Recent Comments

Prev  2433  2434  2435  2436  2437  2438  2439  2440  2441  2442  2443  2444  2445  2446  2447  2448  Next

Comments 122001 to 122050:

122001. daisym at 11:41 AM on 25 March 2010
        Is the science settled?
        From what I've read, CO2 by itself, can raise atmospheric temps by maybe 2oC, and the global climate models have to assume that cloud effects must provide positive reinforcement for CO2 to raise temps further. It also is my understanding that scientists are divided on whether clouds provide positive or negative reinforcement, and by how much. Is it not the case that until cloud effects are better understood, the case for AGW will remain truly unsettled?
        Response: "Is it not the case that until cloud effects are better understood, the case for AGW will remain truly unsettled?"
        
        Arguably the key question surrounding global warming is climate sensitivity. I didn't touch on it in this post as I'm planning to devote a post on this subject shortly. We've established empirically that more CO2 is trapping more heat which raises temperatures. The big question is whether feedbacks amplify or reduce this warming. When you add up water vapor, clouds, ice sheet albedo, etc, is the net feedback positive or negative? And how big is it?
        
        We can sidestep the issue of all the various individual feedbacks and jump straight to the question of net feedback by looking at empirical data - how has climate responded to forcings in the past? A multitude of studies, looking at different periods, using different metrics, all tend to cluster around a single answer - the climate sensitivity for doubled CO2 is 3°C.
        
        This gives us the final overall answer to how climate will respond to rising CO2. The net feedback is positive and the climate is fairly highly sensitive to changes in energy balance. So while we have a lower understanding of the individual feedback components, multiple lines of empirical observations give us a higher understanding of the net feedback response.
122002. HumanityRules at 11:40 AM on 25 March 2010
        Is the science settled?
        "Straight dependence on temperature." What stopped natural runaway warming in the past? Negative feedbacks? Moralising about grandchildren is pointless - I see your future warming and raise you stunted economic growth in the developing world.
        Response: "What stopped natural runaway warming in the past? Negative feedbacks?"
        
        This is a very interesting question - I've been reading about this in Hansen's Storms of my Grandhildren. There are a number of factors. One is that the sun's output was lower back in the days when CO2 was much higher (in fact, it is BECAUSE the sun's output was lower that CO2 was higher but that's a discussion for another time).
        
        Another factor is that warming in the past was over geological time periods, thousands or millions of years, so over these periods, negative feedbacks have stopped natural runaway warming. This is because negative feedbacks also act over thousands or millions of years - continental weathering removes CO2 from the atmosphere, terrestrial sinks absorb CO2, etc.
        
        The difference between then and now is that current warming is happening so fast that these long-term negative feedbacks don't have time to make a significant impact in slowing down the warming. I find this a particularly fascinating (albeit disturbing) subject and would like to take some time to track down Hansen's references and write a post about it. Now, to find some time...
122003. scaddenp at 11:18 AM on 25 March 2010
        Is the science settled?
        "what's the certainity about water vapour? What's the uncertainty? Straight dependence on temperature. Can you point me to the controversy? As to others, the uncertainties are bounded. To cause a rise in temperature you have to a trend in the others. At the moment we have a model for climate which does an excellent job of accounting for past and present climate at many different levels. This does not discount the possibility of some unknown which will give rise to an even better model - but that's not the way to bet. Got grandchildren you want to stake on the possibility of some future better model giving us less rapid warming? Me, I am too risk-averse. The prediction is at least good enough for killing all subsidies on fossil fuel and investment in sustainable energy instead.
122004. PaulK at 11:11 AM on 25 March 2010
        Understanding Trenberth's travesty
        Zinfan94, You wrote: "Why is it that the skeptics claim both low ice sheet melts and level OHC. These two extremes taken together contradict observed SLR, and contradict GRACE data." Further to my post above, you really should read Cazenave et al 2008, which is the consensus science view on reconciliation of TG data, altimetry, ocean mass balance (including GRACE data) and ARGO data. It calculates steric sea level rise (thermal plus salinity) from 2003 to 2008 from Altimetry minus mass balance (two different ways) as 0.31mm/year, and independently calculates the value by thermal expansion from ARGO data as 0.37mm/year. This uses 0-900m ARGO data. It concludes:- QUOTE The steric sea level estimated from the difference between altimetric (total) sea level and ocean mass displays increase over 2003–2006 and decrease since 2006. On average over the 5 year period (2003–2008), the steric contribution has been small (on the order of 0.3+/−0.15 mm/yr), confirming recent Argo results (this study and Willis et al., 2008).ENDQUOTE You will note that there is no room in this analysis for any additional deep OHC, quite the contrary. Either Schuckmann or Cazenave has some further explaining to do in order to reconcile these two papers.
122005. HumanityRules at 10:58 AM on 25 March 2010
        Is the science settled?
        loehle link http://www.ncasi.org/publications/Detail.aspx?id=3282
122006. HumanityRules at 10:56 AM on 25 March 2010
        Is the science settled?
