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Chris G at 03:19 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
RSVP, Maybe this will help you with the time scale question. Oh, look, there is a link to this site near the bottom of the first page where this topic has been covered before, and you were part of the debate. -
michael sweet at 03:06 AM on 20 October 2010Explaining Arctic sea ice loss
Garethman, The problem with AGW is that it is a very, very slow train wreck. The changes from one year to the next are not noticable. Even most of the changes from one decade to the next are difficult to observe: sea ice is an exception. It takes careful observations over 20 or more years to see most of the effects of AGW. People like you who expect sea levels one meter higher tomorrow will always be able to say there is no change. You do not pay attention to the record heat in Russia or the record floods in Pakistan. They are not in your backyard. That does not mean that the changes will not be substantial, expensive and difficult to adapt to. As time goes on the changes are accelerating. Only 20 years ago Lindzen testified in the US Congress that the climate was not changing. Now it is common on this web site for deniers to say everyone knows it is getting warmer, they dispute the cause. If you care about what the world will be like in 30 to 50 years then you need to pay careful attention now. Starting in 30 years to mitigate will be much more expensive than starting now. -
dana1981 at 02:55 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
This post sums up perhaps one of the worst skeptic contradictions. They love to say the MWP was hot, and they love to say the climate isn't sensitive. You can't have it both ways. Humanity Rules raised a valid point in #11 that climate sensitivity isn't identical for different forcings. There's a factor called "efficacy" and in fact it's likely that the climate is less sensitive to changes in solar irradiance than changes in atmospheric greenhouse gases. I discussed this in the Advanced 'climate sensitivity is low' rebuttal. But the bottom line is that the efficacies of different forcings aren't wildly different, so if you're arguing for a hot MWP, you are arguing for a high climate sensitivity, including to CO2. -
archiesteel at 02:50 AM on 20 October 2010It's the sun
@KR: "You've repeated the same arguments over and over despite multiple corrections. At this point I'm out of this discussion." I think this is Ken's strategy: obfuscate, reiterate and ignore other arguments until people are fed up with him and leave, at which point he claims victory. Better to ignore him. It's not as if his arguments will be reused by other "skeptics" anyway... -
Chris G at 02:49 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
Not a complaint, but whenever I here someone say, "the hockey stick", I have to wonder 'Which hockey stick?' Most often, they mean the one from Mann, et al, 1998, and they complain about using tree rings as though the researchers had no idea that there are other things beside temperature which affect tree growth. (Rest assured that they are well aware of the nature of the proxy that they chose.) But that is one study of many, and whether you use tree rings, pollen counts, isotope levels in corals, or other proxies alone or in combination, you still get a hockey stick. Here as a small sample of hockey sticks from other studies. HR, Regarding, "Why would clouds respond the same to CO2 variation in the industrial period as they might have to solar variation in the pre-industrial period?" There will be differences in the pattern of heating, or cooling, depending on the mechanism of the forcing, see the topics on human signature on this site, but, for instance, a collection of water molecules with an opportunity to evaporate does not care whether its energy came in the form of shortwave solar radiation, or longwave emissions from the atmosphere. In the aggregate, you have not presented any reason for things like, in what latitudes the rain bands are, and how much water is locked up in ice sheets, to be determined by things like whether nighttime temperatures are rising more than daytime temperatures. Also, the actual calculations performed, and factors considered, by researchers are exceedingly more complicated than anything presented here; saying that what is here is simplified is telling us what we already know, and doesn't mean that it's wrong. It's like you are trying to obscure the forest with trees. -
archiesteel at 02:47 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
@TIS: "To be specific. The chart shown is Moberg 2005. The hockey stick that is the central point of controversy is the one by Mann in 1998 that was part of the IPCC report." Mann revised his original hockey stick in 2008. Why don't "skeptics" ever talk about that one? -
It's the sun
