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Comments 71751 to 71800:

71751. RW1 at 06:56 AM on 24 October 2011
       Clouds provide negative feedback
       DB, Is net negative feedback required for basic stability and maintenance of the current energy balance or not?
       Response:

       [DB] Your question presumes that there is a current energy balance at the TOA; the best understanding of the science indicates otherwise. 

       Energy in ≠ energy out (energy in exceeds energy out).

       You also do not define what physical process you refer to that is providing the "net negative feedback required for basic stability and maintenance".  Energy balance is the sum of physical processes, not hypothetical ones.

71752. RW1 at 06:30 AM on 24 October 2011
       Clouds provide negative feedback
       CBDunkerson (RE: #192), "You argue that 'the notion' of positive feedback from water vapor cannot be reconciled with 'tightly constrained' temperature variations in various other cycles (e.g. ENSO, seasons, day/night, 11 years solar cycle, et cetera)." No, I'm arguing that positive water vapor feedback in conjunction with positive cloud feedback cannot be reconciled with how the planet's energy balance is so tightly - but dynamically, maintained.
       Response:

       [DB] "I'm arguing that positive water vapor feedback in conjunction with positive cloud feedback cannot be reconciled with how the planet's energy balance is so tightly - but dynamically, maintained."

       The casual reader will note that, in the absence of doing the physics and showing your work, your statement is devoid of substance and amounts to empty assertion without merit.

71753. SoundOff at 06:28 AM on 24 October 2011
       Test your climate knowledge in free online course
       On further reflection, I think the question asked was: If the current rate of SLR stays the same, then how much would sea level rise by 2100 [over present]? At the current rate of 3.0 ± 0.4 mm/yr, I suppose the best answer would be 30 cm, of the possible answers offered. I’m very doubtful that 30 cm is realistic although it agrees with AR4 projections. The SkS page on this topic shows a range of 75 cm to 180 cm (depending on the scenario) based on findings reported in Vermeer 2009. The A1F scenario that we seem to be tracking looks to be headed for 140 cm by 2100, according to Figure 3, or 120 cm if the A2 scenario is preferred. [A very minor point: these numbers are referenced from 1990 so they should be reduced by 6 or 7 cm to put them into the present context.] SkS - How much will sea levels rise in the 21st Century? I won’t go into Dr. Hansen’s ten-year doubling time for ice sheet disintegration, somewhat of a thought experiment, but I remind you that he’s often ahead of his peers. He said the following in 2007:

       The nonlinearity of the ice sheet problem makes it impossible to accurately predict the sea level change on a specific date. However, as a physicist, I find it almost inconceivable that BAU climate change would not yield a sea level change of the order of meters on the century timescale.