        I take your point on the evolutionary development of science. I also think that most, if not all, of paragraphs 2 and 3 are non-contraversial for alarmists and nearly all deniers. You skipped an important and contraversial point with regard to CO2 radiative forcing. The energy trapped by CO2, as shown by figure 1, is insufficient to cause the catastrophic effects imagined by the IPCC. It requires help from water vapour, whats the certainty around that? Because this seems more contraversial than CO2 itself. Again most thinking skeptics seem to accept CO2 as a mild GHG. About the last paragraph. It seems that many of the possible 'natural' variations in the system a poorly understood and this lack of knowledge seems to strengthen the case for CO2. Convince me that the certainty we have about CO2 isn't in some part derived from the uncertainty we have about other parts of the sytem such as clouds, aerosols, the bioshpere etc. Something missing from this article is future projections. Take this work from Loehle which suggests many possible snenarios for future CO2 levels, many of which fall below the IPCC lower limit. I wonder about the speculative nature of this process. You seem to have highlighted some of the less contraversial aspects of climate science.
122007. jamesqf at 10:37 AM on 25 March 2010
        Was Greenland really green in the past?
        Seems like you all are missing a very important point about Greenland, which you can discover for yourself by visiting any site (like Google Maps) that has satellite pictures taken in the summer. Greenland IS green around the edges (and probably always was), and those edges are all that you're going to see from a Viking longship, or from a settlement on the shore. Around the southern part (where the Viking colonies were) the icecap is many miles inland. (Nor would the Vikings have been unfamiliar with the idea of inland glaciers, or thought them remarkable, as both Norway and Iceland have plenty of them.) There are a lot of theories as to why the Greenland settlements failed. "Climate change" is only one, and in my (non-professional) opinion, at best at minor contributing factor. More likely is that the colonies were just too small to be self-sustaining, so that when regular European trade stopped, they dwindled and failed. More information on past & present Greenland can be found here: http://www.greenland-guide.gl/
122008. nealjking at 10:14 AM on 25 March 2010
        Is the science settled?
        nernt, #28: Isolating the effects of the different greenhouse gases can be done using models, but is not trivial, because they do not just add up linearly: The effect of water vapor and CO2 is not the same as the sum of the effects of each alone: It just doesn't work that way. Unfortunately, the atmospheric physics involved in understanding how the models work is not too simple either. You could look at Pierrehumbert's book, if you're up for the math. A historically oriented approach is Weart's "The discovery of global warming", at the AIP website: http://www.aip.org/history/climate/summary.htm The scientific support is not based only on correlations, as if people had seen a trend and then tried to explain it. The PREDICTION of global warming was made over 100 years ago, and argued for several decades. The correlation comes as a CONFIRMATION of an expected result: That's very different from a "post hoc, ergo propter hoc" ("after this, therefore because of this") approach. It's more like "I was looking for this, and here it is!"
122009. jondoig at 10:10 AM on 25 March 2010
        CO2 lags temperature
        Modelling of past deglaciation by Ganopolski & Roche (2009), summarised in this PIK media release, found both the delayed Arctic warming and the rapid onset of Antarctic warming (i.e. leading CO2 rise) was mainly due to melting northern ice sheets cooling the oceans and disrupting ocean circulation: "During the terminations of the glacial cycles due to orbital forcing, the vast ice sheets covering Northern America and Eurasia melted rapidly causing a large fresh water flux into the oceans sufficient to disrupt the Atlantic meridional overturning circulation (AMOC) over many thousand years. The disruption of AMOC, in turn, dramatically reduced the oceanic heat transport from the Southern to the Northern Atlantic and led to a delay in the Northern Hemisphere warming and, at the same time, a more abrupt and strong warming in the Southern Hemisphere. The latter is the primary mechanism explaining Antarctic temperature lead over CO2."
122010. Marcel Bökstedt at 10:01 AM on 25 March 2010
        Is the science settled?
        kdkd> I am not an expert on this stuff, I'm trying to learn, but I think that the numbers quoted by Ken Lambert are not directly relevant to the question. In the paper, Trenberth tries to figure out how heat moves around different parts of the Earth. The "imbalance" is heat that has not been accounted for. However, the global warming does show up in the balance as the "radiative feedback" of -2.8 W/sq.m, which is supposed to correspond to the observed increase in temperature of 0.75 degrees C. According to Trenberths paper, the imbalance was very small 40 years ago, but has now grown substantially. It seems that we don't know exactly where it goes. That we don't know what happens to it makes Trenberth sad (cf the purloined letter), but he assumes that besides warming the surface of the planet, it goes into warming the ocean, making clouds and such. Clever guys, please correct me if I have misunderstood.
122011. Marcus at 09:40 AM on 25 March 2010
        Is the science settled?
        Berenyi, by world standards the United States pays an unusually low price for electricity. Here in Australia the average price of electricity is around AU$0.25/kw-h, yet we get very little of our electricity from renewable sources-so there seems little correlation between electricity type & electricity costs (a fact further emphasized by a look at the domestic energy price list provided by Turboblocke). Also, whilst the cost of renewable energy technologies has actually fallen over the last 20 years (& is predicted to continue-due to improvements in materials costs & storage technologies) the price of electricity from coal & nuclear have risen, & are predicted to rise further as the fuels become more scarce & as the price of oil & diesel continue to increase. Might I also remind you that the price of coal-fired electricity in the late 1800's & early 1900's was around US$3.00/kw-h (in today's terms), but this didn't stop the development of an electricity grid!
122012. Marcus at 09:33 AM on 25 March 2010
        Is the science settled?
