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Comments 125451 to 125500:

  1. 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.
  2. 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!
  3. 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)
  4. 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?
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. 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. :)
  10. 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!
  11. 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.
  12. 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
  13. 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.
  14. 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, :)
  15. 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.
  16. 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.””
  17. 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.
  18. 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).
  19. 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?
  20. 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.
  21. 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.
  22. 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.
  23. 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.
  24. 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.
  25. 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.
  26. 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.
  27. 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?
  28. 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).
  29. Why does CO2 lag temperature?
    Thanks all for the wonderfully informative posts & comments. I've learned a lot just from reading this one page!
  30. 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.
  31. 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.
  32. 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....
  33. 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.
  34. 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.
  35. 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...
  36. 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
  37. 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…
  38. Sea level rise is exaggerated
    Re: 1 & 2 - I can't find much on Morner other than his Wiki page which suggests his work was often cited and though now seemingly discredited he must have once been a leading authority on sea level rises or the lack of them. He certainly claimed to be the best in the world in the external links to interviews from Wiki in which he rages about the IPCC bringing in modellers rather than sea-level experts.
  39. Why does CO2 lag temperature?
    According to the graph presented here and in a previous article: http://www.skepticalscience.com/The-correlation-between-CO2-and-temperature.html (figure 2) a 10 degree change in Earths temperature causes a change of 90 ppm CO2, while a change of 60 ppm CO2 could possibly have partially effected 1 degree of change in the Earths temperature. This data indicates that temperature drives CO2 much stronger than CO2 drivers temperature.
  40. Why does CO2 lag temperature?
    Boba, interesting comments. I've always felt that CO2 coming from warming oceans didn't seem quite right from a simple chemistry view point (it seemed to me that it was unlikely that the oceans would be saturated because of various cycles). Have you considered that the increase in CO2 during deglaciation periods could be from methane released by the retreating ice and permafrost? The methane will then be oxidized both biologically and photochemically to CO2.
  41. Why does CO2 lag temperature?
    First I’d like to commend John for a great blog. This is a fabulous resource and your careful, thorough, and prompt explanations of new science papers is very impressive. Thanks! Temperature’s lead over CO2 in Antarctic ice core records keeps getting mentioned as proof against human impacts on climate, so it’s good to have an objective discussion of the issue. Here I present some additional perspective from the paleoclimate community I’m sorry this comment is so long, but it’s a complex issue. John - It seems that the link to Shemesh et al., 2002 is still broken. At least I get a damaged file. Presumably this is: Shemesh, A., Hodell, D., Crosta, X., Kanfoush, S., Charles, C. and Guilderson, T., 2002. Sequence of events during the last deglaciation in Southern Ocean sediments and Antarctic ice cores. Paleoceanography, 17(4): 10.1029/2000PA000599. Turboblocke - Henry’s law absolutely applies to CO2, as it does to all gases. The CO2SYS document from the CDIAC web site doesn’t support that claim. The main difference between CO2 and other gases is that once CO2 dissolves from air into seawater it undergoes further reactions, dissociating into bicarbonate and carbonate ions. This makes the chemistry of carbon dissolved in seawater complex, but CO2 gas still obeys