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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 101951 to 102000:

  1. The human fingerprint in the seasons
    I think this should be corrected: "What we observe instead is the poles warming around 3 times faster than the equator." That's only valid for the North Pole, but not for the South Pole. What we expect from greenhouse warming is Arctic amplification, rather than polar.
  2. The Scientific Guide to Global Warming Skepticism
    Moderator @19 Dang yes you're right. I think there's something about the sequence "Most Likely", "Likely", "Very Likely" that looks wrong, but yes when you think about it more ... Sorry for the false alarm
  3. The Scientific Guide to Global Warming Skepticism
    Bob Guercio @13 Though not highly technical, this might help. I pay attention to night time dew, because it can effect my work. What I have observed is that there is less dew on overcast or cloudy nights. On clear nights, heat radiates out into space faster, causing more dew. Similarly, greenhouse gases slow the radiative cooling at night, hence warmer night time temps. If the sun was the cause of warming, you would expect to see more daytime warming, when the sun is out. But instead, night temps are rising faster than day temps. Bacisally the same idea for summer / winter. Now I'm wondering if the overcast nights being warmer has more to do with mixing between layers of the atmosphere, in which case, the analogy is not as good. Anyone?
  4. The Scientific Guide to Global Warming Skepticism
    Great job John but ... there's a mistake in the figure on page 8 where the captions at the top "Likely" and "Very Likely" are the wrong way round :-( I'd vote for "Its frigging cold" being included in the next edition, if only because where I am, it is - at the moment. And whilst I'm on the subject - any plans for a blog post on this "WACCo"(Warm Arctic, Cold Continent) weather modeling ?
    Response: No, the captions for Likely and Very Likely are correct (I checked now just to be sure). The shorter thicker bar (off the top of my head) means there is a greater than 66% chance that climate sensitivity falls within that bar. The longer, thinner bar means there is a greater than 90% chance climate sensitivity falls within that range. When you think about it, it makes sense that there is a greater chance (eg - very likely) that climate sensitivity falls within the wider range of values.
  5. 1934 - hottest year on record
    "Globally, the ten hottest years on record have all occurred since 1998, with 2007 as the hottest." Shouldn't that say 2005, not 2007?
  6. The Scientific Guide to Global Warming Skepticism
    Bob Guercio @13- This is a laypersons understanding of the night/winter issue, so please excuse and correct any misstatements or misconceptions, but I'll give a try at explaining my understanding as maybe we are on a similar level scientifically. Think about daytime being when the earth absorbs heat from the sun and nighttime as when heat is radiated back out through the atmosphere. That's why it's almost always coldest in the early morning just before dawn after an entire night of losing heat. The warming effect of CO2 is related to how it interferes with the heat radiating back out through the atmosphere. Since there is more radiating of heat during the night it is the nighttime temperatures that will be most affected by the increasing CO2. Although I'm sure there is some radiation of heat occurring during the daytime, I imagine it must be less because the gradient in the temps between the earth and the atmosphere is less than at night. Also the temperature moderation during the daytime from radiating heat would be relatively small compared to the temp moderation driven by heat absorption. With regards to winter temps I think the concept would be the same since you have less insolation, longer nights etc during the winter so the effect of the CO2 would show up more. One question that occurs to me from writing this up is why doesn't CO2 have an equal effect in blocking the heat coming into the earth as it does on blocking the heat leaving? My guess is it has to do with the radiation coming in (sunlight) being of different wavelengths compared to the heat radiation going out.
  7. The human fingerprint in the seasons
    Cris G wrote the following... "take to mean that you think there is a limit to how hot CO2 can get." based on my comment 79, which contained... "Given that water vapor has double the heat capacity of CO2, and abounds in excess of 100 times the anthropogenic contribution in CO2, this retained "energy" you are talking about represents at most 0.5% of the total ambient. I suppose that is energy, but it doesnt seem like much. " From this I can only "take to mean" you did not read what I wrote.
  8. The human fingerprint in the seasons
    #141: "Yet the Arctic had a higher amplification than current, this would be very strong evidence" That's not really strong evidence. Look here for a more thorough discussion of arctic amplification than in the Chylek paper you reference. We also said here that the early 20th century warming had a different cause than the current warming; why would expect the same responses?
