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Comments 125601 to 125650:

  1. Skeptical Science now an iPhone app
    Well said Doug-that's exactly why they average the temperatures over a 30-31 day basis, then over a 20-year basis, because that helps to smooth out the irregularities from the odd extremely hot or extremely cold day. Its worth pointing out that-according to the Met Office-average UK temperatures for Winter 08/09, Spring 09, Summer 09 & Autumn 09 were all between 0.6 & 1.5 degrees warmer than the 1971-2000 mean http://www.metoffice.gov.uk/climate/uk/2008/winter.html http://www.metoffice.gov.uk/climate/uk/2009/spring.html http://www.metoffice.gov.uk/climate/uk/2009/summer.html http://www.metoffice.gov.uk/climate/uk/2009/autumn.html which is why I find it odd that people are so focussed on the extreme cold of the last 30-odd days, whilst happily ignoring the fact that the UK spent the bulk of the remaining 13 months with temperatures that were well above average!
  2. Skeptical Science now an iPhone app
    "That (Pielke's) is a specious "argument" shawnhet. If one inspects the science in which these issues are described, it's pretty obvious that the effects of El Nino's/La Nina's (especially) and ocean circulation changes like the Arctic oscillation result in modulation of the warming, which has little effect on the long term warming trends [*]. It is the latter that are likely rather well predictable, and important for consideration of impacts from largescale augmenting of the earth's greenhouse effect." It may be pretty obvious to you, Chris, but that doesn't mean it is accurate. If one plots the PDO index against the temperature one gets a very good correlation for as long as we have had decent records. Yes, it is possible that there are other explanations for this besides the fact that the PDO has a strong influence on climate, but they have not yet been established. IAC, my point here was not to defend this position in detail, but rather to correct the impression that Pielke was arguing that warming had stopped. Cheers, :)
    Response: Some of the later comments address this issue thoroughly but for the record, we look at the correlation between the PDO and global temperature here...
  3. Skeptical Science now an iPhone app
    How many times must it be said, in how many different way? With 6.5 billion persons on the planet, probably a few million different ways. Weather is more difficult to predict than climate. How so? For commuters: We accept that our daily commute might involve different delays at different places on different days but we know that we'll generally arrive at our destination more or less within a certain window of time. Climate change is a variation on the same boring routine. Arrival at a commute destination is governed by -average- speed, arrival at a certain future climate regime is governed by -average- energy input versus loss. It's just not that complicated to reason out, unless somebody is constantly trying to confuse readers, that is. Shame on Pielke; he should hand in his sheepskin.
  4. Skeptical Science now an iPhone app
    "The obvious response to these claims is that if we cannot predict weather features such as the Arctic oscillation or an El Niño under current climate, how can anyone credibly claim we have predictive skill six months into the future from both natural and human caused climate forcings? The short answer is that they cannot." His point was not that the Earth has stopped warming, but that we cannot reliably predict what warming will happen in the future.
    I've changed Pielke's statement in a way that should make the falseness of it obvious. The fact that we can't predict near-term weather with great accuracy says nothing about our ability to make sound predictions on other time scales. Average July temps will be warmer than average January temps in Portland, Oregon. Our understanding of the fact that natural forcings on this timescale far exceeds any change due to anthropomorphic causes, and that we know how those natural forcings change, allows me to make this claim. If you believe Pielke's claim is correct, I am willing to make a wager on it.
  5. Skeptical Science now an iPhone app
    That (Pielke's) is a specious "argument" shawnhet. If one inspects the science in which these issues are described, it's pretty obvious that the effects of El Nino's/La Nina's (especially) and ocean circulation changes like the Arctic oscillation result in modulation of the warming, which has little effect on the long term warming trends [*]. It is the latter that are likely rather well predictable, and important for consideration of impacts from largescale augmenting of the earth's greenhouse effect. Pielke's is the same tired argument that "one can't possibly predict the consequences of greenhouse release on future climate if we can't even predict the weather a few weeks in advance". To invoke El Nino's as a flaw in our predictive ability of climate consequences of greenhouse enhncement is pretty pathetic....and to similalry invoke short term modulation of surface temperature by ocean circulation effects, which seem to average out to near zero on meaningful timescales (much as we should expect), isn't much better. [*] For example Swanson and Tsonis (much cited by those who wish to use similar specious "arguments" to downplay likely consequences of mssive greenhouse gas release), have analyzed the contribution of ocean circulation changes to 20th century warming and concluded that their nett contribution is near zero [**] Likewise Keenleyside and Latif (also widely misrepresented to support specious "arguments" about supposed cessation of warming) predict an extremely marked warming over the next 10-15 years [**]. [**] K. L. Swanson, G. Sugihara and A. A. Tsonis Long-term natural variability and 20th century climate change http://www.pnas.org/content/106/38/16120.abstract N. S. Keenlyside, M. Latif et al. (2008) Advancing decadal-scale climate prediction in the North Atlantic sector Nature 453, 84-88 http://www.nature.com/nature/journal/v453/n7191/abs/nature06921.html
  6. Skeptical Science now an iPhone app
    We've been having a rather warm winter here in Southern California. So far.
