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Comments 60151 to 60200:

  1. Return to the Himalayas
    #30 - many of these regions are dry for extended periods of the year. With a glacier present upstream, there's a water supply all year round, even in long dry periods. The ice cube is a reservoir that lasts through the dry season, holding back the precipitation that fell earlier in the year and gradually releasing it through the dry season. Snowpack is a much weaker and less stable form of this, often diappearing quite quickly in the melting season, leaving you with no water reservoir. Remove the ice cube altogether, and your river flow is much less reliable in the dry season. you might have a season with lots of snowpack and be fine, but how many season with little snowpack will you even survive?
  2. Cliff Ollier: Swimming In A Sea of Misinformation
    Skywatcher, Thanks for the comment
  3. Cliff Ollier: Swimming In A Sea of Misinformation
    #4 And if you read through the presentation slides themselves (noting that you are missing a vast amount of information as we are not hearing the presenter speak), you'll note a number of slides discussing why there's an apparent slowdown in the altimeter era. Chief among the culprits appears to be ENSO - the 1990s were dominated by El Nino, leading to higher apparent sea level, and the 2000s were dominated by La Nina, giving the reverse (histogram slide #15). There's an expectation that the apparent slowdown will reverse when El Nino conditions return. Hence the altimeter era is highlighting the variation of sea level around the obvious accelerating trend in sea level seen in Figs 1 & 2 above. The above graph is shown first at slide #9, discussions of possible reasons starts at slide #10, continuing to the summary at slide #23. Perhaps Steve Case could point us to where he thinks the presentation fundamentally contradicts our understanding of long-term sea level rise acceleration, as seen in Figs 1 & 2 above?
  4. Newcomers, Start Here
    tmac57, tamino's got Spencer's latest slip covered at Open Mind.
  5. Return to the Himalayas
    Daniel Bailey at 10:07 AM on 16 April, 2012

    How does the process of taking in snow in the accumulation zone, rain in the ablation zone and emitting water from the lower reaches vary all that much from melting snowpack and rain?

    I had said that this discussion would boil down to the difference between the melt rate of ice and snow.

  6. Cliff Ollier: Swimming In A Sea of Misinformation
    If you go to

    You will find this link:

    And this illustration on the last page of the presentation:
    http://i39.tinypic.com/nr14bq.jpg

