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scaddenp at 14:49 PM on 5 August 2010Confidence in climate forecasts
BP - I'll bite on entropy. I would say GHG increase should increase entropy - the earth has become more efficient at converting high entropy photons to low entropy photons. I am not sure what point you are aiming at. By the way, as "heat engine", what is the Work that the working fluid is doing? -
RSVP at 14:40 PM on 5 August 2010Three new studies illustrate significant risks and complications with geoengineering climate
doug_bostrom #14 Interesting article. In commenting about these "options", it includes the following... "launching mirrors into space to deflect the sun’s energy away from Earth — could have far more unpredictable and potentially destabilizing effects." Funny how the opposite, the proliferation of "black asphalt highways" arent considered "destabilizing". Just think how much white paint would be needed to neutralize the extra heat coming off our roads. -
RSVP at 14:21 PM on 5 August 2010Waste heat vs greenhouse warming
180, 181 Strange. Given the model as described in 180 and 181, it would seem the more GHG, the greater the pathway for IR. Such that the more GHG, the more cooling. However, it doesnt work like that, at least as described here: http://en.wikipedia.org/wiki/Greenhouse_effect Wikipedia "The greenhouse effect is a process by which radiative energy leaving a planetary surface is absorbed by some atmospheric gases, called greenhouse gases. " -
Doug Bostrom at 14:05 PM on 5 August 2010Three new studies illustrate significant risks and complications with geoengineering climate
I'm trying to think of a way to get C02 out of air with a reasonably small energy input and nothing's coming to mind. There are some hills to ascend even if scrubbers are very efficient. More on atmospheric scrubbing tech here: Pulling CO2 from the Air: Promising Idea, Big Price Tag Also some helpful background at RealClimate which mentions off-grid thermal air capture, something promising-sounding. It's all probably worth another post!Response: Someone tweeted me this new solar powered carbon scrubbing technology which makes some pretty big calls re it's potential. Still, interesting technology... -
Bern at 14:04 PM on 5 August 2010Three new studies illustrate significant risks and complications with geoengineering climate
angliss: your comment prompted a quick google search, and I came up with this article, which (along with the referenced comment) suggests that CO2 removal will cost 933kWh per ton of CO2 extracted with that method. There may be others, but that's a whole lotta energy (granted, the bulk is thermal energy that may be provided readily by solar concentrator systems). -
Daniel Bailey at 14:02 PM on 5 August 2010Communicating climate science in plain English
Great discussion. Observations:1. Tabs seem to make more sense than a slider 2. One comment section linked to the 3 tabs, if doable, would minimize confusion while accentuating the discussion. Not everyone on each of the 3 levels of understanding will have a question needing answering. One comment thread should do. 3. There will still be a need for an in-depth as possible level, even for those who have a deeper level of knowledge and understanding than most. How many times is it in these discussions that the ones who have the background and training to know better are the ones most confirmed in their "skepticism"? Plus, some have a near-terminal case of D-K Syndrome. 4. No matter how foolproof and complete you make this site (love all the hyperlinked sections), you can't make it damnfoolproof, as those types are so ingenious. Plus, the intractable ones never RTFM anyway.