  7. Skeptical Science now an iPhone app
    Since Pielke's position is at issue here, I think it would be fair to mention his main point which he lays out here(from the above linked post): "The obvious response to these claims is that if we cannot predict weather features such as the Arctic oscillation or an El Niño under current climate, how can anyone credibly claim we have predictive skill decades into the future from both natural and human caused climate forcings? The short answer is that they cannot." His point was not that the Earth has stopped warming, but that we cannot reliably predict what warming will happen in the future. Cheers, :)
  8. Skeptical Science now an iPhone app
    dhogaza #11 You copied and pasted my post inaccurately, misrepresenting my post, which refers to a statement in the article. No problem really. :)
  9. Skeptical Science now an iPhone app
    Marcus, I assume the data is accurate, however, I thought it might help to get an idea of what "unusualy warmth" is like in Greenland. As far as "anomalies", you might note how much the temperature fluctuates in this region just from one day to the next.
  10. Skeptical Science now an iPhone app
    RSVP posts ... ""On the other hand, Greenland, eastern Siberia and the Arctic ocean are experiencing unusual warmth." Weather forcast, Ilulissat, Greenland http://www.wunderground.com/global/stations/04221.html Tue, high -1, low -10 C Wed, high -6, low -25 C Thu, high -19, low -28 C Fri, high -17, low -18 C Sat, high -16, low -29 C" Hmmm, OK, the cold is returning to Greenland, meanwhile warmer than average temperature has temporarily returned to Denver, Colorado. Temps in Boston will rebound and be above normal by Friday. And in Madrid, temps are bumping up by several degrees C. Gee, RSVP, when the cold air gets pushed south, places like Greenland are warmer than normal. Now the huge high apparently is breaking down, cold temps are returning up there, and warmer weather is appearing in the south. Gosh geewillikers. Some ice age!
  11. Predicting future sea level rise
    This common misinterpretation was worth a climate crock of the week.
  12. What ended the Little Ice Age?
    batsvensson, since DeNihilist and I were talking about climate sensitivity and you commented, i assumed you had a knowledge of the subject. I always assume that people commenting on a topic have at the very least the basic knowledge. I was wrong, apologize; i guess there's no need to point you to wikipedia for a general introduction to climate sensitivity. Anyway, your ignorance of the subject does not allow you to presume mine, just explicitly ask for a reference. I probably made the same mistake assuming you are aware of the basic statistical analisys on the temperature time series. This would explain your (wrong) reasoning on my negative confirmation procedure, it's the opposite indeed. It's the analysis of past climate forced variability one of the strong point of AGW theory. And, for example, it's the statistical analysis of unforced variability that strongly contrast the claims of the halting of global warming. Similarly, the fact that a low climate sensitivity can not explain glacial cycles is *not* negative confirmation but analysis on data already statistically assessed. You know, physics works this way, at least if we stick to physics and not to the metaphysics of all the possible worlds.
  13. Skeptical Science now an iPhone app
    I think this weather pattern is in large part due to global warming. In Northern Europe, we have had the western winds "missing" us for about one month now, they are going south of us or north of us, where temeratures are 7-10 C above normal. - And it's not the first time for this to happen in recent decades. Because of its stability this does in fact produce some cold records - very little in single measurements (the troposphere is way too hot for that), but in cold periods. And because of the reduced diurnal variation, daily mean temperatures are extremely low - some 15-20 C below recent years' Dec/Jan average many places.
  14. Predicting future sea level rise
    No, A. Bakker, that claim of impending global cooling by the Daily Mail "reporter" has been vehemently rejected by Latif--the very scientist it misquoted.
  15. Predicting future sea level rise
    It seems that we all agree that sea level rise depends mainly on global warming. So will the sea level descend with cooling, I assume. Therefore it is very interesting to read the article “The mini ice age starts here” from David Rose in the Daily Mail, link: http://www.dailymail.co.uk/sciencetech/article-1242011 Professor Mojib Latif, a leading member of the IPCC, together with Professor Anastasios Tsonis explain that we are entering a mini-ice-age for the next 30 years. Thus the sea level will even descend the next 30 years. Climategate and the above mentioned story will make the discussions easier about what is going to happen the next decades!
  16. CO2 lags temperature
    John, This article is a nice explanation of how things have gone in the. Regarding the skeptic argument that the modern CO2 rise would be a result of current temperature rise and not the vice versa, there's at least one additional point one could make. Just looking at the numbers in your Fig. 1 would suggest that in order for the CO2 to naturally reach the current level of 385 ppm, would require something like a 7 degrees rise in temperature, instead of the 0,7 degrees observed. Fig. 1 of Falowski 2000 ( http://www.precaution.org/lib/carbon_cycle.000601.pdf ) nicely demonstrates this point. Plus, of course, this rise in temp. should have happened a thousand years ago (yeah I know, maybe it did, but people just didn't realise that because they had no thermometers ;) ) Plus, if the CO2 was still rising naturally to reach a higher equilibrium concentration set by the higher temperature, it wouldn't make much sense that the carbon cycle is currently acting as a sink for the antopogenic emissions... These things might also be worthy of pointing out here (or maybe they have already been pointed out in some other article, and I just haven't realised)
  17. Skeptical Science now an iPhone app
    So what's your point RSVP? You're not suggesting the December satellite data is a *lie* are you?
