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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 102001 to 102050:

  1. It's the sun
    Ned, I had kind of (lost interest really in someone determined not to understand physics) so perhaps "noone" was optimistic. Let try "no physicist doubts..."
  2. A Cloudy Outlook for Low Climate Sensitivity
    #102: "we're currently on pace to double atmospheric CO2 levels in the next 75 years or so. That's doubled from current levels," Dana, even at 3ppm per year, 75 years is 'only' another 225 ppm. I'm sure we'll hit 390 this spring, but it'll take a while longer to double than 75 years. Besides, I'm thinking by 450ppm, things will get downright ugly.
  3. CO2 lags temperature
    #214: "... co2 greenhouse effect sufficient to influence temperature." Try to substantiate your claims, rather than just make such declarations. You might want to do some reading before you engage in so many blanket dismissals. Start here, here and here, then we can talk.
  4. CO2 lags temperature
    I don't buy this theory. External event rises temperature. Soils and vegetation release co2 in a global burnoff. Probably the ocean mass heat memory with dissolution is the likely explanation of the centuries delay. If co2 amplified minor temp rises then it should be in synch without delays of centuries. Eventually the temperature goes down and the plants etc can reabsorb the gas back to photosynthesis equilibrium levels. You never get the amplification process because photosynthesis is such a dominant process. Perhaps when the conc goes above 1 per cent is co2 greenhouse effect sufficient to influence temperature. Look if co2's lifetime was several centuries then do the calculation of 100 years of fossil consumption with 5gt per year for the last 20 years. What should the co2 concentration be? I don't know the mass of co2 in the air currently, but some have done it and say that half the mass is missing, ie perhaps a 20 year lifetime, some say 5. This stuff is scrubbed from the air.
  5. Stratospheric Cooling and Tropospheric Warming
    Joe Blog - 174 We discussed the big issues and only nitpicking is left. I want nitpicking and your wording is much better than mine was. Thank you. I want very much to get a pro. I corresonded with Rasmus Benestad who is one of the pros on Real Climate. He said he hadn't thought about all of this since graduate school but gave me some ideas including the need to combine those graphs. He also recommend two scientists from Real Climate to send it to. So I'm not going to just send a new email. I'm going to forward his mail to me recommending the scientist. That will pretty much force him to critique it. I combined the graphs by painting pixel by pixel. Laborious is a word that comes to mind. John is going to do some artwork for me. Something to clarify the first process. Thanks again. Bob Bob
  6. It's cosmic rays
    Continuing from a comment on the Cloudy outlook thread. "high degree of blocking from local stratospheric warming from GCR spikes." I know a lot of people who are actively monitoring cosmic ray air showers of the type associated with GCRs; I don't see lots of evidence coming forth. These 'GCR spikes' do not last more than a few fractions of a second at most. And they do not necessarily come in 'swarms.' Big events can be years apart. Here, however, is evidence from a rather old study on the impact of GCRs on the earth's electric field: Data have been obtained which suggest that changes in the Earth's electric field of 10–20 V/m occur close to the cores of extensive air showers initiated by primary particles of energy greater-than or equivalent to 10^17 eV. The earth's fair weather electric field is nominally 100-150 V/m near the surface, so this might be variation on the order of 10%. However, as one E field meter company states, "foul weather electric fields can reach values of well over 10,000 volts per meter at the ground". So why is anyone chasing cosmic rays? Climate change must be caused by lighting!
  7. Renewable Baseload Energy
    @377 swieder I have no doubt that the underlying German discussion is "Do NPP "hinder" fast introduction of renewables or not?" But that is not the "right" question. The right question is "What are the lowest cost low emission technologies and how can they be combined system wide to generate the lowest cost, low emission electricity? ". As James Hansen recently remarked "I must start with a fundamental law: as long as fossil fuels are the cheapest energy, they will continue to be burned. This law is as certain as the law of gravity." Hansen made this remark in a review of his recent trip to China. I'm not sure I would be quite as emphatic, as I do think there is some willingness worldwide to pay something to mitigate climate change. However, vested interests militate against the acceptance of even a small increase in cost and there can be no doubt whatsoever that the lowest possible cost of clean energy is the surest route to achieving meaningful emissions reductions.