    Moderator Response: TC: Link fixed.
  7. Data Contradicts Connection Between Earth's Tilt and the Seasons
    Hi Manny. For a look at that predictive power, you might to look at this. The question is similar to how can you be sure that our experience of space-flight to the moon is enough to guide a space craft to pluto. The answer of course is that our confidence is based on understanding the basic physics. You should also be aware that modelling on one scale or another extends well past last century and seems adequate to explain most aspects of the evolution of climate through the history of the planet. For the evidence to support this, then please see the rather overwhelming detail found in the IPCC WG1 report. In the "Paleoclimate" (Chapter 6), you can see very much the graphs you are asking for. I would also strongly recommend you study this post from one of the modelling groups to understand what those model outputs mean.
  8. Newcomers, Start Here
    Looks like Roy Spencer has 'slipped up' again: Virtually all of the USHCN warming since 1973 appears to be the result of adjustments NOAA has made to the data, mainly in the 1995-97 timeframe. Does this deserve a new post at SKS?
  9. Return to the Himalayas
    wow - what a difference between the Guardian and BBC articles. You could use them as an educational example of how to place a story into context and how not to. Of course, one author is a science writer, the other a glaciology professor, and the difference in understanding is stark. Well done Prof Bamber!
  10. 2012 SkS Weekly Digest #15
    Alexandre @19, having reviewed a large number of "home experiments" purportedly proving or disproving the greenhouse effect, my conclusion is that people conducting those experiments nearly always fail to control for other factors, and execute the experiment poorly. Even the Myth Buster's attempt may only show that the containers in the center catch more stray light from adjacent spotlights. What is more,the do not demonstrate the GHE, but only the fact that methane, and CO2 absorb IR radiation. This is more directly demonstrated by Iain Stewart for the BBC: A proper "home" demonstration of the GHE would require an investment of several hundreds of dollars for materials and instruments.
  11. Cliff Ollier: Swimming In A Sea of Misinformation
    I observe that in most puddles the water spreads as the surface rises so even a linear rise or a small fall might still represent an accelerating increase in volume. "Sea level rise" is measurable of course which is why we use the term ,yet predictions and explanations of change in sea level are based on volume - volume of ice melting, measurable, volume of rain fallen as in floods, volume of ice still to melt, volume of water in the atmosphere as represented by percentage of water vapour. Discussion of Arctic Sea Ice Extent is a kind of analogue. It's readily measured but is highly dependent on how the winds are blowing. Do they push the floating chunks of ice together or drive them apart? But sea ice volume is quite another animal. As the ice thins it could increase in extent at times, depending on the winds. These differences between what is readily measured, ice extent or sea level, and what is really goin on, changes in volume, provides plenty of room for misunderstanding and misrepresentation. Noel
  12. Rob Honeycutt at 09:31 AM on 17 April 2012
    Return to the Himalayas
    muoncounter @ 19... The Guardian actually did a good job with this one. The glaciers are still shrinking – and rapidly
  13. Rob Honeycutt at 09:24 AM on 17 April 2012
    Return to the Himalayas
    Steve... I checked. Your comment was not deleted. But I do take exception to your "no comment" response at 16. An enhanced hydrological cycle means both more evaporation and more precipitation. Wetter and drier conditions.
  14. Global Warming in a Nutshell
    davpaf @24, there is no reason why TS should equal TE, and unless you remove all greenhouse gasses it will not be. In removing all greenhouse gases, you need to remove not only well mixed GHG, but also water vapour and clouds. In the model runs by Lacis et al 2010, whose results I showed @22 above, TE is reduced by about 15 degrees C because the albedo in increased from 0.3 to about 0.42. That is compensated for by the remained greenhouse effect from water vapour and clouds so that by coincidence TS approximately equals the value of TE prior to the removal of CO2. Please note that in his comment @27, KR assumes zero greenhouse effect, which is a different thought experiment (see his comment @ 32). CBDunkerson @30, as already noted by KR, the model results I presented are for the removal of CO2 (strictly, all well mixed GHG so that it removes methane as well as CO2), not for the removal of all GHG including water vapour. Personally I am surprised at the results. It is known that the Earth entered a "snowball" state, with extensive continental ice at sea level at the equator, at least twice between 1 billion and 600 million years ago. The sun emitted about 10% less radiation then, which would make that easier, but the model results suggest that it is no longer possible for the Earth to enter a Snowball state, even with the complete removal of all CO2. A solution to the paradox may be that the model does not allow for the growth of ice sheets. That is, it only incorporates fast feedbacks. With the growth of ice sheets temperatures may fall further, flipping the Earth into a true snow ball state. Lacis et al also mention the simple ocean they use in the model as also potentially introducing a false stability to temperature. Regardless, I think we are in safe territory if we conclude that the removal of all well mixed GHG would reduce the Global Mean Surface Temperature by at least 30 degrees C, and probably significantly more if (as you say, magically) the Earth's atmosphere could be kept free of well mixed greenhouse gases.
