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chris1204 at 15:53 PM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
Phila @ 50: I'm not saying, 'Things won't be that bad.' I'm saying, 'There are many things we don't know which we really need to know.' I certainly think what we know is sufficient to warrant action and I have said so often enough. In my professional life, I'm no stranger to the need for decisive action in the face of major uncertainty. I have to explain this uncertainty to people - indeed, if I failed to do so, I would expose myself to a malpractice suit. Moreover, I prefer being honest with my clientele (it actually feels better doing things that way). At the same time, I certainly want to know more whether it's in my professional life or in an area of interest. -
alan_marshall at 15:52 PM on 20 October 2010Throwing Stones at the Greenhouse Effect
If some skeptics were right in claiming the greenhouse effect had indeed been falsified, then that would apply to the greenhouse effects of water vapour and methane as well as CO2. Sorry to point out the obvious, but any high school kid can demonstrate the greenhouse effect of water vapour simply by correlating overnight minimum temperatures with cloud cover. An example of this simple exercise is provided on my web site (www.climatechangeanswers.org/science/homedemo.htm). (My apologies to the better informed skeptics, but outright denial of the greenhouse effect has to dealt with forcefully) -
chris1204 at 15:38 PM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
kdkd: Wide error bars arise because of limited information. Do you prefer making decisions based on limited information by artificial foreclosure or would you prefer informed decision making in the context of acknowledgement of uncertainties? Would you rather everyone decided to treat clouds as an inconvenient distraction or would you prefer to see climatologists striving to understand their role better? Eyeballing the AR4 graphic, the cumulative aerosol and cloud albedo effect even *without* the error bars actually approaches the CO2 effect. This is not trivial. The size of the error bars in this context highlights the urgency of the need for better data and better understanding. -
dana1981 at 15:34 PM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
Humanity Rules #40 - I suggest you do some reading on efficacies of different forcings. The aforementioned (and linked) climate sensitivity rebuttal is a good starting point. -
alan_marshall at 15:28 PM on 20 October 2010Throwing Stones at the Greenhouse Effect
In your rebuttal it might be worth adding that, as Tyndall and others have proved in the laboratory that CO2 absorbs infrared radiation, the onus is well and truly on the skeptics to prove that CO2 behaves differently in the atmosphere. This is how I worded it on 22 Sep 2010 in my article Climate Change: The 40 Year Delay Between Cause and Effect: "There should be no dissent that CO2 absorbs infrared radiation, because that too has been demonstrated in the laboratory. In fact, it was first measured 150 years ago by John Tyndall using a spectrophotometer. In line with the scientific method, his results have been confirmed and more precisely quantified by Herzberg in 1953, Burch in 1962 and 1970, and others since then. Given that the radiative properties of CO2 have been proven in the laboratory, you would expect them to be same in the atmosphere, given that they are dependent on CO2’s unchanging molecular structure. You would think that the onus would be on the climate skeptics to demonstrate that CO2 behaves differently in the atmosphere than it does in the laboratory. Of course they have not done so." -
TOP at 15:20 PM on 20 October 2010Throwing Stones at the Greenhouse Effect
@DSL Very good point. "Seriously, take a little time off and study radiative transfer and what happens to incoming solar radiation when it hits the various surfaces of the earth system." The albedo of the ocean is microscopic when compared to the land or clouds. In other words the ocean absorbs almost all the radiation that hits it. So what keeps it so cool? Water is the ultimate greenhouse liquid. There are minor forcings to this effect like plankton, wind and the angle of the sun's rays. Most likely it is not radiation back into space, it is evaporation (phase change) and convection. The heat is re-radiated into space from the upper levels of the atmosphere when the water vapor changes phase back to water. That's why you can see the tracks of hurricanes in the ocean surface temperatures for a time after a hurricane passes. Mess with evaporation and you really do have a problem. -
Phila at 15:18 PM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