  8. A Cloudy Outlook for Low Climate Sensitivity
    #100: "the high degree of blocking from local stratospheric warming from GCR spikes." You've totally lost me with that idea, but I am taking this comment over to the cosmic ray thread.
  9. The human fingerprint in the seasons
    From my analysis of the temperature data, the only way that clouds could be a significant factor in the current trends is if they were covariate on CO2 concentration and also contributed a positive effect, as CO2 is currently masking any of the other major feedback effects (although solar variability is still contributing a small proportion to measured temperature anomaly).
  10. Stratospheric Cooling and Tropospheric Warming
    Bob thats a good article... one nit pick ;-) Where you say "K.E. of these particles will be transferred to the CO2 resulting in excited CO2 molecules and a lowered stratospheric temperature" "I" would say, "K.E. of these particles will be transferred to the CO2 resulting in excited CO2 molecule, which will radiate this energy away, resulting in a cooler stratosphere etc etc." Overlaying the graphs was a good idea. There are also one or two places when you say "atmosphere" when you are obviously talking about the stratosphere. Are you going to get a pro to have a nosey? Science of Doom may be worth asking to give it a quick look over if you are looking, he knows his stuff.
  11. The human fingerprint in the seasons
    #136: "If clouds are a factor then CO2 is only partially responsible for the observed warming trend." I suppose we could also throw in a few dozen other unknown 'factors' if you like. But let's get back to the topic of this thread and the 'fingerprint' question. Cloud theories, electrical currents, little green men, don't produce the observed seasonal warming differentials. Further, In the latter 20th century, man-made forcing accounts for nearly all the observed temperature changes (Braganza et al 2004). If nearly all the temperature changes are accounted for, why dream up these other 'could be' and 'wannabe' ideas? If you want to be a skeptic, please be objectively skeptical -- look critically at all proposals, not just the one that involves CO2.
  12. The human fingerprint in coral
    Nice writeup on coral bleaching over at ClimateProgress today:
    "The atmospheric levels of CO2 we are already committed to reach, no matter what mitigation is now implemented, have no equal over the entire longevity of the Great Barrier Reef, perhaps 25 million years. And most significantly, the rate of CO2 increase we are now experiencing has no precedent in all known geological history. Reefs are the ocean’s canaries and we must hear their call. This call is not just for themselves, for the other great ecosystems of the ocean stand behind reefs like a row of dominoes. If coral reefs fail, the rest will follow in rapid succession, and the Sixth Mass Extinction will be upon us — and will be of our making." - J.E.N. Veron
     Veron is the former chief scientist of the Australian Institute of Marine Science. He is principal author of 8 monographs and more than 70 scientific articles on the taxonomy, systematics, biogeography, and the fossil record of corals. His books include the three-volume Corals of the World and A Reef in Time: The Great Barrier Reef from Beginning to End (2008). His research has taken him to all the major coral reef regions of the world during 66 expeditions. The Yooper
  13. Stratospheric Cooling and Tropospheric Warming
    Hi All, Here is my latest iteration. John Cook is going to help me with some artwork in order to help explain the first mechanism. Bob Stratospheric Cooling and Tropospheric Warming - Revised Increased levels of carbon dioxide (CO2) in the atmosphere have resulted in the warming of the troposphere and cooling of the stratosphere which is caused by two mechanisms. One mechanism involves the conversion of translational energy of motion or translational kinetic energy (KE) into Infrared radiation (IR) and the other method involves the absorption of IR energy by CO2 in the troposphere such that it is no longer available to the stratosphere. The former dominates and will be discussed first. For simplicity, both methods will be explained by considering a model of a fictitious planet with an atmosphere consisting of CO2 and an inert gas such as nitrogen (N2) at pressures equivalent to those on earth. This atmosphere will have a troposphere and a stratosphere with the tropopause at 10 km. The initial concentration of CO2 will be 100 parts per million (ppm) and will be increased to 1000 ppm. These parameters were chosen in order to generate graphs which enable the reader to easily understand the mechanisms discussed herein. A short digression into the nature of radiation and its interaction with CO2 in the gaseous state follows. Temperature is a measure of the energy content of matter and is indicated by the translational K.E. of the particles. A gas of fast particles is at a higher temperature than one of slow particles. 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. Molecules undergoing this vibration are in an excited state. 