Recent Comments

Prev  2485  2486  2487  2488  2489  2490  2491  2492  2493  2494  2495  2496  2497  2498  2499  2500  Next

Comments 124601 to 124650:

124601. yocta at 09:30 AM on 2 February 2010
        The role of stratospheric water vapor in global warming
        Thanks Turboblocke, i'm still learning. If anyone knows of a good text on weather and climate science they could recommend I'd be much obliged? :) I'm slowly rereading my old Sturman & Tapper book from undergraduate days but would like to hear of other ones out there...
        Response: All you could want and more is found in the online textbook Principles of Planetary Climate. UPDATE: my mistake, the book is no longer available online, now in press. Well, a good introduction to global warming, not as technical as Principles of Planetary Climate, is The Discover of Global Warming by Spencer Weart.
124602. Turboblocke at 09:02 AM on 2 February 2010
        The role of stratospheric water vapor in global warming
        Yocta at 11. The change is about 10% of +/- 5ppmv of the stratospheric atmosphere. That isn't very much water in absolute terms, compared to the water in the troposphere.
124603. chris at 08:55 AM on 2 February 2010
        The role of stratospheric water vapor in global warming
        I haven't read Solomon et al so I'm not going to make any specific comments. However at face value the paper (as paraphrased here) seems to be yet another reason to be concerned about the massive release of greenhouse gases. Right now there seems to be a number of contributions "piling up" that should be causing significant cooling: (i) 2003-2009 the sun has dropped to the bottom of the solar cycle (this should contribute around -0.1 oC of to the surface temperature over this period). (ii) 1980's to present: a slow (and rather small) negaitve trend in solar output (-0.05 oC?) (iii) Since around 1998; apparently the oceans have switched regimes to one with a cooling influence on the surface temperature (negative phase of the PDO). This might contribute around -0.1 oC relative to the long term ocean regime trend (which is zero). (iv) Stratospheric water vapour effect (see top article) which according to Solomon has reduced warming in the period 2000-2009 by 25% (so around -0.05 oC say). And yet 2009 was tied for the second warmest year on record. So if all of these contributions are real (and we are at least pretty confident about the solar cycle contribution)....they have been unable, colectively, to outweigh the warming contribution from enhanced greenhouse forcing...
124604. pedex at 08:27 AM on 2 February 2010
        It's Urban Heat Island effect
        Furthermore as per the 3rd paragraph of the explanation laid out in this blog about UHI is patently false and anybody that has checked out the weather stations and locations in the US can easily see that. Their excuses do not jive with reality at all. Most NOAA stations do not even come close to meeting NOAA's own specs. This is why as part of the data set the terrain factors are included for each station as far as urban or rural and what kind of land they sit on. That way you can easily separate stations subject to urban warming from those that are not influenced by it.
        Response: I would suggest reading the paper I reference in the 3rd paragraph, Peterson 2003, and then explain the flaws in their methodology. Noone is denying that there are urban weather stations that are warmer than their rural neighbours - but statistical analysis shows there are almost an equal number that are situated in cool parks and show a cooler trend. Either way, urban stations are normalised to their rural neighbours to ensure there is no contamination of the temperature record.
124605. pedex at 08:22 AM on 2 February 2010
        It's Urban Heat Island effect
        actually if you work with the adjusted data it isn't corrected for properly either, same problems show up this blog cherry picked an instance and claimed it was valid for everything and that's hardly the case at all which has already been demonstrated furthermore guys like Jim Hansen have already claimed single stations can and do reflect what is going on with complete continents or even globally which of course is false in its own right satellite data doesn't go back far enough to be of much use
124606. Doug Bostrom at 08:03 AM on 2 February 2010
        On the reliability of the U.S. Surface Temperature Record
        Riccardo at 02:57 AM on 2 February, 2010 "Here is my bet, they will focus on the raw data. " If you look at the data collection sheets provided for volunteers, you can see that there is little "data" beyond a photograph and geographic location information, which will never produce numerical results beyond what Menne did. The sheet includes space for anecdotal site information but coding that into some normalized form is going to be virtually impossible. If Watts had designed his survey better, he might have been able to produce something beyond Menne, but the information needed for that doing was not collected. I'm not even sure it would possible to do so; presumably adding prevailing winds at sites could help, getting some kind of quantitative readings of factors introducing errors, but in that latter case, how? Nobody can read Watts' mind, but I don't think he had a clear plan for what data he needed or for that matter even what he was trying to show, other than embarrassing photos. Who know, maybe there's something that can be done with all that effort. Hopefully.