  18. Skeptical Science now an iPhone app
    I've seen similar things in Weather Underground Phillip. Everywhere around the Mediterranean is experiencing temperatures well above the average for this time of year. The cold snap is an entirely localized event. Also, this cold snap hasn't even lasted an entire month, wheras the above-average temperatures which occurred in Spring & Summer lasted a good 3-4 months, just as the above average temperatures in the S. Hemisphere have been going on for months. Also, don't forget that the temperatures endured by Europe & North America are not the coldest of all time, but simply the coldest since the 1980's-that's record territory, but not record-shattering territory-that title belongs to Adelaide's 40+ degree weather in November-a month most frequently known for temperatures in the early to mid 20's.
  19. Skeptical Science now an iPhone app
    A very informative piece. It might be worth re-running an updated version of it once data for January 2010 is in. As far as the UK is concerned it's really since New Year that the worst of the weather has arrived. I heard from a friend in Greece recently, where typical early January temperature highs are about 12C degrees. The other day it reached 22C.
  20. What ended the Little Ice Age?
    Riccardo, Yes I take the measurement data “as is”, because it is a quiet common practice as a method of basic scientific investigation to first collect, statistical analyze, inter compare and then synthesize data, not to do it the other way around by interpreting data in a context, which is the method know as positive confirmation, or “data fitting”. However if you think my approach of investigation is incorrect, then please explain why you think that is not recommended to do. In the same comment you also wrote, "we are looking for the link" which, if one bases evidence on negative confirmation, suggests that the null hypothesis must be false or else there exists no special reason to “look” for anything particualar at all in a data set, except to test different model to see if data can be fitted or not, and if it can be fitted this is, of course, interesting but not conclusive unless the null hypothesis is falsified. Is there any studies published that has falsified the null hypothesis? When I asked a definition of "larger than expected" I did suspect to get some kind of reference to a quantitative measure which shows it is larger than some other numerical “expected” value and not “It can not take any value” that it is the " the best estimate" of "many different phenomena" which are "physical". Such sweeping answer doesn’t make me, or anyone else for that matter that reads this, more enlightened about what you do mean with "larger than expected" except that it may be taken as you wanted to say “I don’t know, but I have heard it said to be so”. Unless I grant myself to believe in some kind of authority wisdom, which I will not, then this type of answers is complete and utterly nonsense. To address the last point, you wrote the reason to believe why this is hard to explain is that “a high sensitivity cannot explain the glacial cycles”, but this is just another way of saying “given what is known it cannot be explain in another way”, which is the same thing as saying “given what is known it can not be imagine in another way” so when you claim it “is not that "I can not imagine how it can happen"”, you are not only assuming in the premises what you are to explain but you are also contradiction your own beliefs. So again you answer is utter nonsense as to what the reason are for use to the believe this to be true.
  21. Skeptical Science now an iPhone app
    Article says... "On the other hand, Greenland, eastern Siberia and the Arctic ocean are experiencing unusual warmth." Weather forcast, Ilulissat, Greenland http://www.wunderground.com/global/stations/04221.html Tue, high -1, low -10 C Wed, high -6, low -25 C Thu, high -19, low -28 C Fri, high -17, low -18 C Sat, high -16, low -29 C The north pole this time of year is in complete darkness.
  22. Skeptical Science now an iPhone app
    Marcus, I think you might have a different opinion about the cold spot if you were sitting through it! Internet chat and even stuff I've overheard in pubs suggests a lot of public opinion thinks this snow shows the end of global warming or even the beginning of a new ice age. Example posts from the dailymail.co.uk's forum include: 'Climate Change, What a joke', 'the breached hull of the global warming ship', 'Could we be in for 30 years of global COOLING?'. Admittedly a number of these are from people who fall close to the 'denier' category because they refuse to accept science as it's all a watermelon socialist plot (unless it says something they want to believe, of course). In terms of science, what's going on makes sense. In terms of people's perceptions, it's potentially a PR disaster that the fossil fuel industry has won over logic. Also, in case you didn't see, I left a link to and quick explanation of the RSS satellite data in the DIY thread. :)
  23. Skeptical Science now an iPhone app
    Even before I knew about the warm spot over the Arctic & Greenland, I still felt that the cold snap neither proved-nor disproved-that global warming was over. After all, most of the Northern Hemisphere had significantly above average temperatures for the Spring & Summer of 2009. Here in Australia, we had the 2nd warmest winter on record (& the warmest August on record) & November temperatures for much of Southern Australia were *TEN DEGREES* above the long-term average! December & January have also proven warmer than the long-term average to date-giving us 3 months on the trot of well above average temperatures. Several years in a row we've had heat-waves (several days of above 36 degrees) as late as March. Now individually, none of these things *prove* anything, but taken together they definitely suggest that global warming is *far from over*. Yet its funny how many denialists here in Australia will blissfully dismiss our increasingly frequent heat-waves, yet point to a single month of cold weather in Europe as "definitive proof" that Global Warming is over! Thank you, John, for putting this unusual phenomenon into perspective!
