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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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Comments 128501 to 128550:

  1. How we know global warming is still happening
    re #73 That doesn't accord with the evidence Shawnwt, in at least four different ways: (i) Remember that most of the estimates of climate sensitivity are empirical, based on phenomenological analysis of climate responses in the past (e.g. during ice age cycles or from paleoCO2/climate responses duing the deeper past). Thus any cloud response is implicitly included in the analysis. The best estimate of a climate sensitivity near 3 oC (plus/minus a bit) incorporates all feedbacks/amplifications (except very slow ice sheet responses and methane release feedbacks). R. Knutti and G. C. Hegerl The equilibrium sensitivity of the Earth's temperature to radiation changes Nature Geoscience 1, 735-743 (ii) The evidence is reasonably good that the direct resonse to a doubling of CO2 (around 1 oC) is amplified to around 2 oC by the water vapour feedback, and therefore the "neutral" situation without extra amplifications would give us more than 2 oC of warming over preindistrial levels during the next century at current rates of CO2 emissions. With albedo feedbacks that will be larger still (let alone any large feedbacks from greatly accelerated release of methane from clathrates or tundra). (iii) we've had around 0.8-0.9 oC of warming during the last 100 years. That's entirely consistent with a climate sensitivity near 3 oC of warming per doubling of atmospheric CO2, and it's rather difficult to take seriously your notion that we might have "only ~0.5C of anthropogenic warming over the next century" with a negative cloud feedback. After all where has this supposed "negative cloud feedback" been for the last 100 years? (iv) We've already seen that we don't need a positive cloud feedback to give us well over 2 oC of warming during rhe next 100 years, and that there isn't any evidence of a negative cloud feedback. Is there evidence of a positive cloud feedback? yes: A. C. Clement et al. (2009) Observational and Model Evidence for Positive Low-Level Cloud Feedback Science 325, 460 – 464
  2. What does past climate change tell us?
    re #4 Whether or not the warming effect of solar activity is "amplified" or is "increased by a positive feedback" is immaterial to the question of climate sensitivity, unless one considers that there is something "special" about the forcing from solar activity that doesn't apply to other forcings. We’ve already seen, for example, that there is evidence for a positive cloud feedback (call it an “amplification” if you like!) as a result of radiative-forcing-induced ocean warming: A. C. Clement et al. (2009) Observational and Model Evidence for Positive Low-Level Cloud Feedback Science 325, 460 – 464 And one has to be a little careful in taking Shaviv's analysis at face value, due, amongst other things, to his selection of data sets. For example much of his analysis is based on a set of tide guage records of Douglas (1997), which shows a marked cyclic variation of local sea level that matches the solar cycle. However, this doesn't match the globally averaged sea level variation, especially the satellite-derived record which doesn’t show a marked variation with the solar cycle; e.g.: Church JA, White NJ, Aarup T, et al. (2008) Understanding global sea levels: past, present and future Sustainability Sci. 3, 9-22. It’s proposed that the tide guage measures, many of which are close to continental margins, have solar forcings magnified by more rapid warming/cooling in shallow waters, and that this amplifies the amplitudes of responses to forcings by a factor of 2-3 relative to the globally averaged response. So Shaviv’s use of this data to determine a radiative forcing from sea level response may well be erroneous (greatly overestimated) by that sort of factor. Whatever the origin of the discrepancy between tide guage measures and satellite measures with respect to amplitudes of response to solar cycles, I suspect that Shaviv’s analysis will be found to be a rather marked overestimation of the solar cycle response and his required “amplification”.
  3. What does past climate change tell us?
    The climate sensitivity has been introduced to allow comparison between different forcing. Given a starting condition, it can be considered the same for all forcings essentially because you average both anomaly and forcing over space and time. The only exception i'm aware of is the Galactic Cosmic Rays feedback that works only for the sun forcing. (Incidentally, this explains why many sceptics are stuck to the beloved GCR). The logical consequence is that if you try to explain the trend with just one forcing you need a larger sensitivity (amplification factor). But if you put back all the forcings, everything's screwed up; this last step is too often missing.
  4. Comparing CO2 emissions to CO2 levels
    Alexandre, during a rather obsessive period a couple of years ago, I investigated some of Jaworowski's claims concerning ice core CO2 measures, and wrote the following in another cotext, which I've re-edited in response to your question (apols for the long post): I’m looking at his piece written supposedly for a US Senate Committee hearing (you can probably find this, but I don’t like linking to this sort of rubbish). Here’s a summary of the essential points that Jaworowski makes with respect to ice-core data: 1.Physical processes and technical problems mean that the data is incorrect as a representation of true CO2 levels 2.ice core records show an inverse correlation between load pressure (ice weight) and CO2 levels (his Fig 1a) (in other words deeper ice has CO2 "squeezed” out of it by the ice load above and this is reflected in the ice-core record) 3. ad hoc assumptions are used to “normalize” trapped gas age with the direct atmospheric CO2 measurement (his Fig 1b) 4. stomata frequency of fossil leaves indicate CO2 levels significantly higher than direct measurement of trapped CO2 in ice cores 1. Physical processes/technical problems These are (according to Jaworowski): -the presence of liquid water in the ice -the formation of gas hydrates (or clathrates) -drilling contaminates these with drilling fluid -drilling decompression causes cracks through which gas escapes Notice that these are generalized problems; Jaworowski, doesn’t indicate that any particular studies have any particular problems but infers that these in general negate the validity of ice core data. Notice also that Jaworowski refers to rather old data (the Siple core is from 1980). So let’s have a look at something a bit more modern and see how Jaworowski’s problems are dealt with: Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn; DM Etheridge et al J. Geophys. Res. 101, 4115-4128 (1996) These authors drilled three cores at Law Dome Antarctica to obtain a 1000 year record of CO2 (this is the data in Figure 1 (green line) of John Cook's top article): ice melt: Etheridge et al show that regions of ice melt are readily identified in the cores. They say “At most five melt layers, less than 1 cm thick, were identified in each of the DE08 cores, and even fewer in DSS” [n.b. the DE08 core was 234 metres deep; the DE08-2 243 metres; the DSS 1200 metres]. clathrates: Etheridge et al say “no clathrates were observed in any of the cores, which is consistent with the dissociation relation with temperature and pressure [Miller 1969]” drilling problems: Etheridge specifically take note of the potential problems of stress cracks caused by certain drilling methods and of fluid contamination, by drilling each of the three cores using a separate coring method: they say: “The drilling methods used were thermal, electrochemical and fluid-immersed electrochemical for DE08, DE-082 and DSS, respectively. This allowed a useful confirmation that the ice core CO2 was not influenced by effects such as ice heating during thermal drilling or the presence of drill fluid or stress cracks (occasionally caused by thermal or electrochemical coring and subsequent pressure release after removal from the ice sheet).” Since the data from the three cores overlap and the equivalent data match, the problems that Jaworowski highlight simply don’t apply. He's insinuated problems that don't, in reality, exist. 