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johnd at 06:10 AM on 30 September 2010New temperature reconstruction vindicates ...
Rob Honeycutt at 05:40 AM, on the other hand, unless the reconstructions track the instrumental data, then the assumptions made to enable the reconstruction have not been validated. The whole purpose I believe is that recent data should validate the proxy data. -
johnd at 05:40 AM on 30 September 2010Blog review of scientific coherence
Stephan, the use of the sheep analogy is a very very poor choice, though it may appeal to some, and that in itself may be telling. Those who are aware of how free markets work will say that in fact the person who offered that advice quite conceivably could be someone in touch with the real world. It could have been advice profferred on any commodity, even gold, or shares, and whilst the bean counters sit at their desks making all manners of predictions about future price directions, more often than not it is the contrarian who buys when others are selling or vice versa, or the those who have practical experience in the real world and can see the subtle signs of change that all others cannot, that offer the best advice. The apples example could perhaps be a valid analogy, but only for those who are susceptible to attracting such advice, whilst the bloke offering the sheep advice may well have his feet firmly on the ground, but unfortunately his advice may well be rejected by those without the practical knowledge of how markets work in the real world. -
Rob Honeycutt at 05:40 AM on 30 September 2010New temperature reconstruction vindicates ...
fydijkstra @ 39... "The red curves in the reconstruction graphs should be omitted, because the instrumental data are not comparable to the proxy records" Wouldn't that be a case of "hiding the incline?" The whole purpose, as I understand it, to looking at these reconstructions is to compare them to current warming. -
Philippe Chantreau at 05:39 AM on 30 September 2010Blog review of scientific coherence
HR says "that the acceleration in warming during 1977-2008 is a consequence of natural variability." It's nice for a skeptic to acknowldedge the existence of that acceleration, when so many are saying that it's cooling, one of the most common skeptic arguments that this site addresses. -
archiesteel at 05:08 AM on 30 September 2010The Phony War: Lies, Damn Lies and the IPCC
@CW: "That is certainly not true for the Arctic or even the Northern Hemisphere, probably not true for the globe." By "overall" I clearly meant global averages. "Look at the noise in the whole Holocene ( plus or minus 1 degree C ). We haven't even exceeded that." It's not very useful to look at the proxy noise to determine averages were higher during the HCO than today. This is like looking at individual temperatures today and claiming such snapshots accurately reflect global temperatures (you know, what some deniers have done because it snowed a lot in their backyard last winter?) "And as I pointed out, the mean can be meaningless, as the seasonal variation was more extreme in the HCO." Not in the Mesopotamian settlements. The difference would have been barely noticeable at 30 degrees. "Extreme weather is caused by increased gradients." Define "gradient" in this context, I'm not sure I follow. Do you simply mean a higher difference between minima and maxima? My argument is that increasing global temps will disrupt long-phase natural fluctuations, and thus likely cause more extreme weather events. "To the extent that CO2 forcing is significant, as modeled it should REDUCE gradients and thus REDUCE storminess." Please provide some sort of science for these affirmations, and that "gradients" are a bigger factor in determining storminess than global temperature increases and the disruption to natural cycles this causes. You have yet to make that case. "I don't think it's that significant." Of course not. Your severe bias agaisnt AGW theory won't allow you to believe otherwise. "There have been weather disasters through out human history in 'warm periods' and 'cool periods'." True, but completely irrelevant. -
Hockey stick is broken
gallopingcamel has kindly moved the discussion of Loehle and Ljungqvist over to the new thread, but I just want to make sure this doesn't remain here un-amended: gallopingcamel wrote This 2000 year reconstruction (Loehle 2008) shows temperature excursions greater than 1 degree Kelvin and Medieval temperatures higher than 2010. It does show a >1K temperature difference between the peak of the MWP and the bottom of the LIA. It does not, however, show Medieval temperatures higher than 2010. In fact, the warmest decades in Loehle's MWP are 0.5K cooler than 2010. Loehle's reconstruction is centered on its own 2000-year mean, and the final datum is from around 1930. In order to compare Loehle's MWP to current temperatures, it is necessary to re-center Loehle's reconstruction to match some other temperature series (e.g., the instrumental record) that actually shows the current temperature. An example of this is included in the update to this post. -
New temperature reconstruction vindicates ...
KR: Yeah, it lacks context. Lots of people conveniently assume that the final point on Loehle's reconstruction is indicative of current temperature. Nope! The quote that Albatross cites a few comments back is rather illuminating. Loehle writes: my own reconstruction is set to a zero baseline for the entire 2000 yrs, so it is only possible to compare to other series that are centered likewise To be technically precise, it would only be possible to directly compare Loehle to other series that are centered on the 2000-year mean of Loehle's own reconstruction. That, of course, is probably the null set. If you want to see whether Loehle's MWP is warmer or cooler than the present, you need to re-center Loehle to match some other series that includes present-day temperatures. This is what we do in the update to the post (above). -
Albatross at 04:12 AM on 30 September 2010New temperature reconstruction vindicates ...