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. The energy content of IR radiation can be indicated by its IR spectrum which is a graph of power density as a function of frequency. Climatologists use wavenumbers instead of frequencies for convenience and a wavenumber is defined as the number of cycles per centimeter. Figure 1 is such a graph where the x axis indicates the wavenumber and the y axis indicates the power per square meter per wavenumber. The area under the curve represents the total power per square meter in the radiation. The interaction of IR radiation with CO2 is a two way street in that IR radiation can interact with an unexcited CO2 molecule and cause it to vibrate and become excited and an excited CO2 can become unexcited by releasing IR radiation. Consider now the atmosphere of our fictitious model. N2 and CO2 molecules are in motion and the average speed of these molecules is related to the temperature of the stratosphere. Now imagine that CO2 molecules are injected into the atmosphere causing the concentration of CO2 to increase. 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. In order to discuss the second and less dominant mechanism, consider Figure 1 which shows the IR spectrum from a planet with no atmosphere and Figures 2 which shows the IR spectrums from the same planet with CO2 levels of 100 ppm and 1000 ppm respectively. These graphs were generated from a model simulator at the website of Dr. David Archer, a professor in the Department of the Geophysical Sciences at the University of Chicago and edited to contain only the curves of interest to this discussion. As previously stated, these parameters were chosen in order to generate graphs which enable the reader to easily understand the mechanism discussed herein. Figure 1. IR Spectrum - No Atmosphere The curves of Figures 2 approximately follow the intensity curve of Figure 1 except for the missing band of energy centered at 667 cm-1. This band is called the absorption band and is so named because it represents the IR energy that is absorbed by CO2. IR radiation of all other wavenumbers do not react with CO2 and thus the IR intensity at these wavenumbers is the same as that of Figure 1. These wavenumbers represent the atmospheric window which is so named because the IR energy radiates through the atmosphere unaffected by the CO2. Figure 2. CO2 IR Spectrum - 100/1000 ppm A comparison of the curves in Figure 2 shows that the absorption band at 1000 ppm is wider than that at 100 ppm because more energy has been absorbed from the IR radiation by the troposphere at a CO2 concentration of 1000 ppm than at a concentration of 100 ppm. The energy that remains in the absorption band after the IR radiation has traveled through the troposphere is the only energy that is available to interact with the CO2 of the stratosphere. At a CO2 level of 100 ppm there is more energy available for this than at a level of 1000 ppm. Therefore, the stratosphere is cooler because of the higher level of CO2 in the troposphere. Additionally, the troposphere has warmed because it has absorbed the energy that is no longer available to the stratosphere. In concluding, this paper has explained the mechanisms which cause the troposphere to warm and the stratosphere to cool when the atmospheric levels of CO2 increase. The dominant mechanism involves the conversion of the energy of motion of the particles in the atmosphere to IR radiation which escapes to space and the second method involves the absorption of IR energy by CO2 in the troposphere such that it is no longer available to the stratosphere. Both methods act to reduce the temperature of the stratosphere. *It is recognized that a fictitious planet as described herein is a physical impossiblity. The simplicity of this model serves to explain a concept that would otherwise be more difficult using a more complex and realistic model. Copyright 2010 - Robert J. Guercio
  14. It's the sun
    scaddenp writes: Secondly, noone doubts changing albedo (with no other change) will affect temperature You obviously haven't been keeping up with the thread on the second law of thermodynamics, where someone just wrote: "The idea that planetary temperature is affected by its albedo is quite mistaken."
  15. Eric (skeptic) at 11:54 AM on 8 December 2010
    A Cloudy Outlook for Low Climate Sensitivity
    #101, Rob, it was the Tim Lenton article discussed at http://www.realclimate.org/index.php/archives/2007/08/musings-about-models/ After reading it I pointed out that the tipping points were local and had essentially no chance of "tipping" the global temperature (my comments are #17, #65, and later). There are some good responses to those as well. The article link seems to be broken, I will try to find it later. #102 Dana, thanks for the correction. I see now that 0.2 per decade (if that is sustained decade by decade) would actually be a 3C sensitivity. Your CO2 as a pollutant thread has some interesting discussion: legal definitions, the contribution of science to policy, etc. I think BP has a special knack in those areas.
