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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. -
Rob Honeycutt at 02:46 AM on 17 April 2012Polar 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. -
Tom Curtis at 02:14 AM on 17 April 2012Polar 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. -
DMarshall at 01:52 AM on 17 April 2012Cliff 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) -
davpaf at 01:41 AM on 17 April 2012Global 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 folksModerator 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
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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. -
Chris G at 00:55 AM on 17 April 2012Global 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. -
TOP at 00:55 AM on 17 April 2012Polar 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. -
danielc at 00:50 AM on 17 April 2012Shakun 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. -
Chris G at 00:43 AM on 17 April 2012Global 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.) -
jzk at 00:36 AM on 17 April 2012Polar 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. -
Michael Whittemore at 00:34 AM on 17 April 2012Shakun 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) -
davpaf at 23:12 PM on 16 April 2012Global 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 -
davpaf at 22:49 PM on 16 April 2012Global 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. ThanksModerator Response: [DB] The Lacis paper I linked for you in the earlier response to you is published. -
Tom Curtis at 22:33 PM on 16 April 2012Global 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:
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Tom Curtis at 22:23 PM on 16 April 2012Polar 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. -
CBDunkerson at 21:55 PM on 16 April 2012Global 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.
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davpaf at 21:30 PM on 16 April 2012Global 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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jyyh at 21:12 PM on 16 April 20122012 SkS Weekly Digest #15
I think it's 'Stephanie McMillan' though artists sometimes go by another name or short of their given name.Moderator Response: [JH] Corrected. Thank you. -
Michael Whittemore at 20:49 PM on 16 April 2012Which plants will survive droughts, climate change?
This paper is such a game changer for the Ecology field, all the controversy has simply been put in its place. -
Lionel A at 20:48 PM on 16 April 20122012 SkS Weekly Digest #15
One problem I note that could fit the issue of the week is that on blogs protagonists on both sides can end up talking past each other. For example I can cite Skeptical Science only to have it thrown back in my face with accusations of SKS being a PR site, which charge of course is totally out of order. I will then be pointed at the likes of WUWT, which I don't bother visiting on the grounds of not wishing to up Watt's hit count. A typical case arouse with a protagonist Cole at Concordiensis . It looks like I could have misinterpreted the context in this search on Cole here at SKs , not having seen the original exchanges with Cole here. Despite that it looks like Cole has done a 'Monckton Manoeuvre' and flounced off, possibly because of the evidence for, even though I could not see examples of, his 'carpet bombing' of topics here. On ecocide E O Wilson produces a fine assessment of the problems in his 'The Future of Life' (Wilson's earlier 'The Diversity of Life' provides more context) and Richard Pearson provides other interesting perspectives in his 'Driven to Extinction'. The parlous state of the biosphere and the lack of realisation of how much we are in debt to it for services provided is something that appears to be much under represented in discussion right now. -
jzk at 20:32 PM on 16 April 2012Polar bear numbers are increasing
"Polar Bears are in Danger of extinction." What does that mean "in danger?" The cited evidence from the IUCN states that Polar Bears face a risk of a greater than 30% but less than 50% population decline within 100 years. The report specifically states that speculation of their extinction within 100 years is not very realistic. -
William Haas at 19:08 PM on 16 April 2012Shakun et al. Clarify the CO2-Temperature Lag