Nice figure @ 50 Ned. It seems that now matter how you slice and dice the data (i.e., which baseline one uses), Loehle is the outlier. I agree the amplitude of anomalies the Loehle reconstruction are clearly too high for the excellent reason that you provided. If anything, going by that Figure @ 50, Ljungvist agrees best with Mann08, not Loehle08. WUWT should have a post saying that Mann08 has (yet again) been vindicated...not going to happen of course. Anyhow, IMHO, the important observation here is that current warm temperatures in the N. hemisphere are very likely to be unprecedented over the last 1500 years. Exactly how much is difficult to say, but I do not think that one can simply say "we can't be sure today's N. Hemisphere temperatures are warmer than those in the MWP". Zeke has demonstrated that current N. Hemi. temperatures are almost certainly warmer than those observed during the MWP, so has Tamino, apeescape, Ned and Alden......a nice coherent picture. The only incoherence that I can see is in the scrambling and weaseling going on by the "skeptics" and "lukewarmers". -
New temperature reconstruction vindicates ...
OK, I've updated the post (see the "update" above). I particularly like the comparison of LIA and MWP in the various reconstructions, after recentering them all to match the instrumental record as closely as possible during the overlap period:
Figure 4. Warmest decades of the Medieval Warm Period, and coolest decades of the Little Ice Age, after re-centering each reconstruction to match the instrumental temperature record during the period of overlap.
Moberg is a bit on the cool side overall -- which might just mean it was anomalously warm during the calibration period used for centering. Mann and Ljungqvist agree very closely on the Medieval Warm Period, though Mann's Little Ice Age is not as cold.
Loehle manages to be both too warm and too early on the Medieval Warm Period and on the cool side during the Little Ice Age. This difference would not be all that noteworthy, except for the fact that Loehle 2008 is supposed to be a global reconstruction ... and the magnitude of the MWP-LIA difference should almost certainly be smaller for a global reconstruction than for a Northern Hemisphere one.
The other obvious point is that when we compare these to the current instrumental temperature record, the Medieval Warm Period seems to be about 0.7 degrees C cooler than the 2000-2010 mean temperature.
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dorlomin at 03:50 AM on 30 September 2010Blog review of scientific coherence
One the one had I like to call the gulliable belief in anything but AGW, the ABCers (anything but CO2). But to put a devils advocate hat on, it is possible to explore alternative ideas without endorsing them. There is a defence of being 'open minded'. It is even possible within science to have to remain open to contradicory ideas while the evidence is built up on which is right. But I think in the cases of the more prominent ABCer blogs this defence fails with the tabloidesque enthusism each idea is greeted with and the lack coherent narrative do weaken such a defence. -
Doug Bostrom at 03:28 AM on 30 September 2010Does Climate Change Really Matter?
Another way of asking, "does climate change really matter?"Just another coincidence in the weather, surely. Graph from this article, which makes today's coverage of the Powell-Mead system in the NY Times look optimistic.
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dorlomin at 03:11 AM on 30 September 2010A detailed look at the Little Ice Age
As I understand it, Milankovitch forcing would strongly indicate that the past 300 years should have been the coolest period of the past 6000. -
ClimateWatcher at 03:07 AM on 30 September 2010The Phony War: Lies, Damn Lies and the IPCC
"you're still missing the point that overall temperatures were lower than today." That is certainly not true for the Arctic or even the Northern Hemisphere, probably not true for the globe. Look at the noise in the whole Holocene ( plus or minus 1 degree C ). We haven't even exceeded that. And as I pointed out, the mean can be meaningless, as the seasonal variation was more extreme in the HCO. Extreme weather is caused by increased gradients. To the extent that CO2 forcing is significant, as modeled it should REDUCE gradients and thus REDUCE storminess. I don't think it's that significant. There have been weather disasters through out human history in 'warm periods' and 'cool periods'. http://www.disastercenter.com/disaster/TOP100K.html -
robert way at 02:50 AM on 30 September 2010Is Greenland losing ice? (psst, the answer is yes, at an accelerating rate)
Roger, Do you think that the gulf stream is the exact same thing as the AMOC? -
Albatross at 02:36 AM on 30 September 2010New temperature reconstruction vindicates ...