chriscanaris: I'm not into bargaining (and by implication, denial). I'm getting weary of repeating that I believe rising CO2 very likely heralds warming and that our society should aim to decarbonise. Bargaining doesn't imply denial, as I see it. It implies a preliminary acceptance of a situation, coupled with an unwillingness to face the full implications of that situation. My impression is that you keep saying, in effect, "maybe things won't be all that bad," without offering much in the way of a cogent defense for that position. Again, uncertainty in itself does not provide rational grounds for optimism. Furthermore, I suspect that the scientists who are counseling immediate action actually have a far better grasp of the relevant uncertainties than dilettantes like you or me. Recognizing what we don't know is important, granted. But recognizing what we do know is important, too. Waiting for the science to get "better" is a pretty irresponsible gamble, IMO, especially given that the plausibility of AGW being much less serious than we think seems to rise in inverse proportion to one's actual expertise. -
Throwing Stones at the Greenhouse Effect
Joe Blog - Actually, having less energy leaving than arriving is exactly what is happening. The various feedbacks and systems (ocean temperatures, in particular) have a time lag to changes in forcings, and are still approaching equilibrium. While that is occurring, there will be a net imbalance at the top of the atmosphere. The climate doesn't react instantly - there's always a lag to respond to forcing changes. And positive feedback doesn't indicate a runaway situation unless the gain is >1, as has been repeated discussed here. -
kdkd at 15:04 PM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
Chris #47 For prudence, one should take the midpoint of a value between error bars for your estimated parameter value, unless there's good evidence to suggest that the error bars are somehow wrong. In which case the error bars should be revised to be narrower. Unless there's assessment of greater uncertainty. As a good guess, one should take ±1SD of the error bars as being 66% likely and ±2sd as being 95% likely, with ±3 SD as being 99.8% likely. Attempting to draw strong conclusions by assuming that the true value is between -3 and -2 SD (approx. 17% likely = (99.8-66/2) ) is a fools errand. This appears to be what you're doing. The paper you referred to was merely indicating that the current estimate of the size of the error bars is very wide, which is an entirely different proposition. -
alan_marshall at 15:02 PM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
An excellent article, John. Confronting skeptics (who won’t listen) and the general public (who may listen) with the logical consequences of skeptics’ claims is potentially an effective alternate line of rebuttal. I don’t think you need to complicate the article by discussing the evidence for a global or local MWP. The global temperature reconstructions in Ned’s article posted on 28 Sep 2010 are broadly in line with the reconstruction you have used here, so your argument still holds. The climate sensitivity to a particular greenhouse gas (CO2, CH4 or whatever) is the temperature rise resulting from a doubling in concentration of that greenhouse gas. The value of the radiative forcing corresponding to the doubling is not part of the definition. Your wording: Technically, climate sensitivity is defined as the change in global temperature if the planet experiences a climate forcing of 3.7 Watts/m2 (which is how much climate forcing you get from a doubling of CO2). Suggested alternate wording: Technically, climate sensitivity is defined as the rise in average global temperature resulting from a doubling of atmospheric CO2. (The added radiative forcing from such a doubling is 3.7 Watts/m2.) The text “then current climate change must also also natural” should read ““then current climate change must also be natural”. -
Throwing Stones at the Greenhouse Effect
Joe, I think you make a valid point, but consider that this post is meant as a "basic" version of the argument. Technically speaking, the short term decrease in outgoing radiation is evidence of an enhanced greenhouse effect, not a greenhouse effect in general. It's an important distinction to make, but I think it's a bit too pedantic for a basic version of the post. If you take a look at the intermediate version of this post, you will notice that this distinction is spelled out more explicitly. -
chris1204 at 14:56 PM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
kdkd: The whole point of the paper is that there is a lot we don't know and a lot we need to find out. Recognising the limitations of our knowledge is the sine qua non for progress in science. AR4 however does provide an estimate of cloud and aerosol feedbacks relative to other forcings including an estimate of uncertainties for both cloud, aerosol, and CO2 forcings. While I don't regard AR4 as the Holy Grail of climate science (there is no such thing in any science), I think it's a reasonable starting point. -