The Yooper -
angliss at 13:42 PM on 5 August 2010Three new studies illustrate significant risks and complications with geoengineering climate
John Chapman - The SO2 is readily available from the exhaust of coal power plans. doug bostrom - Scientific American had an article on a free-atmosphere CO2 removal system that's being developed that is the size of a shipping container. IIRC, initial testing indicates that it's reasonably energy efficient, but I don't recall the details. Tony O - I'm all for these studies, as well as limited real world experiments, as they prove concepts and help discover those "unintended and unexpected consequences." For example, there was a test of iron fertilizing in the Southern Ocean which discovered that the unintended consequence of an algal bloom was a population spike in algae-eating shrimp that ate the algae before it could die and sink to the bottom. I'd love to read the report on the tests to see if they think the test still sequestered any carbon. -
mothincarnate at 13:36 PM on 5 August 2010Three new studies illustrate significant risks and complications with geoengineering climate
Great post. A lot of talk like this reminds me of the RAMA series by Clark and Lee, where there was a human population had an enclosure which had an alien super-computer running the weather algorithms. They were told not to use wood fires (they didn't really need them, as the weather was quite pleasant anyway) but decided to cut the trees down anyway and even when a big screen in the sky lit up to tell them to stop, they didn't. In the end they broke out, hacked into the super-computer (and could barely control the weather still) and took over another enclosure. It seems Clark had picked the current events as well.. I liked how you summed it up, it's a bit like a line from the Simpsons, "Dig UP stupid!" -
sailrick at 13:30 PM on 5 August 2010Visually depicting the disconnect between climate scientists, media and the public
John Chapman @32 The figure I've seen is 12,944,000 scientists in the U.S., if you use the same criteria to define scientist as they use to get 32,000 skeptics. The 32,000 skeptics amount to 0.24 percent of the total. Maybe 150 are actually climate scientists. which is 0.3% of the 50,000 members of the AGU in Europe and the U.S., "Scrutinizing the 31,000 scientists in the OISM Petition Project" http://www.skepticalscience.com/scrutinising-31000-scientists-in-the-OISM-Petition-Project.html -
Doug Bostrom at 13:12 PM on 5 August 2010Three new studies illustrate significant risks and complications with geoengineering climate
I forgot to say "thank you" for a very helpful article. -
Doug Bostrom at 13:08 PM on 5 August 2010Three new studies illustrate significant risks and complications with geoengineering climate
Another interesting thing about all of these schemes is the impact they'll have on energy requirements. It's darkly amusing to note, the same ideas that would allow us to continue using coal would also require burning yet more of the stuff. "Laughing all the way to the bank" is the phrase that comes to mind. -
Doug Bostrom at 12:56 PM on 5 August 2010Three new studies illustrate significant risks and complications with geoengineering climate
Worth highlighting the need to continue pumping S02 into the air for centuries. If a science fiction author wrote a story about a civilization that had doomed itself to pumping S02 into its planetary atmosphere for hundreds of years, we might say, "That's not plausible; if they could do that, they wouldn't have gotten themselves into such a jam in the first place." Truth is stranger than fiction? -
chris1204 at 12:46 PM on 5 August 2010Three new studies illustrate significant risks and complications with geoengineering climate
There's a whole parallel debate about deep sea carbon sequestration including sequestration in deep ocean sediments which might be worth a post one day. -
chris1204 at 12:34 PM on 5 August 2010Communicating climate science in plain English
I've heard it said that you don't really understand your subject if you can't give a broad explanation to an intelligent twelve year old (I think I've been in a steady cognitive decline from age 12 onwards!!!!). I think the greatest strength of this site is its engagement of folks variously placed on the 'alarmist-warmist-sceptical-denialist' spectrum in respectful dialogue. Keeping the language simple and accessible is in fact a major intellectual challenge not to be underrated. -
macoles at 12:13 PM on 5 August 2010Communicating climate science in plain English
Hi John, You might want to reassess the "need" for an advanced highly technical section. People who are interested in the "in depth" stuff should be following the links to the peer reviewed papers themselves (rather than just taking our word for it). I suspect the "need" for higher detail is more of a "want" belonging to the author and a small group of regular commentators. There is however a definate need for easy and medium levels of explanation, as this site is an excellent gateway for regular people to understand climate science. -