       Hansen 2007 - Scientific reticence and sea level rise (pdf)
71754. Bob Lacatena at 06:13 AM on 24 October 2011
       Climate's changed before
       225, lancelot, 1. Yes. The term you want to search for is "hindcast" (e.g. "hindcast climate model"). But note that your specific parameters (+/- 0.5 deg C) may be too constrained. There are lots of parameters to be accurately modeled beyond global mean temperatures, and lots of ways in which a model may or may not be accurate, but in particular, models handle climate, not weather. It is nearly impossible to predict weather, and no model attempts to do so. In fact, models work using ensembles (multiple runs with the same starting conditions, which are averaged together). Also, we do not have accurate, precise measurements for starting conditions a thousand years ago. These must be inferred from proxies or just plain guesstimates. We also do not have accurate values for many inputs (solar irradiance, volcanism, etc.). These can only be guessed at. So getting things within any predetermined expectation ("a half a degree in June, 1980") is asking a whole lot, and in the end is not meaningful in evaluating the skill of the model. But yes, obviously one important way to evaluate the models is measure their ability "predict" what we already know has happened. Yes, scientists do this, and yes, models hindcast with enough accuracy to validate their ability to forecast as well. 2. Again, see the answer above. This isn't really a valid criterion. There is a lot more to climate than just temperature, and choosing a point in time is problematic (what if there's a real world ENSO event at that time, but not in the model run?). 3. I don't know that anyone has answered this question in exactly that way, because it's not really meaningful. Various events do affect climate to some degree (active volcanism, solar variations, etc.). There is no real "normal" temperature. Taking an average of the last 2000 years is of little value. Beyond this, proxies are difficult to calibrate and work with. While scientists have done a wonderful job filling in the blanks and trying to infer past temperatures, we just don't have enough global readings (proxies) with enough accuracy to compute anything like what you are asking.
71755. RW1 at 06:09 AM on 24 October 2011
       Clouds provide negative feedback
       lanC (RE: #189), "The earth radiates energy as E=epsilon*sigma*T^4, where epsilon is the emissivity (0.61) and sigma is the Stefan-Boltzman constant. If you increase the average earth surface temperature (287K) by one degrees you'll increase E by 3.3 W/m^2" Correct. Now, why specifically is the emissivity 0.61?
71756. CBDunkerson at 06:04 AM on 24 October 2011
       Clouds provide negative feedback
       RW1 wrote: "Have you noticed that even when the system as whole warms to a significant degree like during an El Nino event, it always seems to revert to its pre-equilibrium state fairly quickly afterward? This is hardly consistent with net positive feedback acting on perturbations." So... because the daily cycle of temperature fluxes due to sunrise and sunset returns to its 'equilibrium' state in short order this is evidence against Summer temperatures being warmer than Winter temperatures? That is essentially the 'logic' you are presenting... 'if A shows steady fluctuations around a flat baseline then B cannot possibly show long term increases'. "Also, the temperature rising as the Sun comes up each day is not the result of net positive feedback acting on the increased incident energy." In part, yes... it is. Most of the temperature increase is due to the increased radiation. However, water vapor feedback also plays a part... as anyone who has lived in a very humid area would be able to tell you. A climate 'forcing' is just a change from a baseline. Most often we choose baselines from on yearly averages. However, it is perfectly valid to look at the incoming solar radiation over the course of a day with the daily average as the baseline. In such case, sunrise would represent a massive warming forcing. We can then look at feedback responses to this forcing... specifically, that warming forcing from sunlight will cause water to evaporate. Water vapor is a greenhouse gas. Ergo, this will create a positive feedback. Further, it is a positive feedback that we have known about and studied for centuries. We use the term 'relative humidity' because the amount of water vapor the atmosphere can hold increases as the temperature does... so the relative humidity is the percentage of the possible maximum water vapor content of the atmosphere for the current temperature. If the temperature goes up the amount of water vapor the atmosphere can hold increases as well. A long understood and thoroughly measured phenomenon. Now, if the temperature of the entire planet goes up... why wouldn't the same feedback apply? If the planet's atmosphere is warmer it will hold more water vapor. That water vapor will produce more greenhouse warming. You argue that 'the notion' of positive feedback from water vapor cannot be reconciled with 'tightly constrained' temperature variations in various other cycles (e.g. ENSO, seasons, day/night, 11 years solar cycle, et cetera). I am saying that there is no logical way to conclude that water vapor will not be a positive feedback, because it is always a positive feedback to warming.