        So apparently 95% certainty isn't high enough to take "expensive" actions to curtail CO2 emissions. If a doctor told you he was 95% sure that the black mark on the X-Ray was a malignant tumor-a tumor which will kill you without expensive & debilitating chemotherapy-would you say "oh well, I'd rather just take my chances"? Unlikely. The whole cost thing is a total straw man anyway. Most of the best methods for GHG mitigation also come with numerous side-benefits. For example using car-pooling or public transport to commute to work every day, instead of driving yourself, will reduce transport-related CO2 emissions, but they'll also reduce your commuting costs, reduce on long-term vehicle maintenance costs, reduce commuting-based stress (& hence lift worker productivity) & reduce levels of harmful emissions such as benzene (a carcinogen) & particulate emissions (a cause of lung disease & asthma). Of course there's the added benefit that it will make oil last longer too. By the sound of it, the only *cost* will be borne by the oil industry, who will see reduced profits due to less petrol being sold. So that leaves me of the view that most contrarians are simply acting to protect the financial interests of the fossil fuel industry!
122013. Berényi Péter at 09:22 AM on 25 March 2010
        Is the science settled?
        #32 Turboblocke at 08:26 AM on 25 March, 2010 "it's not so outrageously expensive as the Wiki article claims" On current rate 0.2671 € cents is 35.59 US cents. It is not much cheaper than the 42.89 US cents found in the wiki article. Remember, US price is 9.28 US cents/kWh. Also, only about 20% of Danish electricity is generated by (extremely expensive) wind turbines. The rest is produced by nuclear plants and/or imported from Sweden and Norway.
122014. David Horton at 09:13 AM on 25 March 2010
        Is the science settled?
        John you might want to look at the "95% probability" business, which, as on this thread, gets misinterpreted wildly. The kind of probability being referred to in science is to do with an individual experiment. You do an experiment, you get a set of results, you do statistical calculations to work out what is the probability (based on number of samples, number of results in a certain direction) that the result could be due to chance. This isn't the case, in any meaningful sense, with global warming. There is no "experiment", there are multiple observations of an astonishing range of different kinds. Some of these observations do lend themselves to statistical analysis - for example storm frequency, numbers of record high temperatures, Arctic ice extent, comparison between temperatures in different decades. Others do not - for example species movements, glacier retreat, droughts, ocean acidification, breeding and flowering seasons. But the point is that ALL of these observations, statistically based or not, head in the same direction. So the question really becomes - what is the probability that all of these observations would trend in the same direction? You can't, as far as I know, calculate a formal statistical probability on this, it would be meaningless. But even taking the ones where you can work out individual probabilities, what are the chances that you would get 95% here, 90% there, on a series of individual observations, where these observations all rely on a well known physical property of greenhouse gases? And then add the non-statistical trends. The "chances" of this set of observations all being due to chance must be trillions to one, not 20 to 1.
122015. kdkd at 09:05 AM on 25 March 2010
        Is the science settled?
        Ken Lambert's argument in #4 has been irritating me for quite a while (on a separate forum). My understand of the physics is not good enough to understand the energy balance equations fully enough, but there are three problems I see with it. 1. He assumes that co2 sensitivity is at the lower range predicted. As far as I can see the minimum co2 sensitivity should be about 1.6ºC - the observed data does not support lower figures. 2. that the negative feedback effects are at the upper range of the confidence interval and the positive feedback effects and co2 responses are at the lower end of their confidence intervals - i.e. he is assuming non random distribution of the parameter estimates, which is a big nono without evidence to back it up. 3. There's a bit of wishful thinking - I think he's making the assumption that co2 sensitivity figures apply only to the first doubling in co2 levels - so to take his conservative estimate that if co2 doubles on pre-industrial levels by 2050 then we get 1.6ºC warming, but then a further doubling by say 2100 will not cause the same warming. This seems to me theoretically suspect. So can anyone help me understand the problems with Ken's argument better, or have I already hit the nail on the head?
122016. KR at 08:56 AM on 25 March 2010
        What CO2 level would cause the Greenland ice sheet to collapse?
        My apologies, Camel - I mixed CO2 predictions with temperature, I suspect due to reading too many climate papers at once. Slapping head now... must get more caffeine! The IPCC models fit the total data for CO2 quite well, and previous predictions from those models were quite accurate. Loehle can't argue that arbitrary curves (from a recent subset of the data) invalidate the IPCC model unless he can argue that the IPCC model doesn't fit (it does) and supplies a possible alternative model with superior data fit and prediction accuracy for consideration (he doesn't). I believe he's just over-fitting a short segment of the data to argue that the IPCC model lacks predictive power, and he hasn't made that point at all convincingly. The existence of alternative theories, such as this interesting one on space/time and metaphysics have no impact on the consensus - unless there's actual evidence for them. Some 'guesses' are indeed better than others.
122017. Peter Hogarth at 08:55 AM on 25 March 2010
        Visual depictions of Sea Level Rise
        Peter Hogarth at 19:58 PM on 22 March, 2010 Where does your second image come from? it seems to link to Monty Python?! I disagree that the overall pattern is "rather similar", apart from the land/sea boundaries. I see as many differences as similarities. I disagree that the Ssalto/NOAA/NASA/ESA/CSIRO etc data products are wrong, and I think you are again confusing reference frames, but this is forgivable. Do you really think the positioning guys have got it so wrong?
122018. KR at 08:28 AM on 25 March 2010
        What CO2 level would cause the Greenland ice sheet to collapse?