2. Ice core data show an inverse correlation. Jaworowski is looking at very early ice core data (like that from Siple in his Figure 1A) and saying “hey, the deeper you go, the lower the CO2 levels. It must just be an effect of pressure." This is foolishly false, especially in light of the 100,000’s of year ice core record where the trapped CO2 levels range up and down in cycles that match the glacial cycle, with CO2 levels around 280 ppm in interglacial periods and 180 ppm in interglacials. Even looking at the CO2 record from Etheridge et al shows that this inverse correlation is fictitious (Figure 1 in John Cook's top summary). Going back in history the CO2 concentration levels off to a steadyish level between the late 1700’s back to around 1600, when it rises again. The period from around 1600 forward to around 1800 is the period known as “The Little Ice Age” with quite a lot of independent evidence for a coldish period certainly in the N. Hemisphere. 3. Ad hoc asumptions are used to normalize the ice core gas “age” with respect to the real age. This is completely false. Going back to Etheridge et al, their normalization of gas age with respect to ice age was determined analytically. Notice that this normalization is necessary, since there is a significant period where air diffuses through the unpacked snow layer before the latter converts to ice and seals off the trapped gas. Thus the trapped gas is not only younger than the ice within which it is trapped, but pre-freezing diffusion averages out the atmospheric CO2 concentrations over a number of years (which can be very large in extremely deep ice cores). Without going into detail, it is known from previous work that a density of 0.8 gm per cubic cm is sufficient to effectively stop diffusion. This density was found at 72 metres in DE08; 72 metres in DE08-2 and 66 metres in DSS. Dating of the ice (by counting annual layers for several proxies like hydrogen peroxide that dispay clear seasonal cycles) indicates that these depths correspond to 40 years old, 40 years and 68 years. Measuring known diffusion rates indicates that the mean age of CO2 in the air at the sealing depths was 10 years in each case. Thus the air trapped in the ice was 30 years (DE08; DE08-2) or 58 years (DSS) younger than the ice age. 4. Stomatal frequency measures of ancient CO2. This is a fascinating insight into Jaworowski’s methods of misrepresenting the science in this area. Notice that his article goes to great lengths to insinuate problems associated with ice core data. He then says: “A study of stomatal frequency in fossil leaves from Holocene lake deposits in Denmark, showing that 9400 years ago CO2 atmospheric level was 333 ppmv, and 9600 years ago 348 ppmv, falsify the concept of stabilized and low CO2 air concentration until the advent of industrial revolution.” The assumption being, I’m sure you will agree, that stomatal frequency measures of CO2 in ancient times is a well-established, foolproof method. After all he’s stating that the measures of CO2 from stomatal frequency “trump” anything from ice-core data. That turns out to be an awesomely dishonest misrepresentation. Notice by the way, that there is nothing wrong with the science on stomatal frequency as a proxy for CO2 levels. It’s a science in relative infancy, and one that may make a very interesting contribution to the field. But the notion that this provides a valid measure of ancient CO2 levels has yet to be established. That’s clear from looking at the papers published within this specific field itself. The method relates to the way that plants respond to changing CO2 levels. It turns out that when CO2 levels go down they increase the stomatal aperature and increase the number of stomatal cells (and vice versa). These cells contain the pores that allow exchange of gases with the atmosphere. If you can calibrate some stomatal index (SI) with respect to CO2 levels then you might be able to use this as an indirect measure of CO2 levels. The procedure is complicated by the fact that the SI is species specific and assumptions have to be made about moisture levels and other factors that can indpendently affect SI. There seem to be two major groups doing these analyses. That of Visscher (Jaworowski’s stomatal index comments refer to his measures) and Rundgren and Beerling. The latter published a brief overview a few years ago: Fossil leaves: effective biomarkers of ancient CO2 levels? Rundgren M and Beerling D Geochem. [Geophys. Geosys. 4, 1-5 (2003)... in which they showed that their reconstruction of ancient CO2 levels tracked the ice core data very reliably during the entire last 6000 years. There was more variation during the previous years (back to 12,500 years ago) but CO2 levels from their SI measure never went above 290 ppm. They comment on ice-core data and Visscher’s data: “Other early Holocene and Lateglacial records [Wagner et al, 1999; McElain et al. 2002] have reproduced similar CO2 patterns, indicating self-consistency in the approach both between species and sites. Some stomatal-based records however have reconstructed atmospheric CO2 values higher (maximum 40 ppmv) than those obtained in ice core studies [Wagner et al 1999, McElwain et al, 2002; Wagner et al, 2002]. The overestimation in these studies may relate to the use of fossil leaf assemblages containing a mixture of closely-related species. Leaf SI responds to CO2 in a strongly species-specific manner [Royer et al, 2001; even closely-related species capable of hybridising with each other differ in their CO2 responsiveness[Rundgren and Bjork, 2003]. Additionally, studies involving fossil betula leaves may be compromised by developing calibration functions with trees of very restricted genotype diversity [Birks et al, 1999]” Likewise in another paper from the SI community: On the relationship between stomatal characters and atmospheric CO2, CD Reid et al Geophys Res Lett 30, 2003... ...the authors explore the SI index in relation to plants response times: they say: “We examined the phenotypic response of stomatal index (SI), density (SD) and aperature (AP) to rising atmospheric CO2 gradient (200 to 500 micromol per litre atmospheric CO2) at three Free Air CO2 Enrichment (FACE) sites. Along the CO2 gradient SI and SD showed no evidence of a decline to increasing CO2 while AP decreased slightly. ..Without evolutionary changes, SI and SD may not respond to atmospheric CO2 in the field and are unlikely to decrease in a future high [CO2] world.” So what does all this mean? It means that stomatal analysis of ancient fossil plants is a fascinating research area. But it surely also means that taking the results from one or two SI studies and suggesting that these completely negate the observations from ice-core data is a wilful bit of cheating, especially without stating that (i) much of the SI data actually matches the ice-core data and (ii) that even within the SI community it is clear that the issues of methodologies and analyses haven’t yet been normalized such that consistency in data can be achieved. After all if you're going to throw the book at ice-core methods with a vast list of problems (that in fact turn out to be generally overcome in modern studies), one might expect a critical approach to the SI data. SUMMARY: Jaworowski makes a negation of the ice-core data with a blanket dismissal based on every possible technical problem he can think of. He ignores the fact that these factors are considered carefully and overcome in modern coring studies. He misrepresents the methods of data analysis. And he then completely uncritically accepts the results from one or two studies from a field of indirect measures of CO2 levels based on stomatal indices in fossil plants, that is still sufficiently underdeveloped that the proponents themselves haven’t yet agreed on reliable methodologies.