Hi Ned, Thanks. That is what I understand reading this (I was trying not to "lead" you). But Loehle seems to be invoking the above quote as evidence that when done his way, his reconstruction is vindicated. Worse still, some are now using that quote above to suggest that people who are trying to realistically compare Loehle's reconstruction with Ljungqvist's are not being honest. But what the heck does one do when Loehle's poor methodology has made it almost impossible to properly compare his reconstruction with those from other paleo groups? IMO, people are nevertheless sincerely trying (despite all the hurdles). Besides why should we take Loehle's word for it? That is how scientists test/validate their colleagues work/hypotheses. Scientists "A" (Loehele) makes an assertion, and others then test said assertion. Well, going by the evidence submitted here and elsewhere Loehle's assertion/hypothesis fails horribly. -
shdwsnlite at 02:18 AM on 30 September 2010Blog review of scientific coherence
I like where you are going with this but as a non-scientist working to understand it all there is some phrasing that grates a little bit on these American ears. Part of it might be eased by using synonyms in a couple places for "coherence" and "incoherent". I would especially add a short synonymic phrase after this sentence to add emphasis. "Your kids’ future, and the future of their kids, very much depends on logical coherence"... And a suggestion for the last ..instead of "That" use This is the science knowledge that is coherent, backed by peer-reviewed science, and endorsed by all major scientific organizations in the world. -
Doug Bostrom at 02:11 AM on 30 September 2010Does Climate Change Really Matter?
The present Tory UK Foreign Secretary delivers reasons why climate change matters, from a foreign policy perspective: I will first argue that an effective response to climate change underpins our security and prosperity. Second, our response should be to strive for a binding global deal, whatever the setbacks. And third, I will set out why effective deployment of foreign policy assets is crucial to mobilising the political will needed if we are to shape an effective response. To learn more about what a usefully functional conservative grounded in reality sounds like when confronted with facts, click the link. -
New temperature reconstruction vindicates ...
Albatross, my take on that is that there's no direct and uniquely correct way to compare Loehle's reconstruction to anything else (other reconstructions, instrumental temperatures, anything). It's just centered on a value of 0. To compare it to anything else, you have to pick a period of time and assume that both Loehle and whatever-it-is should have the same mean during that period of time, then recenter Loehle's reconstruction to match that mean. Loehle chooses to assume that his reconstruction and Ljungqvist's have the same mean over the entire 2000-year period (I basically did the same in Fig. 2). Alden Griffith's very nice graphic here is based on the assumption that Loehle should have the same mean as the instrumental data during their period of overlap. Both of these are probably defensible choices but it's important to understand the differences. If you're most interested in comparison to the instrumental record, it's probably best to recenter Loehle's reconstruction to match that. Unfortunately, the period of overlap is only 80 years, since Loehle ends so early (1930s). -
archiesteel at 02:00 AM on 30 September 2010The Phony War: Lies, Damn Lies and the IPCC
@CW: you're still missing the point that overall temperatures were lower than today. Sure, humans and polar bears survived the HCO. That's besides the point - what we're seeing today is different than the HCO, it's happening faster, and it's already reached higher global temperatures. As for climate being more extreme, I'm not sure you can be that categorical. I believe a high rate of decadal increase throughout the world (i.e. the current situation) is going to cause more extreme weather events than the relatively stable system in place during the long (even if seasonal minima/maxima were higher in the NH). -
ClimateWatcher at 01:51 AM on 30 September 2010The Phony War: Lies, Damn Lies and the IPCC
scaddenp and archiesteel, The climate was more extreme because the annual variation was greater. (hotter summers, colder winters as discussed) This meant a more extreme seasonal transition. This also meant a greater pole to equator gradient. It is the meridional gradient which is the basis of the thermal wind ( jet stream ). The HCO is NOT an analog of what CO2 is theorized to do. CO2 is theorized to warm some in summer, slightly more in winter. CO2 then is modeled to slightly DECREASE thermal gradient and transitions. However, the HCO IS an important comparison. Greenland, the polar bears, and humans all survived the HCO, and human civilization, as exemplified by the Mesopotamian era, flourished during the HCO. archiesteel, I stand corrected with respect to Absolute Zero. Better stated, the point should read were winters a hundred degrees cooler and summers a hundred degrees warmer, the mean would be zero, which would appear benign, but not at all reflect the extremes.Moderator Response: In the interest of readability, please tame whatever device you're using for text input so as to better exploit the white space available for comments. Thank you! -
Albatross at 01:36 AM on 30 September 2010New temperature reconstruction vindicates ...