124607. NewYorkJ at 07:58 AM on 2 February 2010
        The role of stratospheric water vapor in global warming
        Some questions that the abstract doesn't seem to be clear on: Are the authors considering stratospheric water vapor a forcing or feedback, both, or can no conclusion be drawn? Since it doesn't determine the cause of the water vapor changes, it seems the conclusion would be one of the latter two. Could a conclusion from the study be that water vapor is a stronger positive feedback than previously estimated? It mentions stratospheric water vapor increased in the 90's and decreased in the early part of this decade. We also saw a leveling off of methane emissions, reduced solar activity, and a transition towards negative ENSO conditions. If any of these are a cause of the water vapor change, it seems to further support the positive feedback from water vapor. One thing that seems clear is that it might help improve mean climate model estimates at the decadal scale. 1990's warming exceeded the average climate model projection while 2000's warming generally is a little lower. Including the water vapor data seems likely to resolve model/observation discrepancies on short time-scales.
124608. Albatross at 07:44 AM on 2 February 2010
        The role of stratospheric water vapor in global warming
        Peter re #21, I for one do not appreciate your unsubstantiated insinuations here. Drawing parallels between climate science and what happened in the financial sector is just wrong. Anyhow, this is a scientific debate about the Solomon paper and SWV, can we please stick to that? PS: Re OHC. The same "spike" ~2003 is also evident in 2003 in the global SST data (Smith et al. 2008, J. Climate, ERSST.v3b), Spencer looked into this and found that the spike in ERSST 3b was real. Can you provide proof that this spike is b/c of the Argo data, a published reference would help. I just perused the Smith et al. paper and there is no mention of the Argo data being included in their analysis. Anyhow, the *long term* trend of 0-700 m OHC is up, see also the papers that Chris provided.
124609. shawnhet at 07:09 AM on 2 February 2010
        Lessons from the Monckton/Plimer debate
        Oops, sorry upon re-reading I appear to have had some poor phr in my last post(#83) that make what I was trying to say more than a lit obscure. from line 2 of the post "...that IMO there is also reason to believe that sensitivity is constant either" should read: that IMO there is also no requirement to believe that sensitivity is constant. 3rd papragrahp should read :From the above we can see that **while** changes in insolation due to orbital forcing are sometimes coincident with the temperature highs, not every high forcing situation leads to a high temperature regime. My apologies for any confusion.
124610. chris at 06:38 AM on 2 February 2010
        The role of stratospheric water vapor in global warming
        re #20 Peter, there is certainly evidence that abyssal waters in the world's oceans may be warming (and deoxygenating), especially from Johnson's lab in Seattle (Pacific Marine Environmental Lab) [*] I suspect that considering the problems with the Argo floats, it's too early to say whether there is any discrepency between upper ocean heat content and expectations; after all we've only got a few years of Argo data. It's worth pointing out that the longish term (decadal; bi-decadal) accumulation of upper ocean heat is pretty close to model predictions up through 2008 [**] [*] Johnson GC et al. (2006) Recent western South Atlantic bottom water warming Geophys. Res. Lett. 33, L14614 Johnson GC et al. (2007) Recent bottom water warming in the Pacific Ocean J. Climate 20, 5365-5375 Johnson GC (2008) Warming and Freshening in the Abyssal Southeastern Indian Ocean J. Climate 21, 5351-5363 Ozaki H et al. (2009) Long-term bottom water warming in the north Ross Sea J. Oceanograph. 65, 235-244 Johnson GC et al. (2009) Deep Caribbean Sea warming Deep Sea Research. 1 Oceanograph. Res. 56, 827-834 Johnson GC (2008) Reduced Antarctic meridional overturning circulation reaches the North Atlantic Ocean Geophys. Res. Lett. 35, L22601 [**] S. Levitus et al. (2009) Global ocean heat content 1955-2008 in light of recently revealed instrumentation problems Geophys. Res. Lett. 36, L07608
124611. Prasad Kasibhatla at 06:27 AM on 2 February 2010
        The role of stratospheric water vapor in global warming
        I posted this comment on RealClimate - thought I'd post it here as well to see if anyone here has any insights: Re the contribution of the post-2000 decrease in stratospheric water vapor contributing to the ‘flattening’ of the global warming trend – I am struck by the dissimilarity between the observed and modeled temperature curves post-2000 in Figure 3b. It looks like the model’s response it to simply adjust (almost instantaneously) to the drop in water vapor in 2001, and I see no evidence of a ‘flattening’ of the trend. Am I missing something?