  5. What does past climate change tell us?
    Just for the record, I think here is a contrary view, where solar activity is amplified(it is not increased by a positive feedback). http://www.friendsofscience.org/assets/documents/Shaviv-Ocean%20as%20calorimeter-solar%20forcing.pdf Using the oceans as a calorimeter to quantify the solar radiative forcing Nir J. Shaviv Over the 11-year solar cycle, small changes in the total solar irradiance (TSI) give riseto small variations in the global energy budget. It was suggested, however, that different mechanisms could amplify solar activity variations to give large climatic effects, a possibility which is still a subject of debate. With this in mind, we use the oceans as a calorimeter to measure the radiative forcing variations associated with the solar cycle. This is achieved through the study of three independent records, the net heat flux into the oceans over 5 decades, the sea-level change rate based on tide gauge records over the 20th century, and the sea-surface temperature variations. Each of the records can be used to consistently derive the same oceanic heat flux. We find that the total radiative forcing associated with solar cycles variations is about 5 to 7 times larger than just those associated with the TSI variations, thus implying the necessary existence of an amplification mechanism, although without pointing to which one. Cheers, :)
  6. Comparing CO2 emissions to CO2 levels
    Why might we be skeptical of Beck's weird data with its absolutely massive rapid jumps and falls in CO2? Here's some pretty obvious reasons for skepticism: (i) Beck assures us that the measures were precise (1-3%). But we're really more interested in their ACCURACY with respect to global atmospheric CO2 concentrations. We know that a large proportion of the measurements were made in individual scientists laboratories in cities (Paris, Kew gardens London, Belfast, Clermont Ferrand, Copenhagen, Vienna, Frankfurt, Giessen, Bern, Poona India, Rostock in Denmark, Ames Iowa...etc. etc. etc.). We know that if one goes to a city today and makes CO2 measurements in the air in our city laboratories, large variations in CO2 levels will be recorded, with high values relative to the true atmospheric concentrations. Just as in the 19th and early 20th century, we’re surrounded in cities by CO2 sources (pretty much all transport and heat/cooling generation). See for example point (ii) below. Competent scientists understand the essential difference between PRECISION and ACCURACY. A local CO2 measure may be beautifully precise but wildly inaccurate with respect to the global atmospheric CO2 value. That's where Becks "analysis" is likely to fool the unskeptical. (ii) We can look at this problem of accuracy in more detail by focusing on the individual series of measurements highlighted by Beck. For example, Beck highlights W. Kreutz’s series of very high CO2 measures in 1939/40. These measurements were made just S of the city of Giessen not far from the railway station. Beck fails to point out that Kreutz’s values differ by an astonishing 40 ppm between morning and afternoon (in other words measured atmospheric CO2 values are 40 ppm higher in the afternoons compared to the mornings), that atmospheric CO2 is much lower on windy days compared to windless days and so on. This is all outlined in Kreutz’s paper on the subject (translation available here: http://www.biokurs.de/treibhaus/literatur/kreutz/Kreutz_english.pdf Clearly atmospheric CO2 measurements in, or near, urban centres give massively high CO2 values however precisely they are measured, the CO2 levels will rise dramatically in the afternoons when everyone and their machines are active, and on windless days when generated CO2 isn’t dispersed, measured CO2 levels will be higher still. That’s all pretty obvious. A skeptic might be expected to notice these rather obvious facts…. It's fascinating that Kreutz identified and postulated that some of the high values and extreme variations in atmospheric CO2 levels in his measurements were due to soil sources and industrial sources...sadly, and rather typically, the data of the honest and competent Kreutz has been usurped to support a creepy agenda... (iii) It takes an effort to make truly accurate and unperturbed atmospheric CO2 measurements. Some early practitioners made this effort. Jules Reiset, for example, in the late 19th century, developed a methodology for CO2 measurements taken on the windy Atlantic coast, far from urban centres, and determined values rather similar to those measured in contemporaneous ice cores (around 190-200 ppm in the 1890’s). We can be rather more confident in the ACCURACY of Reiset’s measurements since he (unlike pretty much all other measurers of CO2 in the 19th and early 20th century) identified the clear signature of seasonal variation due to plant growth and decay dominated by the N. hemisphere flora. (iv) We have been observing atmospheric CO2 levels with extraordinary precision and accuracy since the late 1950’s from the Mauna Loa observatory, as well as dozens of other locations around the world. Atmospheric CO2 levels simply do not undergo massive jumps of up to 100 ppm over a few years. It beggers belief that CO2 sources could release and reabsorb extraordinarily massive amounts of CO2 (see (v) just below) during a period when we weren’t actually monitoring CO2 levels very well, and yet just when we started to monitor levels with considerable ACCURACY and PRECISION, atmospheric levels immediately stopped jumping around wildly. A skeptic would be inclined to doubt the accuracy of early measurements from urban centres. (v) According to Beck, atmospheric CO2 rose and fell with massive jumps/falls of around 100 ppm or more during the early and mid 19th century, and the 1930’s-40s’. Since the pre-industrial level of atmospheric CO2 (around 180 ppm) is rather similar to the entire repository of CO2 in terrestrial plantlife, the assumption is that these 100 ppm jumps/falls over a few years are associated with the rapid loss and regrowth of around half the entire plant biomass on earth? Did we really lose terrestrial plant matter equivalent to the entire Amazon and African rainforests and much of Asia during a few short years, and have these regrow again in a few years afterwards? No. We know this can’t have happened during the 1930’s and 40’s since we were monitoring the terrestrial biosphere already during these years. (vi) we have rather abundant ice core measures of atmospheric CO2. Since these measures of atmospheric CO2 locked within ice are in regions far from centres of CO2 sources (urban/plant growth) they are rather reliable measures of unperturbed and well-mixed atmospheric CO2. These show rather constant levels of atmospheric CO2 near 177 (+/- around 6 ppm) during the period from 1000 AD to the mid 19th century, and then slow gradual rises that merge in the late 1950’s with the directly measured Manua Loa and other modern CO2 measures. One can certainly argue that the ice core measures are averaged, since deposited snow in ice sheets doesn’t compact and trap ice for several years after deposition, such that there is exchange with the atmosphere for some time until the atmospheric sample becomes sealed within bubbles in solid ice. However one can’t really postulate massive rise of atmospheric CO2 apparently to value as high as 470 ppm during the late 1930’s and 1940’s, without some rising of ice core CO2 levels that match this time period. Even if the ice core CO2 values are averaged over several years, high CO2 values would have to appear for this period in the ice cores. They don’t. [*] [*] I wrote this last year for another context but it's appropriate in relation to Alexandre's question
  7. What does past climate change tell us?
    "Ironically, when skeptics cite past climate change, they're in fact invoking evidence for climate sensitivity and net positive feedback. Higher climate sensitivity means a larger climate response to CO2 forcing." In fact, "it's the Sun" skeptics tend to support the idea of a positive climate feedback because it's required to boost the impact of relatively weak solar forcing. Skeptics of the "Hockey Stick", claiming larger variance than all multi-proxy studies indicate, need an even stronger positive feedback to explain such variances with natural factors. Here is an example from Willie Soon, who believes reduced solar output will result in substantial global cooling (which hasn't happened yet despite a decade of solar activity trending down): "1. A reduced energy input from a dimmer sun will result in less heating of the oceans' surface, which would lead to less evaporation from the ocean surface. The result of this would be a decrease in water vapor, which is by far the earth's major greenhouse gas." Positive water vapor feedback - check "2. Less water vapor would result in a decrease in high cirrus clouds, which trap more heat than they reflect." Positive cloud feedback - check "3. A reduced energy input from the sun would equal less energy to bring water vapor high into the atmosphere, so more would end up collecting a few kilometers from the surface, resulting in more low clouds. Low clouds are much more effective at reflecting sunlight, which would produce a net cooling effect." Positive cloud feedback - check http://global-warming.accuweather.com/2009/04/plausible_scenarios_of_a_dimme.html Willie Soon is essentially supporting the idea of not only positive water vapor feedback but positive cloud feedback as well, with negative forcing leading to more reflective low clouds and less heat-trapping high clouds. One has to wonder, then, what Soon's complaint with the scientific consensus is? It seems then that he must then be disputing the direct forcing component of CO2, rather than the feedback that other skeptics generally dispute. Soon and Lindzen should debate the issue, perhaps at the "contrarian-only" Heartland Institute political conference. But that would violate their doctrine "speak no evil of other contrarians". Still, it would be nice to see two contrarians take turns calling each other "alarmists".
  8. What does past climate change tell us?
    The statement you have a problem with is really a no-brainer Mizimi. If the climate didn’t respond historically to changes in forcings it would have a very low sensitivity…..if it changed a lot it would have a high sensitivity. There’s nothing controversial about that. Of course that doesn’t mean that the climate sensitivity is “a fixed multiplier”. It likely varies a bit according to the position of the continents, ocean currents, whether or not the world has significant ice sheets etc. But we expect that the essential factors involving water vapour feedbacks to be rather constant and so don’t expect the climate sensitivity to vary that much between different epochs. The fact that climate sensitivity determined by analysis of temperature changrs involved in ice age cycles of the last several 100s of 1000’s of years, and that determined from analyzing the relationship between paleoCO2 and paleotemp proxies during the last several hundred millions of years, yields a similar climate sensitivity (around 3 oC of temperature rise per doubling of atmospheric CO2), tends towards that conclusion. In fact the long term climate sensitivity in our present world with lots of polar ice is likely somewhat larger (large albedo amplification) than during ice-free periods in the past. Past climate surely “shows” more warmer than colder phases. In any case your statement is a logical non sequitur….and what is a climate sensitivity “historically less than unity”??? The reason that the Earth had cold periods in the past is because the climate has a moderate to high sensitivity to changes in forcings. For example, the extended glacial periods of the Carboniferous were due to the sensitivity of the climate system to drops in atmospheric CO2. Climate sensitivity works in both the warming and cooling directions! A very significant reason why enhanced CO2 levels are particularly problematic now (apart from the fact that they’re racing upwards at a rapid rate), is that solar constant is much greater now than in the past (the sun shines around 4% more strongly now than 400 million years ago). So the absolute surface temperature with CO2 levels now are considerably greater than the surface temperature at the same CO2 levels then.
