of them suggests in terms of the climate sensitivity. > [@](#): > > This is indeed a “cautionary lesson” … but about the climate models, not the climate sensitivity. This shows that current models don’t understand the basic fundamentals of the climate, since they cannot explain the Eocene without including … hey, guess what, cloud feedback. Which is what I have been talking about, the fact that the models don’t properly represent the cloud feedback. However, his claim that including the proper cloud feedback in the models will increase estimates of future climate change is un-cited, un-referenced, and without any basis in fact. Which is OK, after all, this is his personal viewpoint … but I hope you don’t think it is more than that, I hope you don’t mistake his viewpoint for established science. However, the point is that such feedbacks are needed not to explain why the climate was so stable but why it was so unstable. And, I don’t know why you feel that his claim is unreferenced since the previous sentence discussing the special feedbacks needed provides you with 2 references. > [@](#): > > Also, his estimates of past sensitivity to small perturbations is based on these very same climate models that can’t successfully model the Eocene … which doesn’t exactly inspire confidence. The point is not that the climate models are perfect…but rather to the extent that they imperfectly explain the past, the problem seems to be that the underestimate the sensitivity of the climate to perturbations. > [@](#): > > Do “the current climate models estimate the temperature on your Pacific island to be considerably hotter than it actually is?” Haven’t you been following the discussion? The problem is not that the models don’t get the rough numbers right, they’re tuned to do just that, so of course they do. How many times do we have to go over that? THE MODELS ARE TUNED TO THE PRESENT CLIMATE, SO THEY FACT THEY GET IT RIGHT PROVES NOTHING. Look, the point is that you brought up a situation that was meant to highlight something that you apparently felt was missing from the current understanding of the climate incorporated into the climate models. Now, you are admitting that in fact the current climate models get the right answer but still trying to imply that they do so only because they have been tuned to agree. However, besides the fact that your description of tuning…and the degree to which the model parameters can be tuned to fit the whole wealth of available climate data…is at odds with almost the entire climate science community, this still begs the question: Clearly, the models have processes in them that keep your Pacific island from unrealistically roasting. What exactly do you think are unphysical about these processes as currently modeled? > [@](#): > > The problem is that they don’t get the feedbacks right, which has much larger implications. You seem to think that the models calculate the feedbacks … not so. The feedbacks in the model are set by the modelers based on their particular beliefs. They are _inputs_ to the models, not _outputs_. They set certain parametrizations that control the feedbacks but do not set the feedbacks themselves. And, this process is severely constrained by the physics of the processes themselves, as well as the huge wealth of climatic data which has orders of magnitude more degrees of freedom than the number of degrees of freedom that the climate modelers have through changing the parameters. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [May 10, 2008, 2:25am UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/316 "2008-05-10T02:25:51Z")
By the way, for what it’s worth, [here](http://www.sciencemag.org/cgi/content/full/320/5873/195) was a recent paper that proposed a biological cloud feedback that they argue can explain the mystery of the extensive warmth of some of the past climates. One distressing thing, if they are correct (and clearly, their work is still pretty speculative), is that they estimate that a 4X increase in CO2 above pre-industrial levels was enough to cause dramatic declines in biological productivity. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [May 10, 2008, 2:48am UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/317 "2008-05-10T02:48:15Z")
[QUOTE=brazil84] Anyway, here’s the full section: [/QUOTE] Actually, a section that explains it a bit better is here (from the report available [here](http://www.climatescience.gov/Library/sap/sap2-1/finalreport/default.htm)): > [@](#): > > Each modeling group first produced a reference scenario under the assumption that no climate policies are imposed beyond current commitments, namely the 2008-12 first period of the Kyoto Protocol and the U.S. goal of reducing reduce GHG emissions per unit of its gross domestic product by 18% by 2012. The resulting reference cases are not predictions or best-judgment forecasts but scenarios designed to provide clearly defined points of departure for studying the implications of alternative stabilization goals. As instructed in the Prospectus for the study, the modeling teams used model input assumptions they considered meaningful and plausible. The resulting reference scenarios provide insights into how the world might evolve without additional efforts to constrain GHG emissions, given various assumptions about principal drivers of these emissions such as population increase, economic growth, land and labor productivity growth, technological options, and resource endowments. > > Each modeling group then produced four additional stabilization scenarios framed as departures from its reference scenario. The stabilization levels are common across the modeling groups and are defined in terms of the total long-term effect on the Earth’s heat balance of the combined effect of the primary anthropogenic GHGs: carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). The potential for climate-related controls on other human emissions, such as aerosols and their precursors, was not incorporated into the stabilization constraints, although the participating models represent the emissions of many of these substances. With the exception of these stabilization levels, and a common hypothesis about the sharing among nations of the mitigation task, there was no direct coordination among the modeling groups either in the assumptions underlying the reference scenario or the precise paths to stabilization. So, in other words, the modelers were free to make plausible assumptions about what the baseline…or reference…scenario of how greenhouse gases would grow in the absence of new mitigation policies. And, then from this they also produced four different stabilization scenarios. The IPCC then apparently looked at the results, chose which of the stabilizations scenarios corresponded to their various categories of stabilization scenario (i.e., what the stabilization level for greenhouse gases was) and noted whether the baseline assumed was a higher or lower one and reported the results. I’m not sure exactly what your point is. This, by the way, was a study conducted by the U.S. Climate Change Science Program, created by President George W. Bush. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [May 10, 2008, 7:36am UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/318 "2008-05-10T07:36:17Z")
[QUOTE=jshore] I’m not sure exactly what your point is. [/quote] The IPCC presented these non-predictions as predictions and completely snowed you, notwithstanding your physics degree. That’s the point. To make things worse, you would rather join in the deception of yourself rather than just admit you’ve been had. ---
**Author:** ![jshore](https://avatars.discourse-cdn.com/v4/letter/j/b5e925/32.png) [@jshore](https://boards.straightdope.com/u/jshore)\ **Post date:** [May 10, 2008, 2:32pm UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/319 "2008-05-10T14:32:30Z")
[QUOTE=brazil84] The IPCC presented these non-predictions as predictions and completely snowed you, notwithstanding your physics degree. That’s the point. To make things worse, you would rather join in the deception of yourself rather than just admit you’ve been had. [/QUOTE] The IPCC has always made the distinction between “predictions” and “scenarios” or “projections” given the complications of predicting future societal behavior, which is based on choices that we as societies make. And, they were clear in their report which results were based on higher baselines and which were based on lower baselines. ---
**Author:** ![brazil84](https://avatars.discourse-cdn.com/v4/letter/b/8491ac/32.png) [@brazil84](https://boards.straightdope.com/u/brazil84)\ **Post date:** [May 10, 2008, 3:39pm UTC](https://boards.straightdope.com/t/need-proof-of-global-warming/443879/320 "2008-05-10T15:39:26Z")
[QUOTE=jshore] The IPCC has always made the distinction between “predictions” and “scenarios” or “projections” [/quote] They can distinguish all they like, but it doesn’t change the fact that they suggested X while actually stating Y. Nor does it change the fact that you (with your physics degree) were taken in by their dishonesty. You referred to the non-prediction as a “best estimate.” When in truth and in fact, it was just a (worst case?) “scenario” based on some assumptions that were “plausible” (and others that were clearly not). [Previous page](https://boards.straightdope.com/t/need-proof-of-global-warming/443879.md?page=15) [Next page](https://boards.straightdope.com/t/need-proof-of-global-warming/443879.md?page=17)