        Gallopingcamel (#48), the IPCC estimates range up and down quite a bit, based on different model inputs for our CO2 activity - previous predictions from these models (even the worst case) all appear to underestimate the current temperature. Loehle posits a couple of curve fits, with no discussion of how they were selected, and states that he has "no assumption of mechanisms". His curve fits are lower than the IPCC's model, which has previously been shown to underestimate the temperature trend. That would hint to me that his curves (not models!) are unlikely to be accurate representations of the underlying physics. Add that to his previous papers, and I might suspect an agenda shaping his interpretations, rather than data-driven modeling. Now, I could fit a near infinite number of curves to the data, depending on how many degrees of freedom and fit error estimates I wanted to apply. Some would be higher when extrapolated out, some would be lower. The IPCC curves fit the data within known noise limits, with high confidence - I can't tout my assorted fits as an argument against the IPCC model unless I have a compelling alternative model, one with (a) descriptive power (fits past data), (b) predictive power (makes testable assertions about the future), and (c) some support in physics. Loehle also doesn't use anywhere near as much data as Hofmann; I consider that a critical failing in any argument for data fitting. 210 years versus 51? Dropping 75% of the data makes for a poor argument, which I think you have argued in the past. I have ongoing issues with trash on my lawn - random garbage. I could look at known behavior of my neighbors (beat up trash cans), wind (gusty), and model my neighbors trash blowing onto my yard. Or, I could posit invisible gnomes with personal grudges who bring in trash at night from miles away, placing them in cryptic patterns with mystic importance. That might be a better fit to the trash pattern. Which guess is right? Well, I suspect the one based on observed physical interactions would be more likely... Loehle's curves are (IMO, mind you) the equivalent of the gnomes. No basis in a model of the world, not driven by any p<95 issues with the curve fitting; they seem driven more by a wish for a different conclusion than scientific criticism.
122019. Turboblocke at 08:26 AM on 25 March 2010
        Is the science settled?
        Re # 21 Danish energy comes at a price... from the EU official source here: http://www.energy.eu/#domestic it's not so outrageously expensive as the Wiki article clims.
122020. scaddenp at 08:14 AM on 25 March 2010
        What CO2 level would cause the Greenland ice sheet to collapse?
        "Do a few 100 ppm of CO2 matter?" Well without our GHG we would be a frozen ball. Does that matter to you? Are you seriously positing that our GHG in the atmosphere arent giving us a warmer planet? In context of geological time, humans dont matter but they do to me. As to your contempt for statistics,- well they are abused in political dialogue but they are essential tool for science. What science operates without statistics? The problem is that statistics need to be wielded by the competent.
122021. Marcel Bökstedt at 08:10 AM on 25 March 2010
        CO2 was higher in the past
        thatnumber5> Yes, the radiation from the sun is increasing. But as Ned says, it increases very slowly. I don't have a good reference for this right now, but try this wiki article on the faint young sun paradox. The general idea is that astronomers think that they have good models for the evolution of stars like the sun, so in particular, they can compute solar output from the age of the sun.
122022. unreal2r at 08:06 AM on 25 March 2010
        Is the science settled?
        The "it will cost too much" or "it will wreck the economy" arguments are among the most misdirected. In relative terms, fixing the levees around New Orleans would have been much more economical than repairing the damage - without accounting for the human consequences. If you apply Occam retrospectively it becomes pretty apparent that, on the off chance the still "unsettled" science has some probabilistic merit, it will be far less costly to act now than wait until every property within surge distance of an ocean or tidal estuary is rendered valueless.
122023. JMurphy at 08:04 AM on 25 March 2010
        The 5 characteristics of scientific denialism
        RSVP, Climate Science involves a lot more science than the use of models. There is lots of 'hard' science going into substantiating the present situation and the projected situations coming from models. But don't despair : there are lots of people out there improving the models all the time and I doubt if they would agree that they are ignoring or unable to consider all significant factors. What factors do you think they are missing or not working on, or do you think they should just give up because it's too difficult ?
122024. gallopingcamel at 08:00 AM on 25 March 2010
        What CO2 level would cause the Greenland ice sheet to collapse?
        KR (#46), My reasons for wanting to reduce CO2 emissions have nothing to do with the CO2 concentration in the atmosphere. That is the IPCC's motivation, please don't try to associate me with their Alarmist science. With regard to the Loehle paper, this is another example of the inability of statisticians to reach agreement. When you are talking about small changes, statisticians will tell you whatever you want to hear. Does a few hundred ppm of CO2 matter? In my opinion the answer is "NO" if you think in the larger context of geological time. Loehle may be "low balling" the CO2 trend while the IPCC is more inclined to exaggerate. Who is right? Your guess is as good as mine.
122025. KR at 07:57 AM on 25 March 2010
        A peer-reviewed response to McLean's El Nino paper
        A quick note about my last comment - I'm commenting on the abstract, content, and conclusions of Mclean's (submitted, rejected) reply, not the original paper.
122026. KR at 07:54 AM on 25 March 2010
        A peer-reviewed response to McLean's El Nino paper
        Looking at the Mclean reply HumanityRules pointed out, they spend a lot of time defending their derivative operator, and argue the coherence of their results with the known temperature variations. Great - I have some arguments with what their bandpass filtering method actually shows, and the Foster paper (submitted) has a strong argument that this bandpass fits arbitrary data equally well, but those are all parts of reasonable scientific discussions. In the paper McLean et al in fact say; "Fea10 state that the method of derivatives that we employed would minimize long-term trends. We completely agree..." However, in their abstract and conclusions they then state something else: "We explain that there are natural mechanisms that might account for the strong coherence of Southern Oscillation Index and mean global temperature. Our research did not set out to analyse trends in mean global temperature, but, should any such trend exist, it follows from our analysis that in most part it could be a response to the natural climate mechanisms that underlie the Southern Oscillation." (Italics added for emphasis) This statement about long term temperature trends is, by their own admission, unsupported. There is NOTHING about long term trends discussed. It has no place in either an abstract or conclusion for this paper.