  9. keithpickering at 06:53 AM on 9 December 2010
    The Scientific Guide to Global Warming Skepticism
    For the next edition, I would also add Human Fingerprint #8: Decreasing atmospheric O2, caused by the burning of fossil carbon. If the increase in CO2 had come from natural sources, O2 would not be decreasing by similar amounts. Langenfelds et. al. (1999), GRL 26:13, 1897-1900.
    Response: That is mentioned in passing on Page 1 on the 'Human Fingerprints on Climate Change' graphic but there were only so many green box Human Fingerprints I could fit into the rest of the Guide. If we ever do an "extended edition", I'll get the opportunity to flesh out more fingerprints.
  10. The Scientific Guide to Global Warming Skepticism
    For some reason, I'm having trouble really understanding why nights warm faster
    Thinking about it as why nights cool more slowly helps, maybe, since the cooling all takes place through the radiation of LWIR?
  11. How Jo Nova doesn't get the tropospheric hot spot
    Schnorkel dismissing a complex issue with innuendo brings us nowhere. You can find a good historical perspective here.
  12. The Scientific Guide to Global Warming Skepticism
    Oops. Not "online newspaper readers" but "online newspaper commentators".
  13. The Scientific Guide to Global Warming Skepticism
    Thanks. I've been working on the issue for several years but probably reaching the wrong audience, online newspaper readers, most of whom are repetitive ideologically-driven trolls. Fortunately, your document is clear enough that perhaps even the politicians might understand and they are my current target. I won't try to convince the MP for my riding in Canada, John Baird who is probably the worst possible choice for the job in our parliament. At the COP15 in Bali when he had the substantive role rather than the current "temporary" one, he left a high-level meeting and was seen minutes later drinking a cocktail at a party. There is no way that he's getting my vote. But it appears very likely that votes alone won't help us to deal with the issue. I guess that it's time to "get in their faces".
  14. A Cloudy Outlook for Low Climate Sensitivity
    Arkadiusz Semczyszak @108, It would be helpful if, instead of simply posting quotes from papers, you provided some context or explanation for them. What point are you trying to make?
  15. The Scientific Guide to Global Warming Skepticism
    Folks, I have a technical question related to the guide. I don't mean to say that the guide is incomplete; it's just that I would like more information for myself. The guide, as is, is perfect. For some reason, I'm having trouble really understanding why nights warm faster than days and winters warm faster than summers. For some reason, understanding this is eluding me. Thanks, Bob
    Response: I am intentionally brief about those fingerprints in the Guide, acutely aware that you can't fit everything into a single guide without it bloating to unwieldy proportions. Fortunately, I have a blog to flesh out the details and in anticipation of these kinds of issues, I'd even already gone into more detail about the daily and annual cycle (my original plan was to have blog posts about all the human fingerprints before the Guide came out but well, I'm just not that well organised):

    The human fingerprint in the daily cycle
    During the day, the sun warms the Earth's surface. At nighttime, the surface cools by radiating its heat out to space. Greenhouse gases slow down this cooling process. This is why deserts cool so much at night. Water vapour is a strong greenhouse gas and the dry desert air traps much less heat than more humid areas. A more extreme example is the moon which has no atmosphere. At nighttime, there are no greenhouse gases to trap the outgoing heat. Consequently, the difference between day and night is more extreme with daytime temperatures getting up to around 118°C and nighttime temperatures falling below -168°C. In other words, the stronger the greenhouse effect, the smaller the difference between daytime and nighttime temperatures.

    The human fingerprint in the seasons
    During summer, a region receives more sunlight and warms. During winter, the region receives less sunlight and cools by radiating heat to space. Greenhouse gases stop some of this heat from escaping to space so an increased greenhouse effect slows down the winter cooling. Consequently, if greenhouse gases are causing global warming, we expect to see winters warming faster than summer.
  16. A Cloudy Outlook for Low Climate Sensitivity
    Camburn @64 1. Statistically, and this is important unless you want to throw statistical analysis out with the wash, we have not warmed for the past 15 years. "Because the temperature has random ups and downs on top of the long term warming trend, you need about 16 years to conclude (with 95% confidence) that a trend in those 16 years is not a result of chance. So if the only temperature data we had was 1995-2009 (15 years!) we couldn't conclude with 95% confidence that there was a trend. But we also couldn't conclude...that there is no trend -- there simply isn't enough data for a firm conclusion. But we have more data than just 1995-2009, so we can conclude (with greater than 95% confidence) that there is a warming trend. "In fact, since we have data for 2010 now, it is even now true that we have statistically signficant warming since 1995." I'd like to join archiesteel in asking you to acknowledge your error.