Henry’s Law. Dennis, Riccardo - Yes, the uncertainty in the overall age model for an ice core gets larger further back in time, as does the uncertainty in the difference between the ages of gas and of ice at any given depth. For those who aren’t familiar, at any given depth in an ice core the ice is at least a few hundred years, and sometimes a few thousand years, older than the gas. This is because gases diffuse through firn (packed snow) before it is sealed off as ice. The age offset between gas and ice increases as the accumulation rate of snow decreases. Therefore, the ice-gas age difference is much greater during ice ages, when there is less snow accumulation, than during interglacials. Uncertainty in the ice-gas age difference has been a big problem in establishing reliable lead-lag relationships between temperature and CO2. People have done statistical analyses of gas-ice age differences, but the best statistics still produce meaningless results if the age models for ice and/or gas are inaccurate. This applies to the data set cited by Ari Jokimäki. Age models for ice cores are constantly being revised. See: Bénédicte et al., Consistent dating for Antarctic and Greenland ice cores. In Press, Quaternary Science Reviews, Available online 3 December 2009 The uncertainty between gas age and ice age can be virtually eliminated at glacial terminations (i.e., at the end of an ice age) when the initial warming is recorded by the isotopic composition of argon gas, which can then be compared directly against CO2 concentration. Since both temperature and CO2 come from the gas phase, there is no age offset in need of correction. This is how Caillon et al. 2003 (cited by John) was able to show that temperature started to rise in Antarctica before CO2 began to increase. This direct evidence is more robust in my opinion than the statistical comparison of CO2 and temperature on different age models, each with their own uncertainty. I think Caillon et al convinced paleoclimate scientists that the initial increase in temperature in Antarctica leads the initial rise in atmospheric CO2 at the end of an ice age by several hundred years. This leads to the main point that I wanted to make, namely: Why did temperature start to rise in Antarctica before concentrations of CO2 began to increase at the end of an ice age? Does this mean that CO2 does not have an impact on climate? Two hypotheses have already been described. I will summarize those and add a third. The first hypothesis invokes changes in earth’s orbit (Milankovitch) and its effect on spring insolation around Antarctica. Increasing insolation in spring is suggested to cause sea ice to melt back earlier in the year, which allows more CO2 to escape from the ocean to the atmosphere. A scenario like this was invoked by Shemesh et al. (2002) and would follow from the conclusions of Huybers and Denton (2008; cited by Chris). The general principles are described in a paper by Stephens and Keeling: (Stephens, B.B. and Keeling, R.F., 2000. The influence of Antarctic sea ice on glacial-interglacial CO2 variations. Nature, 404(6774): 171-174.). However, if you read the papers that comment on Stephens and Keeling, you will find skepticism in the paleoclimate community about whether or not sea ice can truly serve as a “lid” holding CO2 in the ocean. Second, Chris described a hypothesis that is commonly invoked for the sequence of events at the end of an ice age, namely: 1) Changes in Earth’s orbit (Milankovitch again) led to warmer summers in the Northern Hemisphere. 2) Warmer summers started melting the large northern ice sheets that built up during the ice age. 3) Freshwater from melting ice flowed into the North Atlantic. Because of its lower density, the freshwater slowed or stopped the overturning circulation that transports heat northward. 4) This had a global impact, but here some hypotheses diverge (denoted A and B below). According to the ocean bi-polar seesaw hypothesis described by Chris: A5) Reduced northward flow in the Atlantic allowed heat to build up in the Southern Hemisphere, a phenomenon known as the bipolar seesaw. A6) Warming of the Southern Ocean caused CO2 to be released from the ocean due to the lower solubility of gases in warmer water. Rising CO2 followed the initial warming of the Southern Ocean and of Antarctica, and also contributed to warming of the Earth as a positive feedback. (See Chris - Post 6, point 2c) A problem with this hypothesis is that the temperature dependence of CO2 solubility in seawater is well known, and the rise in ocean temperatures during deglaciation is not nearly large enough to have caused the observed rise in CO2. This was pointed out long ago by Broecker and others. The principle is firmly established in the scientific literature. Broecker, W.S., 1982. Glacial to interglacial changes in ocean chemistry. Progress in Oceanography, 2: 151-197. Something other than warming must have caused CO2 to be released from