Again sorry for the slow response. I see that I am getting responses to my posts but I am trying to comment on them in order. I thank you for the effort that you are all putting in. 81 Danieic You wanted me to state a "plausible mechanism". A plausible mechanism is that orbital forcing drove up tempertures enough to release H2O that then amplified the forcing signal. We are talking about the first 2,500 years since the last LGM where the article says that 7% of the warming took place and CO2 levels did not increase. H2O is a green house gas. There is plenty of H2O in both solid and liquid form to evaporate or sublime and enter the atmosphere. As long as the air is above -22 degrees f, there will be H2O in the atmosphere. If the temperature of the atmosphere increases the average amount of H2O will increase. According to the green house gas effect, more green house gases in the atmosphere will cause more heat to be trapped which will cause the temperature of the atmosphere to increase even further. It is often modeled as a feed back mechanism as I have stated before. In the first 2,500 years since the LGM H2O could not possible be a CO2 feedback mecaanism because according to the article, CO2 did not increase. Yet the temperature increased so H2O had to increase. One could probably write a recursion relation to compute what is happening. I think of it, myself, as a low pass filter with a well damped step response. The system is fundamentally stable so there is no chance of runaway heating. Rising temperatures causes the atmosphere to increase its capacity to hold water vapor. Relative humidity varies with time as a function of weather but what we are concerned about are averaged values of atmospheric H2O capacity because we are talking about changes in climate and not weather. -
Michael Whittemore at 18:48 PM on 16 April 2012Shakun et al. Clarify the CO2-Temperature Lag
@William Haas The initial warming was caused by the extra amount of sunlight hitting the planet in the far north. This started around 20 kry as shown on the graph below and CO2 had "nothing" to do with it. This warming caused the (AMOC) to stop which forced the north to cool and the south to warm, which is marked on the graph below as the seesaw. This process also had "nothing" to do with CO2. With all the extra water vapor being produced in the south, it did "nothing" to global temperatures. Look at the graph below, its all local warming as would be expected from water vapor. Global warming did not start until CO2 was released, which is clearly shown.
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Philippe Chantreau at 17:41 PM on 16 April 2012Polar bear numbers are increasing
"The bears are kind of integrating the PCB content of the water over time which may act like a proxy for long term effects of the currents." By what exotic biological process would that work? Absorbtion through the skin? Bear fur is so dense that water does not even touch the skin, hence their ability to withstand cold water temperatures during long swims. Or do you think bears drink sea water? More plausibly, they absorb the PCBs throug their food, mainly seals or other mammals that concentrate the PCBs because they are near the top of the ocean food web and they have a high fat content where they accumulate a lot of PCBs and other toxins. Where the bears' preys get their food, and the travels of that food are the more interesting questions. -
OPatrick at 16:30 PM on 16 April 20122012 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? Perhaps the overarching nature of the issue. Climate change affects so many aspects of our lives but in many cases is just one of the contributory causes and for each problem, looked in isolation, might not appear to be significant. As an example take the drought in the UK - most discussion is about water companies failing to prevent leaks, which is a valid criticism. Then there is the natural variability in the weather which may only be marginally influenced by changes in climate. It can be difficult to get people to understand the multiple, cummulative impacts from climate change and consequently the urgency of the problem when the tendency is always to focus on specifics. From your perspective, has SkS adequately addressed this particular issue? Possibly not, though posts like Global Warming in a Nutshell help. -
lurgee at 16:27 PM on 16 April 20122012 SkS Weekly Digest #15
(Which, of course, has nothing to do with the science itself, but a perennial bugbear of mine.) -
lurgee at 16:25 PM on 16 April 20122012 SkS Weekly Digest #15
"I'd agree, it appears to be an emerging tactic of some sort, but little different to the playground bullies who have run out of taunts and say they're not interested anymore." I'd like to think it was that simple, but my more paranoid and suspicious side suspects a tactic of some sort. First of all, as Stephen Schneider pointed out, scientists had to play the media game to get the attention the issue deserves. Then they were accused of alarmism and retreated. Now it's a dying issue. Seems like, if they ain't gotcha one way, they gotcha another. What's it all about? My other issue of the week (I suspect "fading concern" may be an issue for weeks to come) is the instant conflation of any trash media story with considered scientific opinion. Like the story WUWT dug up, about 4.5 billion people being dead by 2012. Not a single scientist named, no references, just some dreck posted on a website by a weevil. But immediately paraded about the interweb by a million deadhead followers of the Wattsacious One. -