122027. Jesús Rosino at 07:51 AM on 25 March 2010
        Humans are too insignificant to affect global climate
        Damn it, I have ruined the cartoon by giving the clue just in the following line! :P
122028. Jesús Rosino at 07:48 AM on 25 March 2010
        Humans are too insignificant to affect global climate
        When facing this argument I always like to bring this cartoon. (Clue: cyanobacterias)
122029. Adam C at 07:15 AM on 25 March 2010
        What CO2 level would cause the Greenland ice sheet to collapse?
        Missing from this discussion (I believe) is a mention of why there exists a tipping point beyond which collapse of the Greenland ice sheet becomes inevitable. The key to the continued existence of the ice sheet is altitude - the ice is over 2500 m thick in places, including the southern extent which lies below the Arctic Circle. For every hundred metres lost to melting, the temperature of the surface ice will rise by (roughly) another Celsius degree simply from the effects of lower altitude. Once the height of the ice sheet decreases below the current equilibrium line, Greenland will continue to completely melt even if temperatures go back down.
122030. KR at 06:42 AM on 25 March 2010
        What CO2 level would cause the Greenland ice sheet to collapse?
        Camel, in 31 I would have to say that you're throwing up a strawman argument. I don't believe anyone expects that controlling carbon emissions would drastically (if at all) drop the 380ppm current CO2 levels, throwing us into massive glaciation. That would require halving CO2 levels AND a solar minimum! It would be nice, however, if we could moderate the current climate changes to minimize disruptions to sea levels, drinking water supplies, weather patterns, etc. Posing a complete and well-nigh impossible reversal of a centuries long trend is really just a distraction... Second topic: Reading the article you point to in 33, the Loehle paper fits various curves (including a 'Saturated' one?) to 51 years of data, arguing that the recent Hofmann fitting the IPCC models to it (exponential growth) is inaccurate. I haven't downloaded the original Hofmann paper ($$$), but even in the abstract they state: "Here we show that the anthropogenic component (atmospheric value reduced by the pre-industrial value of 280 ppm) of atmospheric carbon dioxide has been increasing exponentially with a doubling time of about 30 years since the beginning of the industrial revolution (~1800)." That's x4 as much data than Loehle uses; why didn't Loehle use all the data? And if Hofmann doesn't use all the data, why didn't Loehle pointedly note that!? I also observed that Loehle states his alternate curves "...capture current trends in both the first and second derivative without any assumption of mechanisms." I do a _lot_ of curve fitting; over-fitting a short curve segment with an arbitrary equation is almost unavoidable. You need to restrict the potential curves to those based on the best understanding of the mechanisms involved, or you will be thrown off by data noise. The IPCC curves he's comparing to are based on carbon emission estimates - Loehles' alternate (and short) curve fits are not based on _any_ physical process described in his paper. The only time you should try arbitrary fits is if you have no idea as to the underlying mechanism, and there as to get clues as to what that mechanism is. You certainly can't assert predictive power beyond WAG's from arbitrary fits, nor invalidate a mechanism without a compelling alternative. I have to say I'm not impressed by any scientific insights from the various Loehle papers...
122031. thatnumber5 at 06:33 AM on 25 March 2010
        CO2 was higher in the past
        More a question than a comment. What is the science behind the statement "solar output was about 4% less than current levels"? Is the sun's output increasing over time?
122032. Berényi Péter at 06:28 AM on 25 March 2010
        What CO2 level would cause the Greenland ice sheet to collapse?
        20th-Century Industrial Black Carbon Emissions Altered Arctic Climate Forcing McConnell et al. Science 7 September 2007: 1381-1384 DOI: 10.1126/science.1144856
122033. John Russell at 05:21 AM on 25 March 2010
        Is the science settled?
        The sceptics now tend to say, "the science isn't settled", because for a long time politicians and others have been saying, "the science IS settled". And from their standpoint those politicians are right. I would suggest that from any practical, meaningful point of view anyone but a scientist would be very sensible to believe that at 95% probability, to all intents and purposes, the science IS settled. At those odds, to stake one's children's future on that 5% doubt is sheer irresponsibility. Of course, that's not to say scientists should not constantly test and retest the theories while ever any doubt remains; until a time arrives when to continue questioning whether the world is really flat puts the remaining sceptics firmly in the lunatic fringe. Though, of course, there's still a very faint chance they could be right...
122034. CoalGeologist at 05:21 AM on 25 March 2010
        Is the science settled?