  24. Skeptical Science now an iPhone app
    Pieleke has lost it. Honestly, he is now getting truly desperate. What those data demonstrate is that the AO and NAO are reginal internal climate modes which do not teleconnect globally. I do not understand the confusion. Global warming refers to the increase with time (on a decadal time scale) of the global mean temperature. These internal climate modes can increase or suppress the global anomalies, but typically on for short periods of time. The UAH mid-trop temp anomlay in December was +0.28 C. That is the globe was warmer than average for this time of the year. I undertsand it is difficult for people in portions of Europe or the Southeastern USA to grasp that, but that is the reality. Global warming does not equal warming everywhere all the time. Someone needs to tell Pielke Jnr that. What is truly sad is that he should know better. What is true concerning regional impacts of AGW is that certain regions will warm more than others. For exmaple, the Antarctic Peninsula, the Arctic, Australia etc, and yes warming over the high regions is of concern b/c of posirive feedbacks which could reinforce the long term warming trends observed there. This is clearly evident over the Arctic.
  25. Skeptical Science now an iPhone app
    "After taking a broader look at global temperature, Pielke is forced to conclude that it's preferable to focus on small pieces of the puzzle than the bigger picture. Better that is, if the global picture isn't giving you the result you're looking for." Ouch! A well-deserved slam. The quality of comments by Pielke Sr. has deteriorated significantly in recent years. Note the clever rhetoric: "...a global average is not of much use in describing weather that all of us experience." He then criticizes a media report for focusing on the global average. Yet the article he's referring to is discussing global climate change, not regional weather. Does Pielke understand the difference? He also throws out the "if we can't predict the weather..." argument: http://www.skepticalscience.com/weather-forecasts-vs-climate-models-predictions.htm
  26. Skeptical Science now an iPhone app
    John, this post could have begun "There is a dramatic hot spell sweeping across Australia" (44oC in Melbourne yesterday for example). A major tool of deniers has been to exploit the shift in seasons. "Hot in the northern hemisphere in July? Well, yes, it's Summer, whaddya expect, besides, it's cold in Australia". "Hot in Australia in January? Well, yes,it's Summer, whaddya expect, besides, it's cold in Europe." Seasonal variation is a gift that has kept on giving to deniers for many years.
  27. Why does CO2 lag temperature?
    It is I think important to remember that prior to human industrial activity CO2 was, for all practical purposes, a feedback not a forcing. Given that we know that the CO2 increase by ~15ppm per deg C., we can calculate that at the depths of the ice age there was a CO2 feedback of 1.12(assuming CO2 concentrations of 205 and 190 respectively). (ln(205/190)/ln2)*3.7w/m2 gives ~ 0.4/W/m2 ~temp increase is ~.11+ .11^2+.11^3.... is approximately equal 1.12. IOW if the sensitivity of the climate not counting CO2 was 3 deg. K/W/m2, the sensitivity of the climate including CO2 should be ~3.36K/W/m2. Cheers, :)
  28. Why does CO2 lag temperature?
    You know, I wish this thread had a different title. CO2 lags temperature sometimes. See, e.g., Milankovich cycles. CO2 leads temperature sometimes. See, e.g., flood basalt episodes, vaporization of carbonate rocks during bolide impacts, and combustion of fossil fuels. Somebody or other once compared CO2 and temperature to two individuals handcuffed together. Wherever one goes, the other has to follow. Right now, we're very much in a situation where CO2 leads temperature.
  29. Why does CO2 lag temperature?
    An interesting article which explains why a period of extreme global glaciation could also be simultaneously a period of extremely high levels of atmospheric CO2. There is one point which the article does not make as clear as possible. When the earth is extremely cold, humidity is also extremely low. What happens in a cold climactic setting is that the effect of CO2 as a greenhouse gas is amplified simply because CO2 and H2O both absorb energy from the two of the same spectral bands. Currently H2O exists at levels 50 times greater that CO2 (20-25,000 ppm vs 387 ppm). So, now, most of the IR energy for the overlap bands is absorbed by H2O. However, if the air was nearly bone dry while CO2 concentrations were in the range of say 10,000 ppm, CO2 could actually become a much more influential greenhouse gas. To view the overlap spectra of CO2 vs H2O use this link... half way down the article shows a graph of the impact of various greenhouse gases on the IR spectra of energy that is reflected from the earths surface .. http://forthegrandchildren.blogspot.com/2009/03/best-global-warming-discussion-ever.html Link to the entire article http://www-eps.harvard.edu/people/faculty/hoffman/snowball_paper.html “”In the late 1980s, Joe Kirschvink at the California Institute of Technology pointed out that during a global glaciation, what he termed a "snowball" Earth, the supply of carbon dioxide to the atmosphere and oceans from volcanism would continue because of plate tectonics. However, if the Earth were so cold that there were no liquid water on the continents, weathering reactions would effectively cease, allowing carbon dioxide to build up to incredibly high levels. Eventually, the carbon-dioxide-induced warming would offset the ice albedo, and the glaciation would end. Given that solar luminosity 600-700 million years ago was about six percent lower than today due to stellar evolution, Ken Caldeira and Jim Kasting at The Pennsylvania State University estimated that roughly 0.12 bar of carbon dioxide (about 350 times the present concentration) would have been required to overcome the albedo of a snowball Earth. Assuming current rates of volcanic carbon dioxide emissions, a Neoproterozoic "snowball" Earth would have lasted for millions to tens of million of years before the sea ice would begin to melt at the Equator. A "snowball" Earth would not only be the most severe glaciation conceivable, it would be the most prolonged.””
