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Comments 46001 to 46050:

46001. Mark Bahner at 11:38 AM on 23 April 2013
       It's not bad
       

       Mark @344 - first off, almost all of the estimates in the Tol paper you reference are from the most conservative economists doing climate research (Nordhaus, Tol, Mendelsohn, etc.),

       Richard Tol is a conservative? That might be news to him! But OK...what do the "non-conservative" ("liberal?") economists say?

       Despite these underestimates, the paper still concludes that the net impact on GDP at 2.5°C will be negative, and we're already committed to about 1.5°C warming and still rising fast. So I'm not really sure what your point is.

       My point is that global surface temperature is rising by about 0.15 degrees Celsius per decade. So 2.5 degrees Celsius isn't likely to happen even in this century.

       In fact, per that paper, 1 degree Celsius warming from the present value was the peak of the positive effect on GDP. At 0.15 degrees Celsius per decade, that's more than 60 years in the future.

46002. Synapsid at 10:35 AM on 23 April 2013
       2013 SkS News Bulletin #8: Alberta Tar Sands and Keystone XL Pipeline
       

       I'd like to address the idea that stopping Keystone XL will result in the oil sands being left in the ground.

       The permit that the White House will accept or reject applies to the portion of the pipeline that actually crosses the US / Canada border, not to the rest of it.  Last year Canada exported more crude oil, mostly from the oil sands but some from the Bakken (which is mostly in North Dakota and Montana, not Canada) than in any previous year, and did so without the Keystone XL.  The oil was taken by truck from the fields to rail-loading terminals, and that whole part of the rairoad industry is being expanded rapidly.  This effort will grow anyway, but especially if Keystone XL is turned down.

       The TransMountain pipeline from Edmonton, Alberta to Burnaby near Vancouver is to see a second pipeline open by 2017, in the existing right of way; no approvals needed.  The resulting combined capacity will be 850 000 barrels a day, which is larger than the planned capacity for Keystone XL.  This pipeline supplies crude to refineries in Washington State.

       Enbridge is planning expansion of its existing network for delivering oil that will make its way to the Gulf Coast, aiming for a daily volume that, again, is larger than that planned for Keystone XL.

       The above two projects aren't getting the attention Keystone XL is, but they represent more than twice the capacity that pipeline would have, and they serve to carry Canadian oil to the US.

       The southern portion of the Keystone XL-associated, get the crude to the Gulf Coast, program is already under construction, and will help drain the backup at Cushing, Oklahoma, which has pushed down crude prices in the Midwest.  There is no Federal approval required, as the pipeline will operate within the US.  Currently, Midwest refiners are taking advantage of this low-cost crude to produce gasoline and diesel and sell those products, at world not Midwest prices, to Latin America and the Caribbean, just as Gulf Coast refiners would be able to do with crude delivered by Keystone XL.

       So:  Keystone XL would lower the price of transporting Canadian crude to Gulf Coast refineries but that oil is making its way there now and will continue to do so, in increasing quantity, Keystone XL or not.  Denying the permit will not keep the oil sands from being used--will certainly not result in the oil remaining in the ground.

       The way to keep oil in the ground is to reduce the demand for the products refined from it, not to convince ourselves that pushing up the transport price of crude will get people out of their cars.

       All this is taking attention away from the huge amounts of coal which is not only still being used in the US (though use is declining)  but which the US is exporting to Europe in large quantity.  Export terminals planned for locations on the coasts of Oregon and Washington will allow a great deal more coal to be sent to eastern Asia, if those ports are built.  Coal is a worse producer of greenhouse gases and other nasties than crude from the oil sands is.

       In view of all the above, focusing on Keystone XL seems to me to be a case of skewed priorities.  Coal is a worthier target but it isn't getting the attention it deserves.

       By the way:  tar is a refinery product, not a type of oil.  Canada's oil sands produce bitumen, which is heavy oil.