TOP at 16:02 PM on 16 April 2012Polar bear numbers are increasing
@DSL I've done some more reading on the subject. #2 is interesting. I found a map showing the PCB levels in polar bears and that highest levels appeared to be around eastern Greenland and the southern part of Hudson Bay. In my opinion the only way PCBs could get up there is by transport in the ocean from farther south (at least the Greenland PCBs). The bears are kind of integrating the PCB content of the water over time which may act like a proxy for long term effects of the currents. #2 and #4 kind of work together some times. It turns out that polar bears aren't real picky as to what they eat and have been killed by eating lead acid batteries/hydraulic fluid and antifreeze. In other words polar bears can be killed/harvested by eating polluted human castoffs/garbage. Until the icepack is gone I would expect the polar bears to go where the food is. Their food is mobile too. So a decline in their population in one area might mean a move to another area where there is more food. If a decline in sea ice means a less extensive feeding ground it might also mean a denser source of food and at least short term an increase in polar bears in particular areas. One thing that a decrease in sea ice might mean is that fishing ships expand into the polar areas previously off limits. That would cut into the polar bear's food's food. I didn't see any mention of that on the IUNC Red List. -
skywatcher at 16:00 PM on 16 April 2012Shakun et al. Clarify the CO2-Temperature Lag
William Haas #107, you're making no sense at all. I fear I'll just have to repeat scaddenp in reminding you that water vapour is a feedback, not a forcing. This is a crucially important concept that you're failing to grasp, and it is not something that there is the least bit of doubt about. It is (and physically must be) that way, even though water vapour is the largest single component of the greenhouse effect. It does not matter how wet our planet is (it is very wet!), we need the stabilising effect of long-lived CO2 to provide a warming 'base' for the WV feedback to be propped up on, or else the combination of precipitation, freezing and albedo increase would turn our planet quickly into the ice house it would be at this distance from the Sun, were there not long-lived greeenhouse gases (dominantly CO2) in our atmosphere. CO2 does not precipitate out of the atmosphere, so when you change the CO2 level it stays changed for a century or more until slow carbon cycle processes, if favoured, remove it. It lasts long enough to impact ice volume (albedo) and ocean currents (CO2 ventilation), which operate on the decade-to-century scale. That makes it the most important control knob on climate. Thus long-lived greenhouse gases regulate the water vapour, which precipitates out at the drop of a hat (less if you are in Glasgow...). -
Mond from Oz at 15:38 PM on 16 April 2012Global Warming in a Nutshell
I guess I'm representative of the sort of people this post is intended to inform. I started to inform myself a couple of years ago, and came up with the following hypersimple outline of the scientific argument: 1. Earth’s human population has grown, very rapidly in the last 80 years. from about two billion, to around seven billion in 2011. It is predicted to exceed nine billion by 2050. 2. Human activity – manufacture, agriculture, trade, travel - has increased. Not only are there more of us, but per capita we are doing more. Together, (1) and (2) are what we call ‘growth’ 3. Growth takes energy. 4. The energy has been supplied by the heat from burning carbon: wood, then coal , then oil and gas. 5. Burning (oxidising) carbon produces carbon dioxide. 6. Carbon dioxide in the atmosphere causes the planet to warm. It seems to me that each of the above points, elaborated, is as near to incontrovertable as you can get. So the issue now is how to get the message out, and how to stoke action on the basis of the science. To that end I have tried to develop a website for use in a small-group, net connected educational project. See www.theclimateargument.com (Sorry: dunno how to make the link active) The central information source for the project is a paper 'convergence' which is on the website.It covers much the same ground and uses many of the same figures as Larry's Of course, beyond all this is a question for politics and political economy.....What is to be Done? S.H.Moderator Response: TC: Added html link. The comments policy contains a number of hints for using html code, including basic commands for links, pictures and emphasis (italics, bold, underlining). -
Tom Curtis at 15:38 PM on 16 April 2012Global Warming in a Nutshell
Chris G, you may appreciate this attempt to not leave people behind. -
skywatcher at 15:37 PM on 16 April 20122012 SkS Weekly Digest #15