  30. Why does CO2 lag temperature?
    CO2 lags temperature change for one obvious reason. The ocean contains 93% of all of the CO2 in our biosphere in one form or another. Some of the CO2 which is locked up in the ocean in the form of soluble gas is exhausted into the atmosphere when the ocean warms and it is reabsorbed by the ocean when the ocean cools. Out-gassing... This phenomenon of the change in the solubility of gases in liquids as a function of temp and pressure has been of course been measured many times over and can be proven with the simplest lab experiments. In other words, on this issue, the science is really truly and honestly "settled". This phenomenon is also the reason that ocean CO2 concentrations are greater in the polar regions than in the tropics and this is why tropospheric concentrations of CO2 in the atmosphere are greater in the tropical regions than in the polar region. As my daughter would say, its a "Henry's Law" thingy... http://en.wikipedia.org/wiki/Henry's_law That is why warmer climactic periods usually result in higher levels of atmospheric CO2. Of course, that is not necessarily true. Periods of exceptional volcanism can temporarily create a climate which is simultaneously cold and rich with CO2.
  31. CO2 lags temperature
    I would like to ask a question that I would regard as common sense (the true deficiency of our planet IMHO). If temperature increases, whether from co2 or other sources, and that in turn causes the release of more co2 wouldn't that cause what is known in my industry a "feedback loop" which is a perpetual increase where it reaches a limit according to a viability of materials to handle such a load. So basically, it would either keep increasing until something "breaks" or would reach an equilibrium of perpetual continuance. That "balance" would look like; temperature increases with co2 until enough water vapor (the biggest greenhouse gas) would block enough incoming radiation to halt the increase of temperature resulting in a new perpetual balance between co2's greenhouse effect and water vapor's? I'm looking for an answer to what ended other warm periods in our history like the Paleocene period. Because if co2 levels lag temperature by roughly 800 years so would it's greenhouse effect, continuing it's "greenhouse" warming creating a cooling buffer but it doesn't, it just drops off like a fat lady falling off her chair at an all you can eat buffet.
    Response: Good question - I considered addressing this in the original article above but opted to keep things simple and address it in a future post. In the case of Milankovitch cycles, just as orbit changes initiate the warming, they also end the warming. Towards the end of the deglaciation, orbit changes cause the amount of June sunlight falling on the northern land masses to change by several tens of percent (not an insignificant change). Gradually over time, northern ice sheets start to grow again.

    For greater time scales (eg - over millions of years), rock weathering is another factor that keeps the climate regulated. Rock weathering is the phenomenon where CO2 is scrubbed out of the atmosphere by chemical reactions with rock surfaces. As temperatures warm, the rate of rock weathering increases - this acts as a natural thermostat to keep CO2 levels from getting too high. However, this process occurs over millions of years so don't expect rock weathering to bail us out of our current situation (although interestingly, there is research into using artificially accelerated weathering as a technique in sequestering CO2).
  32. Why does CO2 lag temperature?
    Ned I dont think I have introduced anything tangentially into the discussion, and any comments, opinions, or deductions have been based on the material as presented on this website. Usually these comments address aspects of the apparent "fundamental harmonic" of what is being presented. For instance, in #15, using the data as given, I imply Milankovitch cycles have tens times the weight of CO2 in affecting climate. I am not inventing anything here, just commenting on what the data seems to suggest. Is that so out of order?
  33. Is the airborne fraction of anthropogenic CO2 emissions increasing?
    Still further thoughts on the problems with Lindzen's 2009 paper here. Trenberth et al. seem to have really demolished that hypothesis.
  34. Is the airborne fraction of anthropogenic CO2 emissions increasing?
    Marcus writes: By contrast, though it has still to be independently verified, Lindzen's hypothesis regarding "The Iris Effect" is based on quite sound scientific principles (yes, I have read the paper, & understand enough of it to make this judgment)-even though Lindzen is a noted Skeptic. Actually, there really isn't good evidence for Lindzen's iris; in fact, there's now quite a bit of evidence against it: Chambers et al. 2002 Lin et al. 2004 Rapp et al. 2005 Trenberth et al. (in press) There's some good discussion of this here and here.
  35. A visual deconstruction of a skeptic argument
    Also, nofreewind-to date only a couple of scientists (Lindzen & Spencer-both noted skeptics) have proposed that GHG-induced warming will lead to a negative feedback as a result the so-called "Iris Hypothesis". Yet many other scientists have failed to find supporting evidence for their hypothesis, instead finding evidence that the decline in cirrus clouds resulting from sea-surface warming actually has a net *positive feedback* effect. This view has been backed up by data from the CERES satellite (louds and the Earth’s Radiant Energy System), that shows that any increased heat-escape potential generated by the decrease in cirrus clouds in the canopy is more than made up by the increased sunshine allowed in by the decrease in Earth's albedo. According to scientists working on CERES, the countervailing forces results in a modest, *positive* forcing caused by the Iris Effect.