124612. Berényi Péter at 06:12 AM on 2 February 2010
        The role of stratospheric water vapor in global warming
        Alabatross, there is a step like increase in NOAA OHC time series in 2003. That much is true. However, it was the year Argo floats were deployed en masse. That is, the measurement system changed radically at that time. It's got much better, at least down to 1000 m, perhaps. It was supposed to do measurements down to 2000 m, but due to instrumental problems that has not worked until recently. No warming detected since then in the upper 700 m, a level well below the thermocline. There is some speculation that heat went to the abyss, but water down there being about as cold and salty as it can get, it is not easy to figure, how substantially warmer water could slip there.
124613. chris at 06:11 AM on 2 February 2010
        Lessons from the Monckton/Plimer debate
        Peter, it seems unfair to cite a set of scientists in support of a poorly-characterized theory, and then to call them names ("reality-denialist"?!) when their papers turn out not to agree with your notions. According to recent work by Price (who you have cited in relation to Schumann resonance), what you consider to be obvious, isn't actually obvious at all. The question of how lightning activity responds in a warming world isn't straightforward (see Price's recent paper [*] and abstract below [**]. Likewise, whereas you consider Schumann resonance a means of determining global lightning activity, Price prefers to determine global lightning activity from The Tropical Rain Measuring Mission (TRMM) satellite. This has the obvious advantage (over your preferred Schumann resonance method) [which Price uses to analyze possible lightning/upper tropospheric water vapour variability (see my post #58 and #63)], that the spatial distribution of lightning can be determined and correlated with local phenomena. In fact Price concludes [as does Pinto and Pinto (see my post #58)] that lightning activity seems to be consistent with predictions from climate models. I would have thought that if the scientists who's work you cite don't actually agree with your notions, that it might be worth considering whether your notions have merit. [*] Price C (2009) Will a drier climate result in more lightning? Atmos. Res. 91, 479-484 [**]

        With recent projections of a warmer climate in the future, one of the key questions is related to the impact of global warming on thunderstorms, and severe weather. Will lightning activity increase in a warmer world? Since the majority of global lightning activity occurs in the tropics, changes in future global lightning activity will depend on changes in the tropical climate. The latest IPCC [Intergovernmental Panel on Climate Change (IPCC). 2007] projections show a partial drying out of the tropical landmasses as the global climate getswarmer. This is caused by both changes in rainfall patterns, but also due to increases in evapo-transpiration. We would expect a drier climate to produce fewer thunderstorms, and less lightning. However, experimental and modeling studies have shown that as tropical regions dry in the present climate, they experience greater lightning activity. This paradox may be explained by noting that while drier climate conditions result in fewer thunderstorms and less rainfall, the thunderstorms that do occur are more explosive, resulting in more lightning activity.

124614. shawnhet at 06:06 AM on 2 February 2010
        Lessons from the Monckton/Plimer debate
        #77, GFW since the issue of sensitivity is the core of the warming debate, let me just say that IMO there is also reason to believe that sensitivity is constant either(rather than debate sensitivity vs. forcing in detail). I don't know the particulars of Monckton's or Plimer's position, so I don't know their specific position In re: Milankovitch cycles, while it is of course true that insolation changes due orbital shifts have an effect, things are a lot more complicated than a simple constant response to forcing would imply. http://en.wikipedia.org/wiki/File:Vostok_420ky_4curves_insolation.jpg From the above we can see that changes insolation due to orbital forcing are sometimes coincident with the temperature highs, not every high forcing situation leads to a high temperature regime. This situation allows a wide variety of possible explanations to be feasible, but does not seem consistent with a simple linear relationship btw forcing and resultant temperature change. Cheers, :)
124615. Albatross at 05:28 AM on 2 February 2010
        The role of stratospheric water vapor in global warming
        Arno @16, please cite some reputable and published references to back up your assertions. 0-700 m OHC actually increased significantly circa 2003, a time when there were no super El Nino: http://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/ Also, this is what the global surface-air temperatures have been doing: http://data.giss.nasa.gov/gistemp/graphs/Fig.A2.lrg.gif And global tropospheric temperatures: http://www.remss.com/msu/msu_data_description.html#msu_amsu_trend_map_tlt (Look at Fig. 7 Ch TLT) Have you been reading Bob Tisdale's page perhaps?