Chris G at 14:20 PM on 20 October 2010Increasing southern sea ice: a basic rebuttal
This might belong under the intermediate version, but thinking of the complexity... It's pretty clear that less ice in the winter, (as mentioned in the article), when it's dark, would have negligible warming effect because albedo doesn't play a factor when it's dark. However, to add to what GT just wrote, if there is more ice at the beginning of the melt season, I'm thinking that will be a negative feedback to regional warming. I'm not saying it will be stronger than the other effects; I'm just thinking it will exist and wondering how it will all add up. -
kdkd at 14:18 PM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
chriscanaris #45 Without wading through the detail of the Stephens 2005 paper, it doesn't seem to be offering any information on the order of cloud feedbacks relative to other climate forcings. As a result the paper quite rightly does not offer strong conclusions about the sign and magnitude of climate sensitivity itself, but defers this to other literature. From looking at the paper, it does not offer any justification of the strong claims that you are trying to make. -
Joe Blog at 13:52 PM on 20 October 2010Throwing Stones at the Greenhouse Effect
"This 33C worth of energy in transit in the atmosphere is the proof. " This average increase of 33C at the surface as a result of energy in transit through the lower atmosphere is the proof... being pedantic again. -
Same Ordinary Fool at 13:41 PM on 20 October 2010Increasing southern sea ice: a basic rebuttal
Ldavids = Larsen B ice shelf pieces did become 'sea ice' after they broke off. Before that, as a floating ice shelf they were still attached and considered land ice. Yours is the first mention I've heard of the interesting idea of possible changes in the thickness of Antarctic sea ice. There aren't any multi-year issues, as in the Arctic. But have there been any changes in Antarctic sea ice thickness from year to year? Sigmond and Fyfe(2010) have apparently taken away the simpler to express, "its the ozone hole" explanation for the recent increases in Antarctic sea ice. So now we really will have to learn the much more complicated density/salinity/stratification/warmer-Southern=Ocean story. -
chris1204 at 13:24 PM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
kdk @ 43: See the excerpt from the Stephens 2005 abstract as above. I think this deals with your questions (2) & (3). If you want to scrutinise the paper itself, there's no paywall :-). -
Joe Blog at 13:22 PM on 20 October 2010Throwing Stones at the Greenhouse Effect
Sorry, but im going to have to reiterate my objection to this part of the last paragraph: "The most conclusive evidence for the greenhouse effect – and the role CO2 plays – can be seen in data from the surface and from satellites. By comparing the Sun’s heat reaching the Earth with the heat leaving it, we can see that less long-wave radiation (heat) is leaving than arriving" This is unphysical, no two ways about it, if it were true we would be heading for the Temperature of the surface of the sun. It is disingenuous to try and cure a misconception, with another misconception. By comparing incoming energy, vrs outgoing,vrs thermal capacity of the surface, you can determine that the average T should be -18C... But its not, that is the proof of the GHE. The fact that the average T is 15C. This 33C worth of energy in transit in the atmosphere is the proof. -
adelady at 13:21 PM on 20 October 2010Increasing southern sea ice: a basic rebuttal
John, remember the pure water melted from the land ice has a freezing point of 0C, (and of precipitation in the form of rain and snow). The freezing point of sea water varies but it's usually around -1.8C. Philippe's remark about salinity and stratification is the key. -
chris1204 at 13:16 PM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
angliss @ 42: Your point about modelling in relations to period of rapid transition valid. However, as I understand it, the uncertainties extend well beyond this issue. From the abstract of the Stephens 2005 paper: '...What emerges is the importance of being clear about the definition of the system. It is shown how different assumptions about the system produce very different conclusions about the magnitude and sign of feedbacks. Much more diligence is called for in terms of defining the system and justifying assumptions. In principle, there is also neither any theoretical basis to justify the system that defines feedbacks in terms of global–time-mean changes in surface temperature nor is there any compelling empirical evidence to do so. The lack of maturity of feedback analysis methods also suggests that progress in understanding climate feedback will require development of alternative methods of analysis. It has been argued that, in view of the complex nature of the climate system, and the cumbersome problems encountered