Doug Bostrom at 11:45 AM on 5 August 2010Grappling With Change: London and the River Thames
I'm not assessing the reasons for closure of the barriers, HR, I found the latest source I could and reported that. Experts (which group does not include either of us) take the closure trend to be consistent with climate change projections and something to be taken into consideration when looking for confirmatory evidence. Research tells us it's very important for some of us to find paralytic uncertainty and thus some kind of psychological comfort in any and all sources of information on the matter of climate change. If you have to construct a world of doubt to feel happy, that's your personal choice and of course I cannot and will not stop you. If truncating the record and producing a graph makes you feel better that's also a matter of personal choice. Publicly reporting that result and disagreeing with people who are notably more informed on this topic than either of us is sort of like assertively evangelizing your religion to people who are not interested in conversion, arguably rude. Your need for doubt should remain largely a private matter. As to the strawman of "a justification for doubling based on the past 2 decsdes," that figurine exists in your own mind. Cherish it if you must. -
michael wood at 11:45 AM on 5 August 2010Why I care about climate change
John, I'm grateful for your honesty and transparency in making clear some of your underlying motivations. As a Christian and Anglican priest, I resonate deeply with your reflections. As a parent of two teenagers, your comments as a parent also resonate deeply - in fact it was the '50 year' question posed by Al Gore, which really provoked my passion for action on Climate Change. Whilst your site rightfully continues to be 'science based' and that is it's powerful contribution to the world, it adds a lovely humanity to hear some of the 'story' behind it. Science and Theology need not, in fact, should not be in conflict. -
adelady at 11:34 AM on 5 August 2010Three new studies illustrate significant risks and complications with geoengineering climate
Ocean acidification, yes. That was my first reaction too. It wouldn't much matter if the temperatures were livable if the food supply is crashing around us. (I'm ignoring the intrinsic value of maintaining a rich biosphere here.) -
Three new studies illustrate significant risks and complications with geoengineering climate
Wouldn't pumping SO2, while not reducing CO2, continue ocean acidification? -
adelady at 11:20 AM on 5 August 2010Three new studies illustrate significant risks and complications with geoengineering climate
I'm not all that enamoured of the bright blinding white roof, but what's wrong with the softer creams and greys? Who decided that black and chocolate brown are a good look on a roof! - they're a neat accent on doors and window frames, but more is just plain depressing. I think a lot of people have yet to learn the "less is more" principle in exterior decoration. -
scaddenp at 11:17 AM on 5 August 2010Confidence in climate forecasts
"After IPCC reviewer Dr. Vincent Gray pointed out that no model had ever been validated and could not predict global climates the title of the relevant WG1 chapter was renamed “Model evaluation” and the word “predict” was replaced with “project”. Just in case people think "ipcc reviewer" is stamp of authority, note that you can become a reviewer by requesting the draft and signing an NDA. Gray's contribution to the review process can be followed by searching for "Gray" at ipcc collection. He claimed (8-76) "There is no evidence for this statement. No model has ever been tested successfully against its future prediction." The editors responded in rejecting the review. "Disagree Decades ago, climate models predicted warming in the late 20th century, strongest near the poles, and this has been observed. As a second example, a climate model predicted the cooling due the Pinatubo before it occurred." If Hansen 2006 paper isnt a validation of the 1988 model against the actual data, then what is? JohnD - GCMs do not "weight inputs" - they are not statistical models. They calculate the response to input from the physics. Different kind of model completely. If you want a statistical model with physical basis, then better to try and predict temp from forcings of solar, aerosol, GHG. For an example, try Benestad and Schmidt -
John Chapman at 11:15 AM on 5 August 2010Communicating climate science in plain English
brief / more info / detail ? -
John Chapman at 11:08 AM on 5 August 2010Three new studies illustrate significant risks and complications with geoengineering climate
Where would one find giga tonnes p.a. of sulphur dioxide to pump into the atmosphere anyway? -
Tony O at 10:56 AM on 5 August 2010Three new studies illustrate significant risks and complications with geoengineering climate