  17. The human fingerprint in the seasons
    Norman @148, Thanks for clarifying. I must still, however, agree the assessments made by CBDunkerson and others. I might take issue with the John Cook using the dichotomy of the tropics and poles-- maybe he meant to discriminate between the tropics and high latitudes. The northern mid-latitudes have also been warming more in the winter than in the summer.
  18. How Jo Nova doesn't get the tropospheric hot spot
    #29: "Gee, I think I understand ..." Might be easier to understand if you actually read the post before commenting. the hot spot is not caused by the greenhouse effect. In fact, we expect to see an amplified warming trend in the troposphere no matter what's causing the warming. ... Detecting the tropospheric hot spot is not a test of the greenhouse effect but of the moist adiabatic lapse rate. Most folks would agree that its better to do some research before forming opinions. SkS has a search feature; try it, you might like it.
  19. A Cloudy Outlook for Low Climate Sensitivity
    muoncounter #105 - by "current pace" I was referring to an accelerating, not linear increase. For example see the upper IPCC emissions scenarios, which are what we're currently on pace with.
  20. Steven Sullivan at 04:16 AM on 9 December 2010
    Phil Jones says no global warming since 1995
    John, Tamino's 'How Long' post seems to have vaporized. But he has another, more recent, one that treats the Phil Jones quote http://tamino.wordpress.com/2010/11/11/hey-david-whitehouse-why-is-the-sky-green/
  21. Stratospheric Cooling and Tropospheric Warming
    Tom Curtis at 02:05 "Convection doesn't work in the stratosphere because the temperature increases with altitude in the Stratosphere, not because of the low density." As i understand it, convection stops working in the upper troposphere, because radiative transfer moves energy to quickly, preventing a build up/heating of a layer above that above it, the inversion between the troposphere and the stratosphere would prevent convection. But it is the result of the opacity reaching a level where radiation is the dominant means of energy transport... and the opacity is the result of the decreasing pressure. obviously higher up in the stratosphere convection once again plays a role, from the O3 absorption. Interesting points. Particularly about number two.
  22. How to explain Milankovitch cycles to a hostile Congressman in 30 seconds
    Spiff... I think Alley's brilliance is as a teacher. You have to know he's used exactly that same demonstration ("my bald spot") with 100's if not 1000's of the students he works with. Even the wording he uses is wonderful. "Your brightness is the sun..." Makes listeners feel good about themselves. You have to remember Rohrabacher is not the audience when Alley is speaking to him. He is merely the antagonist in the forum. What is important is that people hear Alley teach the antagonist the error in his thinking. Therefore, it's not Alley's job to convert Rohrabacher, it's his job to teach the broader audience by politely responding to Rohrabacher's misinterpretations. I try to use exactly this thinking when I engage climate change deniers on various forums. I try to be polite. (I really do try!) I try not to make it a personal goal to convert the person I'm talking to. But I try, to the best of my abilities, use that denier as a way to teach the broader reading audience what I've learned about the science of climate change. Science that I have primarily learned here at SkS.
  23. Stratospheric Cooling and Tropospheric Warming
    VTG @185, from trial and error, I have figured out that it only adjusts the ground temperature. It uses several standard temperature profiles, which you choose by selecting "tropical" etc. It doesn't calculate the temperature at all. Rather, it determines the radiation out given a specific temperature profile and atmospheric composition. If you read the paperwork, you will see that the version available at David Archer's site is one from the early 1990's. I don't know the capabilities of more recent models. If you want to calculate equilibrium temperatures, you should probably use the NCAR model at the same site. I have not played with it very much, so I cannot advise you except for two caveats: it also is an obsolete model, and it does not handle cloud albedo well, giving non-physical results for significant change in cloud cover. Regarding convection, as convection operates in the mesosphere, presumably it would also operate in the stratosphere without the inversion. You may find these lecture notes a usefull summary of basic facts about the upper levels of the atmosphere.