71757. Bob Lacatena at 06:00 AM on 24 October 2011
       Clouds provide negative feedback
       RW1, You have now demonstrated extreme ignorance on climate science (a complete failure to understand Stefan-Boltzmann, the Planck response as a feedback, and the way that we know that this response is 3.3 W/m² per degree K). At this point, you must recognize the need to study and learn a whole lot more before you "authoritatively" comment any further on things that you clearly do not grasp.
71758. Bob Loblaw at 05:52 AM on 24 October 2011
       Human CO2 is a tiny % of CO2 emissions
       Sphaerica@212. Exactly. You appear to understand perfectly. The numbers I calculated were based on the assumption that the extra sucking applies only to anthropogenic CO₂ and the new magical natural source that looks just like anthropogenic CO₂ (i.e., same isotopic signature, etc.). The numbers I present say that if this removal ratio is 99%, then this mysterious natural source is 49x larger than the anthropogenic one - i.e., the 30 Gt anthropogenic source is running in parallel with a natural source of 1470 Gt. Kind of hard to miss in the grand scheme of things, since we seem to be able to identify the long-existing natural sources of much smaller quantity than this. This new source also seems to be rising at the same rate as anthropogenic CO₂. Another astounding coincidence. ...but at least you have a conjecture as to the source. Unlike the "skeptics". And as muon points out, the same logical applies to any new sink we haven't noticed - it is "emerging before our very eyes". It has some magical property that allows it to turn on and grow at just the right rate. ...but muon's hypothesis seems a bit far-fetched. I think it is more likely that Sphaerica's alien race has introduced a cap-and-trade scheme, and some enterprising alien has realized that they can make oodles of money by scarfing CO₂ out of our atmosphere and get credit for sequestering it. Unfortunately, the same conspiracy that made up the AGW hoax is also hiding the fact that we've made contact with these aliens, and have one of their teleportation devices stored at Area 51. We're not allowed to use it to solve our problem. [Yes, I know that it is inconsistent to have the same conspiracy both make up the problem and hide a real solution to the same problem. In the People's Republic of Made-up-istan, consistency is not a legal obligation.]
71759. lancelot at 05:17 AM on 24 October 2011
       Climate's changed before
       Great site! Questions which I swear I have searched for, but this is also a vast site, and I do have a day job: 1 is there any climate model that can simulate in full using natural forcings alone the generally accepted natural temperature variations of the last 1100 years, up to 1850.? (the variations appear to be +/- 0.5 deg c.) 2 if not, what is the magnitude of the gap in degrees c? 3 How much in degrees c is current temperature above the historic mean of the last 2000 years (proxy measurements of course)? Thanks for any answers.
71760. KR at 05:17 AM on 24 October 2011
       Clouds provide negative feedback
       RW1 - "What I'm asking is why specifically is it 3.3 W/m^2 per 1 degree of warming? Why not 0.33 W/m^2 or 33 W/m^2 (some other number), for example?" I'm more than a bit appalled by this question. You look at the physics, you run the numbers, and you get a result. The only reason the number would be different is if the physics were somehow different, RW1. But reality is a harsh critic.
71761. IanC at 05:15 AM on 24 October 2011
       Clouds provide negative feedback
       188 RW1 The earth radiates energy as E=epsilon*sigma*T^4, where epsilon is the emissivity (0.61) and sigma is the Stefan-Boltzman constant. If you increase the average earth surface temperature (287K) by one degrees you'll increase E by 3.3 W/m^2
71762. RW1 at 04:57 AM on 24 October 2011
       Clouds provide negative feedback
       Riccardo (RE: 187), What I'm asking is why specifically is it 3.3 W/m^2 per 1 degree of warming? Why not 0.33 W/m^2 or 33 W/m^2 (some other number), for example?
71763. Riccardo at 04:53 AM on 24 October 2011
       Clouds provide negative feedback
       RW1 try here, but let's not go offtopic here and choose a more appropiate place to discuss sensitivity.
71764. RW1 at 04:15 AM on 24 October 2011
       Clouds provide negative feedback
       Riccardo (RE: 185), "the so-called Plank sensitivity or response is derived from the Stefan-Bolzman law." OK, explain to me how it's derived? Why the 'Planck sensitivity' 3.3 W/m^2 per 1 degree of warming?
       Response:

       [DB] "OK, explain to me how it's derived?"

       Try here:

       http://scienceofdoom.com/2010/10/24/planck-stefan-boltzmann-kirchhoff-and-lte/

71765. RW1 at 04:13 AM on 24 October 2011
       Clouds provide negative feedback
       CBDunkerson, Are you aware that the system is almost always in a state of energy imbalance to some degree? Have you noticed that even when the system as whole warms to a significant degree like during an El Nino event, it always seems to revert to its pre-equilibrium state fairly quickly afterward? This is hardly consistent with net positive feedback acting on perturbations. Also, the temperature rising as the Sun comes up each day is not the result of net positive feedback acting on the increased incident energy. You seem to be confusing a causative positive response to an increase in 'forcing' with positive feedback in response to the causative change. They are two different things. No one disputes that increased energy from GHGs or the Sun will cause warming.
71766. Riccardo at 04:13 AM on 24 October 2011
       Clouds provide negative feedback
       RW1 the so-called Plank sensitivity or response is derived from the Stefan-Bolzman law.
71767. CBDunkerson at 03:37 AM on 24 October 2011
       Clouds provide negative feedback
       RW1 wrote: "The global temperature anomaly barely moves by more than a couple tenths of a degree per year..." Which, is a massive amount of heat. You dismiss the idea of positive feedbacks (which BTW are estimated at a 200% increase on the forcings - 300% would be the combined total) because the average annual temperature anomaly is so 'constrained', but that is a completely groundless argument. I could just as easily claim that the massive average annual temperature anomaly shows how large the positive feedbacks must be. In reality, there is no direct connection between the two and thus the argument is meaningless. We know feedbacks are positive because every past and current warming forcing which we can estimate with any degree of accuracy has been enhanced by positive feedback effects. Frankly, it is ridiculous to claim that feedback effects will not be positive given that measurements of forcing and feedbacks from every El Nino, every Summer, and indeed every sunrise prove otherwise. The sun comes up, temperatures rise, dew evaporates, atmospheric humidity increases, that water vapor causes further warming... positive feedback. Happens all the time and not remotely controversial. The idea that this would suddenly just 'stop' happening if the warming comes from increasing atmospheric CO2 levels is without any justification at all.
71768. RW1 at 03:18 AM on 24 October 2011
       Clouds provide negative feedback
       Riccardo, I assume you're talking about the so-called 'Planck' response of about 3.3 W/m^2 per 1 degree of warming?
71769. Riccardo at 03:12 AM on 24 October 2011
       Clouds provide negative feedback
       RW1 given an incoming heat flux, it is the emission of radiation that mainly constrains temperature. Why on earth the Stefan-Boltzman law, the most important negative feedback, is so often forgotten?
71770. WheelsOC at 03:02 AM on 24 October 2011
       The BEST Kind of Skepticism
       "The problems that have been associated with the CRU and NASA data sets" were largely known to be fictional before BEST began, as previous studies had already shown.
71771. RW1 at 02:41 AM on 24 October 2011
       Clouds provide negative feedback
       The climate system's energy balance is extremely dynamic. It's constantly changing spatially and in time - all the time, yet long-term averaged it's very tightly constrained. The global temperature anomaly barely moves by more than a couple tenths of a degree per year despite such variability. This is hardly consistent with net positive feedback on imbalances, let alone net positive feedback of 300%. Water vapor and clouds are also not a homogeneous distribution - they are by far most dynamic component of the entire atmosphere. The notion that the feedbacks of water vapor and clouds are both strong net positive cannot be reconciled with physical process and feedbacks that so tightly constrain planet's energy balance as a whole.
       Response:

       [DB] Fixed text.

71772. muoncounter at 02:15 AM on 24 October 2011
       Should The Earth Be Cooling?
       Dikran#71: "Land use change emissions have indeed being going on for a very long time, and fossil fuel emissions only overtook land use change emissions in the early 60s" Here's a CDIAC graph of emissions from land use change: full scale Here is the current CDIAC graphic of emissions from fossil fuel consumption: full scale The land use graph is scaled in Terra grams C (million metric tons) with values in the hundreds; prior to the post WW2 period, the total is less than 1 Gton. The fossil fuel graph is scaled in million metric tons, with values in the thousands. So it looks like the period of rapid growth immediately following 1945 was the crossover; from then on fossil fuel carbon dominates. Wouldn't it be the case, based on population density alone, that land use changes prior to 1800 are insignificant on these scales?
71773. Daniel Bailey at 01:32 AM on 24 October 2011
       Should The Earth Be Cooling?
       Additionally, I find Fig 4 from the study fascinating: Figure 4. Comparison of atmospheric [CO2], [CH4], δ13CCO2, δ13CCH4, and population data for the Americas: (A) Concentration of atmospheric CO2 (Etheridge et al. 1996; Meure et al. 2006; blue and black symbols) and CH4 (Ferretti et al. 2005; red symbols from Law Dome; (B) δ13C of atmospheric CO2 (Francey et al. 1999; blue symbols) and CH4 (Ferretti et al. 2005; red symbols) from Law Dome; (C) population estimates for the Americas (Rosenblat 1954; Dobyns 1966; Denevan 1992a; Henige 1998) and Neotropics (this study). Gray vertical bars as in Figure 3.
71774. Daniel Bailey at 01:16 AM on 24 October 2011
       Should The Earth Be Cooling?
       Sphaerica It is indeed an interesting paper, tying as it does directly into the work of William Ruddiman (author of Plows, Plagues, and Petroleum: How Humans Took Control of Climate). Note that Ruddiman has a very interesting guest post on Real Climate: http://www.realclimate.org/index.php/archives/2011/04/an-emerging-view-on-early-land-use/
71775. Bob Lacatena at 00:34 AM on 24 October 2011
       Should The Earth Be Cooling?
       I'd like to point out that the original paper cjshaker references is available for free here: The Columbian Encounter and the Little Ice Age: Abrupt Land Use Change, Fire, and Greenhouse Forcing It looks like a very interesting read. I will get to it later today (after I play a little bit of soccer with some other 50 year old men).
71776. Bob Lacatena at 00:26 AM on 24 October 2011
       Should The Earth Be Cooling?
       69, cjshaker, Thank you for the reference to an enlightening article. I did not realize that there was a measurable drop in CO₂ just prior to the Little Ice Age. It would seem that it's possible that CO₂ and anthropogenic actions could have been a factor in that event, which would make it all the more probable that a heavily industrialized and technological society like ours could further impact the climate. I like the tongue-in-cheek way that you attribute the entire episode to one man (Columbus), when of course the article clearly shows that the real problem was the entire European arrival, but more importantly the introduction of diseases which are well known to have ravaged the Native American populations, killing as much as 90% of them and completely exterminating them on some Caribbean islands. That this lead to a huge amount of cleared land being abandoned and reclaimed by forest does not seem incredible in the least. The unexpected result that the new forest growth required carbon to grow those trees, and so over time extracted large amounts of carbon from the atmosphere (the exact same amount of carbon that is recorded as vanishing from the atmosphere at that time) is an unexpected but perfectly logical consequence. All in all, a very, very interesting article, which highlights the usefulness of a number of scientific techniques and leads to what at first appear to be unbelievable, fantastical results (as you were able to demonstrate with your cleverly cute misleading synopsis), and yet these turn out to be perfectly logical conclusions. Of course, one never knows if the result will hold up. I have to do the skeptical thing myself, now, and find and read the paper in detail. News articles about science are rarely trustworthy. But thanks for the find! Definitely worth a look.
71777. Bob Lacatena at 23:50 PM on 23 October 2011
       Clouds provide negative feedback
       177, RW1, Your "intelligent design" approach which requires that the earth's climate system be constructed and constrained like an electrical engineering project imposes any number of requirements (such as the idea that there be a single controller) which are quite simply fabricated. Your "coincidences" are mere observations of known physics. You imply that because they exist, they must be primary factors in the system, but you provide no evidence of such. You imply that because you haven't bothered to list any other mechanisms here, they cannot exist or must be inconsequential. Your position amounts to argument from ignorance. Your argument boils down to "I can only envision things happening this one way, so how can it be anything else?" Your position amounts to recognizing that you cannot touch the sun but it moves through the sky, therefore it must be the flaming wheel of the sky god's chariot. How could it be anything else?
71778. Rob Painting at 21:38 PM on 23 October 2011
       Corals are resilient to bleaching
       cjshaker - note the following from the post: "The critical issue with global warming induced coral bleaching, as it is for many eco-systems, is the speed of warming. They are simply not being given sufficient time to evolve tolerance" As for the Great Barrier Reef (GBR), the worst mass coral bleaching episode was back in 2002/2003. The ocean has steadily gained an enormous amount of heat in that time, and the GBR appears to have been protected by a largely La Nina-dominant pattern - especially since 2005. Sadly this is unlikely to last. I'll have a post on this topic soon.
71779. Dikran Marsupial at 21:33 PM on 23 October 2011
       Ice age predicted in the 70s