        Like so many other skeptical “cocktails”, this one is 2 parts straw man, 1 part red herring, with a dash of plausibility, shaken, not stirred. The "straw man" misrepresents the degree to which scientists both recognize and acknowledge that there are still legitimate areas of uncertainty and imprecision in our understanding. In this regard, the IPCC and the climate community have been very frank, in general. For example, see: NASA: Global Climate Change Uncertainties One almost never hears actual climate scientists saying, "The science is settled" (or if they do say something like that, it's usually misunderstood), whereas one hears this frequently from skeptics. I'm particularly bothered when skeptics precede their complaint that ‘the science isn't settled’ with the disingenuous lead-in, "I'm tired of hearing... (that the science is settled)" If they are so tired of hearing this, why do they keep saying it? The "red herring" aspect of the argument represents an apparent effort to shift the dialog away from the actual scientific evidence toward a contrived argument over whether the scientific "gestapo" is trying to stifle dissent and suppress alternative views. There is, unfortunately, a tiny dash of plausibility to this, although there’s no indication that it has posed a serious problem in the peer-reviewed literature. Focusing on an imagined conspiracy to suppress debate is a distraction from consideration of the real evidence. One recurrent straw man entails confounding of two distinct conclusions reached by the IPCC: 1) "Warming of the climate system is unequivocal..." and 2) "Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations." Here's how one AGW skeptic combined these two statements in a recent Op/Ed piece in the Wall Street Journal (21 Feb 2010): "'Unequivocal." That's quite a claim in this skeptical era, so it's been enlightening to watch the unraveling of the absolute certainty of global warming caused by man." Tragically, what is unraveling in this “skeptical era” is honest debate.
122035. nerndt at 05:18 AM on 25 March 2010
        Is the science settled?
        I found this a very well written article addressing the most fundamental concern I have always had for AGW - CO2. Correlation or causation. Do any models and charts show the margins of error of the instruments used to gather the data and then compare it to the CO2 correlations? Can the effects of water vapor be removed from the studies to better isolate the effects of CO2? It all seems to easily be explained as results that are well within the noise characteristics of the studies! Having close friends who design space stations where deciding whether to paint portions white or black because they caused drastic effects on the thermal expansion of the material and the localized heat effects constantly points me back to the issue that black soot resting on the ground from coal power plants probably cause more radiative energy collection than an entire atmosphere of increased CO2 levels produced by man (by probably orders of magnitudes). Our knowledge of clouds and how they function in regards to reflecting or absorbing the suns energy is still a complete mystery(being the largest contributor by 20x more than any other to atmospheric warming effects). I feel the information showing we have increased the levels of C02 in the atmosphere are clear. The effects are extremely unclear (isolation of only gas effects in parts per million in effecting thermal radiation have never been shown). We need to step back, try to isolate as many components as possible so we can scientifically determine what we actually know and what we do not know. Trial and error. True isolated research studies of CO2 gas fluctuations in parts per million in atmospheric conditions, removing effects of containers, liguids, and solids which may bias the results tremendously. By taking a complex system, isolating the components and understanding their effects, then putting them together piece by piece into a system we can begin to understand the truth. I have not seen anything close to this approach yet in looking for the scientific evidence to support AGW. Just correlation papers without proving causation. Can anyone help steer me to meaningful scientific information?
122036. SLRTX at 04:58 AM on 25 March 2010
        Is the science settled?
        Marcel (#27) - Well said. As for the on-going policy discussions on this thread, keep in mind: 1. Climate science and policy are 2 different things. The consensus is that the science of AGW/ACC is real. Policy consensus is highly debatable. 2. The timing of the effects of climate change are still unclear. We see changes now. We can predict other changes, given different rates of rising global temperatures. But there will be effects. Some too rapid for societies or ecosystems to adjust. Food riots? That's nothing compared to water riots. Overall though, there is growing concern that even if we halt all CO2 output, and other forcing effects of humans immediately, we may not be able to stop these effects. We just don't know where that tipping point is with a high degree of certainty. (That's where we continue to learn more about the positive/negative forcings on our climate.) Have we passed the tipping point? Are we near it? Is it far enough in the future that we can stem the tide of negative effects with proposed policy changes? That's the uncertain part of climate change. But the science proving our contribution to AGW/ACC to the point of consensus is solid and sound.
122037. tobyjoyce at 04:55 AM on 25 March 2010
        Is the science settled?
        oracle2world: "How about the default assumption is that the result is uncertain?" Well, when I drive to work tomorrow, there is a low probability that I will be involved in a car smash, the outcome is undertain so it is ok not to wear my seat belt? I will be dropping my daughter at school - should I tell her not to bother with her seat belt because the chance of a car smash is "uncertain"? The possible negative consequences would be so catastrophic that I fully intend to wear my seatbelt, even with the low expectation of a smash, and make sure my daughter has "belted up". Suppose out best theory says that the global surface temperature will change by between -1C and +4C between now and 2100. Should we bet the farm on the -1C being more correct than the +4C, given that a rise over +1.5C would be catastrophic for large regions of planet earth? There is a very important Prudential Principle that says we act in good time to take preventive action as efficiently as possible.
122038. ProfMandia at 04:45 AM on 25 March 2010
        Is the science settled?
        BTW, the Trenberth paper is available here: http://www.cgd.ucar.edu/cas/Trenberth/trenberth.papers/EnergyDiagnostics09final2.pdf A great paper for the science provided but it is also a great paper because it clearly shows how scientists think, i.e. they are not looking for reasons to support AGW, they are just looking for answers and using data get those questions answered.
122039. tobyjoyce at 04:43 AM on 25 March 2010
        Is the science settled?
        Dear Oracle2world (#9) I did not follow the OJ case closely, but it is only a metaphor. Don't get hung up on it. Simpson's success in avoiding a guilty verdict at his first trial came from an $1million+ defence team who knew how to exploit human doubts and human empathy. My point is that opponents of AGW are similarly engaging with human emotions. Knowing the case is scientifically unanswerable, they are using similar fallacious arguments as were used in the OJ case. It is a case that tells us something about how we form a judgement from evidence, and how we so often can get it wrong.