the oceans. This is why some people invoke the melting of sea ice to allow more CO2 to escape (see above). However, (a) as noted above, others have argued that sea ice is not sufficiently effective as a barrier to gas exchange and (b) changes in sea ice driven by orbital forcing cannot explain the tight correlation between CO2 and Antarctic temperatures on the millennial time scales that are shown in Figure 1 of: Ahn, J. and Brook, E.J., 2008. Atmospheric CO2 and climate on millennial time scales during the last glacial period. Science, 322(5898): 83-85. A third hypothesis not yet described in this thread of comments involves a reorganization of global wind systems toward conditions more favorable for mixing in the Southern Ocean that drives CO2 from the ocean to the atmosphere. The process begins as above, with changes in Earth’s orbit melting northern ice sheets and slowing Atlantic overturning circulation (Points 1 - 4). Then the emphasis switches from the ocean to the atmosphere: B5) When freshwater shuts down Atlantic overturning circulation, winter sea ice expands over the North Atlantic, causing severely cold winter conditions. B6) Cold winters cause changes in atmospheric circulation, which are well documented for the Intertropical Convergence Zone and for the Asian Monsoons (see Cheng et al., 2009, cited by Chris, and references therein). B7) Reorganization of the winds extends all the way to Antarctica, strengthening the Southern Hemisphere westerlies so that they are more effective at driving CO2 out of the ocean. According to this hypothesis, intense cooling in the northern hemisphere causes warming in the southern hemisphere by changing wind patterns. The initial warming in Antarctica is caused more by a redistribution of heat from north to south than by a global rise in temperature. The winds then drive CO2 out of the ocean so that the observed rise in CO2 lags slightly the initial warming detected in Antarctic ice cores. It takes a few thousand years to melt the northern ice sheets. During this time when meltwater is being dumped onto the North Atlantic, the winds are shifted and CO2 is being driven out of the Southern Ocean. These conditions can experience brief reversals, as happened 14,500 years ago during the Bolling period. After the Bolling warm period, the conditions resumed during the Younger Dryas period. Increased atmospheric CO2 together with reduced albedo following the meltback of the northern hemisphere ice sheets provided the feedbacks to Milankovitch forcing that brought the earth out of the last ice age into a warmer interglacial period. The principles underlying the forcing of CO2 by shifting winds over the Southern Ocean are described by Toggweiler (2006). Evidence to support the principles, but modifying the timing, are described by Anderson (2009). See also comment by Toggweiler (2009). Toggweiler, J.R., Russell, J.L. and Carson, S.R., 2006. Midlatitude westerlies, atmospheric CO2, and climate change during the ice ages. Paleoceanography, 21(2): doi10.1029/2005PA001154. Anderson, R.F., Ali, S., Bradtmiller, L.I., Nielsen, S.H.H., Fleisher, M.Q., Anderson, B.E. and Burckle, L.H., 2009. Wind-driven upwelling in the Southern Ocean and the deglacial rise in atmospheric CO2. Science, 323(5920): 1443-1448. Toggweiler, J.R., 2009. Shifting Westerlies. Science, 323(5920): 1434-1435. These hypotheses all need to be investigated further. Each has strengths and weaknesses. Given the complexity of Earth’s climate system and its connection to the global carbon cycle, the correct answer is likely to be “all of the above”.
  42. What happened to the evidence for man-made global warming?
    - Satellites measure less infrared radiation escaping out to space at the wavelengths that CO2 absorb energy (Harries 2001, Griggs 2004, Chen 2007) - Surface measurements find more infrared radiation returning back to the Earth's surface (Philipona 2004), specifically at the wavelengths that CO2 absorb energy (Evans 2006) I think these two arguments are very strong. What would be the clincher, however, is if the radiation loss going outward and radiation increase going back onto the surface where mathematically equivalent to the energy increase in the athmosphere. Are you aware of any such calculation? The argument would be problematic if, for instance, the increased radiation back would be much less than the increase in temperature.
  43. Can you make a hockey stick without tree rings?
    The only link that worked for me here was Oerlemans'. Is it just me or have the links indeed been moved? Another question: why does the Mann graph show a 0.8+ degree warming after de mid-century pause? Shouldn't it be some 0.5ºC?
  44. What ended the Little Ice Age?
    Thank you for an excellent post Chris. John your site is a wonderful model of how knowledgeable lay people and scientists should interact with ordinary inquisitive folk such as myself whose initial approach to the subject is skeptical.