  16. It's the sun
    Ray Ladbury just offered up this juicy bit which aptly describes the focus on GCR's and magical other postulated electric-thingy's:
    "First, you have to look at ALL the evidence. There is no way you get simultaneous stratospheric cooling and tropospheric warming without a greenhouse forcing. And increased tropospheric water vapor ain’t gonna give you that. Second, one cannot simply posit a mystery forcing and say it will behave like a greenhouse gas without specifying the candidate mechanism. If they were saying the mechanism were increased insolation, then perhaps you would see warmed nights, but it is very unlikely you’d see the seasonal effect (WV persists only on a timescale of days). I cannot emphasize this second point enough. I mean ferchrissake, they could posit Martians with heat rays sending in IR photons to exactly mimic greenhouse forcing by CO2. They need to propose a mechanism and see what sort of signature it would give. Simply saying, “Well, it could be something else” ain’t science."
    I love it when PHd's get riled... The Yooper
  17. It's the sun
    Norman, firstly, your calculator is too simplistic. Clouds both warm and cool. Secondly, noone doubts changing albedo (with no other change) will affect temperature. So magical fairy dust might increase albedo but "electrical connection between sun-earth" is in same category until someone presents some believable physics to show how this could work instead of gobbledegook. You appear to preferring wild speculation backed by dodgy "facts" in preference to a working model, conforming to known physics.
  18. The human fingerprint in the seasons
    Re: Norman (136) So you're saying it was cloudier before 1980...doesn't parse. I don't think you're standing back far enough & giving this enough thought. Because it seems to this observer you're grasping at straws. The Yooper
  19. The human fingerprint in the seasons
    #131 Daniel Bailey, "No observable mechanism other than the rise in CO2 explains also the rise in temperatures we've measured since 1980." Not totally correct. There is possible observations of Tropical clouds (the ones that would result in cooling due to albedo effect) decreasing at the same time the Globe has demonstrated warming. When I posted this possibility another guest demonstrated that the satellite data showing decrease in tropical cloud formation may not be valid. It does remain a possible explanation for at least some of the warming, other can be attributed to CO2. The question would be, If clouds are a factor then CO2 is only partially responsible for the observed warming trend.
  20. It's the sun
    Sorry Ned, I neglected to link to the albedo calculator. albedo and TSI calculator.
  21. It's the sun
    Ned, On a previous thread I posted a albedo calculator. Located on the page I will link to. It is a calculator that will determine temp with no GHG, just the two variables. TSI and albedo (basically to simplify so you can see relative contribution to temp). If you play with this calculator a bit you will see TSI has little effect at the ranges during sunspot cycles. But alter the albedo a few %points and you can see it has a rather large effect on global temps. If sunspot cycles alter the Earth's albedo even a few percent points, they can have a large effect on global temps. Not saying that is the cause but if sunspot number does effect cloud formation via the Earth's electrical circuit then that is a mechanism to explain how sunspot number can alter climate.
  22. It's the sun
    Re: Ned (737) Based upon my (admittedly) skimming through of the paper, I saw some data cherry-picking, chance correlations and gibberish (to use some technical descriptors). Maybe I'm under-selling it, but no physical mechanism postulated in the study also postulates why the physical processes of GHG's work for the remainder of the paleo record, but not for the past 30 years. Hence my gibberish descriptor. Maybe if it had been written in Yooperese:
    "Aino went down by da crick where he'd seen dat 8-pointer da year gone by, eh? And what da ya know, der was da biggest cayoat standin' next to da still! Next time mebbe der will be a bare! - Toivil"
     The Yooper
  23. It's the sun
    #737 Ned, A quote from the article: "Despite the difficulty in identifying cause and effect in a chaotic system such as the atmosphere, it remains possible that the global atmospheric electrical circuit provides a neglected feedback in the climate system, and with it, an amplification of the solar variability signal in the climate records. This is the principal reason why the topic now deserves further exploration." The basic point was cloud formation physics and how the electrical circuit effects this phenomena. Clouds are what cause the Earth's albedo to be around 0.3. If not for clouds the albedo would be around 0.1 (ocean's make up 70% of the surface) and the Earth would be much warmer.