Ned, apeescape, Zeke and Alden, First, thanks for your valuable contributions here. There is some squirming going on at AirVent, where Loehle has said this: "but I eventually have remembered that my own reconstruction is set to a zero baseline for the entire 2000 yrs, so it is only possible to compare to other series that are centered likewise." How might doing this affect the comparisons? -
Tarcisio José D at 01:14 AM on 30 September 2010Blog review of scientific coherence
Sr Moderador. O argumento de que o vapor de água é o mais importante dos gases de efeito estufa é furado. Quem disse isto pela primeira vez foi John Tyndall nos idos de 1858. Mas com o desenvolvimento da termodinamica da atmosfera, a partir de 1884 quando H. Hertz criou o diagrama denominado "EMAGRAM" pôs em evidencia o mecanismo de convecção vertical que é responçavel por elevar as parcelas de ar aquecido para a alta atmosfera, onde o efeito estufa age ao contrario aumentando a perda de energia para o espaço. Os ceticos não enchergaram isto ??? O vapor de água esquenta como todo o motor que produz trabalho. Mas o trabalho por ele executado deixa um saldo muito positivo para o clima. Mr. Moderator. The argument that water vapor is the most important greenhouse gases are stuck. Who said this first was John Tyndall back in 1858. But with the development of thermodynamics of the atmosphere, since 1884 when H. Hertz has created a diagram called "EMAGRAM" put in evidence the mechanism is vertical convection responçavel for raising portions of heated air into the upper atmosphere, where the greenhouse effect acts contrary to the increasing energy loss to space. Skeptics do not spotting it?? The steam heats the water as any engine that produces work. But the work he does leaves a positive impression for the climate.(google transl)Moderator Response: What I meant in my previous comment to you is that you should: 1) Read the post on water vapor. 2) Put your comments about water vapor on that page, not this one. -
Blog review of scientific coherence
Argus, whenever someone refers to Galileo and mainstream dismissal in regards to their theories, I am reminded of a very relevant quote: "But the fact that some geniuses were laughed at does not imply that all who are laughed at are geniuses. They laughed at Columbus, they laughed at Fulton, they laughed at the Wright Brothers. But they also laughed at Bozo the Clown." - Carl Sagan Heliocentric ideas didn't take root until there were (a) reliable measurements contradicting prior theories and (b) newer theories that made some sense, supplying predictive power. AGW skeptics have not satisfied either requirement. -
archiesteel at 00:37 AM on 30 September 2010A detailed look at the Little Ice Age
@Arkadiusz: what is your point? Simply putting quotes without an argument is pretty meaningless, especially since those quotes do not concern the past 50 years, but the period before 1860. -
archiesteel at 00:32 AM on 30 September 2010Blog review of scientific coherence
@Argus: "For a long period in human history, mainstream science agreed that the earth is in the centre of the universe, and that the sun and the planets all revolved around us." I don't think you can talk about "mainstream science" when the scientific method wasn't articulated. You seem to think that, because an idea garners a consensus amongst the learned, then it must be wrong - at least that's what you're suggesting with your cliche of a parable. A more faithful retelling of this story would note it was actual scientists (i.e. who used the scientific method, even though they might not know about it) who figured out the truth, while learned non-scientists thought otherwise. Today, the same kind of people following the scientific method have figured out the current warming is due to anthropogenic CO2, while the same kind of sycophants (this time towards oil companies rather than the clergy and the royalty of Europe) are denying this reality. -
New temperature reconstruction vindicates ...