in diagnosing feedbacks, understanding cloud feedback will be gleaned neither from observations nor proved from simple theoretical argument alone. The blueprint for progress must follow a more arduous path that requires a carefully orchestrated and systematic combination of model and observations. Models provide the tool for diagnosing processes and quantifying feedbacks while observations provide the essential test of the model’s credibility in representing these processes. While GCM climate and NWP models represent the most complete description of all the interactions between the processes that presumably establish the main cloud feedbacks, the weak link in the use of these models lies in the cloud parameterization imbedded in them. Aspects of these parameterizations remain worrisome, containing levels of empiricism and assumptions that are hard to evaluate with current global observations. Clearly observationally based methods for evaluating cloud parameterizations are an important element in the road map to progress.' -
kdkd at 13:13 PM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
chriscanaris #41 It seems to me that you need to expand on what you mean by your answer to questions 2 and 3, in order to attempt to show that you're making a valid claim. At the moment your answer is an assertion, and is not backed by evidence. -
DSL at 13:12 PM on 20 October 2010Throwing Stones at the Greenhouse Effect
It is relevant, John. The problem with the Bible, though, is determining with any degree of precision just when the relevant parts were written. The stories that make up the Bible--even those of the NT--were developed over centuries--perhaps longer. The Jesus stories may be imported from other, earlier cultures (Egypt, Horus--that sort of thing). If you question tree ring proxies, you shouldn't be moving toward the Bible as a proxy. RSVP, if any climatologist had made your claims on this thread, even the folks over at WUwT would be ROFL (ABSTTN - and blowing soda through their noses). Seriously, take a little time off and study radiative transfer and what happens to incoming solar radiation when it hits the various surfaces of the earth system. -
adelady at 13:04 PM on 20 October 2010Increasing southern sea ice: a basic rebuttal
Ldavids - volume isn't an issue for sea ice in the Antarctic. There's little to no multi-year ice because it pretty well melts out fully each summer. Volume is only possible in the Arctic because sea ice doesn't melt out every year. Even the record minimum extent in 2007 was caused as much by winds piling the ice up towards the end of the season as it was by melting throughout the season. Unfortunately as extent and volume are steadily decreasing, more ice is melting out by the combination of warm waters from the Pacific and Atlantic and more water movement because of larger areas of open ocean within the Arctic basin. -
Philippe Chantreau at 12:25 PM on 20 October 2010Throwing Stones at the Greenhouse Effect
"the quote is using the term green house effect for the specific effects of the so called green house gases, not the green house effect of the atmosphere as a whole." Total nonsense. The atmosphere can not have a greenhouse effect unless GH gases are part of it. This thread is going nowhere fast. -
Philippe Chantreau at 12:20 PM on 20 October 2010Increasing southern sea ice: a basic rebuttal
John, salinity and stratification are more likely to have major roles. -
angliss at 12:16 PM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
chriscanaris - I'm not sure that it is an assumption that current models satisfactorily model clouds. Climate sensitivity is an equilibrium value and it has been derived repeatedly using multiple sources of data (not modeling information, actual data) over multiple time periods. The results do vary, but they all have similar ranges that overlap. Given the time scales involved and the fact that climate sensitivity is an equilibrium value, it's probably reasonable to say that climate models likely model clouds sufficiently for equilibrium conditions, given that climate models independently derive ranges for climate sensitivity that are roughly similar (and that overlap) with the empirically-derived values. The question is whether clouds are modeled well enough for periods of rapid transitions. In mathematical parlance, how much do the clouds change the slope of the differential equation in time from the base level of the climate sensitivity? Will they increase or decrease the slope, and by how much? -
John Chapman at 11:58 AM on 20 October 2010Increasing southern sea ice: a basic rebuttal
If land ice was melting, I would expect it to cool the water into which it melts thus making it 'easier' for sea ice to form when the temmp drops in winter. Well that's my explanation for the increasing sea ice! -
Rob Painting at 11:54 AM on 20 October 2010DMI and GISS Arctic Temperatures: Hide the Increase?