Ken Lambert - Your hypothesis appears to be that an unmeasured amount of TSI, one mis-calculated since the beginning of TSI measurements, is providing a dominant effect on global temperatures rather than CO2 and greenhouse gas accumulation. In other words, that it's the sun, not CO2. The satellite TSI readings appear to have cross-platform calibration issues, as each is self-calibrated to internal standards. This has improved over the years, not to say that it's not a work in progress, but it's improving. Note that the precision, the repeatability of these measures, is extremely good - the accuracy may be off a bit. But high precision means excellent tracking of changes, of deltas in TSI forcing. Now, if there's a linear offset in TSI measures (direct or using sunspots as proxies), as you have argued, there would be a difference in slope between measured TSI responses and temperature over the entire temperature/TSI record, not just the last 60 years. One look at the Temperature vs. Solar Activity chart on the Basic version of this thread will disprove that. I certainly know that all forcings are part of the picture; I'm not certain from your statements that you do. The two lines have separated. The temperature changes correspond to changes in GHG forcings, they do not correspond to changes in TSI. That is entirely supported by the numbers you presented here, as kdkd pointed out statistically - you've just disproven your hypothesis again. You are incorrect on the basis of correlation of ΔT versus ΔForcings, on the magnitude of the TSI changes, and on somehow not crediting the forcings of GHG's. You've repeated the same arguments over and over despite multiple corrections. At this point I'm out of this discussion. -
Ned at 02:39 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
chriscanaris, with all due respect, you're missing the point. It's not that there aren't uncertainties about, e.g., cloud albedo feedbacks or whatever. The statement "The MWP was very warm" implies a certain assumption about those feedbacks. Specifically, it implies that positive feedbacks outweigh negative feedbacks by more than we currently expect ... in which case climate sensitivity will be on the higher side of what we expect. You have to be consistent in your argument here. It's not reasonable to assume a high value for climate sensitivity in order to get a large MWP, while also assuming a low value for climate sensitivity in order to minimize the effect of AGW. HumanityRules, the default assumption should be that cloud feedbacks would respond the same way to a warming atmosphere. If you think that differences in how you warm the atmosphere would be large enough to make significant differences in cloud feedbacks, it's up to you to provide evidence for that. -
The Inconvenient Skeptic at 02:38 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
To be specific. The chart shown is Moberg 2005. The hockey stick that is the central point of controversy is the one by Mann in 1998 that was part of the IPCC report. Moberg shows more temperature variation than Mann does on a consistent basis. Many skeptics consider Moberg to be reliable. Mann is the one that irks them. I personally think Moberg does good work. I have reviewed many of his proxy reconstructions and see no problem with them. Calling a Moberg chart the Hockey Stick is very imprecise. -
archiesteel at 02:34 AM on 20 October 2010It's the sun
Two things: first, blatant denier spam such as Howard at 697 should be deleted. Second: KL, I get what you're saying, I guess I just don't see the point you are trying to make. It seems you've lost yourself in your own arguments. -
Sordnay at 02:27 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
Just wondering, on your first graph, is CRUTemp NH, but what is exactly this serie? a 12 month mean of CRUTempNH does not rise more than 0.657, according to this: http://woodfortrees.org/plot/hadcrut3vnh/mean:12/from:2000 Even that would be too noisy, but on your figure,it's a noiseless signal, and it goes up to about 0.87-0.88 more or less... Anyway, looking again to the first figure, the recent temperature anom. would be about the same as the drop estimated from around 1480-1550 (eyeballing) without a net forcing and in time period somewhat similar to recent anom, a bit higher. What is the reason for this drop? -
Doug Bostrom at 02:17 AM on 20 October 2010Throwing Stones at the Greenhouse Effect
Sorry, forgot to credit that transmission image. It's from Global Warming Art. -
RSVP at 02:13 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
doug_bostrom There is a big difference between exposing chicken on a spinning skewer to a flame for 1 minute and 1 hour. -
RSVP at 02:11 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
Ned #9 Thanks for the explanation. If I understand correctly, sensitivity has to do with the steady state average global temperature as affected by incremental forcing. Using "sensitivity" in this context is odd when what matters is getting the system under control in time. -