46003. Tom Curtis at 09:28 AM on 23 April 2013
       Global Warming: Not Reversible, But Stoppable
       

       Gingerbaker @36, if all anthropogenic emissions ceased, CO2 levels in the atmosphere would approximately halve over the course of 200 years as CO2 is absorbed into the ocean.  This reduction in CO2 concentration (shown in red above) approximately balances the increase in global temperatures due to the "commitment", ie, the increase as the Earth achieves equilbrium.  Therefore the two approximately cancell out, resulting in no change in temperature.  

       Over the following 10 thousand years, the CO2 will be removed from the ocean, drawing down CO2 levels to preindustrial levels.  The draw down is sufficiently slow that in one to two thousand years, when slow feedbacks have had time to reach equilibrium, the temperature will still remain at current elevated levels, ie, the draw down in CO2 will be approximately balanced by the increase in temperature resulting from such slow feedbacks as reduced albedo due to the melt back of icesheets.

       "Aproximately" in both cases is leaves a fairly wide margin and there may be a slight increase or decrease in the long term, and disparities of rate may result in significant temperature fluctuations.

       These scenarios are only relevant if we in fact cease net anthropogenic emissions.  As some emissions (eg, methane from rice paddies) are simpy unavoidable, that means an ongoing deliberate sequestration process.  Further, it is economically unfeasible to cease emissions in less than 20 years, and probably in less than 40 years.  Finally, such scenarios are only relevant if there are no large increases in natural emissions as a feedback to increased global temperatures, something some people argue has already started happening.

46004. Tom Curtis at 09:13 AM on 23 April 2013
       Renewable energy is too expensive
       

       J Dixon @4, according to wikipedia, in 2008 Germany emitted 786.7 billion metric tonnes of CO2, or 2.63% of global emissions.  Also according to wikipedia, by 2008 Germany has reduced its emissions by 22.4% relative to 1990 levels.  So, without its renewable energy commitment, Germany's emissions would have been more than 28%, or 0.73% of global emissions, higher.  That means in each year, Germany's emissions reductions represent at least 64 hours of global emissions for that year.  Over the rest of the century, assuming German emissions remain constant relative to world emissions, that represents  5,500 hours of delay in global emissions.  That is, global warming will have been delayed by German emissions reductions, if they make no further reductions, by  7.5 months.

       According to an Australian Government report, photovoltaic cells represent 11% of Germany's total renewable energy production.  As Lomberg refers explicitly to PV production, that means the emissions reduction involved represents a delay of 605 hours.  To reduce that to 37 hours, Lomborg would need to assume an average global emissions over the course of the 21st century to be over 16 times current levels, or with a linear growth model model, emissions at the end of the century to be 32 times current levels.

       So, all Lomborg needs to do is assume:  

       1) Emissions growth will not be curtailed,  growth in global emissions at ten times the rate projected by the IPCC; and

       2) Emissions growth will in fact be about ten times greater than projected by the IPCC for a BAU scenario. 

46005. grindupBaker at 08:07 AM on 23 April 2013
       Global Warming: Not Reversible, But Stoppable
       

       @Gingerbaker #36. Yes. Dr. Trenberth states the estimate of 0.9+/-0.4 wm**-2 at present time. In my layperson opinion oceans S.B. stated even more profoundly, if only to clarify for the unbiased but unknowledgeable members of public. "Global Warming" IS the increasing trend of heat in the ocean. Surface temperatures are a proxy measurement, subject to periodic vagaries. I think it's misleading to consider that "Global Warming" ends when the TOA radiation becomes balanced. I think it ends when the oceans regain whatever is their natural temperature gradient from surface to sea bed, and then when TOA radiation becomes balanced. This because oceans have ~40 times heat capacity of all freshwater and ~550 times heat capacity of all air + land (as deep as relevant). If, as example, +2.8 degrees C was needed to balance TOA radiation then I would think by simple logic that "Global Warming" ends when the oceans are +2.8 degrees C warmer, in the absence of that warming changing the forcing of course.

46006. John Hartz at 06:55 AM on 23 April 2013
       Renewable energy is too expensive
       

       @jdixon1940 #4:

       The following letter-to-the-editor (LTE) was published by the New York Times yesterday (Apr 21, 2013). It rebutes an Op-ed previsously published by the Times that advocated for the replacement of coal by shale gas in China. The LTE is equally applicable to the Lonberg Op-ed in my opinion.