  9. What does past climate change tell us?
    "The greater climate has changed in the past, the greater the climate sensitivity." I have a problem with this statement. If T is a function of two variables, then a change in either variable causes T to change. Thus T is affected by changes in solar radiation ( from whatever effect) and by the way the planet system as a whole responds to/ influences such changes. In other words, climate sensitivity is never a fixed multiplier, but varies according to various physical, chemical and biological responses. Past climate change shows more colder than warmer phases, indicating climate sensitivity is historically less than unity; so should we not accept this as a reason to maintain ( or even enhance) CO2 levels?
  10. How we know global warming is still happening
    shawnhet, Temperatures will gradually rise in general at a rate of approximately 0.2C/decade, although that growth rate will not be linear just as it has never before been. This expectation DOES NOT include the effects of unleashing a positive feedback with carbon in the form of melting permafrost and methane clathrates which would exacerbate the situation considerably. So we can expect that by the time CO2 has doubled from 280ppm to 560ppm in the atmosphere, world average temperature will have risen by 2C-4.5C over pre-industrial times with the threat of even greater warming if frozen carbon is unleashed.
  11. How do we know CO2 is causing warming?
    I like your explanation but this study did not look at the cooling and weigh the warming and cooling effect of carbon dioxide against one another. Check this http://www.globalwarmingart.com/images/7/7c/Atmospheric_Transmission.png Note that some 30% of the sun's radiation is "absorbed" in the atmosphere, by ozone, oxygen, water and carbon dioxide. Most scientists think that this difference is what heats the atmosphere. I will admit that the aborption of photons may cause some heating but there is a limit to the number of photons that can be absorbed by a substance. The radiation is then re-emitted. I believe the larger amount of this 30% is re-emitted (the same principle as the greenhouse effect) and a large portin is reflected out from the atmosphere back into space. Did anybody of you ever thought of measuring the cooling effect of carbon dioxide? I want to know the nett effect.
  12. How we know global warming is still happening
    WeatherRusty:"If low cloud amount does increase due to a warmer more moist atmosphere so will the greenhouse effect of water vapor be increased. The increased water vapor must be in place first, so at best increased low cloudiness can reduce warming not negate it." The point is how much warming will we end up with? If cloud feedback canceled out other forms of feedback we might end up with only ~0.5C of anthropogenic warming over the next century, OTOH, if cloud feedback is strongly positive, then we might end up with as much as 2C in the next century. Cheers, :)
  13. How we know global warming is still happening
    Even if cloud amount is sensitive to other factors other than temperature variation, what is the point? What matters is if cloud amount is sensitive to a warming climate or changes in temperature since that is the factor humans are altering. Are there studies linking long term changes in cloud amount, both high and low cloudiness, to the warming trend of the past century? If GCR's impact on low cloud amount, we can do nothing about it. If we stick to the physics we know, there is no reason to expect a change in average relative humidity and there are already more than enough nucleation particles in the atmosphere upon which to condense water vapor to form clouds. If low cloud amount does increase due to a warmer more moist atmosphere so will the greenhouse effect of water vapor be increased. The increased water vapor must be in place first, so at best increased low cloudiness can reduce warming not negate it.
  14. It hasn't warmed since 1998
    FYI: the Murphy 2009 link right under the total-heat graph isn't working . . .
  15. It hasn't warmed since 1998
    I suggest that the fill-in color areas under the lines in the total heat-content graph be removed. As experts in the graphic display of quantitative information often point out, such filling-in encourages the reader to compare the magnitudes of the areas under the curves rather than the actual graphed quantities -- giving an impression of a difference between the two quantities (in this case) that is roughly proportional to the square of the actual difference. In other words, the fill-in colors amount to inadvertent exaggeration (technically, they encourage ambiguity about whether one is comparing the curves or their integrals). Why give denialist critics even the slightest toe-hold? Simplify the graph. Trust people to get it without the big splashes of color.
  16. It's cooling
    Thank you for a website that provides information without a political agenda. I would like to understand the global warming debate without feeling like I am being manipulated by someone with a political agenda and most web-sites seem to promote an agenda for one side or the other. Thanks.
  17. Empirical evidence that humans are causing global warming
    Robbo, I'm afraid I've let you waste my time (which I assume is your goal -- otherwise, why not link directly to the page you reference instead of to home pages?). You require monthly data to show that multidecadal cycles are responsible for long term trends? You deem my focus on the higher Arctic temperatures after 2000 (in response to your claim that post-1998 should be cooling) as being cherry picking, but you can go back and pick a couple of (less) warm years around 1940 and pretend those provide the proper context for our discussion of your claim? You fib and misrepresent things but say that you are morally constrained from betting? (Good one!) We haven't discussed odds, yet you're already to call it a sucker bet? (Goodbye.)
  18. Robbo the Yobbo at 09:44 AM on 20 October 2009
    Empirical evidence that humans are causing global warming
    Steve, The conclusions depend a great deal on whether you use monthly or annual averages. I always use monthly data because the annual data averages out the interesting peaks. Compare the 2 at Professor Ole Humlum's page. http://www.climate4you.com/ - polar temperature page. So really you are absolutely right about Arctic temperature - but everything needs to be seen in the appropriate context. The difference is a small example of claim and counter claim in a highly polarised debate - or non debate depending on your perspective. Are the differences scientifically meaningful? The answer to that is no. ‘Over most of the past century, the Arctic Oscillation alternated between its positive and negative phases. Starting in the 1970s, however, the oscillation has tended to stay in the positive phase, causing lower than normal arctic air pressure and higher than normal temperatures in much of the United States and northern Eurasia.’ http://nsidc.org/arcticmet/patterns/arctic_oscillation.html Yes I know I said that eyeballing was OK – but you need more context. These are very complex issues - you can’t do a quick Google and cheery pick items that seem to support some sort point or other. But look carefully at your Arctic temperature graph – the peak in the 1940’s is the result of multidecadal modulation of temperature in the Arctic. I am morally constrained from gambling with you on this – I think it is a sucker bet. Cheers Robert
  19. Empirical evidence that humans are causing global warming
    amplificate=amplify :P
  20. Empirical evidence that humans are causing global warming
    RSVP, "Ilustrative example???? Magnetism???? There is no point of any significance." What you do not understand or is poorly explained does not mean it has no significance. First, the electricity and magnetism analogy was not about global warming itself; read the original post on real climate to better understand. Second, i explained why it was an illustrative example. The shift is in 1970 but the fit in the figure starts in 1950; this was clearly done intentionally to amplificate the divergence between the fit and the data in the last decade. Again, look at the post on realclimate and try a fit yourself. The RC analogy is a good one. Although "it does not necessarily mean that the overall heat of the Earth has to increase", this is exactly what is being obeserved. If for example less heat is irradiated to space at night due to CO2 (increase of the RC constant), it certainly will warm. I'll say it explicitly one more time. Nowhere in the AGW theory it is excluded the very existence of fluctuation (more or less or not at all periodic). But they cancel out in the long run leaving a clear, detectable, measurable etc. upward trend.