There will come a time to panic. We should study geoengineering now so when that time comes we might avoid the worst side effects of whatever geoengineering systems we use. Maybe a little bit of this and a little bit of that will not be as bad as a lot of one. The climates where you live and I live are hot, white roofs make so much sense. If all new houses in Australia had a white roof that alone would make a significant difference. Yet I am told again and again that black looks good. We are getting so close to brownouts how cool will the black be with no air conditioning when it is century plus in the water bottle. What hope is there when we will not even use the no cost options? -
MattJ at 10:50 AM on 5 August 2010Three new studies illustrate significant risks and complications with geoengineering climate
The first and 2nd study have conclusions that should surprise no one. The idea of geoengineering by dumping huge amounts of SO2 into the air has always been a bad one. This should have been obvious. It is the third study that interests me most. For it shows that even the best case scenario of geoengineering is nowhere near as good as emission reduction. That, of course, is the conclusion we need to get people to realize must be accepted: we must reduce emissions ASAP, we really should have done it two or more decades ago. There can be no excuse for continuing at current levels, far less for increasing it more. Yet we still have lemmings bent on pushing us all over the cliff by digging up fossil fuels even more furiously, fighting over oil reserves around the North Pole! -
HumanityRules at 10:47 AM on 5 August 2010Grappling With Change: London and the River Thames
Doug I'm still curious why you think the Thames Barrier closures have doubled in a decade (30 in 1990's, 74 in 2000's)? Doubled is a lot! From what I have read there was an increase in storms from 1950-1990 followed by a decrease in recent decades, i.e. the years covered by this graph.Which maybe fits well with the link between NAO and UK storminess. Closing the barrier is based on a complex model with multiple data sourses. How this model has changed over the years is unclear but it certainly has changed. A curious aspect of the decision to close the barriers comes after the model spits out its result. There is ultimately a subjective call made by the barrier controller, she/he makes a final decision about whether to close in cases of marginal forecasts. Which suggests a model cutoff for closure isn't quite a cut off. There is a list of closure events which include data for each event. I graphed the High Water Level and surge numbers. Both have a downward trend. When it comes to tidal events it seems that the decision to close is being made for less and less severe events rather than severe events becoming more common. This seems to make sense in our more risk averse, precautionary principle kind of world. It looks difficult to believe that the Thames barrier is being closed more often because of real climate events. It looks more likely that the methods used to make the decision and/or the more risk averse world we live in leads to more closures. I'd like to read a justification for doubling based on climate change over the past 2 decades. -
chris1204 at 10:46 AM on 5 August 2010Confidence in climate forecasts
Dappled water: You say: Continuing with your analogy - the models demonstrate a 90% probability of the aircraft crashing, but because of the remaining uncertainty you want to board the plane and fly anyway. With respect, you missed the point. I have no overwhelming desire to get onthe plane. I'd just like to make sure the models are right. -
adelady at 10:45 AM on 5 August 2010Why I care about climate change
If you're thinking about values and you've got a science bias, try Sam Harris. Michael Tobis has put up a link to his talk on the 'scientific basis for values'. Really interesting stuff - I watched the whole 23 mins. Apparently his anti-religious stuff would *not* be recommended for John or other christians. I might track some down. I find Hitchens intolerably superior and creepy or something unappealing, and Dawkins is just plain irritating. This bloke could be better. -
robert way at 10:02 AM on 5 August 2010Communicating climate science in plain English
I do kinda like the in brief/in full ...etc... -
Doug Bostrom at 09:43 AM on 5 August 2010Why I care about climate change
Those social values come from Christianity. As long as you are truly motivated by them, like it or not, you are a crypto-Christian Or an animal. In nature we see a continuum from what appears to be mindless cooperation all the way to something resembling what we call altruism. We're coming out of a period of hypnosis practiced on us by economists, awakening from some strange conceits about human exceptionalism. It's a bit premature (or possibly too late) to ascribe all acts of charity to hidden proclivities toward religion. -
Doug Bostrom at 09:34 AM on 5 August 2010Confidence in climate forecasts
Model/world comparisons tend to focus on temperature. Here are a couple of items that have me wondering about depending on model limitations to "disprove" climate change. Observations are clearly at variance with model projections of some key climate indicators, in ways that seem consistent, not indicating all's well.