  36. A visual deconstruction of a skeptic argument
    You've got to give nofreewind points for bravely waving the anti-science banner here on behalf of the fossil fuel industry. The reality is that the ice core data quite clearly shows that CO2 levels have remained at around 260-280ppm for the better part of 30,000 years-yet we're supposed to believe that the sudden rise in CO2 emissions-by more than 100ppm-in the last 50 years is *purely* coincidental with the sudden rise in burning of fossil fuels in our cars & power-stations. He also expects us to believe that CO2 will saturate at a low level, when a simple look at the geological record shows a strong correlation between atmospheric CO2 levels of greater than 2,000ppm & average global temperatures of roughly 22 degrees C (compared to roughly 15 degrees throughout the bulk of the Quaternary Period)-in spite of the sun being about 10% *cooler* at that time, no sign of "saturation" there. A basic knowledge of geologic history would also reveal that the relatively low CO2 levels (& cooler climate) of the Quaternary Period are because these vast quantities of CO2 (mostly from tens of millions of years of volcanic activity & land-forming processes) were sequestered out of the atmosphere by the world-spanning forests of the Carboniferous period-& again in the Cretaceous period. These great forests later died & were fossilized deep under the ground. In the last 150 years, we've managed to dig out large quantities of these fossils, & are burning them for energy. You don't need to be a genius to work out what the final result of that will be-most likely the re-release of pre-Quaternary CO2 & the warming of the planet to levels closely approximating pre-Quaternary levels.
  37. Why does CO2 lag temperature?
    RSVP: "The CO2 level lagging suggests, CO2 is subject to the Milankovitch cycles and not the other way around." It works both ways. If you force a temperature change first, CO2 will follow (and amplify the temperature change). If you force a change in CO2, temperature will follow (and amplify the CO2 change). Milankovich cycles are an example of the former. But there are plenty of examples of the latter, too, including: [a] Weathering during tectonic uplift (which removes CO2 and cools the planet; see, e.g., Ruddiman 1997). [b] Chris's examples of the vaporization of carbonate-rich rocks from a bolide impact, or outgassing of CO2 during massive flood basalt episodes, both of which add CO2 and warm the planet. [c] Rapid release of fossil carbon from methane clathrates, or from combustion of coal and oil. With all due respect, RSVP, there are commenters on this site who have a great deal of expertise in earth system science. I for one really appreciate their taking the time to participate here -- it's what makes this site stand head-and-shoulders above most other climate blogs. You could learn a lot by paying more attention to what some of those commenters have to say, rather than just tossing out one argument after another.
  38. Why does CO2 lag temperature?
    Chris, The CO2 level lagging suggests, CO2 is subject to the Milankovitch cycles and not the other way around. As concerns eccentricity, obliquity, and precession, it would seem that precession would not affect climate at all, except in shifting seasons with respect to their relation to the stars. Furthermore, depending on the phase relation of eccentricity and obliquity, you could either have a reinforcing or cancelling effect. I did not see any mention of this in the article, however based on the sawtooth waveform, where the temperature rise is punctuated after a long and slow dropoff, this would seem to indicate a reinforcing where the orbital minimum coincides with less tilting. In any event, I agree that my perception appears "less than logical" to anyone who is bent on proving AGW.
  39. What ended the Little Ice Age?
    batsvensson, #17 it looks to me that you are taking the data "as is" without adding the physics of the processes involved in climate variations. We are not analizing an unknown signal, we are looking for the link between forcings and temperature. This is what "put into a perspective" present and past climate. #18 "larger than expected" refers to what is now widely accepted as the best estimate. And it does not come from nowhere, it comes from the analisys of many different phenomena. Climate sensitivity is not an abstract concept, it's the physical link between forcing and temperature variation. It can not take any value, it need to be contrasted with what we know had happend. Explaining the glacial cycles requires the knowledge of forcing and feebacks which, together with the climate sensitivy, gives you the temperature variation. Given the forcings and feedbacks (crudely, Milankovich cycles and ice and CO2 feedbacks) a increased sensitivity would results in a temperature variation higher than obeserved. So the problem is not that "I can not imagine how it can happen", it is that a high sensitivity cannot explain the glacial cycles.
  40. What ended the Little Ice Age?
    Riccardo you wrote in #4: "if a small sun variation can induced detectable increases in temperature it can only mean that climate sensitivity is much larger than expected ..." I assume "sensitivity" and "variability" in above are the same, and want to ask: "larger than expected" than what? Yuo also wrote: "it would be hard to explain the temperature difference between glacial and interglacial with such a huge sensitivity" Why would this be hard to explain with an increased sensitivity/variability? Statement like this sound to me like "since I can not imagine how it can happen then it can not have happen." What reason do we have to believe this to be true?
  41. What ended the Little Ice Age?
    Riccardo, thank you for taking time to make the answer in comment #13, however I am well aware of the techniques on how to calculate a bandwidth or variability or whatever label is preferred to use for this. What I am asking about is our knowledge of the variability in the past. Because the "conclusion" that "Meehl 2004 is also confirmation that past climate change tells us how sensitive climate is to radiative forcing." which is not a conclusion at all is a nonsense statement unless we can put into a perspective of past variability or "sensitiveness" (which is yet another label for the same thing).
  42. Why does CO2 lag temperature?
    Thanks all for the wonderfully informative posts & comments. I've learned a lot just from reading this one page!
  43. 1998 DIY Statistics
    RE: #26 Ricardo Thanks that is a helpful paper. I wanted to know how the variances were recorded. The methods in Section 3 "Aggregation of the Raw Data" seem to address that.