  24. How to explain Milankovitch cycles to a hostile Congressman in 30 seconds
    Ned and Glenn, Thank you for your comments: Regarding EPICA -- yes. I wanted to work out the bugs and user interface on a smaller data set first. The jump you observe at the origin is a programming challenge that I need to remove; but right now it is helpful when I add a new graph and fail to scale it correctly (it tells me which direction off the screen it is). Regarding scaling factors, I estimated scaling to match similar graphs I've seen, but this is an inadequate answer. I welcome suggestions. Glenn, please elaborate on what you mean by showing differences between NH and SH insolation. I currently allow a comparison between, e.g., Northern Summer to Southern Summer, are you asking for Northern Summer to Southern Winter or some calculation between datapoints? thanks again, jg
  25. A Cloudy Outlook for Low Climate Sensitivity
    Yes, what Rob said. Melting ice decreases both local and overall planetary albedo. I don't think it's possible to justify the claim that melting ice will not have a significant impact on global temperature. Particularly if significant methane deposits are released. The other issue is that we're currently on pace to double atmospheric CO2 levels in the next 75 years or so. That's doubled from current levels, not pre-industrial levels. So with a 3°C sensitivity to 2xCO2, you're talking about 3°C warming from now, 4+°C warming from pre-industrial levels. Or if you choose to believe the low end of the sensitivity range - which according to the article I just wrote, you probably shouldn't - it's 2°C warming between now and the end of the century, 3°C above pre-industrial. And remember, the 'danger limit' is 2°C above pre-industrial.
  26. How to explain Milankovitch cycles to a hostile Congressman in 30 seconds
    I've just finished reading 6 Degrees by Mark Lynas. The disconnect between that and the boofhead, oops, sorry ... Congressman was staggering and terrifying jg Awesome! This will really help in a debate I am having on a sceptic site right now. Interesting how the shape of the Methane curve tracks temps more closely than CO2. Quicker response time for Methane and closer temperature dependence probably. And to 100 ky eccentricity cycle seems to be the stronger driver. As with any piece of software, if it is good we want more more more... Any chance you could add a feature to allow differences between the NH & SH insolation to be shown.
  27. How to explain Milankovitch cycles to a hostile Congressman in 30 seconds
    jg, that is really supercool. I'm going to refer to it often. The navigation bar at the top took a few minutes to figure out, but having gotten used to it I quickly came to like it. The rest of the interface is great. Have you thought about using EPICA data, for a longer record than Vostok? Also, I noticed that the insolation curves and the orbital geometry curves approach the Y-axis smoothly, then suddenly jump up to meet the other lines. Come to think of it, how did you decide on scaling factors for the different data sets? Anyway, for others reading this ... check it out.
  28. How to explain Milankovitch cycles to a hostile Congressman in 30 seconds
    I just discovered this blog and have been enjoying the comments on this topic. Much comment is on a graph in comment 18 that is difficult to resolve in fine detail. I hope it's not too off topic to share an alternative, a graph I created for examining palaeoclimates against milankovitch cycles. I've taken Vostok CO2 and temperature data (Petit, J.R., et al., 2001) and graphed it against orbital parameters (Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A.C.M., Levrard, B.: 2004) in a Flash-based program here: Vostok data and insolation graphs The fun is that you can zoom in to periods like the HCO. I hope it's helpful to this type of discussion, and if not, your criticisms here would be helpful to me. jg
  29. It's albedo
    Ha. While I was writing that all out, the appropriately-named "e" snuck in and expressed it much more concisely.
  30. It's albedo
    I just realized that some people may not be that familiar with the terminology here. There's a very important distinction between * "absorptance" and "absorbed energy" and likewise between * "emissivity" and "emitted energy" "Absorptance" is a unitless fraction (from 0 to 1) that says how efficient something is at absorbing radiation. It's defined as alpha = L_a / L_i where L_a = absorbed energy and L_i = incident energy Note that as L_i fluctuates, (say, as the sun rises and sets), L_a fluctuates too, but alpha stays constant. Similarly, M = e * s * T^4 where M, the total amount of emitted energy, is a function of emissivity (a unitless fraction from 0-1 that says how efficiently something is able to emit, compared to a blackbody) and T is temperature in kelvins. So, the amount of energy that gets absorbed by an object (L_a) is determined by how much energy is incident on it and its innate absorptance (the unitless fraction "alpha"). Likewise, the amount of energy that gets emitted by an object (M) is determined by its temperature and its innate emissivity (the unitless fraction "e"). Okay, here's the reason I just walked through all that verbiage: Kirchoff's law says that an object's emissivity (at a given wavelength) must be equal to its absorptance (at the same wavelength). It does *not* say that the object's emitted energy (at a given wavelength) must be equal to its absorbed energy (at the same wavelength). In my experience, people (i.e., undergrads in the first week of my class) can easily get tripped up by this. Bottom line -- the amount of solar energy the Earth absorbs is determined by its shortwave albedo (alpha) and by total solar irradiance. The amount of energy the Earth emits is determined by its longwave emissivity (e) and its temperature. The two quantities are not necessarily moving in lockstep ... thus, the climate can warm or cool.