Ken Lambert writes: Oh, and all the temp charts in this thread seem to stop at year 2000 The data in Ljungqvist 2010 run through the 1990s (they are decadal means). The instrumental data shown in Figure 1 and Figure 2 run through 2010, though it's not particularly relevant at this scale. And; can anybody out there tell me what is the 'equilibrium TSI' and 'equilibrium surface and cloud refection' of the pre-industrial Earth? Without those numbers - an accurate calculation of Solar forcing cannot be made and the relative proportions of CO2GHG and Solar forcing determined over time. Climate forcings can be defined relative to any base period. I don't know why you have this obsession with trying to pin down "equilibrium" conditions, but you shouldn't assume that others here will share that obsession. -
Tarcisio José D at 00:04 AM on 30 September 2010Blog review of scientific coherence
Por que a ciencia está equivocada ? Porque não existe equipamento para medir a evaporação real de agua do solo, apenas a evaporação potencial, Como os "modeladores do clima" dependem do indice de umidade do ar, eles estão sendo enganados com os dados de precipitação menos evaporação potencial e em consequencia não põe em evidencia o feedback negativo proporcionado pelo vapor de água , a verdadeira locomotiva do clima. E os ceticos não percebem este bug. Why science is wrong? Because there is no equipment to measure actual evaporation of water from the soil, only the potential evaporation, as the "climate modellers" depend on the moisture index of air, they are being deceived with the data of precipitation less evaporation potential and in consequence not puts in evidence the negative feedback provided by water vapor, the real engine of climate. And the skeptics do not realize this bug.(google tranl.) www.atmos.washington.edu/~stoeling/WH-Ch03.pdf (thermodinamics)Moderator Response: See the post Water vapor is the most powerful greenhouse gas. -
Arkadiusz Semczyszak at 23:56 PM on 29 September 2010A detailed look at the Little Ice Age
“However, it [the Sun activity] cannot explain the accelerated warming over the past 50 years.” “The variability of the climate during the last millennium is partly forced by changes in total solar irradiance (TSI).: “ Nevertheless, the amplitude of these TSI changes is very small ...” “... the low frequency variability of this mean hemispheric temperature is found to be correlated at 0.74 with the solar forcing for the period 1001–1860.” “... and find a significant relationship between the low frequency TSI forcing and the NAO with a time lag of more than 40 years for the response of the NAO.” -
muoncounter at 23:49 PM on 29 September 2010A detailed look at galactic cosmic rays
#21: Solar cosmic rays are produced by solar wind ions (protons mainly) striking gas nuclei in the upper atmosphere. The flux to the upper atmosphere is thus a product of solar activity (CMEs and flares), observed for several years now by NASA's ACE satellite. The flux at the surface, measured for many years by an international network of neutron monitors and more recently by a network of 'muon counters', varies on a scale of hours, days, months for different types of solar events. These are typically low energy particles, moving at relativistic speeds. The earth's magnetic field (as distinct from the solar or interplanetary magnetic field) is a strong modulator of solar cosmic ray flux. That's why auroral displays (the interaction of charged particles in the earth's magnetic field) are mainly visible in the high latitudes. GCR flux, even in times of the lowest solar magnetic field intensity, is much smaller than solar cosmic ray flux. The key point about GCRs is that they are much higher energy than solar cosmic ray particles. -
Ken Lambert at 23:35 PM on 29 September 2010New temperature reconstruction vindicates ...
Ned #42 I used to get all excited about these temperature reconstructions too, until I started to understand the forcing imbalance components and the significance of the total energy gain or loss of the earth system over time in explaining warming or cooling of a massive body of land, ice, atmosphere and ocean. Oh, and all the temp charts in this thread seem to stop at year 2000 - missing the last 10 years of flattening at a time when claimed AGW forcing is 'the highest decade in history'. And; can anybody out there tell me what is the 'equilibrium TSI' and 'equilibrium surface and cloud refection' of the pre-industrial Earth? Without those numbers - an accurate calculation of Solar forcing cannot be made and the relative proportions of CO2GHG and Solar forcing determined over time. -
Roger A. Wehage at 23:07 PM on 29 September 2010Is Greenland losing ice? (psst, the answer is yes, at an accelerating rate)
Ned@28: "Roger, I don't think you have this quite right." Stand corrected. -
Blog review of scientific coherence
Argus, "skeptics" are fond of comparing themselves to Copernicus, Newton, Galileo, and Einstein. But that doesn't mean the analogy is apt. IMHO, your analogy works better the other way around. For a long time, popular belief held that [the Earth was the center of the Universe / humans cannot modify the climate]. Gradually, however, scientists began to realize that this was not the case. Among scientists, this previous worldview was replaced by the idea that [the Earth revolves around the Sun / anthropogenic greenhouse gas emissions can warm the climate]. For a number of reasons -- political, ideological, and personal -- this conclusion was resisted by powerful institutions outside of science, and scientists who supported the new worldview [Galileo / climate scientists today] were harassed by those institutions. Eventually, however, the evidence became overwhelming and those who had previously resisted the new paradigm were no longer able to resist the ever increasing mountain of evidence in support of the new scientific consensus.... -
Doug Bostrom at 22:46 PM on 29 September 2010New temperature reconstruction vindicates ...