  24. Renewable Baseload Energy
    Quokka, this source from Nebraska (the first hit on google) says 14% of electricity in houses is used for hot water. Solar hot water heaters are currently installed in many places. They are usable in all locations in Australia and most of the USA. That would greatly exceed the 3% you want in post 381. China is reported to be installing a lot of solar hot water. Where I live (Florida)solar pool heaters are the most cost effective method, and save even more energy. Your absolute arguments fall flat. A combination of methods will always outperform a single method.
  25. The Scientific Guide to Global Warming Skepticism
    I like the fact that it has lots of graphics.
  26. Stratospheric Cooling and Tropospheric Warming
    Tom @183 On Modtran, that's what I assumed - I tried adjusting the ground temperature in exactly the way you suggest, but it doesn't affect the atmospheric profile. If not by thermal equilibrium, how does it calculate the temperature gradient through the atmosphere and why doesn't CO2 concentration change the temperature profile at all? On radiative vs convective heat transfer - I'd thought about the inversion limiting convection as well but I'd also assumed that the reduction in density would be sufficient to significantly reduce heat transfer by turbulent mixing. Thank you for your time btw, I've learned a lot. Now, those pics, the red line is effectively the total stratospheric emission I think: 20km altitude, looking up, 100ppm CO2, total emission 6.6 W/m2 And again with 1000ppm, total emission 11.0 W/m2 You can clearly see the increase in stratospheric emissions as CO2 rises. Ergo in equilibrium you'd expect T to decrease.
  27. The Scientific Guide to Global Warming Skepticism
    This is a great summary and presentation of the data. You have done a terrific job of putting it all together. I like the clean look and easy to read summaries.
  28. Stratospheric Cooling and Tropospheric Warming
    VeryTallGuy @181, that is the first explanation in a nutshell, except ... My quibble is with (2). Convection doesn't work in the stratosphere because the temperature increases with altitude in the Stratosphere, not because of the low density. Also, Bob's second explanation is also a significant, if possibly transient effect.
  29. How Jo Nova doesn't get the tropospheric hot spot
    Gee, I think I understand how Jo Nova got it so wrong. Let's see... satellites have trouble reflecting what the models predict. So the sat data must be wrong. Weather ballons are wrong too. But the wind, steady reliable, proves the models supporting AGW are right. Furthermore, when the sat and ballons don't support the models, they also don't detract from AGW theory. But when ANY data is ...what was the term? "adjusted for" well, then it does support the models and hence support the theory of AGW. Yep, I've got it. How could Jo Nova get it so wrong?
  30. Stratospheric Cooling and Tropospheric Warming
    VeryTallGuy @179, Modtran is a radiative transfer model only. That means it calculates the emission and transmission for various atmospheric conditions, but does not adjust those conditions to establish equilibrium. In the version at David Archer's site, you can make a partial equilibrium adjustment for outgoing radiation by adjusting the ground temperature offset until the Iout matches the original value. However, it only adjusts ground temperature so it is not entirely accurate, and cannot (by that means) adjust for equilibrium in the stratosphere.
  31. Spaceman Spiff at 01:49 AM on 9 December 2010
    How to explain Milankovitch cycles to a hostile Congressman in 30 seconds
    Many kudos go to Alley for trying, but I find the piece to be depressing. Rohrabacher gets to spout off tired disinformation and falsehoods as facts that Alley needs to answer for (while constantly admitting he himself knows nothing about which he speaks!). Pat Michaels of the Cato institute gets to serve as an "equal" counterweight to Alley, as if....OMG.
  32. Arkadiusz Semczyszak at 01:41 AM on 9 December 2010
    A Cloudy Outlook for Low Climate Sensitivity
    Under are comments authors to this paper: Boyce et al., 2010.: “But their numbers have dwindled since the dawn of the 20th century, with unknown consequences for ocean ecosystems and the planet's carbon cycle., … the global population of phytoplankton has fallen about 40 percent since 1950., That translates to an annual drop of about 1 percent of the average plankton population between 1899 and 2008., It's very disturbing to think about the potential implications of a century-long decline of the base of the food chain ..., They include disruption to the marine food web and effects on the world's carbon cycle., Phytoplankton productivity is the base of the food web, and all life in the sea depends on it., In addition to consuming CO2, phytoplankton can influence how much heat is absorbed by the world's oceans, and some species emit sulfate molecules that promote cloud formation.