Adrian Smits @ 19 - The above article describes why there may not be much movement in the arctic in the summer time but it fails to explain why its cooling down since 1958 in the summer when c02 should be having its greatest impact. Guess that depends on how one defines "greatest impact". There is indeed a great impact on the Arctic sea ice volume.
And extent:
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chris1204 at 11:43 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
kdkd @ 39 1) See AR4 and literature review as per original post 2) No, However, the same applies to the thesis advanced in the post. 3) No. Again, the same applies to the thesis advanced in the post. Supposition permeates the entire field and we need to acknowledge this if we want to be credible. -
HumanityRules at 11:31 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
30.dana1981 I think you can have it both ways as long as you don't take a very simplistic approach to climate forcings, feedbacks and variability. What seems to lie behind these ideas is that feedbacks are associated with the temperature change induced by these forcings rather than any other factors. For example CO2 traps more energy increasing temp. This increase in temp causes an increase in water vapour which traps more energy and amplifies the warming. Is solar variance (and other forcings) simplified in this way? Because is strikes me there are many ways solar variance might cause changes in the system (feedbacks) that go beyond the simple feedback caused by an increase in temp, through physiochemical processes for example. Can somebody answer this for me. Do we know for sure all the feedbacks associated with increased CO2? Do we know all the feedbacks associated with changes in solar irradiance? Do we know all the feedbacks associated with volcanos? If the answer is no then we can't actually say that an increase in climate sensitivity to solar variation infers an increase in sensitivity to CO2. That seems the basic argument behind the ideas John is presenting and it seems flawed to me. -
TOP at 11:29 AM on 20 October 2010Throwing Stones at the Greenhouse Effect
@Bibliovermis "What relevance does...have to global warming, much less to a discussion about the greenhouse effect? Did you just type "clouds" into a bible search engine & post the first entry it returned?" Actually it's one of those verses that hangs around in my memory banks. Been aware of it's relevance for more than 40 years. I've actually read the Bible cover to cover a few times. I'll leave it to you to figure out it's relevance, but it is very relevant. There are a number of verses in Genesis that discuss climate. They don't necessarily fit into commonly held theories. I was reading this quote from the the first link in the link you posted: "'The influence of so-called greenhouse gases on near-surface temperature - is not yet absolutely proven. In other words, there is as yet no incontrovertible proof either of the greenhouse effect, or its connection with alleged global warming." Heinz Thieme This quote is not from Marohasy. In context the quote is using the term green house effect for the specific effects of the so called green house gases, not the green house effect of the atmosphere as a whole.Moderator Response: Discussions of biblical interpretations are not really appropriate for this blog. Please keep comments on-topic and relevant to the science. -
michael sweet at 11:25 AM on 20 October 2010Throwing Stones at the Greenhouse Effect
RSVP, It is a waste of my time to reply to your posts. Others have covered the material, I liked e at 49 especially. I suggest the moderator delete future posts to keep this thread from becoming another waste heat thread trying to explain to you the basics of heat transfer in the atmosphere. You have extraordinarily strong comments for someone who understand so little science. -
kdkd at 11:25 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
chirscanaris #38 Three questions: 1. What evidence do you have to date that the negative feedback effects are substantial? 2. If the answer to question 1 is that you do have substantial evidence, is this sufficient negative feedback to keep us out of trouble in the future? 3. If the answer to q 2 is no, do you have evidence that the negative feedbacks will increase in the future. You see conjecture alone, or selectively reading the lower range of error bars (*cough Ken Lambert cough*) won't cut it. -