Alexandre: Loehle´s reconstruction deserves less attention than the unpretentious reconstruction Peter Hogarth did here some time ago. Seconded. That was an extremely nice analysis; the comparison between proxies and instruments 1850- was especially intriguing. -
Roger A. Wehage at 22:45 PM on 29 September 2010Is Greenland losing ice? (psst, the answer is yes, at an accelerating rate)
Roger@27: Sorry, I meant to say, "temporary reprieve from global warming," not "temporary respite from global warming." Well, either may be applicable... -
Argus at 22:40 PM on 29 September 2010Blog review of scientific coherence
For a long period in human history, mainstream science agreed that the earth is in the centre of the universe, and that the sun and the planets all revolved around us. It seemed to fit common sense and current scientific knowledge. Just take a look at the sky! Refined subtheories were invented to explain certain mysterious behaviour of the planets (as epicycles). Everything was coherent and nice. Of course there were also some "skeptics" or "denialists" in those times, who refused to believe the obvious truth: that earth is the centre. Unfortunately they did not all agree with each other, which is very suspicious to start with. Some of them advocated a rival theory that we now call heliocentric. During 2000 years, from Yajnavalkya and Heraclides, via Aryabhata and Martianus Capella, to Copernicus and Galilei, there were many thinkers who doubted the official theory, and made various attempts to put the sun in the centre. They were often, consequently, ridiculed (or worse). The sum total of so-called "skeptic" arguments against the geocentric model was an "incoherent muddle of contradictions". In spite of the incoherency, science finally moved forward to heliocentrism and further on to our present beliefs.Response: Don't count your chickens... www.galileowaswrong.com -
Is Greenland losing ice? (psst, the answer is yes, at an accelerating rate)
Roger, I don't think you have this quite right. The driving factor in North Atlantic deepwater formation is salinity, and the presence of a lens of fresh water on the surface will reduce the vertical flux. From Ganopolski and Rahmstorf 2001: For a large freshwater input (such as a large release of icebergs), the model's deep water formation is temporarily switched off ... From Hu et al. 2009: Since Greenland is close to ocean deep convection sites associated with the oceanic meridional overturning circulation (MOC), the discharge of the melting ice sheet water could potentially stabilize the upper ocean at these sites and lead to significantly weakened deep convection there. Presently, some modelling studies indicate a dramatic weakening of the MOC in a future warmer climate after the melting is taken into account ... From Jungclaus et al. 2006: Climate projections for the 21st century indicate a gradual decrease of the Atlantic Meridional Overturning Circulation (AMOC). The weakening could be accelerated substantially by meltwater input from the Greenland Ice Sheet (GIS). Here we repeat recent experiments conducted for the Intergovernmental Panel of Climate Change, providing an idealized additional source of freshwater along Greenland's coast. For conservative and high melting estimates, the AMOC reduction is 35% and 42%, respectively, compared to a weakening of 30% for the original A1B scenario. Even for the high meltwater estimate the AMOC recovers in the 22nd century. and so forth. The conventional description of this is clearly that a reduction in surface salinity caused by inputs of meltwater from decaying ice caps will reduce the vertical flux in deepwater formation zones and lead to a slowdown in the MOC. I have never read an explanation that matches your description of this process, so if you've got a reference to a study showing this, I'd be very interested in reading it. That's not to say that meltwater from the Greenland ice sheet would cause some kind of "Day After Tomorrow" catastrophe. But the general effect is to reduce rather than increase the meridional overturning circulation; RSVP did indeed have this backwards. -
Alexandre at 22:27 PM on 29 September 2010New temperature reconstruction vindicates ...
IMHO, Loehle´s reconstruction deserves less attention than the unpretentious reconstruction Peter Hogarth did here some time ago. Loehle did his best to exaggerate the MWP, LIA and -for added effect- cut off the last 70 years or so, effectively "hiding the rise". To be a denier is a good way of getting attention. -
Mythago at 22:17 PM on 29 September 2010Blog review of scientific coherence
Stephan Lewandowsky at 21:13 PM on 29 September, 2010 Mythago, would prefer for this to remain limited in circulation till reposting of final version next week (Wednesday, together with podcast on RTR at the same time). SL Got the message and will wait until then to share the good news as it were (with your permission of course)?Moderator Response: Sure thing, once posted it's public and feel free to circulate. SL -
New temperature reconstruction vindicates ...