michael sweet at 02:07 AM on 20 October 2010Throwing Stones at the Greenhouse Effect
RSVP, Your picture sounds like nonsense because you do not understand the basic science of heat transfer in the atmosphere. Re-read the 200+ posts in the waste heat thread again and see if you can begin to understand it. In the absence of CO2 the ocean would freeze. Most of the surface heat would be radiated into space without warming the atmosphere. The remainder of the atmosphere is capable of radiating heat, just not as efficiently as CO2. The temperature of the atmosphere would be much lower than it is now. Just because your picture is nonsense does not mean that gpwaynes picture is also nonsense. -
Phila at 01:54 AM on 20 October 2010Throwing Stones at the Greenhouse Effect
Also, I'm really tired of "skeptics" patting themselves on the back for accepting the reality of the greenhouse effect while denying its logical consequences. The basic argument seems to be "When climate scientists say A, B, C, D and E about the greenhouse effect, of course I believe them. It's only when they claim that F follows logically from A through E that I see them as fanatics, liars or dupes." It's a bit like the creationists' equally tenuous distinction between "microevolution" and "macroevolution," where the latter is supposedly some ludicrous extrapolation beyond the evidence, rather than the logical consequence of facts that the creationist claims to understand and accept. -
Doug Bostrom at 01:34 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
RSVP, your question was: "Should'nt sensitivity be related in some way to units of time?" The "Watt" is a measure of power, of energy expressed as a rate, an amount of energy divided by an amount of time, one Joule per second, meaning that sensitivity expressed in Watts is automatically related to units of time. -
CBDunkerson at 01:04 AM on 20 October 2010It's the sun
KL #700: "KR seems to still not get the fact that a forcing component does not have to be rising to be adding energy to the system." The Sun is constantly 'adding energy to the system'. However, if solar activity remained constant then it would obviously not cause any change to the climate. It is only when there is a change in solar activity (that is, a "forcing") that there is a corresponding change in climate... and then only until a new equilibrium is reached. The same is true of all climate forcings. So no, KR probably 'does not get' that flat forcing factors do not change the climate. Because they don't. -
RSVP at 01:03 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
doug_bostrom #12 "RSVP, just as an exercise..." My question was directed to understanding the sensitivity of climate, not climate scientists. -
HumanityRules at 01:01 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
18.skywatcher Why would clouds respond the same to CO2 variation in the industrial period as they might have to solar variation in the pre-industrial period? While you can measure the direct affect from increasing levels of CO2 or changes in solar irradiance (assuming accurate measurements) you can't really calculate what the feedback responses are. Maybe I'm wrong but these sorts of calculations that John are describing seem to assume simple fedback mechanisms shared by all forcings. -
Ken Lambert at 00:38 AM on 20 October 2010It's the sun
KR #692 and kdkd #696 Two points: Firstly - KR seems to still not get the fact that a forcing component does not have to be rising to be adding energy to the system. A steady or roughly constant forcing such as F.Solar (say S) will add energy over time as St - a linear increase. Lets say that F.CO2 is linearly rising wrt time (over a short period of say 25 years). Therefore F.CO2 = Kt where K is a constant. F.CO2 will add energy over time as Kt^2/2 - a squared function increase. Both are adding energy. Secondly, the F.CO2 and other component forcings are theoretical and not directly measured - only the combined imbalance is directly measured at TOA. This is supposed to be +0.9W/sq.m. In fact the CERES satellites are measuring +6.4W/sq.m. So this is 'corrected' down by -5.5W/sq.m to the theoretical imbalance. The problem is that not even the 0.9 is being observed in OHC. The wide error bars on aerosol cooling, and other forcing components mean that the mix of components is not really known accurately. I would like to see a combined forcing chart including S-B cooling over time to see what the energy balance is as well. Anyway - I think my point is made - the Solar forcing component 1950 - now is about 0.4W/sq.m - not 0.12W/sq.m as the IPCC chart implies. -
Doug Bostrom at 00:36 AM on 20 October 2010Throwing Stones at the Greenhouse Effect
You appear to be missing some key concepts, RSVP. Baffling, considering how much time you spend arguing here.