chris1204 at 11:17 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
Ned @ 27: 'It's not reasonable to assume a high value for climate sensitivity in order to get a large MWP, while also assuming a low value for climate sensitivity in order to minimize the effect of AGW.' With respect, Ned, I'm not making any assumptions. I'm simply looking at the range of possibilities which flow from the AR4. On one scenario, clouds may exert a negative feedback greater than the positive feedback of CO2. Is this so? At this stage, we can only guess. However, the assumption that our current modelling satisfactorily incorporates clouds (and to a much lesser extent aerosols) is just that - an assumption. Phila @ 33: I'm not into bargaining (and by implication, denial). I'm getting weary of repeating that I believe rising CO2 very likely heralds warming and that our society should aim to decarbonise. I do however like consistency in the presentation of the science whether it comes from an AGW or 'sceptical' perspective. -
TOP at 11:10 AM on 20 October 2010Throwing Stones at the Greenhouse Effect
@Phila "You've managed to cram a surprising number of logical errors into a very brief comment. First, the Bible is not a reliable guide to what "creationists" believe, since different creationists interpret it in very different ways. Second, Genesis 9:13 has nothing to do with climate science, obviously. Third, modern creationists -- of the activist type, especially -- have had a pretty strong tendency to deny AGW." I'm not talking about AGW rather the green house effect which is the topic of this discussion. Genesis (9:13 in particular) does have a lot to do with climate science unless you arbitrarily throw out data points for no other reason than you don't like the source. It is a clear reference to climate change and global warming. I'll leave it to you to figure out why. Don't mistake logic for presuppositions. We don't share those, methinks. -
Ldavids at 11:09 AM on 20 October 2010Increasing southern sea ice: a basic rebuttal
Is the volume of Antarctic sea ice increasing, or just the extent. With the break off of a number of large pieces og sea ice in recent years, it seems to me that, like the Arctic, the thickness of Antarctic sea ice is probably diminishing. -
Phila at 11:04 AM on 20 October 2010Throwing Stones at the Greenhouse Effect
Roger #20: Why are nearly 75% of Americans, American news media, and American politicians deniers? Do you have a link for that stat, by any chance? I'm curious to see what "nearly" means, in this context. -
Joe Blog at 10:25 AM on 20 October 2010Throwing Stones at the Greenhouse Effect
RSVP at 09:09 AM O2 and N2 are largely transparent to terrestrial radiation(O2 is semi opaque to UV, and this is how O3 is formed, through the break down of O2 to atomic O and the free O combining with a another O2 molecule to form O3, And O3 is very opaque to UV and thus the reason the stratospheres T profile is reversed, due to heating from above from UV, and radiative cooling from below through co2) The only way energy has to leave our planet, is through radiation, truth is convection transports more energy in the lower troposphere than radiation, due to the fact that it already is at those pressures very opaque to LW, but the limiting factor causing the temperature profile in the troposphere, is the altitude where energy can escape to space. Now the reason why its at higher altitudes that it can escape to space/the atmosphere is more transparent, is due to the fact that there is less pressure, less molecules in a given area, so with less opaque gases in a given area, the further the probability of a photon traveling before it is absorbed. Now if you increase the ratio of opaque gases in the atmosphere, you raise the altitude at which energy can escape to space, just by the simple fact, that it increases the amount of molecules in a given area for a given pressure. Increasing the probability of a photon being absorbed for a given distance, at a given pressure. Thus raising the height at which energy can escape from the lower atmosphere to space, and raising the surface T by the need for the T gradient to transport the energy to this higher altitude... in a nut shell. -
Doug Bostrom at 10:23 AM on 20 October 2010DMI and GISS Arctic Temperatures: Hide the Increase?