124616. Berényi Péter at 04:41 AM on 2 February 2010
        Lessons from the Monckton/Plimer debate
        @59. Tom Dayton at 10:05 AM on 31 January, 2010 Tom, you don't need a monitoring network to track global lightning activity. It can be done from a single spot with rather inexpensive equipment. Schumann resonance measurements started for example at Nagycenk, Hungary in early 1960s, automatic digital data collection was installed in 1993 and is performed since then. Your reference to wiki "A strong link between global lightning and global temperature has not been experimentally confirmed as of 2008" referes to the fact that global lightning activity has not increased while global average surface temperature was supposed to go up. Strong local positive correlation between surface temperature and lightning is firmly established, lower troposphere moistening (below 850 hPa) is also well documented. It is an enigma, no matter how much mainstream reality-denialist effort is spent on it.
124617. Berényi Péter at 04:08 AM on 2 February 2010
        The role of stratospheric water vapor in global warming
        Any idea where the extra water vapor went from the lower stratosphere in 2000?
124618. carrot eater at 03:19 AM on 2 February 2010
        The role of stratospheric water vapor in global warming
        How well mixed is stratospheric water? Can the Boulder weather balloon readings be taken as representative? Water content is sensitive to temperature. Though I do see the Boulder readings are consistent with the satellites.
124619. Riccardo at 02:57 AM on 2 February 2010
        On the reliability of the U.S. Surface Temperature Record
        jpark, hint: look at fig.7 of the paper quoted by carrot eater. I'm waiting for a Pielke and Watt paper on this, for years indeed, so hopefully this story will come to an end and archived for ever (just a hope, isn't it?). Judging from their blog posts it won't add much to the subject. Here is my bet, they will focus on the raw data.
124620. carrot eater at 02:33 AM on 2 February 2010
        On the reliability of the U.S. Surface Temperature Record
        jpark: There was no cherry picking in only using 40%. They used the 40% that was publicly available on Watt's website, and then had their own people confirm most of those ratings. They then considered whether there were enough stations in enough places to do an analysis, and they found that they did. If the stations are well-distributed, you don't need a high number of stations to compute a national average. Menne has previously published an analysis discussing how many stations you need to get an accurate idea of the overall picture. See Vose, Menne (2004), Journal of Climate 17: 2961-2971. Adding more stations would help, though you eventually reach a point where adding more stations doesn't change anything.
124621. carrot eater at 02:24 AM on 2 February 2010
        On the reliability of the U.S. Surface Temperature Record
        jpark: You can see the result of the homogenisation for Reno yourself, in the paper I cited. A huge warming trend is significantly reduced. Where some sceptics get confused is that they think UHI is the only thing you'd ever need to adjust for, and then they get angry when they see any upwards adjustments. However, other things can require either upwards or downwards adjustments, and in the US, changes in the time of observation stand out as a requiring upwards adjustments. One thing to not forget is the US CRN network, which is entirely sited to avoid any of these problems. It's newish, but it's been up for a few years now. After adjustments, Menne (2010) showed that even the 'poor' stations matched the US CRN. That would tell you that they're doing something right.
124622. jpark at 02:02 AM on 2 February 2010
        On the reliability of the U.S. Surface Temperature Record
        Carrot eater - v helpful. So the temperatures are adjusted down to counteract the UHI, yes?
124623. jpark at 01:59 AM on 2 February 2010
        On the reliability of the U.S. Surface Temperature Record
        Thanks Ricardo - lets see if they do the analysis then. Pity Menne only used 40% of the available data tho. Bit like only using some bristlecones, like a D'Arrigo cherry picked pie. Pielke says "We will discuss the science of the analysis in a subsequent post and a paper which is being prepared for submission." so it looks like it is happening...
124624. carrot eater at 01:55 AM on 2 February 2010
        On the reliability of the U.S. Surface Temperature Record
        jpark, this is tosh. Anybody knows there are individual stations out there that show urban heating. You don't need Watts for that; you can see it from the people who actually do published work. The question is whether those effects are contaminating the overall surface record, and by any actual analysis, they appear to not do so. It's funny that Watts chose to highlight Reno NV, without telling you that the USHCN's method removes the urban heating for that station. See Figure 8 in Menne, Williams and Vose (2009) BAMS, 90: 993-1007. Link was given above somewhere.
124625. Riccardo at 01:12 AM on 2 February 2010
        On the reliability of the U.S. Surface Temperature Record
        come on jpark, you know very well that when the data are homogenized ("adjusted") people (sceptics) screams out loud. This is the very reason why they show raw data only. We all know that UHI exists and indeed, before being considered for the average of their respective grid point data are corrected for UHI effect, station movement, instrument change, etc. I've never (NEVER) seen Watt do the full analysis. Given that behind Watt there is Roger Pielke Sr., they sure have the skill to do it. If they don't, the reason is clear. That post is just a confirmation that what they say is irrelevant.