  44. Why does CO2 lag temperature?
    A couple of things to add to what Chris has posted: Ian - If the CO2 were coming from methane, then it would have a strong isotopic signature characteristic of the methane. Natural sources of methane are strongly depleted in carbon-13 relative to carbon-12. During the deglaciation there is a small excursion in the isotopic composition of CO2 recovered from ice cores (Smith et al., 1999), but much smaller than would be expected of the CO2 were produced by oxidation of methane. Rather, the carbon isotope signature of CO2 during deglaciation is consistent with the release of CO2 from the deep ocean (Spero and Lea, 2002). Smith, H.J., Fischer, H., Wahlen, M., Mastroianni, D. and Deck, B., 1999. Dual modes of the carbon cycle since the Last Glacial Maximum. Nature, 400(6741): 248-250. Spero, H.J. and Lea, D.W., 2002. The cause of carbon isotope minimum events on glacial terminations. Science, 296(5567): 522-525. David - In Greenland the annual layers of ice can be counted back for about 40,000 years. In older ice they become squeezed so much by the pressure of the overlying ice that they can no longer be identified. (I don’t remember exactly how far back people have counted annual layers, but it’s roughly 40,000 years). In Antarctica the annual layers cannot be counted so far back in time because the annual snow accumulation is generally much less than in Greenland. Therefore the layers start out thinner and it takes less time before they become indistinguishable.
  45. Why does CO2 lag temperature?
    Well yes, RSVP but I think you're falling for exactly the mistake that John Cook highlights in his top post. There's little doubt that during the glacial cycles of about the last million years or so, that CO2 concentrations tracked (and amplified) earth temperature changes that resulted from Milankovitch cycles. However it would be illogical to conclude from this that atmospheric CO2 levels respond to earth temperature changes in a more significant manner than earth temperatures respond to changes in CO2 levels. One could look at the last 1000 years for example [tiny changes in atmospheric CO2 during the temperature variations associated with the MWP and LIA, compared to the mach larger earth temperature rise in response to changes in (anthropogenic) CO2 levels)]. Likewise, inspection of the Phanerozoic temperature/CO2 record indicates that the Earth has responded in a very significant manner to changes in atmospheric CO2 levels. In fact the reason that we now inhabit an earth with very significant polar ice caps is the result of the decrease of atmospheric CO2 levels during the late Eocene/early Oligocene. Just because CO2 tracked earth temperature during a particular set of specific and rather well-understood climate phenomena (Pliestocene glacial transitions), it's illogical to conclude that earth temperature variations are the dominant cause of CO2 variations. In fact the evidence supports the opposite conclusion, namely that changes in greenhouse gas levels dominate earth temperature variations. We're experiencing an example of that during the present era....
  46. Why does CO2 lag temperature?
    chis From what I can tell from the curves above, CO2 tracks Earth temperature like a flea rides on an elephant. Its hard for me to be "less than logical" faced with something so obvious, but I guess you must have some kind of point.
  47. Why does CO2 lag temperature?
    Interesting, I hadn't realised there was a considerable dating uncertainty in the ice record of CO2. I had assumed, because these are long continuous and fine-scaled records, that the dating was something equivalent to tree rings or mud varves. The error margin puts into perspective the constant refrain - "oh, but CO2 increase lags temp rise, how can it be cause and effect?" Seems to me that if there is an error margin on age, then the record should just be read as showing a very close (indeed astonishingly close as such things go) correlation between CO2 and temps over a very long time period as John's graph illustrates. Whether CO2 increase "leads" temp increase (as it is doing in modern times) or whether it is working as a feedback and amplifying mechanism seems irrelevant. Of no more than academic curiosity when we are considering the distant past. The close correlation shows that the two mechanisms are effectively just one, and that is the frightening conclusion as we continue to pump CO2 into the air in a never ending experiment to see just how far we can go before catastrophic change ensues.
  48. Why does CO2 lag temperature?
    re #15, there's a less than logical element to your description of temperature>CO2 and CO2>temperature causalities RSVP. This relates to the likely accessible range of temperature and CO2 variations. So, in fact during glacial-interglacial transitions the global temperature change of around 5-6 oC results in a repartitioning of CO2 between the oceans/terrestrial environment and atmosphere equivalent to around 90 ppm (i.e. something like 15-18 ppm of atmospheric CO2 rise per oC of global warming at equilibrium). However the potential for CO2 rise from non-temperature-dependent repartitioning (e.g. from extraterrestrial impact into carbonate-rice sediments, or massive tectonic events like flood basalt release, or anthropogenic burning of fossil fuels) is much larger than the 90 ppm of [CO2] repartitioned to the atmosphere during glacial-interglacial transitions. So whereas a 90 ppm CO2 rise is near the limit of any realistic temperature-induced enhancement of atmospheric CO2 probably during the past 100's of millions of years, it is very easy for non-temperature-dependent drivers of [CO2] to push CO2 concentrations above 1000-2000 ppm (we could easily manage to reach 1000 ppm during the next 150 years). So in the real world, [CO2] variation is, and always has been, a major effector of global temperature variation, whereas global temperature change is a rather minor effector of atmospheric [CO2] variation. One could look at specific examples. During the Medieval Warm Period, atmospheric CO2 levels seem not to have risen more than a few ppm above pre-MWP levels. Now that likley means that the MWP didn't result in very much global scale warming. The drop in atmospheric CO2 during the Little Ice Age (LIA) from ~ 280-276 ppm was seemingly also very small. That's because the atmospheric CO2 levels respond to a rather small extent to changes in global temperature. On the other hand global temperatures are responding much more significantly to the raised anthropogenic CO2 levels. One can easily be fooled by numbers. It's not the magnitudes of the numbers, as such, that are relevant, but the accessible ranges of likely variation...