  15. Data Contradicts Connection Between Earth's Tilt and the Seasons
    Scadenp, I am male and you are criticizing me for the use of the word "proof". I recognize my error and will therefore ask for "evidence" that one century of hindcast is enough to support climate predictions for the next century. Skywatcher, I am not comparing apples to oranges, I am questioning the predictive power of the IPCC models. With your answer, you are implying that the modelers made no mistake and you are expecting me to trust you. Sorry, I do not. I want to see evidence. All I am asking is graphs of the output of the various IPCC models (there are several) vs observed temperature in order to judge the models for myself. Is this too much to ask?
  16. 2012 SkS Weekly Digest #15
    My own experience is that the well known Groucho Marx crack: "What do I care about posterity? What's posterity done for me? usually applies."I'll be long dead when it gets really bad" is a common response.Personally speaking,I'm a powerless-useless AGW flailer.Trying to pull up people's denialist anchors needs a Hercules because the AGW worry-load that is swopped for the anchor is groaningly heavy cargo.In any case,debunking denialism just creates more denialism feedback--more anchors.All I can offer is that we need to organise a la 350.Org and ACTIVATE! but just how:what's the best way? escapes me. Peter Cummins New Zealand
  17. 2012 SkS Weekly Digest #15
    I don't know if this is THE most difficult aspect of AGW to explain, but I think it's important. It's the difference between 'weather' and 'climate'. There are many tv weathermen out there who are climate deniers, and that's a BIG problem because 1) they have a tv audience of regular people, and 2) they have some science background and therefore some credibility to have a reliable opinion about climate change. They understand weather very well, but weather is more deterministic (meaning models that involve solution of a system of partial differential equations), whereas climate models are more statistical in nature and involve more sampling from probability distributions. We can't predict the weather much more than a week or so into the future, so how the hell can we be predicting it years or decades or centuries in the future? We need to do a better job of getting across to the general public (not just SkS readers) that climate is averaged weather, and it's an entirely different thing to predict and even to think about. And we need to start by educating the weatherpeople.
  18. Global Warming in a Nutshell
    @Chris G #17 and #25: I made a few changes to the caption of Fig. A4 to clarify that it is not just cloud particles but also re-emission of absorbed IR radiation that occurs at lower temperature levels and contributes to the lower effective temperature of the Earth's outgoing longwave radiation as seen from space. The excellent article suggested by @Tom Curtis #18, Greenhouse Effect Basics: Warm Earth, Cold Atmosphere, has also been linked. I also added a link to the excellent article mentioned by the moderator in comment #28, about energy flows in the Earth System, called Trenberth on Tracking Earth’s energy: A key to climate variability and change.
  19. 2012 SkS Weekly Digest #15
    About the Issue of the Week: Debunking is a well-intended effort, but ineffective. It even reinforces those unfruitful "debates" with boneheaded "skeptics" - a waste of good minds. Explaining the science is good. How about some do-it-yourself experiments that the reader could try at home or at some simple lab? This would be much more effective than, say, 1000+ comments trying to explain to some hard-headed commenter why the 2nd law of thermodynamics is correct and consistent with the GHE. Much in agreement with ajki above.
  20. Same Ordinary Fool at 06:13 AM on 17 April 2012
    Which plants will survive droughts, climate change?
    It is truly sad that we really need to know about the importance of cell saltiness, and turgor loss points. Just in case we have to make the selections that Darwin thought natural. And then have to play Johnny Appleseed. But this is a good story about rigorous science. In which they had to solve, for the first time, the mathematical equations of wilting.
  21. Cliff Ollier: Swimming In A Sea of Misinformation
    'Ollier writes: "Note that the IPCC estimates have been falling with each report"' This is another meme that seems to be popular at the moment. Here in NZ, the obnoxious Matthew Hooton was grinding his teeth over this the other day (http://www.nbr.co.nz/article/sanity-prevail-climate-change-policy-115955). 'Falling predicitons' and 'Dying interest' seem to work quite well together, and both play to the publics general preference not to have to think that theior way of life is unsustainable,, destructive and making a horrible mess for their kids and grandkids.
  22. 2012 SkS Weekly Digest #15