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Alexandre at 00:26 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
skywatcher #16 I thought I had said that too on my third paragraph... anyway, if I did not make it clear, I'll rectify it by endorsing what you said now. -
skywatcher at 00:25 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
chriscanaris - why would clouds operate differently in the present day compared to the past? If clouds are a strong negative feedback, we would see far less natural variation than we do in the palaeoclimatic record, be it last 1000 years, or ice ages. There simply haven't been large enough positive natural forcings to allow clouds to operate as a big negative feedback. You'd end up with a palaeoclimate flatter than a Mann et al (1999 vintage) hockey stick shaft... -
robert way at 00:25 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
Philip64, You are correct. Sea level was higher than today during the MWP by between 12 and 21 cm. This is because of the prolonged length of the MWP allowed for losses of ice and thermal expansion to occur over a long period of time. Grinsted et al (2010) conclude that if we saw no increase in temperatures from the year 2008 to 2100 we would see a sea level rise greater than during the MWP as the thermal inertia of the oceans and the ice caps catch up. The article I am citing is here: http://www.springerlink.com/content/527178062596k202/ -
Doug Bostrom at 00:23 AM on 20 October 2010Explaining Arctic sea ice loss
Hi, garethman. There are numerous "periods of recovery" visible in the graph since it began showing an extended decline ca 1970. These have all swiftly ended, to be overwhelmed by subsequent declines. The graph in this article ends in 2009; a look at a graph including 2010's melt season shows another "period of recovery" appearing to draw to a close. This particular article is more about attribution. Peter Hogarth has done a fine job of covering "recovery" here on Skeptical Science. -
skywatcher at 00:20 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
Good post - a topic on which I've had a number of debates with irrational skeptics. A minor text quibble - maybe change the opening "The" in the 3rd sentence to "Their" - the logical leap is only logical if you're a skeptic! Alexandre - it does change the sensitivity to CO2, because if the world's climate responded significantly to the ~ +0.3W/sq m of the MWP, it will respond correspondingly more significantly to the >1W/sq m of anthropogenic CO2 forcing. Few parts of the climate system are particular about from where they get their extra W/sq m. Larger natural variability must result in larger climate forcing from anthropogenic CO2. Unless you can argue that the CO2 forcing is a much lower value in W/sq m, then the latter must follow the former. And there is relatively little uncertainty about the CO2 forcing value, as Ned's posted figure shows. RSVP - the Sun has as much impact now as it did in the past, but the forcing is rather small in comparison to that of CO2. The papers linked in this NASA article are well worth a read: CO2: The Thermostat that Controls Earth's Temperature, particularly two new ones, as they are quite relevant to this post. -
chris1204 at 00:17 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
Ned @ 8 PS: Just take a look at what I presume are the uncertainty bars for CO2 and clouds respectively in your diagram from AR4. -
chris1204 at 00:12 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
Ned @ 8 'Cloud feedbacks remain the largest source of uncertainty.' For example, see: Cloud Feedbacks in the Climate System: A Critical Review (Stephens 2005). Googling 'cloud feedbacks in the climate system' yields 289,000 results - this just happens to be a reference on the first page. I think we can be too quick to dismiss the role of clouds. -
HumanityRules at 00:12 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
...the 0.8oC from the past 1500years isn't natural? should read 150 years. -
Doug Bostrom at 00:10 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
RSVP, just as an exercise, look up the definition of the Watt as a unit of power, eh? Once you've got the notion of a Watt under your belt, you can then begin relating it to mass, specific heat, conversion into sensible versus latent heat, etc. -
HumanityRules at 00:09 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