From OSS Foundation
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thingadonta at 09:32 AM on 5 August 2010Why I care about climate change
#91 Berenyi "Those social values come from Christianity. As long as you are truly motivated by them, like it or not, you are a crypto-Christian". This is an interesting question. I have often wondered where ethics actually, and ultimately, comes from. The universe seems to be completely neutral/capricious. I know the Western tradition is Christian, but you get much the same values in non-Western nations/culutures, so your view can't be entirely correct. Derived values to solve common problems is likely, however any look into human history and one can see that these values are easily and often suspended. So neither nature, nor tradition, doesnt seem to exert much of a leash, either way. As an aside, I like your comments on the 1956 Hungarian revolution. My mother and her family fled the coming Soviets on the gold train in 1945 from Budapest, apparently the day before the russians blew up the train station. A visit in the 1970s where barely anyone had anything for breakfast is consistent with farming methods there under Soviet rule. -
Doug Bostrom at 09:05 AM on 5 August 2010Confidence in climate forecasts
JohnD one of the latest and greatest GCMs is documented here: GISS GCM ModelE. More specific to your question parameters are described here.
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johnd at 08:47 AM on 5 August 2010Confidence in climate forecasts
Anyone who wants to construct a model using the following inputs, weighted as indicated, Solar Magnetic Lagged AA Index 45%, AMO Ocean Index 29%, PDO Ocean Index 21% and CO2 5% will come up with a model that provides excellent correlation with the Global Mean Temperature over the past century. The method of finding the correct weighting each input has to be by applying a factor that results in the best fit between the input index values and the existing temperature data. That does not explain whether or not such weighting is correct based on real world interactions. In order for any projections to be made from such a model then requires assumptions to be made about the each of the inputs going forward. This method is described in an article "FORECAST MEAN GLOBAL TEMPERATURE TRENDS FROM 2009 TO 2050", by Ian Holton found on the http://www.holtonweather.com site. How does GCM models differ in the weighting the various inputs, and making assumptions about the values of such inputs in order to project future model outputs? -
kdkd at 08:40 AM on 5 August 2010Confidence in climate forecasts
BP #31 I see you're still making your best effort to ignore the core of the point that I made in my previous post. Sure, you can take the solipsistic approach and a priori decry the validity of models, but that does not make any meaningful contribution to the validity of your argument. Additionally I note that you need to ignore the independent and convergent lines of evidence to maintain the pretense of the validity of your arguments. -
John Russell at 08:36 AM on 5 August 2010Communicating climate science in plain English
Excellent idea, John. Putting on my advertising copy-writer hat, I'll go for 'in brief / in full / in depth' as short labels for the three tabs. The problem with 'easy' is that it makes the reader feel rather inadequate. I prefer 'in full' for medium as it suggests that this is a comprehensive answer, while 'in-depth' suggests no stone is left unturned. I'll do my best to come up with some easy versions of some of the rebuttals for consideration. I'll leave the in depth explanations to others! -
Berényi Péter at 08:23 AM on 5 August 2010Confidence in climate forecasts
#29 kdkd at 07:28 AM on 5 August, 2010 I think that you mean inferred (via a model), not presumed. "Presumed" is Trenberth's expression, not mine. Anyway, the 0.9 ± 0.5 W m-2 imbalance is not measured, therefore one does not try to convince laymen it is. Inference (via a computational climate model) is very far from actual measurement. The more so, because contrary to mainstream claims, even the basic physics of General Circulation Models is highly dubious (not to mention parametrization of sub-grid processes like storms and cloud formation). The climate system is clearly a heat engine with water as a working fluid. Now, no heat engine can be understood while entropy production and fluxes are obscure. Still, according to this pretty recent review article, misunderstandings abound in climate literature around a question that was settled a hundred years ago (yes, radiation pressure gives a plus 33.3% increment to radiation entropy flux). REVIEWS OF GEOPHYSICS, VOL. 48, RG2003, 27 PP., 2010 doi:10.1029/2008RG000275 Radiation entropy flux and entropy production of the Earth system Wei Wu and Yangang Liu Received 15 August 2008; revised 31 July 2009; accepted 29 October 2009; published 14 May 2010. My question is still pending. Is CO2 supposed to increase or decrease entropy production in the Earth system? What does the model ensemble say? -