       To the Editor:

       In “China Must Exploit Its Shale Gas” (Op-Ed, April 13), Elizabeth Muller argues that shale gas can replace coal in China. However, China’s coal power capacity is already twice that of America’s, and will be triple by the time China begins to fully exploit its shale gas reserves in 10 years. By then it will be too late and expensive to replace these coal plants, most built in the last decade, as they will still be young, efficient and cheap. Gas in Asia is still expected to be two to eight times more expensive than coal.

       Gas is also a carbon-intensive fuel, even if less so than coal, and substituting it for coal will not get us the reductions necessary to stabilize the climate. Seriously attacking greenhouse gases in China, and globally, will require deploying carbon capture and storage for existing and new coal (and gas) plants. Otherwise, it’s game over for climate change.

       ARMOND COHEN
       Executive Director
       Clean Air Task Force
       Boston, April 15, 2013

46007. william5331 at 06:45 AM on 23 April 2013
       Arctic methane outgassing on the E Siberian Shelf part 1 - the background
       

       Two points.  1) Methane is only 25 times as potent a green house gas if it is being given out evenly over the years.  With an accelerated rate of release, it's potency approaches 140 times that of Carbon dioxide.  The rate looks to be accelerating now.

       http://mtkass.blogspot.co.nz/2013/03/the-real-strength-of-methane.html

       2) There is a reasonable chance that a sudden release of methane from under continental glaciers would not show up in bubbles in Antarctic and Greenland ice cores as methane.  The top 70 or so meters of accumulating ice sheets remains in difusion contact with the atmosphere and methane, with it's 7 year half life is reletively quickly oxidized.  An ice core could show a sudden methane pulse from under retreating ice sheets as Carbon dioxide.

       http://mtkass.blogspot.co.nz/2011/09/continental-glacier-meltdown.html

46008. John Hartz at 06:10 AM on 23 April 2013
       Renewable energy is too expensive
       

       @jdixon1940 #4:

       You have an excellent sense of smell. It is very disheartening to see that the USA Today choce to post an Op-ed by Bjorn Lomberg on Earth Day. That it and other MSM outlets in North America have done so illustrates the power and reach of the fossil fuel industry and its allies. (Think advertising revenues.)

       I'll let my more-learned SkS colleagues respond to your specific concerns about Lomberg's tome. Perhaps we can persuade Dana to crank out a formal critique article. 

46009. Andy Skuce at 06:09 AM on 23 April 2013
       Global Warming: Not Reversible, But Stoppable
       

       Gingerbaker: Every report I remember reading has implied that the 0.8C global temperature increase we have seen is by no means all that we can expect 400 ppm CO2 to deliver.

       Indeed, that's what the blue line in Figure 1C shows; albeit for 380ppm, a level that we have already passed and may not see again for centuries or even millennia.

       As I understand it, it is not that the heat in the deep ocean will come back, it is more like the deep sequestration of surface warming, as we have observed it over recent decades may not continue. In other words, the air conditioning currently provided to us by the oceans may falter.

46010. jdixon1980 at 05:26 AM on 23 April 2013
       Renewable energy is too expensive
       

       Questions for the knowledgeable:

       Bjorn Lomborg has a column today in USA Today where he is promoting more fracking as the best approach to global warming.  In the column he claims that "German taxpayers have poured $130 billion into subsidizing solar panels, but ultimately by the end of the century, this will postpone global warming by a trivial 37 hours."  http://www.usatoday.com/story/opinion/2013/04/22/earth-days-good-news-column/2101327/  I have been reading extensively (at least for a layman) on the subject of global warming for about a year now, and this is the first I have heard of anyone speaking in terms of "postponing" global warming by a certain amount of time as a measure of the impact of an emissions reduction, and so I was immediately suspicious of the claim.  I tried googling "postponing global warming 37 hours" and only came up with hits to Bjorn Lomborg's statement itself (today's USA Today column was not the first time he had made the statement), with no analysis or explanation.