124626. Alexandre at 01:08 AM on 2 February 2010
        It's cosmic rays
        Here's the graph I mentioned above about the Laschamp event: http://ossfoundation.us/projects/environment/global-warming/myths/images/galactic-cosmic-rays/LaschampAnomaly.jpg/view I presume it comes from this paper: Muscheler et al. 2005 "Geomagnetic field intensity during the last 60,000 years based on 10Be and 36Cl from the Summit ice cores and 14C" [Muscheler 2005] The graph looks pretty strinking to me. John, do you think it would be worth adding this to a future update on this argument?
        Moderator Response: [RH] Hot linked Musch paper.
124627. Doug Cannon at 00:31 AM on 2 February 2010
        It's cooling
        Note that NODC has updated the ocean heat content figures through 2009. You may want to update your graph.
124628. Berényi Péter at 23:52 PM on 1 February 2010
        The role of stratospheric water vapor in global warming
        I wonder why this drop was not reported earlier. After all it occured almost a decade ago.
124629. Gianfranco at 23:46 PM on 1 February 2010
        Understanding Trenberth's travesty
        Thank you very much for the excellent explanation. One point still puzzles me, though, perhaps because I'm Italian: the word 'travesty'. According to my good old Oxford Dictionary it means 'a description that intentionally misrepresents the original e.g. burlesque poem etc.' etymology being the Italian verb travestire = disguise. It somehow conveys the impression that the whole thing is a farce, a dress up, an attempt to deceive. I understand in private informal correspondence one doesn't care much about wording, but, why didn't he use pity or shame or bad luck?
124630. jpark at 23:38 PM on 1 February 2010
        On the reliability of the U.S. Surface Temperature Record
        Hi is this on topic? http://wattsupwiththat.com/2010/01/31/uhi-is-alive-and-well/ If you live in a city as I do then you know how much warmer it is than the surrounding countryside. To be told that sitings of temp stations dont reflect this is counter intuitive and makes me very suspicious of the way Menne got his results - a bit like Mann's famous, now broken, hockey stick.
124631. J Bowers at 22:20 PM on 1 February 2010
        Lessons from the Monckton/Plimer debate
        RSVP wrote: "In terms of probability, it would seem to make the chances of life on Earth diminish if this were the case, and yet here we are having (supposedly) evolved on this planet for millions and millions of years." But our mammalian ancestors were small rodent-like animals, and were able to burrow into the ground to avoid the effects of brief extreme temperature during the K/T Event extinction. Insects and marine plants would have still been available to eat immediately afterwards. The earliest known tool-using humans, homo habilis, never experienced anything they couldn't adapt to nor migrate from, and were far fewer in population number so resources were less contested. The Late Pleistocene Extinctions affected large herbivores, and each Late Pleistocene event also happened on a different land mass. The causes of the Late Pleistocene Extinctions are still unknown, but the three main candidates that I know of are: Human over-hunting or hunting a keystone species to extinction; Climate change causing large changes in the ecosystem; Hyperdiseases carried by migrating humans. Or, a combination of all three. Even during glacial ice ages, the southern hemisphere was still mostly tropical or subtropical.
124632. RSVP at 21:36 PM on 1 February 2010
        Lessons from the Monckton/Plimer debate
        GFW Up until now, I understood that the Earth could sustain life as we know it because it had an atmosphere, a lot of water, and just happened to be the right distance from a rather average (not too big) non-binary star. (Not to mention other "invisible shields" that magically serve protection as well etc.) All that is pretty awesome in itself, however, there would be a point at which the requirements for sustaining life must loosen, and that the particular amount of carbon you are talking about is not one of these requirements. In terms of probability, it would seem to make the chances of life on Earth diminish if this were the case, and yet here we are having (supposedly) evolved on this planet for millions and millions of years. Something doesnt seem to add up here, and as per Occam's razor, one should look for a simple explanation. It seems like these theories depend almost too much on carbon cycles and make them seem circular in themselves. Anything is possible and maybe we dont realize how delicate the balance really is, however, being an optimist, couldnt the triple point of water along with the vast amounts of it on the surface of the Earth have something to do with this notable clipping?