       CBDunkerson I have just looked into cjshaker's posting history, and it appears that he asks many questions, but rarely replies to the answers.
71780. CBDunkerson at 21:29 PM on 23 October 2011
       Ice age predicted in the 70s
       cjshaker wrote: "Found a much more recent paper, which is talking about a return to ice age conditions in the near future 'This altithermal period may be similar to the Holocene Maximum that began nearly 3,800 years ago. The solar output model suggests that, approximately 20,000 years after it began, the current interglacial period may come to an end and another glacial period may begin.' 20,000 - 3,800 = 16,200 You consider 16,200 years the "near future"?
71781. Dikran Marsupial at 21:14 PM on 23 October 2011
       Should The Earth Be Cooling?
       cjshaker wrote: "According to Professors Reddiman and Kaplan, our climate should be cooling, if not for mankind's CO2 emissions. They say that our CO2 has been modifying the climate since the beginning of agriculture, well before industrialization" Why should that be a surprise? Land use change emissions have indeed being going on for a very long time, and fossil fuel emissions only overtook land use change emissions in the early 60s IIRC. So if the comparatively small CO2 emissions from land use change before the industrial revolution had an non-insignificant effect on the climate, we should expect the vastly larger anthropogenic emissions (both fossil fuel and land use change) since the industrial revolution to have a much more substantial effect. If you are interested you can get data on fossil fuel and land use emissions from the Carbon Dioxide Information and Analysis Center I note that you have been very active today posting a large number of papers for discussion on a wide range of topics. Some constructive criticism: this gives the impression that you are not really interested in the answers, because very few people would be able to hold a worthwhile discussion on so many topics simultaneously. I would advise in future that you stick to a small number of topics at any one time so that you can have an in-depth discussion that science demands.
71782. Dikran Marsupial at 21:06 PM on 23 October 2011
       Freedom of Information (FOI) requests were ignored
       cjshaker I note that you fail to mention that they were ordered to publish the data by the ICO, even if that did violate the confidentiality agreements that they had with national met offices. So there is no contradiction there, you are making a mountain out of a molehill. I note that you have been very active today posting a large number of papers for discussion on a wide range of topics. Some constructive criticism: this gives the impression that you are not really interested in the answers, because very few people would be able to hold a worthwhile discussion on so many topics simultaneously. I would advise in future that you stick to a small number of topics at any one time so that you can have an in-depth discussion that science demands.
71783. Dikran Marsupial at 20:51 PM on 23 October 2011
       CO2 has been higher in the past
       cjshaker wrote "Where is the CO2 going over geologic time?". On geological time scales, the climate appears to be regulated by the "chemical weathering thermostat", where weathering of rocks sequesters carbon dioxide from that atmosphere as carbonates in the lithosphere. There is a very good primer on the carbon cycle by David Archer that does a good job of explaining the behaviour of the carbon cycle on geological timescales and shorter, well worth reading. I note that you have been very active today posting a large number of papers for discussion on a wide range of topics. Some constructive criticism: this gives the impression that you are not really interested in the answers, because very few people would be able to hold a worthwhile discussion on so many topics simultaneously. I would advise in future that you stick to a small number of topics at any one time so that you can have an in-depth discussion that science demands.
71784. Dikran Marsupial at 20:45 PM on 23 October 2011
       The sun is getting hotter
       cjshaker Yes, that is essentially correct, the sun was about 30% dimmer when the Earth first formed 4.6 billion years ago. This is well known. However that process of stellar evolution is so slow it has no effect on the climate on timescales of thousands of years. The only real relevance of this to the AGW is that it explains how a snowball Earth could ocurr with high levels of atmospheric CO2, but that is a subject for a different thread. Note the climate has been much warmer in the past, even with the dimmer Sun, the most feasible explanation is the higher levels of greenhouse gasses in the atmosphere at the time. This is knwn as the Faint Young Sun Paradox. I note that you have been very active today posting a large number of papers for discussion on a wide range of topics. Some constructive criticism: this gives the impression that you are not really interested in the answers, because very few people would be able to hold a worthwhile discussion on so many topics simultaneously. I would advise in future that you stick to a small number of topics at any one time so that you can have an in-depth discussion that science demands.
71785. cjshaker at 20:08 PM on 23 October 2011
       CO2 has been higher in the past
       Was curious, so I Googled 'geological CO2 history'. Found the graph on the top of page 92 in this paper showing the decline in CO2 over the past 160 million years. Am I correct in assuming that this is showing a decrease in atmospheric CO2 over that time period? Where is the CO2 going over geologic time? http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1692169/pdf/YAKVJWBFM62NRFN4_353_83.pdf Thank you, Chris Shaker
71786. chris at 19:58 PM on 23 October 2011
       Clouds provide negative feedback