       Does anybody have a clue as to what Lomborg might even mean quantitatively?  Is he simply suggesting that the amount of emissions reductions in Germany due to solar panels, all other human activity remaining unchanged (my vague understanding is that the possibility of non-linear feedbacks would generally require assuming that all other countries' emissions remain fixed before one could hope to meaningfully predict the impact of one country's reduction in terms of a time lag at the end of the century), would theoretically only reduce the slope of the current long-term temperature trend so as to reach on January 1, 2100 the global average surface temperature that would have been reached 37 hours earlier if not for the reduction in German emissions?  Or perhaps that, integrating theoretical thermal disequilibrium curves in two most-likely scenarios projected out to the end of the century, one with the current German emissions reductions due to implementation of solar, and one without, and fixing all other human activity in both scenarios, it would take until January 1, 2100 for the Earth's total heat content to increase by the amount that it would have increased 37 hours earlier without the German emissions reductions?  

       Assuming he means one of those things, is there any merit to his claim?  

       Since I am not a climate scientist, but rather a patent attorney with a mechanical engineering background that is growing staler by the year, I hesitate to call BS on Lomborg's claim, but it smells very fishy to me, so I would be interested to hear what people here have to say.  

        

46011. Gingerbaker at 04:33 AM on 23 April 2013
       Global Warming: Not Reversible, But Stoppable
       

       According to Aradhna Tripati, a UCLA assistant professor in the department of Earth and space sciences and the department of atmospheric and oceanic sciences:

        

       “The last time carbon dioxide levels were apparently as high as they are today — and were sustained at those levels — global temperatures were 5 to 10 degrees Fahrenheit higher than they are today, the sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland,”

        

       This does not seem to jive with the Science article which asserts that if CO2 emissions were to stop today, the global temperature would not go up. Every CO2 vs global temp graph I can remember seeing indicates that that there is a significant time lag between CO2 concentration and global temp.

        

       We now know that 90% of the heat imbalance caused by AGW is in the deep oceans.  This heat, along some time scale, will eventually become unsequestered and actually increase temperatures, yes?

        

       Every report I remember reading has implied that the 0.8C global temperature increase we have seen is by no means all that we can expect 400 ppm CO2 to deliver.

        

       Now, one article in Science comes out, and we are supposed to believe its assertions?  This is not making sense to me.

46012. shoyemore at 04:09 AM on 23 April 2013
       Major PAGES 2k Network Paper Confirms the Hockey Stick
       

       Roger D #3

       the point is that the flatish average annual surface temperatures mislead the willing-to-be-misled into thinking that no damage is being done between up-ticks in avg. surface temperature.

       A very good description of boiling frog syndrome.

       The premise is that if a frog is placed in boiling water, it will jump out, but if it is placed in cold water that is slowly heated, it will not perceive the danger and will be cooked to death.

       http://en.wikipedia.org/wiki/Boiling_frog

46013. keithpickering at 02:54 AM on 23 April 2013
       Major PAGES 2k Network Paper Confirms the Hockey Stick
       

       Not just the Arctic. The world as a whole is a whopping 0.2°C warmer during the most recent 30-year period (1983-2012) than during 1971-2000, in spite of a 60% overlap in dates.

46014. Bob Loblaw at 02:33 AM on 23 April 2013
       The science isn't settled
       

       engineer:

       I don't think it is correct to just call it a technical problem. To follow on Glenn's comment, when you are trying to model today's climate, you can get away with saying "this is what the vegetation is", or "this is where the ice sheets are", etc., and simply measure the required input parameter for the climate models. You can even do that to a certain extent for past climates, as there are proxies that will give you an indication of vegetation cover, ice cover, etc. Understanding why the vegetation, ice, etc. are the way they are is a help, but not an absolute necessity to be able to develop a good understanding and a reliable model of current climate.