  33. The Scientific Guide to Global Warming Skepticism
    @ Albatross: I have an iphone 3Gs and it comes through fine as PDF via the Safari viewer, not sure about 3G, but most people should be able to see it without problem..
  34. Stratospheric Cooling and Tropospheric Warming
    Bob @180 Yes, I think that's more accurate. Tom @ 180 has put forward what seems to me like a pretty solid case that you need an external heat source (ie UV absorption) to effect cooling with higher CO2.
  35. Stratospheric Cooling and Tropospheric Warming
    Tom Curtis Ah, yes, I realise now that the total power output of the CO2 is limited by it's temperature ie it can't emit more than the equivalent blackbody in its emission bands. So your argument goes that unless there is another factor heating the stratosphere, to raise the CO2 temperature, then CO2 will actually absorb more CO2 from the troposphere than it will emit. In which case, how about this for a really simple explanation: 1) The stratosphere is heated by UV absorption in the ozone layer. 2) Due to low density, radiative heat transfer rather than convective heat transfer dominates. 3) At a given temperature, emissivity of the stratosphere increases as CO2 concentration increases, and at given CO2 conc, total IR emission from the stratosphere increases with temperature. 4) Therefore the temperature must fall to compensate if CO2 rises to keep the overall heat balance satisfied. The issue of the spectrum of IR coming up from the troposphere is then pretty much irrelevant I think?
  36. The Scientific Guide to Global Warming Skepticism
    This guide is simply superlative. Excellent work John & contributors!
  37. Stratospheric Cooling and Tropospheric Warming
    Very Tall Guy 179 Most of your comments are about my writing and I'm going to digest them and change my writeup if necessary. Regarding this comment: "Energy also causes CO2 molecules to vibrate but although this vibration is related to the energy content of CO2, it is not related to the temperature of the gaseous mixture." I think it would have been more accurate to say ""Energy also causes CO2 molecules to vibrate but although this vibration is related to the energy content of CO2, the temperature is not a function of this vibrational energy. The temperature is only a function of the translational K.E." Does this take care of your issue? Bob
  38. Human CO2 is a tiny % of CO2 emissions
    Yeah, most people here know the glass greenhouse analogy isn't great. But it actually works in this case. To answer your question, kdfv, if you insist on the 10m-thick slabs of glass analogy, think of CO2 as the thin line of caulk that seals up the cracks between those slabs. :-)
  39. Human CO2 is a tiny % of CO2 emissions
    Re: kdfv (79) Greenhouses warm by preventing convection (glass barrier). CO2 and the other non-condensable GHG's work by slowing the loss of radiated energy at the top of the atmosphere (TOA) through back-radiation which warms the lower layers of the atmosphere nearer to the ground and cools the mid-to upper layers of the atmosphere, like the stratosphere and the mesosphere. Hope that helps. The Yooper
  40. Stratospheric Cooling and Tropospheric Warming
    OK, I think I've got a good way to show this, although I've also found some more of my own limitations. I've had a play with the MODTRAN model interface available online: http://geoflop.uchicago.edu/forecast/docs/Projects/modtran.html and tried the following. I used the defaults (tropical, no clouds, zero ground offset temperature. I ran the model with 100ppm CO2, altitude 20km (ie at the tropopause), looking UP (ie at stratospheric emissions coming back) then again with 1000ppm. The results are striking. The increase in emissivity is clearly visible, and total IR from the stratosphere increases from 6.6W/m2 to 11.0W/m2. What I don't understand is that the model produces the same temperature profile at both concs, but this clearly shows that for increased CO2 and constant temperature, IR emission increases, ergo in order to maintain heat balance you'd expect the temperature to reduce. Someone who understands MODTRAN better can probably get the temperature profile to work properly too. Bob - this sort of graphical output, once correct, could be used to very effectively demonstrate the effect of CO2 in the stratosphere, I think. Apologies, my html isn't up to pasting the graphics straight in here.