    Based on your personal experience, what is the most difficult aspect of manmade climate change to explain to the average person? From your perspective, has SkS adequately addressed this particular issue? I'm getting more and more pessimistic towards the effectiveness of the whole debunking process. One reason for this has lately publicly been brought up by Dr James Hansen (see Climate scientists are losing the public debate on global warming [Telegraph, UK]). Another reason for me is that the ongoing discourse has lost any rationally based angle (or never had that). When person A says "p!" and B responds with "non p, because...", you'd expect A to argue about the case and, eventually after a longish and intense discussion, A and B will come to an end (be it p, modified p, modified non-p or non-p). This whole concept of a discourse is plain and simple not existing regarding climate change. A very subjective perception is that for every great article on SkS or elsewhere 10 new blogs pop up with myth content that has been totally debunked 10, 15, 20 years ago. One reason for Joe Sixpack (or national equivalent) to "mistrust" the findings of the scientific community may be something like the notion 'This will cost me NOW!'. To counter that, SkS could possibly intensify argumenting within "It's not bad" or "Animals and plants can adapt" or the like. But SkS can't do that, since it can not and will not spread FUD. So beyond "Keep up the valuable work" I can't tell. Best, Andreas
  23. Global Warming in a Nutshell
    A side note to the last few comments: A simple thought experiment of removing GHG's shows an expected temperature of -18C. Tom Curtis linked to a model that included some secondary effects, such as albedo changes from ice growth and cloud cover, which reaches -20C even with some water vapor still present. But the core of the discussion remains, whether you attempt to account for all details of the extreme thought experiment - we're a lot warmer with greenhouse gases than we would be without...
  24. Global Warming in a Nutshell
    davpaf - "...the initial sentence of the paper is the basic assumption, which is unclear" Energy balance in the climate is determined by the difference between what comes in from the sun (240 W/m^2), and what gets radiated out to space (~239 W/m^2 or so at present, given the observed warming). Without GHG's, given the IR emissivity of the ground and water on the Earth's surface, 240 W/m^2 could be radiated with a surface temperature of about -18 C. That's as per the basic Stephan-Boltzmann equation. With the presence of various GHG's absorbing/emitting in the lower atmosphere, and the lapse rate of temperature fall with altitude, the top of troposphere location for those GHG's to effectively emit to space is both higher and colder than the surface - and since IR emission scales with T^4, they emit less energy than the surface or near-surface air could if directly exposed to space. This is often expressed as an "effective emissivity", or the proportion of a theoretic blackbody emission at surface temperatures. For our climate (as measured from space, relative to a 15 C blackbody) the effective emissivity is ~0.612, meaning that the Earth emits ~240 W/m^2 to space - rather than the ~396 W/m^2 emitted by the surface at that temperature. GHG's slow the effective cooling to space - and hence a higher temperature on the surface is required (higher than required without GHG's) to match incoming energy with outgoing IR.
  25. Global Warming in a Nutshell
    CBDunkerson, davpaf - My apologies, I was thinking of the more extreme thought experiment with no greenhouse gases, not just missing CO2 (and methane). However, the link Tom Curtis gave above looks to be a model of just that situation, removal of non-condensing GHG's - a cooling Earth, condensation of water vapor reducing the absolute humidity, tapering off to a temperature of about -20 C.
  26. Polar bear numbers are increasing
    The denier meme identified in the OP is a quote of Mitch Taylor who was billed as a “leading Canadian authority on polar bears.” Thanks to Peter Gleick, we now know that Mitch Taylor receives a monthly stipend from the arch-conservative US think-tank, The Hearltand Institute. For more details about the Taylor-Heartland connection, check out: “What passes for a Brain Trust at Heartland?” by Richard Littlemore, DeSmog Blog, Feb 24, 2012
  27. Polar bear numbers are increasing
    Seems to me that the OP should be updated to reflect the scientific findings that have been published since Sep 2010.
  28. Polar bear numbers are increasing
    Speaking of polar bears, here are a couple of interesting facts about where they came from and where they may be headed. “Polar bears have maternal Irish brown bear ancestors” by Stephen McKenzie, BBC News, Jul 7, 2011 “Brown and polar bears set to mate again due to global warming” by Cathy Hayes, Irish Central, Jul 13, 2011
  29. Global Warming in a Nutshell
    I am not in any way in doubt about the radiative characteristics of the different gases! Here what I understand so far: As you have pointed out in the figure of this article, various gases have different characteristics of emitting radiation. According to the figure the major players seems to be Water vapour & CO2. So if in our thought experiment an atmosphere without CO2 is present, there are still gasses available which will provide radiation to space, hence the atmosphere will be radiating to space. So the two components from before, atmosphere + surface, both radiating are still present, leaving me with my original question why it is valid to disregard the atmospheres part. Thanks for the link to the paper admin. As I understand it is mostly on the effectiveness of the individual greenhouse gases, and how individual and combined effects are important. But still the initial sentence of the paper is the basic assumption, which is unclear: “The global mean greenhouse effect can be defined as the difference between the planetary blackbody emitting temperature (in balance with the absorbed solar irradiance) and the global mean surface temperature. The actual mean surface temperature is larger (by around 33°C, assuming a constant planetary albedo) due to the absorption and emission of long‐wave (LW) radiation in the atmosphere by a number of different “greenhouse” substances.” I have also checked the reference of this quote in this paper (Charney, J. (1979), Carbon Dioxide and Climate: A Scientific Assessment,Natl. Acad. Press, Washington, D. C.) but don´t seem to find its origin.