  49. Why does CO2 lag temperature?
    re #14 Ian, the paper by Ahn and Brook that bobo cites [*] has a very intersting overlay of CH4 levels in Greenland and Antarctic cores, together with Greenland and Antarctic temperature proxies (delta 18-O2) and Antarctic CO2 levels (see Figure 1). Several things are striking (to me)...boba might have some further insight: 1. Within the last glacial period small variations in CO2 levels follow Antarctic temperature variation pretty faithfully, but the large CO2 rise at the termination from ~17000 to ~11000 years ago lags Antarctic warming quite markedly (as described in the top article). 2. Methane levels follow Greenland temperature variation very faithfully indeed, and are non-synchronous with Antarctic temperature change until the termination. The simple explanation would be that methane levels follow high N. latitude warming (perhaps associated with methsane release from tundra melt??). 3. This is very striking. The very sharp warming/cooling pulses in the Greenland cores associated (likely) with on-off shifts in the AMOC have totally synchronous sharp rises/falls of methane levels that are observed (synchronously) in Greenland and Antarctic cores. 4. At least within glacial periods, the slow CO2 rises and falls (of around 20 ppm over several thousand years) associated with slow Antarctic temperature rise and fall, occur well in advance of the methane spikes associated with Greenland warming spikes. That would imply that the enhanced CO2 is not a result of enhanced methane release and oxidation to CO2. Even during the termination where the Antarctic temperature rose rather steadily between ~20-10,000 years ago, the Greenland warming has a cold interval (Younger Dryas) which has a synchronous coincident drop in methane (observed in Greenland and Antarctic cores). So it really does look like methane levels match events in the N. hemisphere. J. Ahn and E. J. Brook (2009) Atmospheric CO2 and Climate on Millennial Time Scales During the Last Glacial Period Science 322, 83-85 http://www.sciencemag.org/cgi/content/abstract/322/5898/83
  50. Why does CO2 lag temperature?
    re #7 Andreas As I mentioned in the post above, there are some other scenarios that involve a more direct S. hemisphere response to Milankovitch-driven insolation changes. It does seem clear that glacial termination is driven by Milankovitch cycles; however Milankovitch driven insolation variation obviously applies to the S. hemisphere as well (see below). It’s likely that the AMOC underwent quite abrupt ice melt driven cessations (and re-establishments); it’s difficult otherwise to explain the sharp temperature drops/rises in the Greenland core (and their lack of appearance in the Antarctic cores). But whether these were active/causal or passive/responsive phenomena is still an open question I believe, ‘though I find the scenario outlined by Barker/Broecker (paraphrased in my post #6) plausible. And one could substitute the enhanced Westerly-driven Southern ocean-destratification mechanism that boba describes (Anderson et al, 2009; Toggweiler 2009 cited in boba’s post) as the warming-driven proximate cause of CO2-outgassing from the Southern oceans, within the same ultimate scenario of Barker/Broecker. In this case the Arctic melt-water induced weakening/shut-down of the AMOC warmed the Southern oceans at the expense of Northern latitude warmth, and shifted the Intertropical Convergence Zone southwards, pushing the Southern westerlies closer to Antarctica and “stirring up” the deep Southern oceans to promote CO2 release. Looking at the alternative proposals, Stott et al (2007) consider that the glacial terminations might be driven by direct Southern ocean ice sheet responses to austral spring insolation variation (Milankovitch), and that the warming-induced CO2 release from the Southern oceans transmits the warming to the N. hemisphere, to give the Antarctic warming > CO2 release > Greenland warming sequence at the terminations. Their plot of the Milankovitch variation of austral spring insolation varies in synch with the N. hemisphere summer insolation at 65 oC… ..and Huybers and Denton, consider that it is the Milankovitch-forced variation of the duration of the S hemisphere summer (which covaries with the Milankovitch-forced variation of the intensity of the N. hemisphere summer), that is important…. If I understand your last question (different phase patterns between insolation and warming) it could be that this is a result of different response of AMOC. Since the insolation variation is extremely regular (and predictable), any non-regular/variable consquences should have their origins in less predictable responses to the regular insolation variation. If the AMOC responds to ice-melt intensity, presumably this has rather non-regular features and will impose a more stochastic pattern onto the insolation-driven changes. But more generally, if (by whatever scenario), N. hemisphere warming is ultimately driven by CO2-release from the vast S. oceans in response to S. latitude warming/reduced S-N hemisphere temperature gradients, the very slow warming, with associated very slow CO release, may, by itself, result in a phase difference between insolation patterns, and warming responses. While there are still some issues with matching the timings exactly between Greenland and Antarctic cores, it seems clear that Antarctic warming precedes Greenland warming during terminations, and even during some of the periodic warming transitions within glacial periods…again variations in the AMOC seem to be implicated in these events…

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