  21. Empirical evidence that humans are causing global warming
    Riccardo, Since you mentioned electricity, I cant help comparing the idea of greenhouse gas heat capture to a circuit analog. A very simple RC circuit with a pulsed voltage source. That is, a resistor (representing CO2) in parallel with a capacitor (Earth). The voltage, a rounded square wave whose voltage changes on each pulse. The voltage would represent the heat left on the Earth in course of a day. Pulse off means night. Anyway, the output voltage would tend to zero during the off part of the pulse, but if R is too big, the voltage would not reach zero before the next pulse (sunrise). If you simulated Winter as many low voltage pulses, and Summer as many pulses with a higher voltage, you would see periods in which the output voltage would rise as heat is supposedly accumulating on the Earth. The point is to illustrate that just because the extra CO2 heat trapping vector has been added to "the GW mix", it does not necessarily mean that the overall heat of the Earth has to increase. Referring to the circuit model, the condition for this to occur requires that the voltage never gets to zero during the entire year (365 pulses later). In this analog, the values of R and C are critical. In the same way, the concentration of CO2 would also be critical to affect global warming, but up till now the only thing I have heard is that "more" is simply enough to raise the Earths temperature because it is causing an imbalance, when instead there might actually be a real critical value to trigger the real thing.
  22. Empirical evidence that humans are causing global warming
    Robbo (or Robert, if you prefer), re: #37. I note you've taken another step back from the Arctic cooling to a greater extent than the rest of the planet to, now, "My exact position is no warming for 20-30 years from 1998". Uhuh. Why not be more exact right away? I'm going to need you to be more exact if we're to find a bet, but for the purposes of discussion... See here: http://www.arctic.noaa.gov/reportcard/atmosphere.html Sorry for the low resolution Figure A1, but it looks like all years to 2007 (except maybe one) from 1998 have higher Arctic surface air temperatures than 1998. Hmmm. Maybe you define "Arctic" differently, or maybe you define "warming" differently than I do. Perhaps you think that the 10 years since 1998 are just noise. (But if so, then why pick 1998 rather than an average of a range of years?). Or maybe you'd prefer to look at sea ice extent instead of surface air temperatures -- oops, that doesn't support your assertion of cooling (er, not warming) from 1998, either. Well, you can see why your claim doesn't make much sense to me. But if you think that Arctic air temperatures or sea ice will show no evidence of warming relative to 1998, then please put up some money. My wife wants to renovate our apartment. Oh, also note Figure A5 in the above url and read the description: the early 1990s had strongly positive AO. This is incongruent with your claim that it was positive in the late 1970s and peaked in the late 1990s.
  23. CO2 effect is saturated
    GFW, as I understand it, Figure 1 shows outgoing radiation. Therefore, if the Earth has warmed, more radiation remains inside, i.e., less radiation goes out. Therefore, the net outgoing radiation must be below zero (less radiation going out, i.e. radiation that remains inside the atmosphere, in a transient radiative imbalance, until the earth warms enough as to "expel" again the same energy that comes in, going back to equilibrium (at zero) but with a higher temperature given that the greenhouse blanket is now thicker). In this graphic the different wavelengths are differenciated, so we can see which exact wavelengths are being trapped inside (those that are below zero), i.e. the exact wavelengths that are responsible for the warming inside. The rest of wavelengths escape to space the same as before (the components for those wavelengths have not changed, so the same energy goes in and out), and that's why they are at zero level. rlasker3, I think you are perfectly right. If the CO2 saturated, we woudn't see that runaway greenhouse effect in Venus.
  24. Robbo the Yobbo at 06:32 AM on 20 October 2009
    Empirical evidence that humans are causing global warming
    The 0.1 C/decade trend fits any period since the 1800's other than 1976 to 1998. Thompson et al reach the same conclusion on the underlying trend ~0.1 K/decade from 1950. Ilustrative example???? Magnetism???? There is no point of any significance.
  25. Empirical evidence that humans are causing global warming
    RSVP, first of all a quote from Swanson post in realclimate: "Electricity and magnetism are those forces of nature by which people who know nothing about electricity and magnetism can explain everything. Substitute the words “modes of natural climate variability” for “electricity and magnetism,” and well…, hopefully the point is made." That is to say that there are several patterns of roughly decadal climate variability of which we know very little. Their study is in its infancy and very interesting. But one thing can be said, in the long run they average out. Having said this, the shift apparently occured in the '70. If you fit a straight line from 1970 to 1997 you can easily see it nicely fits the last decade too. What Swanson shows is just an illustrative example. As for Thompson paper, they pull out the effect of known varibility (nothing spurious) and see what is left. And yes, as all the scientists do they were looking for something, the temperature trend cleaned up of the known variability. But the good news is that did it using no GCM, filtering, strange smoothing techniques, etc.
  26. Empirical evidence that humans are causing global warming
    [ Response: Funny you should mention that, the next post is on that very subject. ] I suppose that the next logical step before discussing feedbacks would be where the approx. 1 C of direct forcing from a doubling of CO2 comes from, although this tends to have much less dispute among already small contrarian circles.
  27. Empirical evidence that humans are causing global warming
    Riccardo I downloaded and perused the pdf from link... I have to give you credit for providing this reference as matching my earlier remarks. If I understand the report correctly, they are filtering spurious data such as that produced by volcanic eruptions and coming up with temperature profiles of the Earth or regions of the Earth and somehow dissociating human induced climate change. I suppose if you are looking for something you will find it, and if not, keep mounting the voodoo until you do.
  28. There's no empirical evidence
    Loads of thanks, and good new article! We have a rather good grasp of the current climate system. The only thing that has change enough to warm the planet is GHG (mainly CO2) and all the observations are consistent with that. Some people still insist that there might be some misterious unknown thing doing it (and some other unknown thing cancelling out the CO2 warming effect) even though there isn't any evedence at all. It seems incredibly twisted to me. It is false that there has been no warming during the last ten years. Why do you cherrypick CRU instead of GISS, Rick? Do you just choose the sources that fit your bias?: http://www.realclimate.org/index.php/archives/2009/10/a-warming-pause/ What happens if you begin one year earlier or later? A remarkable change in your trend? That's why your 10-year trend is not significant, and that's why 30-year trends are significant, because they don't change much if you add or remove some years: http://moregrumbinescience.blogspot.com/2009/01/results-on-deciding-trends.html Are short-term cooling trends unusual under the current global warming? No: http://tamino.wordpress.com/2009/06/26/breaking-records/ http://www.agu.org/pubs/crossref/2009/2009GL037810.shtml If you want to disprove global warming just on a statistical basis you will need more than a statistically insignificant short-term cooling trend.