       That's a rather medieval style of argumentation RW1 - leading questions and anthropomorphism! So no, the climate isn't "trying" to do anything. It responds to forcings according to the laws of physics. Likewise the answer to your repeated "is it just coincidence?" is, in each case, "no, it's physics". RW1, the "controller" is very well understood. It's temperature. The water vapour content of the atmosphere rises as the atmospheric temperature rises. That is very well understood physics, and has been measured repeatedly in the real world. No leading questions about "coincidences" required! Your "mechanism" lacks both physics and evidence. One really needs to consider the response of the atmosphere in terms of humidity. I'm sure you agree that the absolute humidity of the atmosphere has risen as a result of greenhoue-induced warming. That's uncontestable - we can measure this. How about "relative humidity"? There is some evidence that the water vapour content of the atmosphere might maintain approximately constant relative humidity in a warming world. In such a situation there's no reason to expect the levels of clouds to increase since the atmosphere can maintain increased water vapour without enhanced condensation into clouds. If the water vapour content of the atmosphere rises (i.e. the observed increase in absolute humidity) at a level that is somewhat lower than required to maintain constant relative humidity, then the formation of clouds is more likely to be suppressed. That's consistent with the so far rather limited real world evidence. There's zero real world evidence that clouds increase in a warming world. On the contrary, the limited evidence supports a small positive cloud feedback in a warming world (see the top article of this thread).
71787. cjshaker at 19:54 PM on 23 October 2011
       Ice age predicted in the 70s
       In Regards to the Response to item #42, the following articles may be of interest: Controversial New Climate Change Data: Is Earth's Capacity to Absorb CO2 Much Greater Than Expected? http://www.sciencedaily.com/releases/2009/11/091110141842.htm Mathematical Errors Overestimate Persistence of CO2 in Atmosphere http://www.suite101.com/news/royal-society-humiliated-by-global-warming-basic-math-error-a296746 Chris Shaker
       Moderator Response: [Dikran Marsupial] Neither of these articles is of relevance to a discussion of predictions of an impending ice age made in th 70s. Please familiarise yourself with the comments policy, off-topic posts are normally deleted in order to keep the discussion focussed. I'll happily discuss the first article with you on a more appropriate thread. Note that the second article does not appear to be supported by any peer-reviewed science, unlike the statement by the Royal Society, which suggests some skepticism is in order.
71788. cjshaker at 19:51 PM on 23 October 2011
       Freedom of Information (FOI) requests were ignored
       The Climate Research Unit finally released some of the climate data which had been requested under FOI. They claimed that they could not release the data under the FOI, because the countries supplying the data would not allow it, yet they did release most of the data WITHOUT getting that permission, except for the data from Poland? http://blogs.nature.com/news/2011/07/at_long_last_cru_releases_clim.html Found the comments interesting Chris Shaker
71789. cjshaker at 19:48 PM on 23 October 2011
       Ice age predicted in the 70s
       Found a much more recent paper, which is talking about a return to ice age conditions in the near future From the summary, published in 2000: "The solar-output model allows speculation on global climatic variations in the next 10,000 years. Extrapolation of the solar-output model shows a return to little-ice-age conditions by A.D. 2400–2900 followed by a rapid return to altithermal conditions during the middle of the third millennium A.D. This altithermal period may be similar to the Holocene Maximum that began nearly 3,800 years ago. The solar output model suggests that, approximately 20,000 years after it began, the current interglacial period may come to an end and another glacial period may begin." http://www.pnas.org/content/97/23/12433.full Chris Shaker
71790. Riccardo at 19:47 PM on 23 October 2011
       Climate sensitivity is low
       cjshaker I'm a bit surprised to see this old and debunked Shaviv paper pop up again. Honestly, I do not find it that much interesting.
71791. cjshaker at 19:42 PM on 23 October 2011
       The sun is getting hotter
       A believer in CO2 was telling me that the sun's output is now 30% higher than it was when life evolved on the earth. Is that true? Thank you, Chris Shaker
71792. Riccardo at 19:40 PM on 23 October 2011
       Should The Earth Be Cooling?
       cjshaker there are still a lot of things to work out before the so called early human impact can be reliably assessed. It is still at the stage of hypothesis, will see. As for Columbus, let me be pedantic. In the link you provide they say "may have helped augment Europe’s so-called Little Ice Age" and not "was responsible for the cooling" as you say.
71793. cjshaker at 19:20 PM on 23 October 2011
       Corals are resilient to bleaching
       J.E.N. Veron, formerly at the Australian Institute of Marine Science, says that the world's reefs face possible catastrophic losses again, due to acidification. He claims that some of the previous coral extinction events were most likely caused by ocean acidification. He also says "Corals have an intimate symbiotic relationship with single-celled algae, zooxanthellae, which live in their cells and provide the photosynthetic fuel for them to grow and reefs to form. The research showed that this Ecosystems can recover from all sorts of abuse, and coral reefs are no exception. relationship can be surprisingly fragile if corals are exposed to high light conditions at the same time as above-normal water temperatures, because the algae produce toxic levels of oxygen, and excessive levels of oxygen are toxic to most animal life. Under these conditions, corals must expel the zooxanthellae, bleach, and probably die or succumb to the toxin and definitely die. A tough choice, one they have not had to make at any time in their long genetic history." I'm not sure I should believe the last sentence, given that the climate reached a few (several?) degrees C warmer than today during the previous interglacial... Chris Shaker
71794. cjshaker at 19:13 PM on 23 October 2011