  30. Global Warming in a Nutshell
    Tom & KR, note that the original hypothetical was just the removal of all carbon dioxide from the atmosphere... not all greenhouse gases. Of course, it would be impossible to remove all CO2 without also removing all methane (which breaks down into CO2)... and the temperature drop from decreased CO2 would perforce cause a significant reduction in atmospheric H2O... However, I ignored all of that in my response... which was then still just a wild guess. The ~33/34 C values you are citing would be removal of the entire greenhouse effect... though I believe even then it isn't accounting for additional cooling which would result from the albedo shift. Basically, it is a physically impossible hypothetical and thus the answer depends in large part on what assumptions we make to 'gloss over' the inherent contradiction of CO2 levels somehow changing to zero independently of all interconnected factors. It would be cold exactly how cold is impossible to say without understanding the magical process which allows the atmospheric CO2 to drop to zero.
  31. 2012 SkS Weekly Digest #15
    chriskoz@3: You ask: "What is the difference between "denier" and "denialist"? And similarly, between "denial" and "denialism"?" As a paid skeptic (geologist) here's how I define it: Deniers/denialism reject *any* evidence of AGW/CC regardless of its robustness or irrespective of how well vetted the data is. To utilize an oft-used term, they are the 'birthers' of the science world. skeptics, OTOH, question the data and interpretations of data NOT with ad hominem attacks, or hyperpartisanship: they act as any good scientist should, by analyzing the extant evidence then addressing that with science-based rationale.
  32. 2012 SkS Weekly Digest #15
    lurgee@1: As a earth systems scientist who battles this type of disinformation almost daily, the best I can offer as an answer is: -Rampant Dunning-Kruger, coupled with; -wishful thinking, that if the deniers say it loud enough and long enough, the general public will believe it. given their overwhelming success at that tactic so far, I wouldn't count them out. I will, however, continue to add my voice to the side of reasoned, rational and non-hyperpartisan science.
  33. Global Warming in a Nutshell
    davpaf - "Wouldn’t emission to space be from the complete earth surface/atmosphere system, since they both have a temperature." Yes. But in the Gedankenexperiment of no greenhouse gases, you're left with essentially oxygen, nitrogen, and some argon - none of which absorb/radiate significantly in the IR spectra. in the absence of GHG's only the Earth's surface will radiate - at about 0.98 to 0.99 emissivity in IR. See figure A4 above regarding gas spectra. "How much each of these parts contributes to this total emission is of course debatable." No, it is not. Not after 150 years or so of spectroscopy.
  34. Rob Honeycutt at 02:46 AM on 17 April 2012
    Polar bear numbers are increasing
    The figures that seemed more concerning to me, that were quoted by Dr Amstrup here, were the yearling survival rates of 6% in the Hudson Bay population whereas other populations are 22%. It sounds to me like there would eventually be a critical point where polar bear populations would collapse. If the bears can't sufficiently replenish their numbers then you're stuck with a collapse within ~one generation. So, that begs the question, what are the factors that impact yearling survival rates? Because that's what will do them in. If seasonal ice-free conditions have the greatest impact on yearlings, that might be the weak link critical to their survival.
  35. Polar bear numbers are increasing
    jzk @46, in round figures, the difference mean of 20 and 25 thousand bears is 23 thousand. Less a third (8 thousand) leaves you with 15 thousand in 45 years. A further 45 years on (2100) leaves you with 7 thousand. A further 45 years on leaves you with no bears in the wild. If the IUCN projection is correct, absent a radical improvement of conditions for the better the IUCN prognosis is not of a surviving population, but on one going extinct, but more realistically, after 2100 rather than before it.
  36. Cliff Ollier: Swimming In A Sea of Misinformation
    Slightly off-topic - I think Willis Eschenbach needs his own category as in his latest guest article at WUWT he's managed to demonstrate that the "Year without a Summer" of 1816 never happened ( and presumably debunking Thomas Jefferson's record of the unusual weather of that year as false or misleading)
  37. Global Warming in a Nutshell
    KR – Wouldn’t emission to space be from the complete earth surface/atmosphere system, since they both have a temperature. How much each of these parts contributes to this total emission is of course debatable. So I am still unclear why one can assume that the total emission temperature of these 2 parts (surface emission through its temperature) (atmosphere emitting through its temperature) should be equal to the global mean surface temperature. Are there any papers on this specific issue? Thanks folks
    Moderator Response:

    [DB] "How much each of these parts contributes to this total emission is of course debatable"

    Debatable? Not really. This is an area well-studied and well-understood. See this SkS post by Dr. Kevin Trenberth and this attribution study by Schmidt et al, 2010:

    Attribution of the present-day total greenhouse effect

  38. Global Warming in a Nutshell
    davpaf - "This still leaves me pretty uncertain why it is valid to assume that TS should be equal TE." Because if there were no absorbing greenhouse gases (in this thought experiment) emissions to space would be directly from the surface, hence TE = TS. Greenhouse gases shift emission up in the atmosphere to colder regions, hence the present difference between surface and emission temperatures.
  39. Global Warming in a Nutshell
    Neoproterozoic `snowball Earth' simulations with a coupled climate/ice-sheet model There are several items in the References section that look look like good starting points for geologic evidence.
  40. Polar bear numbers are increasing
    @43 Philippe Exactly. That's what the polar bear experts say. Cod --> Seals --> Polar Bear Not sure what the Cod eat yet. Species that ringed seals eat Boreogadus saida and others. This fish feeds on krill and plankton and favors surface feeding and frequents river mouths. [Ref] It is interesting that it survives best at a water temperature of 0-4C. Maybe more than ice loss, a warming of the water above 4C would cause a decline in the food source for polar bears if ringed seals can't adapt to other species. The Russians fish the polar cod commercially so over fishing of Arctic water with more ice free days could impact polar bears.
  41. Shakun et al. Clarify the CO2-Temperature Lag
    @William Haas: You cannot trap the extra heat unless there is a heat-trapping gas already present. That is CO2, not H2O(v). You cannot warm the planet unless you trap extra heat. You have to have a mechanism in place already in order to trap the extra heat (in the north, due to orbital cycling). The heat trapping mechanism that was already in place and available instantaneously was... CO2. H2O(v) is a strong feedback, but not a driver, because without the trapping mechanism to keep that heat, there will be no warming. Without warming, no extra H2O(v) will enter the atmosphere. It will not do so until the atmosphere warms up. The atmosphere warms up only is more heat is trapped. You are getting into a very circular argument in your attempts to downplay the importance of the basic step in the warming cycle... heat trapping due to CO2. That is the important factor, the one that drives and controls the H2O effect.
  42. Global Warming in a Nutshell
    Tom @18, I missed that. Good one; I think these two articles should be linked to each other. Looking at the comments, apparently there Steve Case believes that CO2 has an effect, and here that albedo changes and other feedbacks/forcings do not. Wondering how he would explain how Milankovitch cycles work without mentioning ice albedo. Maybe we should put him and Lindzen in a room together. davpaf @20, It might help to point out the observation that in the past, when the atmosphere has dropped below a certain CO2 level, an icehouse state ensued. (And it took very high levels of CO2 to flip it out of that state.)
  43. Polar bear numbers are increasing
    Tom @45, Thanks for the correction on the 45 vs. 100 year fact. Both the report and the SkS article says that there are 20,000 to 25,000 polar bears. Where do you get 15,000 figure? What are the chances that the Polar Bear population crashes to 7,000 within 45 years? Thanks.
  44. Michael Whittemore at 00:34 AM on 17 April 2012
    Shakun et al. Clarify the CO2-Temperature Lag
    I think this information from Clark et al. 2012 might point to the reason why Shakun et al. paper did not use all the Antarctic ice core proxy data. "whereas in Antarctica, East Antarctic ice cores and two West Antarctic ice cores have similar patterns that broadly follow the classic seesaw pattern, whereas two other West Antarctic ice cores (Siple Dome and Taylor Dome) suggest a more complicated deglacial record (58, 59). It remains unclear, however, as to whether these latter differences are due to uncertainties in chronology, elevation changes, stratigraphic disturbances, or spatially variable climate changes (59–61)." (clark et al. 2012)
  45. Global Warming in a Nutshell