I must say that WUWT's treatment of this makes it hard to stay on topic. Strange blending also leads to such jokes as "Again, the years 2008-2010 is not really supporting any downward trend, although the entire period 1978-2009 shows decline using a banal flat trend." "Oh, Muffy, your trend is so banal, my dear. You should see my stylist at the WUWT salon." -
Throwing Stones at the Greenhouse Effect
RSVP, With the time you've spent on this site I'm surprised you don't seem to understand the basics of how the greenhouse effect works. How can you take such a strong position on a topic without understanding how it works? Let me take a stab at explaining: First off, all matter above absolute zero emits some thermal radiation. The ability to emit thermal radiation alone is NOT what makes GHG's special. The key is that although all matter emits thermal radiation, different molecules may absorb and emit specific frequencies of radiation more readily than other frequencies. In the case of GHG's, they readily absorb radiation in the infrared spectrum, while being nearly transparent to radiation in the visible and UV spectrum. Radiation coming from the sun is primarily in the visible and UV spectrum. Meanwhile, radiation emitted by the earth's surface is primarily in the infrared spectrum. So here's what happens: the visible/UV spectrum radiation coming to the earth from the sun mostly passes through the atmosphere without being absorbed by GHG's. The surface of the earth absorbs this radiation and heats up, and then emits radiation in the infrared spectrum back up towards the atmosphere. This energy is now readily absorbed by GHG's, which is subsequently radiated back out in all directions. The result is that most of the energy coming in is unimpeded, while energy going out is partly radiated back down to the surface. This creates an insulating effect which causes the earth to retain more heat than it would without GHG's. The remaining gases in the atmosphere still emit thermal radiation, just not as readily as GHG's, and more importantly, they do not absorb infrared radiation as readily. If we removed GHG's from the atmosphere, these remaining gases would continue emitting radiation just as they do today. The difference is the extra warming provided by GHG's would be gone, so overall the planet would be much colder. For a good basic overview of these topics, I recommend the following: Thermal Radiation Greenhouse effect -
Doug Bostrom at 09:41 AM on 20 October 2010DMI and GISS Arctic Temperatures: Hide the Increase?
Adrian, before we spend more time on this, can you just confirm that you understand increased atmospheric CO2 won't behave differently depending on whether it's summer or winter, or light or dark for that matter? -
Marcus at 09:40 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
As I understand it, the key issue with the original Manne "Hockey Stick" was that he relied on a single, geographically limited, Northern Hemisphere Tree species as his temperature proxy. Of course, we now know that dendrochronology-even across multiple species-is not the best proxy for climate, given that drought can be as much a cause of small tree-ring size as the cold. His peers rightly attacked his methods &-as was noted-he has since revised his methodology to incorporate a number of other proxies. Of course, at least half a dozen paleo-climatologists (like Moberg) have also produced their own proxy-based climate studies-covering anything from 600 to over 2000 years. Although none of these studies show a *true* hockey stick, they do all show climate variation within a relatively narrow band-& over multi-centennial time frames-up until the 2nd half of last century. Still, nice to see the skeptics prefer to fight battles that are more than 10 years old. Maybe they're the only ones that they think they can win? -
adrian smits at 09:32 AM on 20 October 2010DMI and GISS Arctic Temperatures: Hide the Increase?
Your still not answering my question gentlemen.The above article describes why there may not be much movement in the arctic in the summer time but it fails to explain why its cooling down since 1958 in the summer when c02 should be having its greatest impact. Even a marginal up trend should be occurring during the summer with 24 hr sunlight........What am I missing here? -
skywatcher at 09:31 AM on 20 October 2010Do critics of the hockey stick realise what they're arguing for?