122040. muoncounter at 04:30 AM on 25 March 2010
        What CO2 level would cause the Greenland ice sheet to collapse?
        At 31, gallopingcamel offers this: "With regard to meltwater pulses, Disney did a good job on a collapsing ice dam in "Ice Age"." Hardly. For example, the draining of glacial Lake Agassiz 8500 years ago showed up in the sedimentary record in the Rhine River delta. Although this is a newspaper article, it cites a recently published study by Dutch geologists, quoting: "They determined that the collapse of a glacial wall near present-day Hudson Strait in northern Canada triggered a two-stage draining of the lake that sent global sea levels soaring by about three metres — “double the size of previous estimates,”" Quoting further, "“The (Agassiz) event is often seen as an analogue for possible future freshening of the North Atlantic,” they state, “and serves as a test case for assessing the sensitivity of ocean circulation to freshwater perturbations in climate models.”" And then there's the little problem of drought: Warming air stimulates evaporation from not just the oceans, but from soil as well. From Early warning signs of Global Warming: Droughts and Fires": "The environmental and ecological consequences of the summer 1999 drought in the eastern United States provide examples of situations that may become more frequent as climate changes. Without freshwater to rinse out rivers and streams, salt water encroached further up rivers in many areas of the mid-Atlantic coast (USGS, 1999)." That saltwater kills crops and contaminates fresh water supplies in the lower reaches of the river basins. It's a double whammy: "Decreased freshwater runoff also led to increased salinity and low oxygen conditions in Chesapeake Bay, causing fish kills and other ecological changes. As future sea level rise shifts the saltwater-freshwater boundary farther inland, droughts will exacerbate the geographic extent and impacts of saltwater encroachment into coastal aquifers." And then there's fire: by way of anecdotal evidence, in the US over the past few years, it seems as if each summer's national news is full of more widespread and more intense wildfires. Increasing fire frequency is confirmed by this botantical study. In 41, Mr. Camel posits: "it all depends on whose ox is being gored"? Let's see: floods, drought, fire... drought is often associated with famine and no doubt insects and shallow water critters will figure this out first, giving us locusts and frogs. How many more plagues do you want?
122041. Marcel Bökstedt at 04:22 AM on 25 March 2010
        Is the science settled?
        There is another strong reason for considering the general picture of AGW as settled. The reason is that there is no alternativ theory that explains the climate record we have. With a "theory" I mean a model with an underpinning in theoretical science (physics), which does give precise verifiable predictions. Such a theory is vulnerable in many ways - a climate theory can be falsified by inconvenient data from this century, by various historical data going back millions of years, by attacks on its theoretical foundations etc. The more possibilities to falsify it, the better for the theory: If the attacks don't kill it, they strengthens it. AGW has survived a strong onslaught for a long time. There is no alternative climate theory which has an even faintly resembling status. There are some thoughts which have ended up as "skeptical arguments" on this site, but nothing coherent, nothing that has a strong theorertical backing and gives predictions (or post-dictions) for a large number of measurable quantities. The fact that there are so many "skeptical arguments" shows that AGW is a strong theory - it can be attacked in many ways. Don't misunderstand me. Actually I see a lot of weak spots and unclear areas in the AGW theory. But it is an honest, falsifiable theory. And no one has been able to come up with a competing explanation with an even faintly resembling status. I'm sure there will be modifications of the climate models, as we come to understand the climate better. But I don't see even the beginning of a "paradigm shift" away from AGW. There is no new paradigm in sight to build that shift around.
122042. Philippe Chantreau at 04:20 AM on 25 March 2010
        What CO2 level would cause the Greenland ice sheet to collapse?
        Right gallopingcamel. So we are left with the choice of managing a risk at the 1 to 200 years horizon or at the 20000 years horizon. Tough one. And indeed this blog is not into solutions. It is into addressing widespread nonsense like "it's cooling", "it's the sun", "it's cosmic rays", "Jupiter is warming" and numerous others. That is plenty of work already. Since you are in favor of soon, drastic emission reductions, nothing prevents you from starting a blog on solutions. I will certainly be a reader.
122043. Phila at 03:51 AM on 25 March 2010
        Is the science settled?
        Oracle2world, First, nuclear power is not a "solution" to AGW. It's one element of a response, the value and feasibility and timing of which depends on a number of variables, including logistical and financial and legislative issues. It would need to be accompanied by other measures that, I suspect, you'd be likely to oppose. Second, a number of "treehuggers" -- a term that seems to me to violate this site's commenting guidelines, BTW -- are indeed "hopping all over nuclear," precisely because they think it's necessary to reduce CO2 emissions. This reappraisal of nuclear power has actually been going on for years, so I'm a bit surprised you don't know about it. Here's a story from 2006.
122044. Berényi Péter at 03:39 AM on 25 March 2010
        Is the science settled?
        You may notice Danish elctricity comes at a price.
122045. Ned at 03:35 AM on 25 March 2010
        Is the science settled?
        However, if the negative feedbacks are not understood, then absolutely no conclusion about future temperatures can be made. None. Nada. I don't think that's a productive method for dealing with uncertainty. It's much more useful to try to characterize the uncertainty and use that to guide decisionmaking. If you're building a school in California, you don't know when and where and how large the next earthquake will be. Do you (a) ignore earthquakes, since they can't be accurately predicted; or (b) use models to estimate the risk, then build in an extra safety margin to account for the uncertainty?
122046. Tony Noerpel at 03:10 AM on 25 March 2010
        Is the science settled?