gallopingcamel writes: Good post! Thanks! You say: "It's worth noting that all the reconstructions show the Medieval Warm Period, the Little Ice Age, and 20th-century warming (though Loehle 2008 only runs through 1935)." This is clearly not the case as Mann's original Hockey Stick denied both the MWP and the LIA. "All the reconstructions" refers to all the reconstructions shown in Fig. 2 and discussed in the post. Rob Honeycutt writes: it just seems to me that what is important is that current warming is unprecedented no matter how many crooks the handle has. Yes, exactly. A lot of "skeptics" seem to have some kind of gut-level impression that if they can just keep pointing to evidence for a MWP the case for AGW will magically evaporate. But our confidence that CO2 and other greenhouse gases are responsible for modern warming doesn't rest on the question of how much warmer it is today than during the MWP. The reasoning here isn't "Gosh, it's much warmer now, must be due to all that CO2!" Wally Broecker made the case that AGW was a threat way back in 1975, at a time when temperatures had been more or less flat for a couple of decades. The idea that the existence of previous "natural" climate change would somehow disprove the existence of AGW is very poor reasoning. Does the fact that some fires are caused by lightning mean that some other fire couldn't have been caused by arson? Plus, of course, there's the fact that Ljungqvist 2010 is a mid- to high-latitude Northern Hemisphere reconstruction. We know perfectly well the MWP and LIA were prominent in the extratropical Northern Hemisphere. Albatross writes: Also, the MWP and LIA are both indications that climate sensitivity is not as low as the "skeptics" would like think, b/c fairly large temperature departures in the past were invoked with very little forcing. Yes, that's a very good point. If the MWP turned out to be a large amplitude and globally synchronous event, it would be cause for serious concern. The logical implication would be that climate sensitivity is higher than we think, and therefore the projections for warming in the 21st century should be increased. Alden Griffith writes: I adjusted Loehle, Ljungqvist, and HadCRU instrumental values to the base period 1850-1899. I then plotted the reconstructions with the land / land&sea instrumental values (using the same level of smoothing as the reconstructions), using global or hemispheric datasets where appropriate. Hey, very nicely done. I was hoping that by starting this thread I would provoke other people into doing their own comparisons. (At the time I started writing this, neither Tamino nor Zeke had yet posted anything, so there wasn't really anything out there yet aside from Loehle's own spin over at WUWT). apeescape writes: It's interesting how Loehle (corrected paper) does the "reconstruction." It's just a simple average across years [...] maybe I'm reading it incorrectly, but it seems like a very weak and inconsistent way of reconstructing temperatures [...] Yes, exactly. I didn't want to get into the methodologies involved, but suffice it to say there's a reason why Loehle 2007/2008 was published in E&E. The methods used are absolutely atrocious. Frankly, the wonder is that the results of the reconstruction look as reasonable as they do. There are a lot of different ways you could do a hemispherical/global reconstruction. You could use regression (like in the figure in apeescape's comment) or you could spatially weight the proxy temperature records so they're representative of the region, etc. Lots of different possibilities. But just picking a bunch of time series (virtually none of which are in the Southern Hemisphere), averaging them, and calling it a "global temperature reconstruction"? As I said, there's a good reason it was published in E&E. Shirley_Rocks writes: the record I found shows this as a 2009 release FWIW. I didn't find a 2010 record at all You might be looking at a previous paper: Ljungqvist, FC. 2009. Temperature proxy records covering the last two millennia: a tabular and visual overview. Geografiska Annaler: Series A, Physical Geography, 91(1): 11-29. That was basically an article describing the proxy records that would then be used to create the reconstruction in this year's paper. The new paper, with the reconstruction, is by the same author and in the same journal: Ljungqvist, FC. 2010. A new reconstruction of temperature variability in the extra-tropical northern hemisphere during the last two millennia. Geografiska Annaler: Series A, Physical Geography, 92(3): 339-351. It's new, so perhaps the database you were searching hadn't listed it yet? CoalGeologist writes: The court is now convened. [....] Heh. Very clever! I like the respective sentences... Baz writes: Ah, I get it now! I forgot about different baselines. Thanks. No problem. Dealing with differing baselines for temperature anomalies trips everybody up sooner or later. fdijkstra writes: The red curves in the reconstruction graphs should be omitted, because the instrumental data are not comparable to the proxy records. Using non homogeneous data is an unsound scientific practice. I don't agree. We know (from instruments, and other lines of evidence) that it is much warmer now than it was during the final years of Loehle's reconstruction (1900-1930). Ignoring that fact would be misleading. When these red curves are omitted, Loehle is right, that Ljunggqvist confirms his results. No, actually. The amplitude of the MWP-LIA difference in Loehle is anomalously large, particularly for what is allegedly a "global" reconstruction. The presence of a smaller MWP-LIA amplitude in Ljungqvist's extratropical Northern Hemisphere reconstruction does not "vindicate" Loehle's reconstruction. There's also the issue that, whatever you may think of his results, Loehle's methods were exceptionally poor. ---------------- Whew! Did I miss anyone? -
ginckgo at 22:12 PM on 29 September 2010Blog review of scientific coherence
I predict that the 'skeptic' websites will proudly proclaim that there are no contradictions, they are just showing on how many fronts climate science is wrong: temperature record is wrong AND the temperature record shows cooling AND the warming is natural! Everywhere you turn AGW is wrong! That's the beauty of being a 'skeptic', you can have your cake and dring the lemonade, too. -
Roger A. Wehage at 22:07 PM on 29 September 2010Is Greenland losing ice? (psst, the answer is yes, at an accelerating rate)
RSVP@25 "The question is whether it is happening as much as people need to be concerned, or is this just a merry go round type convenient political distraction?" Ned@26 "Fresh water is less dense than salt water,..." No. Here is an example where too much of a good thing isn't good. Cold fresh water from melting glaciers is denser than returning warm salty ocean water, so it sinks way up north and flows south along the ocean floor, gradually rising on its way down to the equator and mixing with the warmer salty water, to eventually flow back north along the surface. But if the amount of cold fresh glacial water becomes too great, it can't all sink to the ocean floor, so more and more of it will start flowing southward closer to the surface. This surface flow of cold water will have two main effects. First, it will oppose the flow of warm salty water coming up from the equator, which had been tempering the air, and second it will further cool down the air above it. These two factors will work together to keep northern land masses near the ocean from being warmed by the ocean air currents, which may be a temporary respite from global warming for some unlucky folks. -
Doug Bostrom at 21:47 PM on 29 September 2010New temperature reconstruction vindicates ...