John, Roy Spencer in his recent post about the recent Lacis paper has suggested that the past variation in temperature could, in part, be driven by internal mechanisms. for example cyclical changes in the oceans could have an affect on the hydrological cycle and cryosphere thus affecting albedo. This would make the whole process of trying to calculate sensitivity from past climate flawed. It seems like a difficult one to disprove. Also generally on the overall idea you show here, does your analysis depend on the idea that feedbacks are roughly similar depending on the different forcing. Are you saying that if the relatively small changes in TSI have larger affects on surface temperature then this means that doubling Co2 will also have a similar larger affect? The changes in solar irradiance have a complicated affect on different parts of the climate system, take for example the stratospheric effects from UV in the discussion about the Haigh paper and all the possible knock on effects that has. This will be totally absent in forcing from CO2. How can you confidently say that because you deduce great climate sensitivity from solar variance means greater sensitivity from CO2? The same could be said for forcing from volcanos superficially they seem the same by changing the net energy budget but they do it in very different ways that will lead to very different feedback mechanisms. Finally there also seems to be something missing if we accept that solar variance has had a greater effect in pre-industrial times. It must also mean that solar is having a greater affect in industrial times, unless you think solar variance has switched itself off for the past 100years. It must mean that solar is implicated in some of the cyclical features of the 20th century temperature record. The idea that the 1940-1970 'cooling' and recent warming are all about aerosols and CO2 respectively seems flawed. If as Moberg and other say that natural processes can change temp by up to 0.7oC in 5-600years then what's to say some (or much) of the 0.8oC from the past 1500years isn't natural? There seem to be more implications from greater natural variability in the past 1000 years than the one you present (climate sensitivity). (small point Hergel et al is 2006 not 2000) -
Ken Lambert at 00:08 AM on 20 October 2010It's the sun
archiesteel #695 As the planet warms from a forcing imbalance, it emits black body radiation in proportion to the fourth power of the absolute temperature (degK) via the Stefan-Boltzman equation. The forcing imbalance gap then closes and a new equilibrium temperature is approached. The 'emitting temperature' is quoted as about 255degK which is the temperature that space sees the Earth. The average surface temperature is about 15 degC or 288degK. The difference of 33degK is the 'greenhouse effect' of the atmosphere which slows down the heat transfer like an insulating blanket. -
Alexandre at 22:50 PM on 19 October 2010Climate Change Impacts on California Water Resources
Influx of seawater in aquifers is a problem in the Orange County wherabouts for a long time. Sea level rise would certainly worsen this. The problem and -mainly- the efforts in litigation and rule making to solve it have been subject of extensive research, including the Nobel Prize Elinor Ostrom. Her work about common-pool resource management should have more attention than it has had in these times of natural resource overuse. Two recommended books: - Rules, Games and common-pool resources (very academic and technical. Lots of math) - Governing the commons (a still academic but more readable text) Both have these Californa aquifers as one of their case studies. -
CBDunkerson at 22:41 PM on 19 October 2010Explaining Arctic sea ice loss
garethman #56: "The problem with this is that when year after year it does not happen, the warning begin to look like one of these chaps walking around with a billboard saying "the end is nigh" and it has the opposite effect on peoples perceptions." To my knowledge NO ONE has predicted an ice free Arctic ocean in the Summer prior to 2012 at the earliest. Most projections are closer to 2050... or 2100 if you go back about four years. Thus, I can't agree with the 'year after year' bit... it hasn't been projected to happen YET. So the fact that it actually hasn't in several years when no one thought it would doesn't seem particularly 'damaging'. "The other issue is that although the long term trend is obviously down, the short term trend is up from the 97 low. If this continues for another year or two the graph will start to look curiously like a hockey stick." Since we are now far below 1997 ice levels I assume you mean the 2007 low in ice extent... which was only a tiny amount lower than the 2008 and 2010 values. Claiming an 'upward' (barely) trend of three years is like claiming that Summer is going to be below zero because June 2-4 were one degree cooler than June 1. In any case, that's ice extent... which is largely determined by how spread out the ice is. The ice volume, the actual AMOUNT of ice, hit new all time lows of 5800 km^3 in 2009 and 4000 km^3 in 2010. If that trend continues nearly all the Arctic sea ice will be gone within a few years. -
Alexandre at 22:39 PM on 19 October 2010Do critics of the hockey stick realise what they're arguing for?