  29. Robbo the Yobbo at 21:37 PM on 19 October 2009
    Empirical evidence that humans are causing global warming
    Riccardo, The idea of climate shifts is not speculative at all. What Swanson and Tsonis did was use a (undefined) numerical scheme involving long term records of global ocean and atmospheric indices to identify historical climate shifts. They did this instead of eyeballing them in from the graphs. These ocean/climate state shifts occurred in the mid 1940's, the mid 1970's and around the turn of the millennium. Other people have for decades been wondering what happened in 1976 to 1977 in the Pacific Ocean - the ‘Great Pacific Climate Shift' – and whether this was natural or not. That it seems to have turned around again strongly suggests a natural component. There are also decadal changes at the poles and in the Atlantic. I don't think Swanson and Tsonis add much to the science - but they are useful in providing another perspective - and one that even passes the realclimate test. I don't think those guys have more than a passing acquaintance with empirical oceanographic and hydrological science. As a proposed causal mechanism - Swanson and Tsonis posit a synchronous chaotic dynamic ocean system – i.e the states in the global ocean synchronise, have a hissy fit and shift into an alternate state. A mechanistic interpretation. I simply don’t think it’s so but is externally forced by radiative changes associated with variation in Earth albedo. What Swanson and Tsonis 'hypothesised' was: 1. that the trend between 1979 to 1997 was the residual warming trend when climate shifts are excluded - if you look at the trend line at the Swanson real climate blog - it is about 0.1 degrees C/decade; 2. that the current cool mode ocean/climate state could persist for 2 to 3 decades – as they have in the past. Swanson and realclimate characterise this as ‘warming interrupted’ – I think this depends on whether the ACRIM-PMOD or ACRIM-TSI trend for recent total solar irradiance is the more correct result. Regardless, the residual surface warming trend identified (0.1 degree C/decade) for recent warming is about correct - regardless of wehether this results from internal heat transfer between the ocean and atmosphere or is externally forced. If internal - the oceans should continue to warm in the current cool SST mode and the atmosphere cool. If external - the oceans should cool as well. As I say - I think the balance of probability favours external forcing. I have never intended to prove that carbon dioxide is not a greenhouse gas. The idea is that the climate states alternately augment and mask AGW as you suggest. But you cannot look at most recent augmented mode and conclude reasonably that all of the warming in the relevant period is AGW. The climate shift in the Pacific results not only in a cool and warm mode PDO’s – but in Pacific wide changes involving modulation of the frequency and intensity of ENSO events. A cool mode, such as we are now experiencing, has fewer and less intense EL Niño and more frequent and intense La Niña – statistically and hydrologically speaking. The Australian hydrological connection is best characterised in work by Stewart Franks but there are also global hydrological teleconnections of course. The idea of Ocean/climate state shifts has developed in the past decade – but they are based on long term empirical research and provide a reasonable working hypothesis for the lack of surface warming in the past decade. Cheers Robert
  30. It's a 1500 year cycle
    That is the point. As the paper shows, increased greenhouse gases did not contribute significantly to global warming. The methodology and links to the source data (all measured) are given. Do the exercise yourself and discover that many (not all) Climate Scientists have made an egregeous mistake and a lot of people have been misled.
  31. Empirical evidence that humans are causing global warming
    Robbo, the concept of climate shift by itself is speculative. You should note the words used by Swanson, "We hypothesize" and "If this hypothesis". So you should not take climate shifts as given. But even if it will prove to be true, the overshoot is identified in 1998. Before that the trend was roughly 0.2 °C/decade while the full trend up to 2008 is 0.15 °C/decade. Is this you're claiming? And is this that eventually disprove agw or the effect of CO2 forcing? And what about this shifts that produce an overall upward trend and not simply ups and downs averaging to zero in the long run? What is responsible for this? Could it be that this shifts just modulates the average upward trend, as Swanson indeed suggested?
  32. Robbo the Yobbo at 17:54 PM on 19 October 2009
    Empirical evidence that humans are causing global warming
    G'day Steve, My exact position is no warming for 20 to 30 years from 1998. There is no substantive difference between the Swanson quote above and this statement. Indeed it is consistent as well with the Keenlyside et al study in which Latif participated. Not sure what the problem is with the concept of shifts in ocean/climate states – all I get responses with nil substance to the effect that – nah – it just ain’t so. Yet these shifts are evident in the 100 year plus records of surface and ocean temperature and in hydrological regimes. Temperature variation in the Arctic shows an exaggerated response to variation in global temperature – strong decadal variation is apparent in any of the surface temperature records – and I linked to the IARC at Fairbanks Alaska for support. This is also interesting – there were shifts in temperature in Alaska of 3.1 degrees centigrade as a result of the 1976 climate shift. Hartmann, B., and Wendler, G. 2005: The Significance of the 1976 Pacific Climate Shift in the Climatology of Alaska. J. Climate, 18, 4824–4839. ‘The influence of the shift in Pacific Ocean variability on temperature is more pronounced in the continental regions of Alaska (south-central, interior, and west) than in the maritime regions (southwest and southeast). The Arctic, while it showed some response, is most likely governed more by Arctic variation (i.e., the Arctic Oscillation), and the interplay of Pacific and Arctic circulation variation and its effect upon Alaska is a possible subject for further study.’ The Arctic Oscillation is another example of multidecadal variability – albeit with a familiar periodicity – positive since the mid 1970’s and peaking in the late 1990’s. I am quite willing to revise my views if 100 years of ocean and hydrological science is suddenly reversed. But see no reason to do so while the world is currently not warming. Cheers Robert
  33. It's the sun
    Although it is somewhat speculation, lead may have offset warming from 1940 to 1980 and therefore the links between global temperature and sun activity could be weaker then expected http://www.newscientist.com/article/dn16976-did-lead-cause-global-cooling.html Sorry i cant find the actual paper this has been published in. I'm posting this for debate not because i sincerely believe there is a direct correlation here
    Response: The paper is Inadvertent climate modification due to anthropogenic lead (Cziczo 2009). Thanks for the link - an interesting paper. I wonder if it'll have any impact on our understanding of mid-century cooling.
  34. Empirical evidence that humans are causing global warming
    Robbo: "The Arctic should, like the rest of the planet but more strongly, cool over the next couple of decades." It's fun to watch you on the various threads claim something and then get caught by Chris in a fib and then have to step backward. But don't step back on your claim that I've quoted above. I want to bet you on it, and I'll give you good odds.
  35. It's a 1500 year cycle
    The evidence that average global temperatures measured for the entire 20th century and to the present actually are a natural cycle with no influence whatsoever from carbon dioxide is shown at http://climaterealists.com/index.php?tid=145&linkbox=true. There is no Anthropogenic Global Warming (AGW) (and therefore no ACC) from added atmospheric carbon dioxide. It is a mistake to believe that there is.
    Response: The paper (written by Dan Pangburn) you link to (here's a direct link to the PDF) proposes that just the effects of the Pacific Decadal Oscillation (PDO) and solar activity are sufficient to explain temperature trends over the last 130 years. This argument is fundamentally flawed. Over the past 50 years, the planet has been in positive energy imbalance. Globally, oceans have been accumulating heat.

    PDO is an ocean cycle that causes internal variability, where heat is exchanged between the ocean and atmosphere. The PDO cannot explain the strong energy imbalance. Changes in solar activity do affect the planet's energy imbalance but over the last 50 years, the sun has showed a slight cooling trend.

    Lastly, we have experimental observations confirming an enhanced greenhouse effect due to CO2 and CH4. Pangburn's explanation fails to explain what's happened to all the warming caused by increased greenhouse gases.
  36. Empirical evidence that humans are causing global warming
    Respond to respond in Post #31: I am not conceding anything, I am merely reacting to the, for me, obvious fact that the OP are using positive confirmation to led something in evidence and furthermore has failed to show that hypothesis of the form "IF humans release CO2 THEN there exists no global warming" are false. In this I assume the OP is aware of that condition not only must be sufficient but also necessary.
  37. Robbo the Yobbo at 11:16 AM on 19 October 2009
    Empirical evidence that humans are causing global warming
    Let's make this even clearer for Chris and Riccardo - The climate shifts occured in 1976 to 1977 and 1999 to 2001. The 1998 El Nino was said to be a big climate 'overshoot which is radiatively dissipating.' It is not part of the greenhouse gas signal - but an aspect of what is widely referred to as climate shifts. The causes of climate shifts are hugely speculative - so take any statement with a pinch of salt - but they appear in all sorts of climate records. The greenhouse signal is in the temperature record from 1977 to 1997. This is 1/2 of the total warming between 1976 and 1998. There are many other factors in there as well - black carbon, methane, solar irradiation, tropospheric ozone warming etc. Insistence that AGW is 0.2 degree C/decade is unsustainable.