Fydijkstra is apparently suggesting that only one proxy may be used at at time, each presented in separate graph, by extension implying even that each proxy should only be treated in separate publications, presumably authored by different researchers as to do otherwise is "unsound scientific practice." His conclusion is that Loehle, Ljunggqvist, all meta-analyses of proxies are wrong. Nice to get that sorted out. Time to move the conversation. -
kdkd at 21:35 PM on 29 September 2010New temperature reconstruction vindicates ...
fydijkstra: It seems that you are arguing that we should not be using the modern instrumental record at all? Or should we just refuse to countenance comparing it to the proxy record? Or is there some other subtlety I'm missing about your argument? Because my two interpretations seem to suggest that your position is pretty absurd. -
fydijkstra at 21:30 PM on 29 September 2010New temperature reconstruction vindicates ...
The red curves in the reconstruction graphs should be omitted, because the instrumental data are not comparable to the proxy records. Using non homogeneous data is an unsound scientific practice. When these red curves are omitted, Loehle is right, that Ljunggqvist confirms his results. Moreover, Mann's hockestick loses its blade and there is no need for him to hide any decline. -
We're coming out of the Little Ice Age
cruzn246 writes: Prior to 1880 it was averaging well under 1335 for sure for over 500 years. Er, no. Not even remotely. Did you miss this graph?
Figure 1: Reconsructed total solar irradiance (Delaygue and Bard 2010)
Note the Y axis.
The running mean of solar irradiance (after smoothing out the 11-year cycle) has varied by less than 1 W/m2 over the past 1300 years.
If it had actually dropped by 30 W/m2 for "over 500 years" we'd have glaciers running amok all over the place.
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Stephan Lewandowsky at 21:13 PM on 29 September 2010Blog review of scientific coherence
Mythago, would prefer for this to remain limited in circulation till reposting of final version next week (Wednesday, together with podcast on RTR at the same time). SL -
New temperature reconstruction vindicates ...
Ah, I get it now! I forgot about different baselines. Thanks. -
Mythago at 20:35 PM on 29 September 2010Blog review of scientific coherence
PS Good article Steve, which is worth spreading around. Is it okay to post this to the greater population now or would you prefer that it remain here until the minor technical errors in the text are remedied? -
Mythago at 20:33 PM on 29 September 2010Blog review of scientific coherence
To add to what Dave Horton said about all the bits of 'Findings' its almost like an archaeologist who discovers a shard of pottery in one dig which looks similar to a shard in another dig. Put all the shards from one dig together (when they have been found) and you may construct the major part of a pot. Do the same in the second dig and you may well not only have the major parts of a pot but the proof that it is from the same tribal culture that existed at the first dig site, proving that they migrated and occupied a large area (subject of course to the relevant distance between the two dig sites). Now what has this got to do with Dave's posting? Its that all the evidence is on its own not proof of anything until it is put together to form a coherent image, situation, process or fact or a million other possible constructs that could be produced or proven from these associations. So science is right. Coherent arguments devoid of contradictions are the only really conclusive path that we can walk down. As for the conclusive nature of the non-contradictory science? Well that all depends on these incontrovertible 'Theories' which people still think are mere 'Ideas' instead of 'Proof' of a particular process......like gravity. 'In the end even the dust will settle to the bottom of the jar and a clearer understanding will become apparent to all'. Kev Coleman.aka 'Mythago' September 2010. -
New temperature reconstruction vindicates ...
Baz, the instrumental data were recentered to match the reconstructions, which have different baselines. The specific values of the numbers don't matter; just look at the relative differences between different periods (e.g., the LIA was ~0.6C colder than the MWP; modern temperatures are 0.5 to 1.0C warmer than the MWP depending on whether you look at land-only or land+ocean temperatures).
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