  31. It's albedo
    Rovinpiper, Kirchoff's Law refers to a material's capacity to absorb and emit radiation at a specific wavelength, not the actual amount that is absorbed or emitted at that wavelength. The total amount of radiation emitted at a specific wavelength does not need to match the amount of radiation absorbed at that same wavelength. It is no violation of the law to have the majority of radiation absorbed in one wavelength while the majority of radiation emitted is in another. After all, materials don't "remember" how their energy was received.
  32. A Cloudy Outlook for Low Climate Sensitivity
    Eric @ 100... 3C globally means more like 8-10C with arctic amplification. Do you have a reference for the study your talking about?
  33. It's the sun
    Hi, Norman. So how does "an active sun" and "an atmospheric electrical circuit" change the climate? What is the physical mechanism? Can you give me a summary, or do I have to read the manuscript?
  34. The human fingerprint in the seasons
    #133 e I think there may be evidence of a change taking place at this time. Check out this article to see what you think. Possible evidence for e of global scale shift in pressure zones and circulation patterns.
  35. It's the sun
    #735 Ned, "Obviously, the sunspot number itself doesn't influence the earth's climate -- it has to be modulated through some physical process. So if you're not using sunspots as a proxy for solar irradiance, how do you suggest that sunspots affect the climate?" This writer believes an atmospheric electrical circuit can explain how an active sun will change climate other than the TSI. Sun's effect on electrical properties of the atmosphere and how these may cause Climate Change. I am not saying this writer's theory is correct but it does answer your question about how sunspot number can cause changes in climate.
  36. It's albedo
    That's a great question, Rovinpiper. Think about an object at normal Earth temperature, and assume it's floating in a vacuum. This object has an absorptance in the visible (a_vis) and an emissivity in the visible (e_vis). It also has an absorptance in the thermal-infrared (a_tir) and an emissivity in the thermal-infrared (e_tir). Now, Kirchoff's Law tells us that [a_vis must equal e_vis], and [a_tir must equal e_tir]. With me so far? OK, now, as long as this object is at normal Earth temperatures, e_vis is basically irrelevant -- because it's too cold to emit anything in the visible. It still has a value for emissivity in the visible spectrum, but it never gets a chance to use that. So, under normal conditions, the object absorbs visible solar radiation (sunlight) according to a_vis. If we assume it's floating in a vacuum, it only loses energy by emitting thermal-infrared, in proportion to e_tir. Consider a substance familiar to most of us: paint. Typically, paint will have an emissivity of around 0.90 to 0.96 in the thermal-infrared, but the range is mostly a function of the type of paint, not its color. Anyway, that painted surface would also have an absorptance of 0.90-0.96 for thermal radiation. But, in the visible spectrum, that painted surface might have an absorptance way below 50% (for white paint) or almost 100% (for black paint). What about its emissivity in the visible spectrum? If you could somehow heat the painted surface up to 6000 K without changing its structure and composition, the black-painted surface would emit much more radiation than the white-painted one, because in the visible spectrum it would have a higher emissivity. So ... to get back to your question from a few days ago -- if the Yellowstone Supervolcano were to erupt tomorrow, and eject gigatons of aerosols into the stratosphere, that would increase the Earth's albedo (reflectance) in the solar spectrum. But it wouldn't make a corresponding reduction in the Earth's thermal-infrared emissivity. With less radiation coming in, and the same amount going out, the climate would not be at equilibrium, and things would start to get cold. The colder planet would then emit less infrared radiation, and the equilibrium would return, with the planet at a lower temperature (until all the aerosols wash out of the stratosphere...) Let's hope that doesn't happen any time soon!