        Hello Oracle2world The CO2 explanation is rather easy to understand and explains the Earth climate extremely well during the entire Phanerozoic including the hothouse Eocene and also the snowball Earth events during the Proterozoic. It also does a remarkable job of explaining the climate on Venus. The natural variablity you refer to isn't a scientific argument. It does not explain anything, does not pretict anything and cannot be falsified or proven. All one can say is that the Earth can freeze over solid or become an insufferable hothouse rather arbitrarily and any observed change inbetween would be within the natural variability of the Earth climate. Fifty years from now the Earth will have a climate somewhere between a snowball and a hot house. You think? I guess why you are confused is that there are lots of other stuff which affects the climate besides atmospheric CO2 and taking everything into account gets pretty complicated. But the CO2 bit is pretty easy. Also, we are going to run out of fossil fuels. We are just not sure when and the sooner we prepare for that, the cheaper the cost to the economy. It has never been demonstrated that ignoring the AGW problem is less costly than addressing the problem. Denier arguments concerning the economy are pretty weak compared to AGW theory. Heck, replacing the Appalachian water shed lost to mountain top removal is probably enough to break the economy all by itself even if we didn't burn the stuff. I don't understand why it isn't economic suicide not to address AGW. Deniers have never explained that. best regards Tony
122047. oracle2world at 02:56 AM on 25 March 2010
        Is the science settled?
        Dear Ned: "... Since most of the uncertainty involves negative feedbacks, the default assumption should be that warming will in fact occur." How about the default assumption is that the result is uncertain? I don't believe anyone disputes the earth has warmed out of a glaciation 8,000 years ago in our CURRENT ice age (yes we are still in an ice age), and warmed out of a little ice age. The question is whether mankind has a discernable effect on climate. Now you can get a true conclusion from false premises, and every single AGW argument could be false but still correctly conclude mankind is bad bad bad. (Even a blind squirrel stumbles across an acorn from time to time.) However, if the negative feedbacks are not understood, then absolutely no conclusion about future temperatures can be made. None. Nada. Additional cloud cover could easily swamp any contribution of CO2. Within the uncertainty that is as valid a guess as any other. Not well understood means just that, no one knows. Basing conclusions on "I don't know" is just another WAG, that climate enthusiasts have no shortage of.
122048. SLRTX at 02:40 AM on 25 March 2010
        Is the science settled?
        Nothing is absolute certainty. If we expected to understand everything in life to an absolute certainty, society wouldn't function. We ride in a car, knowing there's a chance we'll end up in an accident. We fly in a plane, knowing there's a chance we'll end up in crash. But, we still drive. And we still fly. Why? We, and those around us have reached a consensus that, for all practical purposes, it's safe to drive, and it's safe to fly. The so-called "skeptics" imply that climate science has only worked the issue of climate change from one angle. If that were true, then these "skeptics" are claiming the science doesn't work from a position of skepticism. That's not how this works. Scientists are skeptical, and they check the other side of the argument to cross-check their results. If they miss something, someone else will be sure to call them on it later. They work to answer the question, "can something else explain the results that have been seen?" Is climate change caused by "natural variation?" To some degree (excuse the pun) there are natural forces at work. But under cross-checking, these forces cannot account for the changes we're seeing today. Natural forces cannot account for current changes. Now what about past variation, or current, short-term fluctuations? These have been explained. There are viable, credible explanations for natural causes for these variations. But the current changes cannot be explained, using the same causes for past changes. So yes, there have been changes in the past - all caused by natural forcings. And there are short-term fluctuations - el nino, shifts in the jet stream, etc. But overall, there has been a rise in global temps that cannot be explained by natural forces. There has been NO credible reason for this other than humans causing it. Is this known to an absolute certainty? No. But next time you drive or fly, ask yourself, "How can I be certain I won't die in a fiery crash?" Then decide if you should continue driving or flying, or just get out and walk. After all, science gave you that car and plane. It took a "settled science" to create that. In closing, to anyone who continues to repeat the chants about "there is no consensus", "it's all natural variation", and "it's happened before", I'm skeptical of your claims. Prove your case in a positive manner, instead of throwing up negative arguments, like "what about this", or "what about that". Ok, what about YOUR claims? Where's the proof? I am skeptical of your claims.
122049. Ned at 02:34 AM on 25 March 2010
        Is the science settled?
        oracle2world, you have the application of Occam's Razor backwards here. Since most of the uncertainty involves negative feedbacks, the default assumption should be that warming will in fact occur. We can say with a high degree of confidence that we are increasing the concentrations of CO2, CH4, N2O, halocarbons, etc. in the atmosphere. We also have a high degree of confidence that all of the above act as greenhouse gases, reducing the outgoing flux of longwave radiation. We have a high degree of confidence that a reduction in outgoing LWR will warm the planet until outgoing LWR comes back into balance. Finally, we have a high degree of confidence that on a planet with oceans, this warming will then be amplified by a well understood water vapor feedback. There are less well understood positive and negative feedbacks. You can argue that one or another of these is overestimated or underestimated. But the simplest and most coherent position is that the world is going to warm because of the stuff listed above. If you want to make the case that it's not going to warm, your argument becomes more complicated and uncertain, because you have to either explain away the basic physics or get into the ugly details of biogeochemical feedbacks.

Prev  2433  2434  2435  2436  2437  2438  2439  2440  2441  2442  2443  2444  2445  2446  2447  2448  Next