  45. Why does CO2 lag temperature?
    Dennis, you are correct that there is large uncertainty in measurements, and there is additionally the fact that datapoints for carbon dioxide are typically separated by thousands of years which adds to the measurement uncertainty. This leads to the situation where you can't usually say on individual moments for sure that there's temperature leading. However, the lead/lag situation has been determined statistically from the whole datasets, not from individual events. So, I would say that the temperature leading is real phenomenon but we can't rule out that there might be some individual events where CO2 leads. Here's an example data for carbon dioxide (from Vostok ice core) where you can get the feel of the thing yourself: http://cdiac.ornl.gov/ftp/trends/co2/vostok.icecore.co2
  46. Hockey sticks, 'unprecedented warming' and past climate change
    I have a few relevant points to add here. On my reading of Jared Diamond's book "Collapse" (highly recommended read I might add), there are 3 civilizations whose collapse is consistent with a warming period between the 7th & 14th C AD. The Khmer Empire, the Mayans & the Anasazi all declined/collapsed around the same time, & all the Paleo-climatic data from the respective areas (especially sediment cores from lake beds & coastal regions) show that there was definitely a warming event which triggered/accelerated the decline of these civilizations. So we do have fairly reasonable evidence of warming-induced collapses of civilizations from the low N. Hemisphere & Tropical S. Hemisphere. What is interesting, though, is this-the warming events are believed to have been on the order of +0.5 to +0.8 degrees, but occurred over a period of almost *seven hundred years*. Secondly, solar activity proxies for that time period (Be-10 & C-14) suggest a surge in solar activity not unlike what we saw during the 19th & early 20th centuries. So this again leaves us with the fact that the current warming period is *faster* than any other in the last 2000 years (at least), & is the only one not underpinned by changes in the heliosphere.
  47. Is the airborne fraction of anthropogenic CO2 emissions increasing?
    I'm not sure if I'm witnessing the conception of a new misconception or just a "rebunking" (hat tip to Hank Roberts) but ralphiegm's constant repetition of problems with C02 measurements sure sounds like a launch to me. ralphiegm, all of the measurement sites you worry over show a steady increase in C02 content. How would the poor mixing you imagine comport with that? Is each site measuring a hermetic local atmospheric cell with its own C02 sources? For instance, what about the grandpa site, Mauna Loa? Is Hawaii stuck in a persistent gyre, with the atmosphere isolated from the rest of the world? Does the C02 measured at that site originate just within Hawaii? Or does the imaginary bubble extend to Midway? Japan? San Francisco? Where does the C02 in the contrail of a jet flying to Hawaii make the transition from one magical domain to another? Is there a mysterious atmospheric atomic and molecular sieve at play here, unknown until now but identified via proxy only by you? Remember Chernoybl? Remember how it was detected outside of the Ukraine? How about those radionuclides, hmm? Did the the sieve remove Ukrainian C02 prior to crossing the border? Speaking of isotopes, how about the C02 isotope distribution? Does each mysterious atmospheric bubble include a special synchronizing system so that even while mixing does not take place, isotope ratios are kept at the proper proportion across domains? Wait a minute. Maybe it's more reasonable to accept that the atmosphere is mixed. I dunno. What do you think?
  48. Is the airborne fraction of anthropogenic CO2 emissions increasing?
    I concur Ned. Ralph's comments about CO2 varying by +/- 200ppm sound very reminiscent of the results of the Beck "paper". Ralph's coyness about his knowledge of Beck actually *confirms* that this is his primary source (methinks he doth protest too much). Beck's collection of historical CO2 samplings ignores the poor quality of both the sampling sites, the measurement methods & the sensitivity of the measurement tools-all of which are suspect. For a very good analysis of Beck's data-I suggest going here: http://www.realclimate.org/index.php/archives/2007/05/beck-to-the-future/ Oh, & before Ralph accuses me of merely trying to "squeeze out skeptics"-that claim is simply *not true*. I just want to squeeze out BAD SCIENCE! That's as true of Beck as it is of Manne (he of the awful Hockey-stick. I mean, seriously, what kind of *scientist* uses a single, dubious source of paleo-climatic information & builds a paper round it?) 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.
  49. Why does CO2 lag temperature?
    Dennis, the uncertainty on lag of CO2 is of the order of some centuries, not thousands of years. The precision in the absolute dating of the air bubles depends on many factors, including accumulation rate and temperature, so it strongly depends on the geographic location of the ice core. Whenever possible the dating of the ice core (or part of it) is calibrated using known and well defined events.
  50. Why does CO2 lag temperature?
    Henry's Law is not appropriate for the solubility of CO2 in sea water. See here for more details: http://cdiac.ornl.gov/oceans/co2rprt.html

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