chris at 07:38 AM on 5 August 2010Confidence in climate forecasts
Dan Olner at 17:42 PM on 4 August, 2010 Daisyworld and feedbacks. That’s an interesting point Dan. I would say that Daisyworld is generally a poor analogy for the Earth system and its biosphere, largely because the evidence supports the conclusion that there are no major negative feedbacks of the sort that would maintain a sort of "homeostasis"; on the contrary most feedbacks (at least on the months to 1000’s of years timescale) seem to be positive. (That's not to say that life hasn't had an astonishing influence on the progression of the physical history of the Earth!). Here’s my take; I’m curious what others may think: (i) The sun is the source of energy for the climate system. It is astonishingly constant in its output on the millennial to million years timescale (the solar constant increases by around 10% per billion years). When the solar output does change a bit, so the climate system responds. (ii) The second factor that dominates the energy in the climate system (I’ll use “temperature” for short) is the greenhouse effect. (iii) The third and fourth factors are the distribution of continents (significantly the polar land masses which affects the energy in the climate system through ice albedo), and the earth’s orbital properties which especially modulates the albedo when there is polar ice. I would say that’s pretty much it (one can include land albedo effects and other minor contributions, and we shouldn't forget contingent events like massive tectonic eruptions and extraterrestrial impacts..). How about Daisyworld-like self-regulating stabilizing feedbacks? Earth history tends to support the conclusion that these sadly don’t exist: (i) Ice age cycles. In a world with major polar ice and interglacial greenhouse gas concentrations below 400-500 ppm (?), seemingly rather minor changes in earth orbital properties result in dramatic transitions between climate states differing by 5-6 oC of global temperature. There aren’t self-regulating negative feedbacks that act to stabilise earth temperature; the feedbacks (change in albedo resulting in warming amplified by CO2 and water vapour feedbacks) are positive. (ii) Deep Earth history. During the mid-late Carboniferous a combination of migration of Gondwana to low latitudes and the massive depletion of atmospheric CO2 by non-oxidative biomass burial resulted in widespread glaciations; episodes of “snowball” or “slushball” earth resulting from albedo and greenhouse gas positive feedbacks; large episodic increases in earth temperature via massive tectonic events that released huge amounts of greenhouse gases….in none of these cases is there evidence of homeostatic self-regulation of the climate system. There is one Daisyworld-like self-regulating feedback but this acts only on the multi-millenial timescale. That’s weathering (the hotter it is the more efficient the draw-down of atmospheric CO2, and vice versa). However the latter is ineffective in limiting the effects of positive feedbacks that amplify both cooling and warming forcings on the timescales of 10’s to 1000’s of years. It would be nice to think that there might be a cloud feedback that would act to counter changes in temperature; however the evidence doesn’t support such a feedback. Something that might be considered a “restraint” on surface temperature variation is the huge thermal inertia of the oceans. This tends to dampen the response to changes in forcings and so smooths out cyclic changes in forcings (e.g. solar cycle) and stochastic variations in solar outputs, volcanic eruptions and so on. Returning to models and model success, the fact that the energy in the climate system under a particular state of continental distribution and Earth orbital status is largely defined by the solar output (pretty predictable) and the greenhouse effect (reasonably well bounded given a particular emission scenario) means that the basic energy balance (assessed as surface temperature and its temporal response to enhanced greenhouse forcing) can be modelled pretty well. That’s not to say there aren’t significant uncertainties as indicated by the rather wide range of climate sensitivities of various levels of likelihood, and uncertainties in aerosol and cloud contributions... -
kdkd at 07:28 AM on 5 August 2010Confidence in climate forecasts
BP #22 "TOA radiative imbalance is not measured, it is presumed." I think that you mean inferred (via a model), not presumed. Discounting convergent evidence is part of the slippery slope to solipsism, a philosophical stance whose main use is to unpick a set of propositions via reducto ad absurdam. It's no way to conduct a scientific enterprise. -
kdkd at 07:24 AM on 5 August 2010Has Global Warming Stopped?