    Moderator Response: [Daniel Bailey] 1. First type this symbol: < 2. Next, type: img width="500" src="http://image_url/" 3. Replace the URL in Double Quotes "" with the actual URL intended 4. A common error is to have an extra / at the end of the URL; this can be avoided by using the preview function. Should work for you now
  41. Water vapor is the most powerful greenhouse gas
    A few thoughts on the above post... A comparison is made stating that CO2 is an external forcing and water vapour is a result of temperature. This is is misleading, since CO2 levels in the atmosphere can be affected by temperature (for example oceans) while water vapour is added to the atmosphere by power plants and other industry. Therefore are they actually similar in the source for both gases - both affected by temparature and man made sources. The overall point of the article to state that water vapour warming will amplify CO2 warming is misleading, since there is nothing special about the CO2 warming. A natural sun-inducing warming would have similar effects on water vapour. So it is dangerous to state without qualification that 'Water vapour is also the dominant positive feedback in our climate system and amplifies any warming caused by changes in atmospheric CO2. This positive feedback is why climate is so sensitive to CO2 warming.' It could just as easily read 'This postive feedback is why climate is so sensitive to sun warming'. With this in mind, it leads me to ask why such postive feedbacks inherent in the atmosphere have not lead to runway global warming in the past from any naturally induced changes. The reference to Kiehl 1997 shows the clouds also reflect some sunlight back into space (diagram on page 10). Why is this negative feedback not discussed?
    Moderator Response: I fixed your extraneous line breaks. Please use the Preview button before using the Submit button. Clouds are not water vapor; they are condensed water. This post is about water vapor. See the post Positive feedback means runaway warming.
  42. Human CO2 is a tiny % of CO2 emissions
    If the atmospheric water vapour is equal to 10m spread around the world and co2 is equal to 6mm how does the temperature in a greenhouse alter when 10m of glass is increased by 6mm?
  43. Stratospheric Cooling and Tropospheric Warming
    VeryTallGuy @177, I have thought something similar in the past. Your suggestion is not correct, though, because absorptivity increases with emissivity, so that if you double stratospheric CO2, you double the amount of IR from tropospheric CO2 absorbed. You also double the the amount emitted. Obviously, if the stratospheric CO2 is warmer than the tropospheric, doubling both absorption and emmission will result in a larger increase of emission, thus cooling the stratospheric CO2. If the stratospheric CO2 is cooler, doubling both will result in a greater increase in absorption, thus cooling the stratospheric CO2. In the respective cases, the CO2 was warming (cooling) the stratosphere already, and just does so at an increased rate.
  44. The Scientific Guide to Global Warming Skepticism
    [standing ovation for John's work] Already blogged on my site: Doc alert: The Scientific Guide to Global Warming Skepticism
    Response: Thanks Lou, the post is much appreciated (but for the record, I am definitely defatigable).
  45. Stratospheric Cooling and Tropospheric Warming
    Bob @173, you asked for nit-picking so here goes. "The former dominates" Are you sure - I'd like to see a figure put on this to judge it personally. "Energy also causes CO2 molecules to vibrate but although this vibration is related to the energy content of CO2, it is not related to the temperature of the gaseous mixture." If (big if) I have understood correctly, then this isn't quite right. As temperature rises, a larger proportion of CO2 molecules will enter the higher vibrational states and preferentially emit IR in those frequencies. And this is the mechanism by which stratospheric cooling happens - conversion of thermal energy to IR by CO2. So whilst temperature does not measure vibrational energy, increased temperature does cause more CO2 molecules to enter excited states and hence emit IR. (I think)(Tom makes a similar point @176) "IR radiation contains energy and in the absence of matter, this radiation will continue to travel indefinitely. In this situation, there is no temperature because there is no matter." I think this is just confusing - all it amounts to is saying that vacuum has no temperature, and light can travel through it. Can you just cut this para? "These molecules will then collide with other molecules of either N2 or CO2 and some of the K.E. of these particles will be transferred to the CO2 resulting in excited CO2 molecules and a lowered stratospheric temperature. All entities, including atoms and molecules, prefer the unexcited state to the excite state. Therefore, these excited CO2 molecules will emit IR radiation which, in the rarefied stratosphere, will simply be radiated out of the stratosphere. The net result is a lower stratospheric temperature. This does not happen in the troposphere because, due to higher pressures and shorter distances between particles, any emitted radiation gets absorbed by another nearby CO2 molecule." A suggestion to simplify: "Due to the lower density of the stratosphere, IR is less likely to be reabsorbed, and more likely to escape either to space or back to the troposphere. With increased CO2 concentration, IR emission increases in the part of the spectrum where CO2 dominates. Thermal emissions in the rest of the spectrum must reduce to maintain overall equilibrium, which results in a lower temperature to maintain the heat balance." Tom Curtis @176 "where it not for Ozone being a net absorber of energy in the stratosphere, CO2 would not be a net emitter of energy in the stratosphere. And it is only by being a net emitter that CO2 can cool." I think this may be incorrect. I think that CO2 will increase the emissivity of the stratosphere regardless of ozone and therefore decrease the temperature. However, without Ozone, the temperature of the stratosphere would be much lower, as the UV energy absorbed by Ozone would then be transmitted. The relative effect of extra CO2 would, though, I think reduce the temperature still further. And I'd just like to emphasise I'm no expert in this and could be very much mistaken in my analysis. Interesting to try and understand though.