124633. GFW at 19:39 PM on 1 February 2010
        Lessons from the Monckton/Plimer debate
        Agreed that the behavior for several glacial/interglacial periods has been bounded and fairly periodic, but that's not bi-stable. True bi-stability would be suggested if (a) the system spent more time at the two extrema and (b) the transitions were less regular. You'd also need to propose a negative mechanism (or two) to provide the stability at the two extrema. I'd suggest that the bounds of the observed range are mostly determined by the amount of carbon available, and the period of the dominant Milankovitch cycle. Specifically, temperature falls while the Milankovitch forcing is negative, with the rate of fall limited by the carbon cycle's ability to scrub and sequester carbon (in the ocean, in peat bogs that then get glaciated over, etc.). When the Milankovitch forcing turns positive, slow warming starts, then accelerates as the initial warming causes the ocean to outgas CO2 and the glaciers to start exposing the decomposed peat. One good question would be why the amount of carbon available to the cycle has been roughly constant for several hundred thousand years. I'm guessing that that's not long enough for tectonic processes to bury seafloor carbon, nor reconfigure the topography of the oceans, so each warming releases the same carbon each time. If there were significant uplift under methane hydrate deposits, the amount of carbon available to the cycle would go up for a while, until new deep stores of the hydrates could form. If enough time passed to form new fossil fuel deposits, that would reduce the amount of carbon available to the cycle. If we burn large quantities of fossil fuels ... well, that's the topic of the 3rd figure in the page you pointed to.
124634. Doug Bostrom at 18:58 PM on 1 February 2010
        Understanding Trenberth's travesty
        This article seems like a great candidate for a revisit after Solomon's article on vanished vapor. A significant part of Trenberth's gap is seemingly plugged, if Solomon's results stand it'll be a great improvement in our understanding of variability.
124635. Ari Jokimäki at 18:14 PM on 1 February 2010
        The role of stratospheric water vapor in global warming
        John Cook wrote: "The radiative forcing changes (Figure 3 above) indicate that the overall effect from stratospheric water vapor is that of warming. The cooling period consists of a stepwise drop around 2000 followed by a resumption of the warming effect. This seems to speak against the possibility of a negative feedback." Looking at the overall effect in your Figure 3, it is quite clear that if there is a feedback involved, it is a positive one, not negative.
        Response: I thought so too but as the authors didn't explicitly say that and I was presenting the results of the paper, I didn't say so. That's the opinion of Gavin Schmidt at Real Climate also.
124636. RSVP at 16:37 PM on 1 February 2010
        Lessons from the Monckton/Plimer debate
        GFW If you look at the graph (figure 2) in... http://www.skepticalscience.com/upcoming-ice-age-postponed-indefinitely.html you will notice that there are basically two states, suggesting "bi-stability". The high curiously peaks around the same high temperature, and the low generally hovers around the same low temperature. The system appears sensitive (as seen by the many interrum fluctuations), but this sensitity is only observed within a fixed range of max min temperatures. In other words, it "wants" to be in one state or the other. Why does it always return to the exact same max, for instance?
124637. yocta at 16:20 PM on 1 February 2010
        The role of stratospheric water vapor in global warming
        Any idea where the 10% water vapour went? What I mean is, besides change in global temperatures and radiative forcing is there any say...increase in rainfall on average in some areas, or shrinking clouds over the past decade that could be linked to this? Or is 10% of atmospheric concentration of water (0.40%) to small to notice anywhere else?
124638. Albatross at 16:19 PM on 1 February 2010
        The role of stratospheric water vapor in global warming
        John et al, Regarding "....the effect from stratospheric water vapor contributes a fraction of the temperature change imposed from man-made greenhouse gases. Stratospheric water vapor has a significant effect but it's hardly the dominant driver of climate being portrayed by some blogs." These sentences seem to contradict one another. In the first you state that SWV "contributes a fraction of the temperature change imposed by" anthro GHGs. With this I agree, going by the scale provided, the forcing from SWV in 2000 was ~0.2 W m-2, with the drop in forcing from SWV in 2001 a paltry 0.1 W m-2. [To put these numbers in perspective the radiative forcing for CO2 in 2008 was ~1.74 Wm-2 and that of CH4 0.50 W m-2 (thanks for the link padruig @7). So the forcing from SWV is less than 9% of the forcing from CO2 and CH4 combined.] But, in the second sentence you state that "SWV" has a "significant effect". Perhaps once should say that "the while forcing of SWV is not insignificant (i.e, is not too small to ignore), it is hardly...." There is probably a more eloquent way of stating this, but it is late here. In my humble opinion, while this work of Solomon et al. is valuable and interesting, it does not in any way undermine the theory of AGW. A scale analysis shows that the forcing from SWV is currently <9% of that from CO2 and CH4. Not only that but the long term trend in the forcing of SWV shown in Fig 3. above is positive (the slope of the line after 2001 is almost the same as that prior to 2001). The decrease in SWV around 2001 is interesting, and more work needs to be undertaken to determine the cause of the decrease-- it is not b/c of instrumentation issues because is was detected by independent monitoring platforms. Anyhow, this is not the silver bullet that those in denial about AGW are hoping for. They can try and spin it that way, but doing so is does not going to reverse the slope of the line in Figure 3 above, or the reality that the forcing from SWV is already overwhelmed by that of anthro GHGs. In fact, in 2008 the radiative forcing of SWV was on par with that of N20 (NOAA/ESLR).