  37. Eric (skeptic) at 07:17 AM on 8 December 2010
    A Cloudy Outlook for Low Climate Sensitivity
    #96, muoncounter, there is a lot of supporting evidence that all the factors I have mentioned (and more) affect clouds. The evidence that is lacking is that these factors persist for a period of time long enough to affect climate. Also the link from cloud changes to climate is uncertain and tenuous in some cases. What is speculative is predictions. #97, Albatross, the decadal and centenial rates of warming are caused by the same factors. Obviously you are right that decadal doesn't scale to centenial due to short term factors like PDO. My point was just that sensitivity varies in addition to terrestrial weather like PDO based on external factors like GCR. One example is the high degree of blocking from local stratospheric warming from GCR spikes. That doesn't necessarily cause warming or cooling globally but it does alter the climate's sensitivity to CO2 warming for the period of time of the event. #98 Rob Honeycutt, thanks for the comment. Tipping points are local, the ice can't melt unless the local temperature is warm. So they rely on a variety of local analyses, not "3C global" which means nothing locally. Last study I read, there were several plausible tipping points, mostly arctic. However, none of them would significantly affect worldwide temperature. #99 Dana1981, my statement was a crude but realistic approximation based on the doubling of CO2 in a century. So if sensitivity is 2C and doubling takes a century, then the temperature increase is 0.2C per decade. I can very simply compare that estimate to various temperature measurements with the weather variation caveat above.
  38. It's albedo
    Hi Ned, There's something I don't understand in your explanation of Kirchoff's Law. You say that emissivity is equal to absorptance at any given wavelength, yet the Earth absorbs light in visible wavelengths and then emits that energy as infrared, doesn't it. How can the emissivity be equal to absorptance at the visible wavelengths if the energy is getting converted into infrared? Thanks again.
  39. A Cloudy Outlook for Low Climate Sensitivity
    Eric #95 - you seem to be misunderstanding the concept of climate sensitivity. You're referring to it as 'warming per century', but that's not accurate - it's warming per a certain amount of radiative forcing. For example, if we double atmospheric CO2, the planet will warm approximately 3°C in response to the radiative forcing caused by the increased CO2 and associated feedbacks. So the role of the feedbacks (mainly clouds and water vapor) are the issue at hand. But the climate sensitivity is pretty well constrained to 2–4.5°C for a doubling of CO2. The Lauer study I focused on in the article suggests that based on their cloud observations and model, it's more likely to be on the high end. But when you're talking about warming per century, the factor you need to focus on is CO2, because it's the main determining factor regarding how much warming we'll see. If we double CO2, the feedbacks and sensitivity will tell us if the warming is 2 degrees or 4.5 degrees or something in between, but it's very likely to be somewhere in that range. To use Richard Alley's phrasing, CO2 is the main temperature control knob.
  40. The human fingerprint in the seasons
    #129: "What happened in Moscow in July was and example of a heat pump" I've posted this comment from How warm was this summer? in a number of places, but IMHO the content is so important I repeat it here: Weather in a given region occurs in such a complex and unstable environment, driven by such a multitude of factors, that no single weather event can be pinned solely on climate change. In that sense, it's correct to say that the Moscow heat wave was not caused by climate change. However, if one frames the question slightly differently: "Would an event like the Moscow heat wave have occurred if carbon dioxide levels had remained at pre-industrial levels," the answer, Hansen asserts, is clear: "Almost certainly not." The frequency of extreme warm anomalies increases disproportionately as global temperature rises. "Were global temperature not increasing, the chance of an extreme heat wave such as the one Moscow experienced, though not impossible, would be small," Hansen says.
  41. How to explain Milankovitch cycles to a hostile Congressman in 30 seconds
    Rob @30, That is surprising. However, Curry's defense of Pat Michael's misinforming/deceiving at her blog is surprising. Hang on, then again, maybe it is not entirely surprising given her odd behaviour of late...
  42. The human fingerprint in the seasons
    Norman, Keep in mind that global climate is quite stable, even while local weather can be chaotic and unpredictable as shown by your Moscow example. What you are suggesting would require a global scale shift in pressure zones and circulation patterns; a catastrophic change compared to the effects predicted by the IPCC. At the very least, we would be able to detect if such a change was taking place.