Dikran #58 "assuming the null and alternative hypotheses are complementary" I'm pretty sure that the alternative hypothesis is the logical oposite of the null by definition (i.e. H1 = not(H0) ) -
kdkd at 07:21 AM on 5 August 2010Why I care about climate change
Cornelius #96 Basically we have the choice of two divided (on climate policy) parties, both in thrall to a rather toxic energy lobby, with the right wing party slightly more delusional than the left wing one. Then there's the biggest minor party, the Greens, who are the only sane voice in climate change policy, and look to get the balance of power in the upper house in the middle of next year. We also have fairly powerful state legislatures, but they're largely in thrall to the coal lobby at the moment, although interesting noises are coming out of Victoria. But in many ways we're lagging behind the USA on a lot of climate action right now. -
chris at 07:07 AM on 5 August 2010Confidence in climate forecasts
sheesh..."converge" should say "diverge" in the second paragraph... -
chris at 06:52 AM on 5 August 2010Confidence in climate forecasts
Dappledwater at 05:26 AM on 5 August, 2010 angusmac at 02:43 AM on 5 August, 2010 We need to be a little bit careful here. Remember that Hansen’s model was constructed and parameterized almost 30 years ago. The computational run under discussion used a 100 year control equilibration with no forcings, and simulated the earth global temperature from 1958 to 2020 according to a number of scenarios [*]. Dappledwaters picture (Figure 2 from Hansen et al. 2006) shows that the simulation has done a good job of simulating the actual earth surface temperature through around 2005. Angusmac’s figure updates the data through 2009. The simulation and measured surface temperature data now converge a bit. What do we make of this? I’d say the following are relevant: (i) There’s no question that Hansen’s simulation B has tracked the real world temperature from 1958 through 2005 pretty well. Scenario B is a little above the real world observations. However as Hansen et al. 1988 state [**] their model is parameterized according to a climate sensitivity of 4.2 oC (equilibrium surface warming per doubling of [CO2]). Since the mid-range best climate sensitivity estimate is 3.0 oC, we’re not surprised if the model is a little “over warm”. (ii) Since 2005, the global temperatures haven’t risen much whereas the model has increased. So there is a divergence as indicated in angusmacs picture. However if a model of Earth temperature matches reality quite well up to 2005, the fact that it diverges somewhat during the subsequent 4 years isn’t a reason to consider the model a poor one. As Alden Griffiths discusses elsewhere on this site, short term events can easily result in temporary shifts of observables from long term trends. There’s no expectation that the Hansen model should accurately track reality since stochastic variability is differently represented in reality and in the models. (iii) Is there anything we might say about the period 2005-2009? Yes, it’s a period that has seen the sun drop to an anomalous extended solar minimum, and that has had a largish cooling La Nina that greatly suppressed temperatures in 2008. So we’re not surprised that temperatures haven’t risen since 2005. (iv) Is there anything significant about the fact that scenario B and C are rather similar right now? Not really. Scenario B is a scenario that roughly matches the extant emissions and (serendipitiously) includes a significant volcanic eruption in the 1990s (1995 in the model; 1991 Pinatubo in reality). In scenario C greenhouse emissions were “switched off” after 2000. However since the Earth surface continues to warm under a (non-supplemented) forcing for some time due to inertial elements (the oceans) of the climate system, we don’t expect scenarios B and C to differ to much for a while following 2000. [*] from Hansen et al. (2006)“Scenario A was described as ‘‘on the high side of reality,’’ because it assumed rapid exponential growth of GHGs and it included no large volcanic eruptions during the next half century. Scenario C was described as ‘‘a more drastic curtailment of emissions than has generally been imagined,’' specifically GHGs were assumed to stop increasing after 2000. Intermediate scenario B was described as ‘‘the most plausible.’’ Scenario B has continued moderate increase in the rate of GHG emissions and includes three large volcanic eruptions sprinkled through the 50-year period after 1988, one of them in the 1990s.”