        Response: On the one hand, "is significant" or "is not insignificant" seems a little po-tay-to, po-tah-to, but yes, "is not insignificant" probably does capture the sense of what I was trying to communicate so I've updated the wording :-)
124639. chris1204 at 15:58 PM on 1 February 2010
        The role of stratospheric water vapor in global warming
        Marcus, if you look at http://www.esrl.noaa.gov/gmd/aggi/ you will read: ‘The growth rate of methane declined from 1983 until 1999, consistent with an approach to steady state. Superimposed on this decline is significant interannual variability in growth rate [Dlugokencky et al., 1998, 2003]. The approach to steady state may have been accelerated by the economic collapse of the former Soviet Union and decreased emissions from the fossil fuel sector. From 1999 to 2006, the CH4 burden was about constant, but in 2007 and 2008, globally averaged CH4 began to increase again.’ At the same time, http://www.nature.com/climate/2009/0904/full/climate.2009.24.html whilst raising the alarm about methane emanating from permafrost in fact also states: ‘Ed Dlugokencky, an atmospheric chemist with the US National Oceanographic and Atmospheric Administration in Boulder, Colorado, who oversees their atmospheric-methane measurement program, says indications are that global methane levels remained high in 2008, but he expects to see a return to previous levels over the long term. "If I had to make a prediction about what's going to happen in the future based on the last three decades of observations, I would say that there's a reasonable chance methane will continue to stay flat or even decrease before we see the effects of a warming climate on methane sources," says Dlugokencky. White agrees and says it's too early to tell whether this is a blip on the radar or a true signal that change is afoot. "I think we're going to need to see two to three years or more with increased methane in order to make a strong statement that we're beginning to see permafrost degradation resulting in methane increase," says White.’ So our moderator’s comment: ‘I think we all need to take a deep breath and calm down a little. Not because this isn't an important issue but because this is such an important issue’ is very apposite. At the same time, those at the cutting edge of ‘the science’ seem to be hedging their bets on the issue acknowledging the complexities involved. Returning to the original subject, stratospheric water vapour, I note that ‘The paper doesn't draw any conclusions regarding cause, stating that it's not clear whether the water vapor changes are caused by a climate feedback or decadal variability....’ Accepting for the time being the proposition that ‘The radiative forcing changes (Figure 3 above) indicate that the overall effect from stratospheric water vapor is that of warming,’ I’d be interested in any comments relating to increased atmospheric water vapour and precipitation. This would be very pertinent in relation to other issues raised in these forums such as glacier growth and the impact on regions dependent on such sources for water supply.
124640. Marcus at 14:06 PM on 1 February 2010
        The role of stratospheric water vapor in global warming
        Sorry to be picky, padruig, but I think you mean 1800ppbv. Either way, though, that is much, much higher than pre-industrial levels of barely 700ppbv. Indeed, wheras CO2 levels have "only" increased by 38% above 1750 levels, Methane has increased by almost 70% above 1750 levels!
124641. padruig at 13:35 PM on 1 February 2010
        The role of stratospheric water vapor in global warming
        Using the running mean as a guage, measurements of methane show it leveled off from 1999 to 2002, rose again peaking in 2003 followed by a drop returning to roughly 2002 levels. This was followed by a shallow bump in 2006. A point of concern is that in 2007 the rise observed prior to 1999 began to continue. Currently NOAA is reporting that we've exceeded 1800ppmv for methane. You can read NOAA's AGGI report ( updated Sept 09) here http://www.esrl.noaa.gov/gmd/aggi/ You can also read about terrestrial stores of methane here - http://www.nature.com/climate/2009/0904/full/climate.2009.24.html If I am not mistaken Nature Reports Climate Change is free to download.
124642. Marcus at 13:30 PM on 1 February 2010
        The role of stratospheric water vapor in global warming
        Yet from my reading of it, the rise in stratospheric water vapor, irrespective of its radiative forcing potential, seems to have its likely origins in the oxidation of anthropogenic methane. If this is correct, then in my opinion this paper actually *supports* anthropogenic global warming even more.