  38. Robbo the Yobbo at 08:01 AM on 19 October 2009
    Empirical evidence that humans are causing global warming
    Chris Schuckmann calculated heat content to 2000m. Heat content at lower levels might become important at some time. However, there is no possibility of comparison with other methodologies. Everyone else is finding no to minimal warming to 700m - although even then they are not consistent with each other. Should the planet be warming - Here is Kyle Swanson quoted verbatim from at real climate - http://www.realclimate.org/index.php/archives/2009/07/warminginterrupted-much-ado-about-natural-variability/ 'What’s our perspective on how the climate will behave in the near future? The HadCRUT3 global mean temperature to the right shows the post-1980 warming, along with the “plateau” in global mean temperature post-1998. Also shown is a linear trend using temperatures over the period 1979-1997 (no cherry picking here; pick any trend that doesn’t include the period 1998-2008). We hypothesize that the established pre-1998 trend is the true forced warming signal, and that the climate system effectively overshot this signal in response to the 1997/98 El Niño. This overshoot is in the process of radiatively dissipating, and the climate will return to its earlier defined, greenhouse gas-forced warming signal. If this hypothesis is correct, the era of consistent record-breaking global mean temperatures will not resume until roughly 2020.' Unless Swanson has changed his mind in the past 6 months - the underlying forced rate of warming is less than half of the total 1976 to 1998 warming. Take climate shifts out of the record and warming due to greehouse gases is less than 1/2 of warming between 1976 and 1998. Radiative imbalance is not constant nor linear. I have referred you to Project Earthshine before - again - there is a decrease in shortwave radiation between 1999 and 2008 of 2W/m2. There is no magic but the heat budget of the planet changes on decadal timescales. Latiff said that the difficult questions about multidecadal variability should be asked. The rest of the video confuses interannual with multidecadal variation. Typical clutching at straws.
  39. Is Antarctic ice melting or growing?
    Update: "the mass loss increased from 104 Gt/yr in 2002–2006 to 246 Gt/yr in 2006–2009, i.e., an acceleration of −26 ± 14 Gt/yr2 in 2002–2009" http://www.agu.org/pubs/crossref/2009/2009GL040222.shtml PDF: http://thingsbreak.files.wordpress.com/2009/10/increasing-rates-of-ice-mass-loss-from-the-greenland-and-antarctic-ice-sheets-revealed-by-grace.pdf
  40. There's no empirical evidence
    I think that this post was different in the past and included a list with some fingerprint evidence (rise of the tropopause, expansion of the hadley cell...) with links... Where can I find this?
    Response: Yes, sorry about removing that information. As I added in more info to this page, I simplified the presentation lest it get too long and unwieldy. So I've temporarily removed all the other bits and pieces until I get organised and restructure it to a subpage somewhere. In the meantime, here is other evidence of warming: Note - as you say, some of the evidence listed above are unique to CO2 warming - the carbon "fingerprint".
  41. How we know global warming is still happening
    I don't think it is accurate to say I am the only one who thinks it unlikely that all changes in cloudiness in recent years are a product of feedback from teperature changes. You can try a Google search of Earthshine and albedo if you like. Cheers, :)
  42. Empirical evidence that humans are causing global warming
    Re #24 Poor old Robbo….you keep on saying things that are simply untrue, and attempt to “recruit” science that simply doesn’t support your notions. Keenlyside and Latif, who you want to think support your notion of “cooling influence in the atmosphere and oceans that lasts for 20 to 30 years”, in fact predict a particularly large warming of around 0.5 oC in the period 2010-2030; see Figure 4 of: N. S. Keenlyside, M. Latif, J. Jungclaus, L. Kornblueh & E. Roeckner (2008) Advancing decadal-scale climate prediction in the North Atlantic sector Nature 453, 84-88 So you can’t use these scientists in support of a notion to which they have recently published an entirely contrary projection. Why keep restating what you know is a falsehood Robbo? Likewise your notion that Tsonis and Swanson consider that “at least half of recent warming between 1976 and 1998 was the result of the most recent warm ocean mode”, is another untruth, since we can inspect their analysis of the contribution of ocean circulation effects on surface temperature variability, and find that they consider that ocean circulation effects have made only a small contribution to late 20th century warming (likely no more than around 0.1 oC; i.e. nowhere near half), and essentially zero contribution to the overall warming of the 20th century. That’s not really surprising since the ocean circulation cannot “magic up” heat from nowhere..they merely redistribute the heat in the oceans: see Figure 3 of: Swanson KL, Sugihara G, Tsonis AA (2009) Long-term natural variability and 20th century climate change Proc. Natl. Acad. Sci. USA 106, 16120-16123 Your ad hominem at Schuckmann is ignorant; it's based on a misunderstanding of heat uptake, ocean currents and surface temperature measures. One can have relatively constant heat uptake into the ocean under a radiative imbalance, while having cyclic or stochastic ocean circulation effects on surface temperatures. Schuckmann et al is completely compatible with independent measures of radiative imbalance and other consequences in the natural world. Incidentally, for those like Robbo who might consider that “claiming that Latiff (sic) was misrepresented …is very, very silly”, the following video in which we can hear Dr. Latif’s words as he speaks them indicates rather categorically that pointing out the simple fact that he was (rather amusingly if it wasn’t a serious subject) misrepresented, isn’t “silly” at all: http://www.youtube.com/watch?v=khikoh3sJg8
  43. Empirical evidence that humans are causing global warming
    To the OP: My remark was to draw attention to the fact that it does not follow from the premises, "CO2 is greenhouse gas", etc that "human release CO2 is the causes of temperature changes". The "conclusion" is not a conclusion but a separate statement that need a separate chain of evidence. Those evidence are not presented in the article, nor in the additional references given.
    Response: So you will concede that CO2 causes an enhanced greenhouse effect and the planet is accumulating heat? But not that an accumulation of heat causes global temperature to rise?
  44. Empirical evidence that humans are causing global warming
    RSVP, i don't know exactly what you mean by "unstable", but i'd probably agree. It's the timescale and the causes that are different. Back to the issue of the analisys of the temperature trend you (and other people too) might be interested in this article due to appear in J. Clim.
  45. Empirical evidence that humans are causing global warming
    Riccardo, I dont know what "conclusions" you are referring to, but now that you mention it, the historical data appears to indicate that the Earth's climate is pretty unstable with or without mankind's "help". (Sorry for not being able to point to url for substantiating that thought.)