Lars #1 This does not change the sensitivity argument from John's post. If the MWP was even warmer (as "skeptics" like to believe), that means the climate is even more sensitive to those rather mild forcings that occurred then. And this means climate would be more sensitive than expected to those CO2 W/m2 as well. Moberg points out (as far as I understand it) that natural forcings and natural variability seem to be more present than previously thought, and therefore projections should account for them too - as far as we can predict them, of course. But again, this does not change the sensitivy to CO2. -
Daniel Bailey at 22:22 PM on 19 October 2010An underwater hockey stick
Re: HumanityRules (97) Why on Earth would anyone be happy about that? Unless the increase was less than expected (that I would have been happy about)? You cannot imagine the joy I would feel if I could wave a magic wand and undo what we as a species have done with our injection of the bolus of fossil-fuel-derived carbon into our environment... ...a joy to be un-experienced and un-felt. The Yooper -
Ned at 22:09 PM on 19 October 2010Do critics of the hockey stick realise what they're arguing for?
RSVP writes: Should'nt sensitivity be related in some way to units of time? Yes, it is, in that ultimately climate sensitivity is the product of all feedbacks each of which has its own time scale. Some are very fast (water vapor), some intermediate (carbon cycle) and some are slower (ice albedo and tundra-taiga albedo). Often CS is referred to in terms of its equilibrium value once all of these feedbacks have taken effect. But the time evolution of global mean temperature from T0 to Teq will be nonlinear. -
Ned at 22:01 PM on 19 October 2010Do critics of the hockey stick realise what they're arguing for?
chriscanaris, I'm afraid I'm not following you. The IPCC AR4 section you link to doesn't seem to suggest that CO2 is not the driver of anthropogenic climate change. It merely states the probable range of uncertainty around the best estimate for climate sensitivity, and lists some of the major feedbacks that contribute to climate sensitivity. CO2 is the largest anthropogenic forcing, unless you have something to suggest that everybody's been missing:
Anthropogenic and natural radiative forcings (IPCC AR4 Section 2.1)
The feedbacks mentioned in the IPCC text you link to are not independent actors. They are in fact the mechanism by which the forcings (shown in John Cook's figs 2 and 3 above) translate into temperatures (shown in JC's fig 1).
The point of this thread is that we know pretty well what the forcings have been for the past millennium. If it turned out that the amplitude of the MWP-LIA difference was larger than expected, that would necessarily imply that climate sensitivity is also larger than expected. Nothing in the IPCC section that you cite contradicts this (or even particularly relates to it).
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CBDunkerson at 22:01 PM on 19 October 2010Despite uncertainty, CO2 drives the climate
Joel #28: "IPCC projections are no better than the economic models they use for inputs. The science can be perfect, but with a bad economic model it is GIGO." All of which is smoke since the IPCC projections span a range of emissions scenarios that extends both above and below what you consider likely. They covered everything from impossibly high (i.e. continuous population and economic growth) to impossibly low (i.e. immediate cessation of all fossil fuel use). In short, it's covered. -
RSVP at 21:54 PM on 19 October 2010Do critics of the hockey stick realise what they're arguing for?
John Cook "Technically, climate sensitivity is defined as the change in global temperature if the planet experiences a climate forcing of 3.7 Watts/m2" Should'nt sensitivity be related in some way to units of time? If something responds slowly, it is described as being less sensitive. If something responds faster, more sensitive, etc. -
chris1204 at 21:19 PM on 19 October 2010Do critics of the hockey stick realise what they're arguing for?