       Corals are resilient to bleaching
       It appears that J.E.N. Veron's former colleagues at the Australian Institute of Marine Science are saying that the Great Barrier Reef is not doing so badly "Crown-of-thorns starfish (Acanthaster planci) outbreaks and storm damage were responsible for more coral loss during this period than either bleaching or disease despite two mass bleaching events and an increase in the incidence of coral disease. While the limited data for the GBR prior to the 1980's suggests that coral cover was higher than in our survey, we found no evidence of consistent, system-wide decline in coral cover since 1995. Instead, fluctuations in coral cover at subregional scales (10–100 km), driven mostly by changes in fast-growing Acroporidae, occurred as a result of localized disturbance events and subsequent recovery." http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0017516 Chris Shaker
71795. cjshaker at 19:09 PM on 23 October 2011
       Should The Earth Be Cooling?
       According to Professors Reddiman and Kaplan, our climate should be cooling, if not for mankind's CO2 emissions. They say that our CO2 has been modifying the climate since the beginning of agriculture, well before industrialization http://www.nature.com/news/2011/110325/full/news.2011.184.html They also believe that Columbus was responsible for the cooling during the Little Ice Age http://www.sciencenews.org/view/generic/id/335168/title/Columbus_blamed_for_Little_Ice_Age Chris Shaker
71796. cjshaker at 18:39 PM on 23 October 2011
       Climate sensitivity is low
       You may be interested in Professor Shaviv's writings about climate sensitivity. He explains why he comes up with a lower number http://sciencebits.com/OnClimateSensitivity From: http://sciencebits.com/about "Prof. Nir J. Shaviv, who is a member of the Racah Institute of Physics in the Hebrew University of Jerusalem. According to PhysicaPlus: "...his research interests cover a wide range of topics in astrophysics, most are related to the application of fluid dynamics, radiation transfer or high energy physics to a wide range of objects - from stars and compact objects to galaxies and the early universe. His studies on the possible relationships between cosmic rays intensity and the Earth's climate, and the Milky Way's Spiral Arms and Ice Age Epochs on Earth were widely echoed in the scientific literature, as well as in the general press." Chris Shaker
71797. gpwayne at 17:10 PM on 23 October 2011
       The BEST Kind of Skepticism
       I didn't realise that Judith Curry was a co-author. She writes pretty sensibly about the experience, publication and the results in her blog, concluding: "Although the results of the analysis aren’t particularly surprising relative to previous analyses, I think the BEST project is very important given the importance of the surface temperature data set and the problems that have been associated with the CRU and NASA data sets, not to mention their disagreement. The BEST group is comprised of some extremely distinguished scientists (including Nobel Prize awardee Saul Perlmutter), and this topic has benefitted greatly from the examination of this problem by physicists and statisticians who were prepared to take a fresh look at this problem. I am honored to have been invited to participate in this study, which I think was conducted very well". Berkeley Surface Temperatures: Released
71798. chriskoz at 16:06 PM on 23 October 2011
       Test your climate knowledge in free online course
       SLR is a long term process lasting several centuries up to a millenium until equilibrium is reached with respect to melting of Greenland & Antarctica, as we discussed here. What rise we see now in XXI century may actually be just 30cm, so they may be correct. However, from the paleo history (e.g. PETM) we can find out that for a given amount of CO2, equilibrium SLR rise should be higher. We just don't know how much we've committed already and where the tipping point is. Even if wee're past TP, I am still optimistic: 100y is a lot of time and poeple may learn how to "cool-down" the globe before the land ice starts collapsing in XXII century or so.
71799. RW1 at 15:35 PM on 23 October 2011
       Clouds provide negative feedback
       lancelot, So while RW1 has not proposed a mechanism," The mechanism is the whole of the atmospheric water cycle (ground state water -> evaporation -> water vapor -> clouds -> precipitation -> ground state water), which is the primary way the planet's energy balance and ultimately the globally averaged surface temperature is maintained despite such a large degree of local, regional, seasonal hemispheric and even sometimes globally averaged variability. In general, mechanistically, when clouds are increasing the climate is too warm and trying to cool (more or denser clouds are exposed to space, reflecting more of the Sun's energy) and when clouds are decreasing the climate is too cool and trying to warm (fewer clouds lets in more of the Sun's energy). If water vapor is the primary amplifier of warming, as claimed, what then is the controller? If not clouds via there ability to reflect incoming solar energy and precipitate out the water from the atmosphere, then what? Does anyone think it's just a coincidence that energy from the Sun drives evaporation of water? Is it just coincidence that evaporated water removes heat from the surface, condenses to form clouds and the clouds reflect the sun’s energy? Is it just a coincidence that the water precipitated out of the atmosphere emanates from clouds?
71800. muoncounter at 12:04 PM on 23 October 2011
       Human CO2 is a tiny % of CO2 emissions
       Sphaerica#212: "If you have some sort of sink that takes most of the anthro CO2" Problem solved. A new natural sink is emerging before our very eyes. A place where the low salinity surface waters ... are undersaturated with respect to CO2 in the atmosphere and the region has the potential to take up atmospheric CO2, although presently suppressed. This marvelous new sink for CO2 has tripled over the last 3 decades. Just what the doctor ordered!

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