#1 lurgee - I'd agree, it appears to be an emerging tactic of some sort, but little different to the playground bullies who have run out of taunts and say they're not interested anymore. I think the claim is running in parallel with a trend in which there are progressively fewer and fewer skeptic arguments that even deserve more than about five seconds to debunk (especially if you have SkepticalScience to hand!). More and more people are aware of the vacuity and mutual incoherence and fundamental incorrectness of various skeptic arguments, so they have to resort to claiming that nobody's interested anymore. I doubt we'll have the luxury of them just disappearing off, but it's an interesting possible trend nonetheless. Another angle is that media only tend to report something that's 'different', such as today's example of the Karakorum glaciers on BBC, and tend not to report on the continuations of warming, melting, acidification and so on. Merely confirmatory research does not make such a good 'story', even though it makes up the bulk of research on climate-related issues. The result is that the consensus views get a poor airing even from unbiased news outlets - expanded on in Freudenberg's Asymmetry of Scientific Challenge. I wonder if this effect is furthering, to some people, an impression that the issue is less prominent? There's precious little 'skeptic' research, and so we see that the research that WUWT and co pick up on, such as the recent ones about Antarctic ikaites, deglacial CO2 and Karakorum glaciers, is actually research that confirms the overall scientific consensus. Desperate times for those in denial! As for the issue of what is most difficult to explain to the average person - not so sure, but perhaps the concept that it is something we need to act upon now, and we can't wait/put it off like our parents did. Actually, rather like DSL's comment even if that one was in response to lurgee! - namely that this is stunningly rapid in the context of geological or vegetational change, and so represents a very real threat to large-scale agriculture. Very hard for the average person to realise this as they are not accustomed to thinking on timescales of thousands or millions of years. Has SkS got it covered? - largely in skeptic argument #3, It's Not Bad, and #8,Can animals and plants adapt to global warming? -
Tom Curtis at 15:34 PM on 16 April 2012Shakun et al. Clarify the CO2-Temperature Lag
William Haas @104, I made a major error in my post 73, which I corrected in my post 87. The effect of the error was to overestimate the difference in the GHE between the LGM and the late 20th century by 60-70 W/m^2. In consequence, the unexplained change in GHE is around 30 W/m^2. As noted in my post 73, even that is an over estimate because it does not allow for the effect changes in albedo, nor from minor Greenhouse gases like methane, nor the effect of the increased temperature difference between equator and pole, which allows larger IR emissions from the surface for a given global temperature. Consequently the increase in contribution to the total GHE from water vapour is almost certainly less than 30 W/m^2, but also very likely to be greater than 15 W/m^2. -
William Haas at 15:00 PM on 16 April 2012Shakun et al. Clarify the CO2-Temperature Lag
79 danieic 82 Skywatcher most likely answered your question but let me add something. At lower temperatures the amount of CO2 in the atmosphere relative to H2O will be higher so according to green house gas theory the relative contribution to heat trapping of CO2 compared to H2O will be much higher. At temperatures less than -22 degrees f, H2O vapor disappears from the atmosphere but the level of CO2 does not change. I do not believe that changes in green house gasses are considerd to be the trigger that started the climate change at the LGM but they may have added to the effect. -
scaddenp at 14:27 PM on 16 April 2012Shakun et al. Clarify the CO2-Temperature Lag
William - reiterating earlier commentators: H2O is important feedback - it cannot be a driver. A driver (forcing) is something changes the energy flow independent of temperature. You cannot vary H2O independently of temperature so is feedback only. CO2 is both.Moderator Response: TC: html tags fixed. -
Chris G at 14:21 PM on 16 April 2012Global Warming in a Nutshell
WRT: "...which is colder than the average surface temperature because some of the infrared emission comes from clouds at colder levels in the atmosphere." Mmm, while it is true that the tops of clouds are generally colder than the areas without clouds, I don't think it is necessary to invoke clouds. It might be more accurate to say that the percentage of longwave not absorbed by the GHGs above any point of emission, and therefore actually escaping to space, increases as the altitude increases. Absorption is a function of density, and density drops rapidly with altitude. Near the surface, very few of the photons which could be absorbed by a GHG make it to space without interacting with a GHG. As the density drops, a higher percentage of the photons emitted reach space (and