  46. The Scientific Guide to Global Warming Skepticism
    Brilliant!
  47. We're heading into an ice age
    NQoA wrote: "if accumulated CO2 is causing the globe to warm, then - by the AWG logic - 2008 through 2010 would be below 2007." That's not any 'AGW logic' I've ever heard of. First, sea ice extent is a measure of ice area and how spread out the ice is. The 2007 value was noted at the time to have been in part caused by wind conditions causing the ice to mass up in a small area (which 'skeptics' took as an excuse to ignore it). Now we've had three subsequent years where we haven't seen winds pack the ice into such a small area but the extent has been nearly as low in two of them, because there is now less ice... as we can see from looking at ice volume values, which have continued to drop each year since 2007. Second, there is something called weather which can cause large fluctuations in all kinds of climate readings. The Arctic winds contributing to the low extent in 2007 are one example. In this case the volume (aka 'actual amount') of Arctic sea ice has declined each of the past few years... but if it were to tick up for a few years that wouldn't be contrary to AGW in any way. Just expected natural variation.
  48. The human fingerprint in the seasons
    Norman, as I said somewhere further up in this thread... it is true that various climate feedbacks would take place regardless of what the forcing was. However, it is not true that the feedbacks would be exactly the same. For instance, your claims about water vapor and polar albedo (aka Arctic amplification) feedbacks are demonstrably incorrect. When atmospheric CO2 levels increase they do so globally. The CO2 level goes up for the entire planet and thus the rate of infrared radiation escape goes down. Further, this is a year round phenomenon... the CO2 level only fluctuates slightly during the year, much less than the cumulative increase we have observed (indeed, the annual rate of increase is now about equal in magnitude to the annual fluctuation). As such it causes increased water vapor and increased surface warming worldwide and year round... obviously with large fluctuations for weather events. A solar forcing on the other hand would be geographically and seasonally localized. If it were exactly equal in total magnitude to a CO2 forcing most of that energy would be located in the tropics and during Summer. Thus, while Arctic amplification would still occur it would be much less pronounced because a much smaller proportion of the forcing is at work in the Arctic. Ditto water vapor. It would increase more in the tropics, but less for the rest of the world... resulting in an even more pronounced tropical warming signal over that of the Arctic. Likewise we wouldn't see the accelerated Winter warming that we have with CO2 because a solar forcing would be concentrated in the Summer months. Feedbacks can only respond to forcings when and where they occur. This is inescapable. Thus, you can't have a strong Winter feedback from a Summer forcing... nor a strong Arctic feedback from a tropical forcing.
  49. How to explain Milankovitch cycles to a hostile Congressman in 30 seconds
    jg - that is a superb piece of work, it's bookmarked for future use! I saw the Alley testimony a few weeks ago, and was disturbed by the dreadful way the Republican ignored his answers and kept repeating the most tired old talking points. I agree with archiesteel that Alley should have straightforwardly called out the Mars canard, but I guess he's caught in a hard place where he has to be polite and reasonable with his answers, yet the questioner does not have to be polite (and ignored/spoke over the answers when the got near being utterly inconvenient truths). But the more opportunity that Richard Alley gets to communicate, then the better for all of us, he is fantastic at getting the science across. Alley's CO2 control knob AGU talk should be standard learning material.
  50. The Scientific Guide to Global Warming Skepticism
    Thunderbirds Are Go Push it out there people. G

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