  43. How to explain Milankovitch cycles to a hostile Congressman in 30 seconds
    Mike #29 Or: "Your honor, people have died from natural causes for millions of years! Therefore, my client can't possibly have killed the victim!"
  44. How to explain Milankovitch cycles to a hostile Congressman in 30 seconds
    Interesting. I wandered over to WUWT (something I am usually loathe to do) to find out what their take was on the hearings. I was expecting long winded cheering for Lindzen, Michaels and Curry. But there is almost nothing.
  45. How to explain Milankovitch cycles to a hostile Congressman in 30 seconds
    Alley's patience is remarkable, especially given Rohrabacher's rudeness and schoolyard-bully smirk.
  46. The human fingerprint in the seasons
    Discussion of sunspots, TSI, etc. should probably go on the thread It's the Sun. I just posted a brief reply to Norman's comment over there.
  47. A Cloudy Outlook for Low Climate Sensitivity
    To add to what Albatross said above... That 3C we get for a nearly assured doubling of CO2 puts us in uncharted territory with regards to tipping points. We will be well beyond the MWP. Well beyond the holocene maximum. We start having to look back millions of year, instead of thousands, for clues to what we may face. You think there are uncertainties about how pronounced or extensive the MWP was just 1000 years ago? The Eocene is going to be a real bear to wrestle!
  48. The human fingerprint in the seasons
    Re: Norman (130) It might be helpful to think of sunspot number as a surrogate marker for TSI. When lacking TSI data from modern measurements, sunspot number is a useful metric. But in this modern instrumental era, TSI is much more valuable. And as such, TSI shows at best a 5-10% attribution of the warming measured over the past 30 years. In the absence of CO2 forcing from anthropogenic fossil fuel emissions, such as in the paleo record, changes in TSI can act as a significant forcing (up or down) on global temperatures. As do Milankovich cycles. No observable mechanism other than the rise in CO2 explains also the rise in temperatures we've measured since 1980. So it's not the sun. It is what it is. The Yooper
  49. It's the sun
    In another thread, Norman writes: From information I had, it was not the TSI that effected the Earth's climate but Sunspot number (from the Maunder minimum). They were not measuring the TSI at that time. I was looking for information on sunspot number to correlate with Global temps and that sight had the graph I was looking for. Obviously, the sunspot number itself doesn't influence the earth's climate -- it has to be modulated through some physical process. So if you're not using sunspots as a proxy for solar irradiance, how do you suggest that sunspots affect the climate?
  50. A Cloudy Outlook for Low Climate Sensitivity
    Re #95, "Right now we might be 2C per century, but maybe just 1C (considering that 1998-sized El Nino might have gotten us 0.1C above current temps)." Sorry Eric but your line of thinking (i.e., extrapolating instantaneous rates of warming/cooling to the centennial scale) is just flat out wrong. In fact, the presence of transient internal climate modes and internal climate variability, solar cycles and volcanism are the very reasons why scientists look at long-term trends. Barton Paul Levenson has done some work on this and demonstrated that the standard deviation of the global temperature series plateaus when averaging over about 45 years, see here. The WMO and other groups use 30, and one could possibly get away with 20. There is no magic averaging window, because that itself in part depends on the nature of the data. For example, the time required to obtain statistically significant warming is shorter for GISTEMP than it is for CRU. Lastly, even if we were trapped in a permanent El Nino, it would at most add +0.2 C to global temperatures each year, but that additional warming would not be integrated year-over-year-- ENSO (El Nino Southern Oscillation) does not represent a net gain of heat in the climate system, but a redistribution of heat within the system. It is possible that the additional warming of 0.1 to 0.2 C over and above the underlying warming trend may accentuate the warming by accelerating or enhancing positive feedbacks..... If one looks at probability distribution functions of climate sensitivity (from multiple, independent sources), they are quite skewed towards higher temperatures, with a rapid drop off below 2.5C. Now that long tail to the right (higher sensitivity) is not necessarily an artifact of models, because it is present even for estimates of climate sensitivity derived using paleo and other data. The surprises that may lurk in that tail of the PDF should be very sobering and very much reason for prudence and taking action. Fortunately, there is some relatively good news, Annan and Hargraveas estimate that the likelihood of climate sensitivity for doubling of CO2 (although we will very easily exceed doubling) exceeding about +4 C is highly unlikely, with other research by Annan indicating that +3 C is the most likely value.

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