GHGs both absorb and emit). Temperature drops with altitude, up to the tropopause. The mean emission altitude is around 6km; this is below the mean tropopause height (which varies). So, an instrument measuring outbound photons sees a distribution of photons that represents a temperature that is less that what the surface actually is. More of any GHG effectively raises the distribution of outbound photons a little higher in the atmosphere. Using an environmental lapse rate of 6.5 K/km, and not counting albedo changes, you only need to raise the mean altitude of emission by about 300m in order to cause a 2 K warming at the surface. OK, at this point I think that all I've done is demonstrate that more accurate is sometimes less clear. My longer description is still a simplification, and I suspect I've left some readers behind. Or, maybe I've demonstrated that when things are simplified, you can have more than one seemingly different explanation for the same effect, that might appear to be, but are not really at odds with each other. I suspect that some bloggers take advantage of this kind of inconsistency-that-isn't scenario in order to imply doubt where really none exists. -
William Haas at 14:16 PM on 16 April 2012Shakun et al. Clarify the CO2-Temperature Lag
Sorry for being behind in my comments. I may get caught up eventually. 78 Tom Curtis. Thank you for the good work. According to you the change in CO2 forcing from LGM to the year 2000 was 3.7 watts per square meter. The change in the GHE you say from LGM to the Holocene is somewhere between 50 and 100 watts per square meter. Since H2O is the domanant green house gas then it must be the driver. The effects of H2O really overwhelm that of CO2. This is according to the data that you have presented. We are talking about cimate here and not weather. H2O is in many ways the big weather maker with relative humidity varying quite a bit from day to day. As water precipitates out more is added through vaporazation and or sublimation. What matters is the average amount of H20 in the atmosphere and as average temperatures increase so does the average amount of water vapor. This is commonly used in modeling an increase in retained heat caused by more water vapor that is in turn caused by a warmer atmosphere that in turn is caused by an increase in CO2. It is modeled as a CO2 related feedback mechanism. We live in a water world which was especially true during the first 2,500 years after the LGM. H2O will not only evaporate from liquid water exposed to the atmosphere but it will sublime directly from ice. I assume that, for temperatures less than -22 degrees f, water vapour content will drop to zero but even at the LGM it was not less than -22 degrees f over the entire earth's surface. So far I have been talking about the first 2,500 years after the LGM when according to the article the CO2 levels did not change so there was no CO2 change to effect average temperatures. We are talking about climate change that occoured gradually over a period of 2,500 years. Remember that 2,500 years ago was before the rise of the Roman empire. It is a very long time, and a long enough time for local varinng weather effects to average out. -
scaddenp at 14:13 PM on 16 April 2012Data Contradicts Connection Between Earth's Tilt and the Seasons
I think Manny's comment implies that he/she thinks that there could be unknown natural forcings that effect climate only on century wide scales. "Proof" is a concept for mathematics not science, so it is better to say that there is no evidence for such forcings. There is a very strong believe among scientists in the conservation of energy which would require this natural forcing to manifest as a energy flow that so far has evaded detection. This is possible but highly unlikely. -
skywatcher at 13:55 PM on 16 April 2012Data Contradicts Connection Between Earth's Tilt and the Seasons
#17 Manny, you're comparing apples to oranges. The article is not a parody of a model 'hindcast', it is a parody of amateurs thinking they can predict future temperatures based on drawing a line through a tiny subset of current temperatures. The above article demonstrated that doing a regression over a short timescale (seven weeks, not three months) is insufficient to distinguish the forced winter-summer trend in San Jose, even when we clearly understand the forcing and the result. This is the same argument as someone drawing a trend line through temperature data for a decade or less (they usually start in 1998, 2002 or some other such high point), and thus claiming that they can say something about the long-term trend or the nature of its forcing. Climate models on the other hand are not based on wiggle-matching, or simple correlations / linear / multiple regressions. They are based on the fundamental physical properties of the atmosphere, land and ocean including the energy flows to, from and through each. Validation of a GCM over the past century is to confirm that the model