  46. Empirical evidence that humans are causing global warming
    RSVP, you should invest much more than 15 seconds in reading after an easy google search. Especially when history is concerned you can't just pass by and come so superficially to unfounded conclusions; read carefully. A couple of quotes from your second link: "With just one more degree Celsius of warming, it'll be hotter than ever in the last million years. In other words, we may be witnessing the end of the whole cycle of ice ages!" We're almost there and in mere century or so. "Of course, 1 Celsius ain't much compared to the 15°-20° Celsius cooling throughout the Cenozoic - but it's happening fast, and and it's not over yet! With all the changes the Earth has experienced over its history, one might think one more change is no big deal. In the long run, yes. But the future of humanity depends crucially on what happens in the "short run": the next millennium or two. If we didn't mess around with the climate, our Earth's climate might remain stable for another thousand years or more. As it is, we're bringing on more sudden changes." And this is the conclusion after 65 milions years of history of earth climate. Finally, you question (Where do you draw the line in terms what is acceptable and inacceptable?) is a very important one for the choices that are to be made. To answer, though, one needs to accept the science in first place. After that it's more a political than scientific issue, a tough one indeed. You have to decide the level of damage people have to suffer and who is going to pay. I would not to be in Copenhagen in December ... :D
  47. Empirical evidence that humans are causing global warming
    The problem I see with this article is that it uses the argument "guilt by association". The conclusion that human release of CO2 causes global warming does not follow from the factual observation that atmospheric CO2 levels and global temperature changes are corresponding in time. The second problem I see is that the OP uses positive confirmation to prove the thesis to be correct. However, Popper has taught use that we can only use falsification if we want to investigate something scientifically, and that we only can assign a certain confidence level to our knowledge, not a definite truth. Therefore, to strengthen the confidence in the thesis one should instead focus on falsifying other explanations not confirming a particular thesis. What gives us confidence in CO2 as being the agent for increase in global temperature? The foundation for claiming CO2 to be the agent is based on computer simulated climate models, but there are no definite empirical evidence or experiment so far that has singles out CO2 as the major agent. On the contrary there are evidence from observational data to support the interpretation that CO2 can not be a causal agent. What we know so far from empirical evidence is that those agent that has been investigated until now has not been good enough candidates to be singled out as The Agent of cause, not even CO2. Therefore one may take a step back and start to look over other things and ask oneself the question what we may have missed so far. And this is being done by the scientific community by investigating alternative explanations, but to ridicule this as "skeptic attitude" is to misinterpret the scientific way of approaching a problem. A "skeptic attitude" is a necessary condition to make progress in scientific understanding. Because it is used to exclude other possible explanation – not to prove an explanation. A scientific methodical oriented mind need always to ask them self the question "What if I am wrong?" Knowing this but still claiming that CO2 is the agent is equal to claim that the computer climate models describes the climate with sufficient parameters – in other word that is to claim that the computer models holds the ultimate Truth in this question. The OP asked if this is arrogant to claim - the reader may judge by them self.
    Response: I can only assume that you didn't actually read the article above. I explain in (what I hoped were) easy to understand terms the causal link between more CO2 and an enhanced greenhouse effect (aka warming). I outline the direct measurements that confirm that the enhanced greenhouse effect is actually happening. If you're genuinely interested in learning more about the evidence for CO2 warming, I go into more detail here.

    The whole point of this article is to emphasise that the evidence for CO2 warming is not based on climate models but on definite empirical evidence. Please read the article above then peruse the experimental evidence for CO2 warming (and I recommend following the links to read the actual research papers cited).
  48. Empirical evidence that humans are causing global warming
    Riccardo Investing 15 seconds on a Google search, I found these two links among others http://www.scotese.com/climate.htm http://math.ucr.edu/home/baez/temperature/ both contain graphs that I assume are based on some science, showing that the planet's temperature has "forever" been changing with excursions of about 15 C peak to peak. If anyone wants to make a meaningful statement about man-made global warming, I would think as a minimum requirement that they would need contrast statistically the observed modern trends with this data and clarify how these are dissociated. This issue aside, given all the controversy, it would appear that a definion of "global warming" is wanting, given an understanding that theoretically, all human physical activities add some heat to the planet. Where do you draw the line in terms what is acceptable and inacceptable? I suspect that circular logic is at play here, since the implicit definition indicates that heat generated by greenhouse gases is inacceptable.
  49. Empirical evidence that humans are causing global warming
    Robbo same old (and boring) skeptic attitude: assume what people think, claiming that people (_all_ indeed) said what you would like them say. Is there anyone denying the very existence of variability? I bet no. But you insist just to give yourself the right to say that my claim was foolish, and of monumental proportions ... There's no point at all to post offtopic on this issue for one more reason, variability do not rule out the background trend but is just suprimposed on it. You should be aware that decadal and multidecadal variability alone cannot explain recent temperature trend, as Latif that you quote continues to repeat over and over ... On the contrary, even a simple linear trend added to ENSO-PDO effect (plus volcanoes eventually) accounts for most, almost all indeed, of the temperature record including variability.
  50. Robbo the Yobbo at 14:27 PM on 18 October 2009
    Empirical evidence that humans are causing global warming
    Douglas and Knox looked at periods of radiative imbalance in the light of the multidecadal ocean/climate states - they say that the radiative imbalance changed again with the climate shift in 2000 to -0.2 W/m2. The best argument for a natural origin of decadal climate shift is the shift in climate after 1999. The difference between Schuckman and Douglas is 1 W/m2. There is obviously no agreement. There is also no agreement of Schuckmann to the OHC data at the National Oceanographic Data Center. The Douglass graph you show stops at the most recent climate shift. You certainly can't have read the paper - or even the blog - to come to the conclusion you have. Abstract Ocean heat content and Earth’s radiation imbalance D.H. Douglass and R, S, Knox Dept. of Physics and Astronomy, University of Rochester, PO Box 270171, Rochester, NY 14627-0171, USA Earth’s radiation imbalance is determined from ocean heat content data and compared with results of direct measurements. Distinct time intervals of alternating positive and negative values are found: 1960–mid-1970s (−0.15), mid-1970s–2000 (+0.15), 2001–present (−0.2 W/m2), and are consistent with prior reports. These climate shifts limit climate predictability. The recent change to a -ve radiative imbalance is certainly in line with observations of Earth albedo since 1999. Google Project Earthshine and look at the most recent additions to the bibliography. The PDO is not the cause of anything - but is in itself one outcome of 20 to 30 year global ocean states. There is a 100 years of science on this in both the Atlantic and Pacific and thousands of papers. Don Easterbrok, Pielke Sn, Bob Carter, Roy Spencer and Stewart Franks – amongst many others - have been discussing this for a decade. How this must rankle. Keenlyside has been talking about multidecadal Atlantic influences on global surface temperature for years. Recently Kyle Swanson and Anastasio Tsonis used a numerical method to analyse for shifts in ocean/climate states. They found what was evident for many years from eyeballing (that is, after all, what they are for)the ocean indices graphs. The mid 1940's, the mid 1970's and 1999/2001 are the most recent climate shifts. At least half of recent warming between 1976 and 1998 was the result of the most recent warm ocean mode. We are now in a cool ocean mode - a cooling influence in the atmosphere and oceans that lasts for 20 to 30 years from the last climate shift around the change of the millenium. The IARC is based at the University of Alaska at Fairbanks. I linked to ICECAP to find a nice summary - but by all means link to the IARC directly and search for decadal changes. http://www.iarc.uaf.edu/ If you look at any Artic temperature reconstruction - you will see very pronounced decadal temperature variation. A peak in the 1940's and a recent peak around 2000. There are some temperature anomalies here for instance - http://icecap.us/images/uploads/RECENT_RESULTS.pdf The satellite sea ice anomalies referred to are not of sufficient record length to capture decadal variability. The satellite record doesn’t give enough information to draw meaningful conclusions at this time. The Arctic should, like the rest of the planet but more strongly, cool over the next couple of decades. ‘Multidecadal fluctuations in the Arctic/North Atlantic climate system should be taken into account when assessing long-term climate change and variability. Understanding the key mechanisms influencing the Arctic/North Atlantic multidecadal variability is essential for developing robust climatic forecasts.’ Schuckmann et al is utter rubbish because they – like most people around the world – have not come up to speed with multidecadal ocean/climate shifts. Mojib Latiff said that asking the uncomfortable questions about climate variation was needed lest the questions be asked by less forgiving people like myself. Simply claiming that Latiff was misrepresented – by a right wing journal such as New Scientist for God’s sake – is very, very silly. Clinging to denial of multidecdal ocean/climate states would be foolishness of monumental proportions. It is not suggested that carbon dioxide is not a greenhouse gas - simply that most of the recent warming between 1976 and 1998 was due to natural climate shifts - and all of the current cooling. Do you have another explanation for current cooling? Didn't think so. Ocean heat content is the best way of monitoring for radiative imbalances - but you have to expect that this is not constant nor linear - and none of the researchers - as Susan Wijfells said last month - agree with each other as yet. Obviusly - more development in methods is needed.

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