[**] from Hansen et al. (1988)“The equilibrium sensitivity of this model for doubledC O2 (315 ppmv - 630 ppmv) is 4.2 oC for global mean surface air temperature (Hansen et al. [1984], hereafter referred to as paper 2). This is within, but near the upper end of, the range 3 o +/- 1.5 oC estimated for climate sensitivity by National Academy of Sciences committees [Charney, 1979; Smagorinsky, 1982], where their range is a subjective estimate of the uncertainty based on climate-modeling studies and empirical evidence for climate sensitivity.”
J. Hansen et al. (1988) Global Climate Changes as Forecast by Goddard Institute for Space Studies Three-Dimensional Model J. Geophys. Res. 93, 9341–9364 J. Hansen et al. (2006) Global temperature change Proc. Natl. Acad. Sci. USA 103, 14288-14293 -
Doug Bostrom at 06:52 AM on 5 August 2010Communicating climate science in plain English
One (final? hah!) actual concrete suggestion would be to do some research on cognitive dissonance prior to making any substantial changes to the site, then ask whether such changes as can be made will address that fundamental problem. -
Cornelius Breadbasket at 06:39 AM on 5 August 2010Why I care about climate change
#93, 94, 95 Interesting point though. Here in the UK you'd have to vote for one of two very small and very unpleasant minority parties if you wanted to vote against carbon reduction. In the US its a 50 - 50 decision - and the democrats can't get the climate bill through. What are your choices in Australia? -
Doug Bostrom at 05:51 AM on 5 August 2010Communicating climate science in plain English
Naturally I agree with pohjois! :-) Regarding fragmentation, whatever you do don't divide comments. Their only practical utility in terms of improving public understanding is to serve as an illustration for lurkers of who has the more coherent grasp on reality so to that end they're worthwhile. Breaking 'em up would vastly increase the amount of effort needed to derive any benefit from comments threads. -
Rob Painting at 05:34 AM on 5 August 2010Confidence in climate forecasts
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pohjois at 05:33 AM on 5 August 2010Communicating climate science in plain English
I agree with Doug. Implementing this idea as proposed will lead to tripling amount of work and fragmented discussion. I think that desired effect can be achieved with lower effort and without disadvantages by changing format of the articles. It should start with "Executive summary" - which is basically a simplified and highly compressed version of the main article. Then the normal article would follow, written in the "middle" level. If a more technical description should be useful for some part of text, then one can use boxes, or hyperlinks to supplementary material containing in-depth technical explanations. In this proposed scheme everything is in the single place, the discussion can be coherent and one can simply skip unnecesary fragments. -
Rob Painting at 05:26 AM on 5 August 2010Confidence in climate forecasts
Angusmac @20 - where does that graph come from?. As Dcruzuri has pointed out, it differs greatly from the actual 2006 Hansen paper, which shows actual temperatures tracking very closely to scenario B, and above scenario C. You even provided a link to the actual paper. Do you expect people not to check?. -
Dikran Marsupial at 05:13 AM on 5 August 2010Has Global Warming Stopped?
ABG I think the point Mike was making is that saying "95% confidence" is inviting the public to think this means that the probability of the trend being positive is at least 95%, however that would not be correct. The classic fallacy of significance tests is to treat the p-value as being the probability that the null hypothesis is true, which is the same fallacy as implying that we have 95% confidence in the alternative hypothesis (assuming the null and alernative hypotheses are complementary). The frequentist definition of probability means that it is meaningless to talk of the probability of a hypothesis being correct, it has no long run frequency, it is either true or it isn't - it isn't a random variable. That is why frequentists have to talk of what you might expect from a large number samples from some population instead (i.e. it doesn't actually answer the question you want to ask). The same sort of problem arises in the interpretation of confidence intervals, it isn't correct to say that there is a 95% probability that the true value lies in the 95% confidence interval (even though that would be the natural interpretation of the phrase). Caveat emptor: I am a Bayesian, in part because I find the frequentist approach to confidence intervals so hard to understand and unintitive, so you would probably be better off with the opinion of an expert freqentist statistician for chapter and verse (wierd bunch that they are ;o), if I have got it all wrong, I'm happy to be corrected.
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