of the Earth system (and the physics defined therein) behaves in a manner similar to that of the observed Earth system. That they do so is a powerful validation of that fundamental physics. The basic physics has to be right to replicate not only the overall warming trend, but key wiggles such as mid-century cooling or volcanic eruptions. The basic physics is then used to make projections given a furture evolution of key parameters like CO2 emissions, volcanoes, ENSO and the Sun. Do you see the difference? While some elements of the system have behaviours dominant over longer timescales (including sea level rise, ice sheet disintegration, natural carbon sequestration), most of the other dominant behaviours can be characterised by the models on the century or sub-century scale. There is no reason to think that the forces that have controlled our climate over the past millennium, and even further back through the ice ages, should have changed in their modes of operation. Do you have a reason why those forces might have changed? -
Manny at 13:29 PM on 16 April 2012Data Contradicts Connection Between Earth's Tilt and the Seasons
Moderator has removed one comment I added after my last where I stated that the above discussion about the temperature of the past 6,000 years pulls us away from my initial criticism of this article. Allow me to restate it: With this article you have proven that three months of hindcast is too short to support accurate climate predictions. The IPCC GCM climate models are validated using data from 1900 onward. Where is the proof that one century of hindcast is strong enough to support climate predictions for the next century? -
Michael Whittemore at 13:25 PM on 16 April 20122012 SkS Weekly Digest #15
@ lurgee 1 "Has any thought been given to what seems to be the emerging denier tactic of claiming interest in Climate change is 'dying out'?" Here is a fine example of Andrew Bolt getting a real scientist on his show and getting put in his place when it comes to the truth The youtube video. These money making deniers can not afford the truth are playing the "climate change is dying card". -
Steve L at 13:05 PM on 16 April 20122012 SkS Weekly Digest #15
In response to issue of the week, the following is about those who accept the GW part of AGW, but not the 'anthropogenic' part. I've kind of made a resolution to engage more regular people regarding climate change (i.e., not just on internet fora). Today I sat down and scraped up a general 'gameplan': 1. CO2 in the air blocks infra-red (show this youtube video on smartphone), and we've increased CO2 a lot (explain enormity of change in atmosphere and ocean). 2. Greenhouse effect of CO2 is not a radical new-age idea (very brief listing of Tyndall, Arrhenius, Callendar, video from 1958, Hansen, George Bush Sr and formation of the IPCC). 3. CO2 and climate throughout the ages (faint young sun, natural CO2 sequestration, Milankovic cycles). 4. Predictions for recent and near future temperature measurements (ask them what they think will happen, ask them what they think has been predicted by climatologists). 5. Ask them for either their favoured explanation of recent temperature increase or for their favorite arguments against the consensus explanation. 6. Compare their predictions (for their favored warming mechanism) to those of climate change. Okay, so here I get to the relevant part for the issue of the week. I imagine the myths most needing to be dislodged will be about solar influences. In that case, under item 6 above, I say that a simple solar explanation (increased irradiance) would predict: daytime, summer, tropics would show warming first; stratosphere should warm; satellites should detect increasing radiation (from the sun); more visible radiation should be detected at the Earth's surface; current solar minimum should result in cooling temperatures. AGW on the other hand predicts nights, winters, poles warming faster; stratosphere should cool; satellites should detect decreasing radiation (from the Earth); more infra-red should be detected at the Earth's surface; warming of the planet should continue. Two of these are taken from the 10 indicators post (see 5 & 6 at this SkS fave ). There are citations provided, but I'm lacking a competent layperson's explanation for what is being compared. Satellites detect 'less' infra-red in the CO2 absorption/emission spectrum leaving Earth, but less than what? Less than when? Ground-based monitors detect 'more' infra-red bouncing back down toward them in the CO2 absorption/emission spectrum. More than what? More than when? I should look this up, but there may be other SkS visitors who would benefit from a more complete treatment of the topic here, at this excellent web resource. Thanks. -
DSL at 13:03 PM on 16 April 2012Polar bear numbers are increasing