Alexandre - no problem, sorry if I misinterpreted what you said. RSVP - dana1981 has of course answered your query far better than I could. I see little reason why the largest feedback in the system should operate in a substantially different way when responding to shortwave energy as compared to longwave energy, and as dana1981 suggests, the W/sq m may be a little more effective rather than less effective. I wonder if the albedo feedback is perhaps more influenced by the longewave downward radiation of GHGs (in that this form of radiation is present worldwide and at night, therefore maybe more ever-present to melt snow and ice than shortwave radiation? But I don't know the values involved there so that is just speculation on my part! -
Throwing Stones at the Greenhouse Effect
RSVP - Without any GHG's present (i.e., no gases that absorb/emit at IR wavelengths) the atmosphere would be strictly warmed by conduction/convection, plus latent heat if anything remained unfrozen, from the surface. There would be a very different lapse rate, and no IR from the atmosphere. But: This is a thought experiment. It's clear from the thought experiment that the planet is much warmer with than without GHG's. And that's the point of the thought experiment. The radiative greenhouse effect is real, observed, and part of the current condition of the Earth. We now return to other discussions, other threads, of changes in the level of the greenhouse effect; and the causes of recent global warming. :) -
RSVP at 09:09 AM on 20 October 2010Throwing Stones at the Greenhouse Effect
e "The atmosphere will continue emitting radiation into space whether GHG's are there or not." Either this is true or the term GHG is meaningless. Take your pick. -
Joe Blog at 08:54 AM on 20 October 2010Throwing Stones at the Greenhouse Effect
e at 08:44 Ohh, i see. I thought we were talking thought experiments. -
archiesteel at 08:49 AM on 20 October 2010DMI and GISS Arctic Temperatures: Hide the Increase?
@adrian: did you read the article above? The reason why temperatures pretty much stay around 0 in the summer is due to melting ice. You seem to be under the impression that the CO2 heat trapping only happens during the day, but in fact it doesn't. If so, temperatures at night would plummet down below freezing every night! Furthermore, the greenhouse effect is a *global* phenomenon, not a local one. Heat is added to the global system, and as such it finds its way to all regions of the globe. Instead of focussing on slightly dropping surface temps in summer, you should ask yourself why temperatures during the rest of the year have dramatically increased. "These guys in Denmark actually measure temperature all over the region up there" Yes, and they agree the Arctic has been warming up, as I indicated above. -
Doug Bostrom at 08:47 AM on 20 October 2010DMI and GISS Arctic Temperatures: Hide the Increase?
Regardless of what's happening to temperature in the Arctic summer we can safely forget about some kind of fundamental change in the mechanism of CO2 as a GHG because of the presence or absence of sunlight, Adrian. As a GHG CO2 doesn't really care if it's light or dark. Does somebody at WUWT actually suggest such a difference might be in play? Also, CO2 doesn't act as a GHG by intensifying the sun's rays. It's actually kind of a case of the opposite, with Earth's outgoing "rays" being lessened at certain wavelengths of IR. Further exploration of that is off-topic on this thread but see NOAA's FAQ on global warming to get started. -
DMI and GISS Arctic Temperatures: Hide the Increase?
adrian smits - Did you read the presentation by Peter Hogarth at the top of this thread? Continuous ice presence over the summer limits the rise of temps to just above zero degrees C, clipping temp rise. But the average yearly temperature is rising twice as fast as the rest of the globe - it just doesn't get as cold the rest of the year as it used to. To quote Peter: "Clearly high Arctic Summer surface temperatures just above zero are not really an indication of anything except proximity to a melting ice surface. To claim that the Arctic is cooling is misrepresenting the data. It is also evident from these High Arctic data sets that the average temperatures in the Winter, Spring and Autumn periods have generally increased over the measurement period. It appears that the overall seasonal cycle is riding on a gradually warming average value, but peak positive excursions are being limited by the ice melt temperature in Summer. The energy that would otherwise raise temps above zero is melting the ice. Higher average temperatures mean more ice is melting - the time spent clipped to zero increases, and the total amount of ice melted increases. WUWT is making (oh my - how atypical) a mountain of a trend out of a molehill of variation, ignoring the full data set. It's a pretty appalling misrepresentation of the data.
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