124643. chris1204 at 13:08 PM on 1 February 2010
        The role of stratospheric water vapor in global warming
        The abstract from Solomon 2010 states: 'More limited data suggest that stratospheric water vapor probably increased between 1980 and 2000, which would have enhanced the decadal rate of surface warming during the 1990s by about 30% compared to estimates neglecting this change.' 30% is pretty substantial by any standard bearing in mind that we have systems that are very sensitive to positive and negative feedbacks. It's all the more interesting considering that 1998 seems to have been an exceptionally warm year (whether because of ENSO or other causes) with evidence of subsequent relative cooling. Marcus, the reported levelling off of methane levels is surely very worthy of note given its reported significance as a greenhouse gas. We are dealing with complex systems which we do not undertsand well. With respect, the gratuitous references to 'contrarians' and 'denialists' that often appear on this site have a quasi-religious flavour which are out of keeping with the spirit of genuine scientific enquiry.
        Response: I am making more effort to moderate the labelling and ad hominem comments in order to maintain scientifically constructive dialogue. Consequently, I've been deleting a great number of comments lately (from both sides of the debate). I think we all need to take a deep breath and calm down a little. Not because this isn't an important issue but because this is such an important issue.
124644. Marcus at 13:06 PM on 1 February 2010
        The role of stratospheric water vapor in global warming
        Thing is, though, that it only *started* to level off-it was still rising right up until 2000-2001, though at a slower rate from 1992-2000 than in 1980-1992. Given that methane has a half-life of 7 years, then I think it's perfectly in line with observed drop in stratospheric water. Lets not also forget that the other by-product of methane oxidation is carbon dioxide-another greenhouse gas.
124645. GFW at 13:00 PM on 1 February 2010
        The sun is getting hotter
        The section on independent tests is really good showing multiple measurements and proxies for TSI, with solid agreement. Are you aware of any measurements over the 1990-92 period using radio wavelengths (eg 10.7cm) that would also serve as a calibration? BTW, you wrote Challenge instead of Challenger.
        Response: Fixed the Challenger typo, thanks for the tip.
124646. GFW at 12:43 PM on 1 February 2010
        Lessons from the Monckton/Plimer debate
        @61 shawnhet Yes, one can attempt to reconcile Plimer (non-anthtro forces have changed climate by large amounts in the past) with Monckton (sensitivity to forcing is low) by suggesting that past climate change has required strong forcing. But, the obvious question is then "what strong forcings"? Nothing in physics or paleontology would suggest that our sun has varied its output by enough to force the glacial periods. The most clever idea I heard for such a forcing was cosmic rays causing significant albedo changes by stimulating cloud formation. But recent measurements almost certainly rule that out. The thing is, the glacial/interglacial periods do line up rather well with forcing from Milankovitch cycles - and those forcing are weak. So there'd have to be a strong forcing we can't detect (nor apparently imagine) that just happened to operate at the same times as Milankovitch cycles. It makes a heck of a lot more sense to conclude that sensitivity is high, and there are no significant forcings we haven't thought of.
124647. kmcolo at 12:34 PM on 1 February 2010
        The role of stratospheric water vapor in global warming
        Methane started to level off in early 1990s so not tight correlation with water vapor. Also, apparently (though I too am limited by article access issue) ∆ in strato-water vapor was in lower stratosphere thus not likely methane. All that said if there was a change in tropo-strato exchange then there might be noticeable change in atm concentrations of methane, SF6, etc. Worth looking into...
124648. Marcus at 11:38 AM on 1 February 2010
        The role of stratospheric water vapor in global warming
        Hmmm, as I recall, methane levels rose sharply through the 2nd half of the 20th century-but leveled off between 2000-2008. So maybe that's why there's a drop in stratospheric water vapor post-2000. However, as this additional methane was derived from human sources (sewerage, land fill, fossil fuel extraction, land-use change)-then the stratospheric water vapor contribution to global warming-small though it might be-might well still be ultimately of anthropogenic origin. That certainly doesn't let the contrarians off the hook!
124649. Tony O at 11:33 AM on 1 February 2010
        The role of stratospheric water vapor in global warming
        The article is hidden behind a pay-wall so I have to rely on the likes of yourself to interpret. Even if I could access the article there is no guarantee I could understand it. It is interesting. Thanks.
124650. Riccardo at 10:27 AM on 1 February 2010
        There's no empirical evidence
        samantha, it's basically the same, they just found it hard to get it through peer review.

Prev  2485  2486  2487  2488  2489  2490  2491  2492  2493  2494  2495  2496  2497  2498  2499  2500  Next