TOP, if the Arctic is ice-free within 20 years, Nos. 2 and 3 won't really be a factor, because polar bears will begin to seek out new sources of food, and that will bring No. 4 into play. Unless the ice loss flattens for a few years, polar bears are going to have to evolve flippers and a snorkel. DB: if by "denier" you mean someone who has become psychologically invested in maintaining a position, and any threat to that position is seen as a potential attack on confidence or self-esteem (as if SkS were a game board)--ala Doug Cotton. There are plenty of people, though, who post "sciency" unevidenced stuff because they've been misled by opinion-makers; many of those may be called "deniers" but might actually be willing to engage the science and "come unstuck." TOP I have no opinion on--still weighing the evidence. -
DSL at 12:49 PM on 16 April 20122012 SkS Weekly Digest #15
Lurgee @ 1 -- "Has any thought been given to what seems to be the emerging denier tactic of claiming interest in Climate change is 'dying out'?" This is precisely why so many scientists are willing to 'get all political'. AGW is incredibly rapid on the geologic timescale, but it is slow on the timescale of a human life. When living under an economic mode that, even according to its most steadfast defenders, encourages people to focus on the next month rather than the next hundred years, it's fairly clear that unless the message is strong and delivered by a united front of really smart and/or well-respected and/or well-trusted people, concern will be set aside in favor of short-term economic and political goals. The occasional local manifestation of AGW will produce brief bursts of public concern, but it will take government (the only institution whose purpose it is to think long range in the general human interest . . . well, ideally anyway) to actually do something about it. This is all especially true if institutions (and the humans that populate them) designed to cast doubt on science, such as Heartland, continue to be given a free pass in mainstream media. Given those conditions, is it any wonder why scientists and other concerned citizens do things that allow the unconcerned to shout "alarmists!" -
TOP at 12:46 PM on 16 April 2012Polar bear numbers are increasing
You might look here for information on what is known to be going on and why. -
Michael Whittemore at 12:10 PM on 16 April 20122012 SkS Weekly Digest #15
@ Issue of the week: "Based on your personal experiences, what is the most difficult aspect of manmade climate change to explain to the average person?" Connecting events to anthropogenic climate change seems to be a hard argument. We are only in the beginning of a climate shift, and trying to make people understand that everything is not normal, isn't easy. I have heard it said before, but its going to take some serious natural disasters before people are going to get angry at the likes of Andrew Bolt and Alan Jones for their nit picking of climate science. -
TOP at 12:08 PM on 16 April 2012Polar bear numbers are increasing
There are four main threats to polar bears in the article. 1) Loss of habitat, sea ice (potential threat) 2) Ingestion of seals rich in pollutants (currently going on) 3) Oil spills (potential threat, but likely to happen in a limited time over a limited area) 4) Harvesting in an unregulated manner (current threat) I would have to ask whether #2 will do them in before #1 or #4? There is not much control over #2. -
Doug Hutcheson at 11:47 AM on 16 April 20122012 SkS Weekly Digest #15
Based on your personal experinces, what is the most difficult aspect of manamde climate change to explain to the average person? from your pserpsective, has SkS adequately addressed this particular issue?
Apart from how to use a spell checker? [/sarc] The area most often misunderstood seems to be the difference between weather and climate. When someone is objecting to AGW on the grounds that "locals reckon it was hotter here 50 years ago", it can be hard to get them to see that one local phenomenon is not representative of the Earth over time, or that anecdote is not the same as accurate observation. I find that referring to the melting Arctic is a good way to guide the conversation onto topics related to global effects. I use SkS references extensively, because SkS provides plenty of science to counter misunderstandings.Moderator Response: [JH] Typos fixed. Thanks for pointing them out. "Haste makes waste." -
Michael Whittemore at 11:45 AM on 16 April 20122012 SkS Weekly Digest #15
@ lurgee 1 "Has any thought been given to what seems to be the emerging denier tactic of claiming interest in Climate change is 'dying out'?" This is a point that is being made here in Australia too, I have not looked into it but tend to think people are becoming more educated on the subject of climate change and are not prepared to disregard it, so tv/news networks have to play the card that its "dying out". @ Issue of the week: "Based on your personal experiences, what is the most difficult aspect of manmade climate change to explain to the average person?"
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