Always assuming that you believe anthropogenic climate change as originating *overwhelmingly* with CO2. If some of the uncertainties acknowledged in at least one authoritative source are taken seriously, the picture may be somewhat more complicated and hence close scrutiny of the palaeoclimate record and climate sensitivity and its sources may still be warranted. CO2 is *very* important but it may not be the whole story. I do not buy arguments that suggest that a robust MWP would justify 'business as usual' on an indefinite basis. However, ”The last temptation is the greatest treason/ To do the right deed for the wrong reason.” Pedantry aside, doing the right deed for the wrong reason may cause us to overlook vital elements in planning for an uneratin future. Philip64 @ 4: Interesting that you mention Venice, which has been subsiding because of exploitation of aquifers. Tidal factors seem to be of lesser signhifcance than is commonly supposed. -
JMurphy at 21:09 PM on 19 October 2010It's the sun
I wouldn't waste your time with Howard's site. An example of its 'thinking' : "Ever so Clever Alarmist Tricks of Trade There seems no end to the assemblage of clever tricks and blockades which the bretheren of the alarmist church can dream up. And since they hold pretty much all the top jobs all over their global diocese they for the most part go undetected and unreported." Hm, nice... -
Ned at 20:59 PM on 19 October 2010Do critics of the hockey stick realise what they're arguing for?
John, this is a really clear and well-written post. Just the kind of thing that SkS is known for. Nice work. Philip64's point is a good one. With the MWP being a long, slow rise rather than the steep increase in temperatures from AGW, more of the slow responding components of the climate system should have had time to adjust. That means sea levels, alpine glaciers, alpine/arctic tree lines, etc. -
Philip64 at 20:51 PM on 19 October 2010Do critics of the hockey stick realise what they're arguing for?
Excellent piece with a clear enough message, I think, even if the explanation behind it is (inevitably) complex. I don't know the answer to this, but if the MWP really was longer and warmer than the climate today, shouldn't it have seen a significantly larger rise in sea level than ours to date? Are there any reliable measures of sea level back then? (Anecdotally, I note that Venice was mainly built between the 12th and 15th Centuries, at sea level. No evidence that it was sitting high in the water during the subsequent little ice age, when Canaletto was endlessly painting it!) -
JMurphy at 20:43 PM on 19 October 2010Do critics of the hockey stick realise what they're arguing for?
I don't think the so-called skeptics are actually bothered about any of this because they hold those two propositions in totally separate compartments in their heads. I.E. the MWP was warmer than today, because, well, just because. That's what they are being told by their blog scientists and that is what they believe. Separate from that, climate sensitivity is lower (almost zero, in fact) because Lindzen says it is, and they believe him above all other scientists. To a so-called skeptic, the above can be held and believed at the same time without contradiction - well, to them, at least. -
macoles at 20:03 PM on 19 October 2010Do critics of the hockey stick realise what they're arguing for?
Whoa John, you might want to further add that the MWP was local to the northern hemisphere and had little to do with global climate forcing. While as a thought exercise it is an interesting idea that an increased Global MWP would infer greater climate sensitivity, you wouldn't want to inadvertently confuse people about the actual relationship to a Local MWP. -
Lars Rosenberg at 19:36 PM on 19 October 2010Do critics of the hockey stick realise what they're arguing for?
It may be of some interest to quote the conclusion of Moberg et al. (2005), whose graph You reproduce: ”We find no evidence for any earlier periods in the last two millennia with warmer conditions than the post-1990 period—in agreement with previous similar studies. The main implication of our study, however, is that natural multicentennial climate variability may be larger than commonly thought, and that much of this variability could result from a response to natural changes in radiative forcings. This does not imply that the global warming in the last few decades has been caused by natural forcing factors alone, as model experiments that use natural-only forcings fail to reproduce this warming. Nevertheless, our findings underscore a need to improve scenarios for future climate change by also including forced natural variability—which could either amplify or attenuate anthropogenic climate change significantly.” -
Howard at 19:24 PM on 19 October 2010It's the sun
If you want to know the answer to sun spot production and the link to global temperature variation, then see this site, the answer will surprise you!! http://www.solarchords.com -
HumanityRules at 19:07 PM on 19 October 2010An underwater hockey stick
Jumping around linksd brought me back to this page. I'm just curious if people are happy with the >1.5oC increase in temperature since 1900 seen in this underwater hockeystick?
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