    Yes thank you for the link to this paper. Interesting and valid results, but all based on their statement on page 1: "The difference between the nominal global mean surface temperature (TS = 288 K) and the global mean effective temperature (TE = 255 K) is a common measure of the terrestrial greenhouse effect (GT = TS – TE = 33 K). Assuming global energy balance, TE is also the Planck radiation equivalent of the 240 W/m2 of global mean solar radiation absorbed by Earth." This still leaves me pretty uncertain why it is valid to assume that TS should be equal TE. Thanks
  46. Global Warming in a Nutshell
    Thanks for the info. Have any papers been published on modelling such an atmospheric situation? The -18C you are referring supposedly originate from the Solar Radiation and the Earth's Energy Balance? It would be great if someone could explain to me why such a representation is valid in describing the global mean surface temperature of the planet. Thanks
    Moderator Response: [DB] The Lacis paper I linked for you in the earlier response to you is published.
  47. Global Warming in a Nutshell
    CBDunkerson @21, actually dropping CO2 levels to 0 ppmv would global mean temperature from about 14 degrees C to about - 20 degrees C. That is, the drop would be around 6 or more times the difference between the LGM and preindustrial temperatures:
  48. Polar bear numbers are increasing
    jzk @44, the report says: 1) That some people have speculated that polar bears will be extinct in 100 years; 2) That extinction in 100 years would "indicate a population decrease of >50% in 45 years; and 3) That a more realistic estimate is a population reduction of >30% in 45 years. At no place does it assert an upper limit on the population loss, so your claimed < 50% is entirely a misunderstanding of the report, just as is your stated 100 year time period rather than the 45 years stated in the report. Fairly straightforwardly, a population that has crashed from about 23,000 to about 15,000 or less in 45 years cannot be expected to miraculously stabilize at that number while the conditions that brought about the collapse continue to worsen. Rather, we can expect it to crash further to about 7,000 or less in the next 45 years, and unless you believe that negative population numbers can be turned around, is plainly heading for extinction at a fast rate. So while extinction by 2150 may be more realistic than extinction by 2100, that is hardly cause for comfort. I would be the first to admit that such a simple calculation does not allow for appropriate nuances. Indeed, I have discussed the relevant nuances extensively above. But those nuances do not justify treating a report which classifies polar bears as "... facing an extremely high risk of extinction in the wild" (definition of vulnerable) can be legitimately interpreted as indicating polar bears are not "...in danger of extinction". Finally, the report does not "... specifically states that speculation of their extinction within 100 years is not very realistic"! It states that a reduction of >35% in 45 years is a more realistic assessment than a reduction of >50% in 45 years (and hence of extinction in 100 years). But having learnt that African elephants are larger than Indian elephants, we do not conclude that Indian elephants are not very large at all. To do so would be a complete non-sequitor. Claiming your absurd conclusion as a specific statement of the report is a straightforward misrepresentation.
  49. Global Warming in a Nutshell
    davpaf, the map below shows the approximate extent of ice during the last glacial maximum. Note that the ice sheet extending over North America on this map was more than a mile thick. That ice coverage was due to atmospheric CO2 levels dropping from ~280 ppm to ~180 ppm. Dropping the CO2 level to 0 ppm would cause the temperature to drop by about three times as much as it did during the last glacial maximum. You'd need a complete climate model to get a tightly constrained estimate of the temperature drop and total ice coverage. My guesstimate would be around -18 C and ice extending to the tropics of Capricorn and Cancer.
  50. Global Warming in a Nutshell
    Hello, Can some please make it clear (with some numbers) why the earth would be a frozen ice ball if our atmosphere had zero CO2 content. Thanks!
    Moderator Response:

    [DB] In addition to the help already given below, you will find the numbers you seek here:

    Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature

    "Without the radiative forcing supplied by CO2 and the other noncondensing greenhouse gases, the terrestrial greenhouse would collapse, plunging the global climate into an icebound Earth state."

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