       Contrast that with the future: we can't measure the vegetation cover or ice sheet distributions - we have to model them. But uncertainties in how vegetation responds to a changing climate is not a problem that necessarily requires increased understanding of climate dynamics - it is a problem of understanding vegetation dynamics. Predicting something like future aerosols not only requires estimating future levels of existing emission sources (which requires economic modelling), it also requires assumptions of what future combustion technology might produce, and what social policy choices might be made. You can start by assuming they won't change, but proper policy decisions require that you also evaluate what might happen if they do change (using realistic ranges of possibiliites).

       It's a classic multi-disciplinary issue.

46015. jdixon1980 at 02:27 AM on 23 April 2013
       The History of Climate Science
       

       Neilrieck @ 15, I would point out to those friends and relatives that Weart's interactive html history is divided into subtopics addressed in many bite-sized "essays" (his term) that can easily be read in a single sitting and don't have to be read in any particular order, and the writing is excellent.  I find the Weart essays (which I downloaded as PDF's to my e-reader for reading on my daily commutes) to be page-turners, albeit speaking as someone who was already interested in this subject.  Still, this post adds something in that, as a comprehensive treatment, it is far more condensed than the entirety of Weart.  

46016. John Hartz at 02:24 AM on 23 April 2013
       The science isn't settled
       

       @engineer

       Here's a concise descpriton of how global climate models evolved and function.

       By the mid-1990s, it was possible to investigate the causal mechanisms behind changes in Earth's climate using relatively sophisticated mathematical models of Earth's climate. These models solved the same complex equations of atmospheric physics that numerical weather prediction models did. But they also took into account components of the climate system other than the atmosphere, including the oceans, the continental ice sheets, and even life on Earth (collectively known as the "biosphere"), and they attempted to account for the physical, chemical, and biological interactions among these components. Of course, no theoretical model is ever perfect; even the best model is only an idealization of the actual world. There are always real-world processes that cannot be captured—for example, in the case of a numerical climate model, individual clouds or small-scale air currents like dust devils—that are simply too small for the model to resolve. The key question is, can the model be shown to be useful? Can it make successful predictions?

       Source: How Do We Know Humans are Responsible for Global Warming? by Michael Mann, WeatherUnderground, April 22, 2013

46017. jdixon1980 at 02:17 AM on 23 April 2013
       Global Warming: Not Reversible, But Stoppable
       

       Small typo: I think there was supposed to be a "(C)" after temperature change in the Figure 1 description.

       Moderator Response:

       [AS] Thanks, fixed.

46018. Martin Lack at 02:08 AM on 23 April 2013
       Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years
       

       Bill Everett @22, 52, and 74.

       I am 100% with you on your persistent advocacy for use of the 'thermostat' analogy (rather than 'control knob').  As you have pointed out, promoting the view that atmospheric CO2 acts as a thermostat reinforces the reality that there is a great deal of inertia in the climate system.  Without this, 0.8 Celsius for 40% increase would imply 2.5 C for double. However, since there is inertia in the system, we are heading for 3 to 6 C for double pre-Industrial CO2 levels.  Therefore, given the disruption being caused by 0.8 C, I really do not understand how anyone can remain complacent about where humanity is taking this planet...  To mark Earth Day 2013, Michael Mann has posted an excellent extract from his book, The Hockey Stick and the Climate Wars, on the Weather Underground website today:

       http://www.wunderground.com/earth-day/2013/how-do-we-know-humans-are-responsible-for-global-warming

46019. dana1981 at 01:55 AM on 23 April 2013
       Major PAGES 2k Network Paper Confirms the Hockey Stick
       

       Roger @3 - bear in mind that the Arctic is now considerably warmer than the 1971–2000 average.

46020. Roger D at 01:49 AM on 23 April 2013
       Major PAGES 2k Network Paper Confirms the Hockey Stick
       

       Thanks for the post. The study's finding that "The Arctic was also warmest during the twentieth century, although warmer during 1941–1970 than 1971–2000 according to their reconstruction." is not what I would have expected. However, looking at the natural climate/ temperature indicator of July sea ice extent reconstructed back to 1870 a smoothed-line fit starts to curve downward at about in the 1941-1970 period. The ongoing loss of ice in a region that is on average not wamer in the latter part of 60 years (1941-2000) seems like a good reminder that it does not take a constant yeaer on year increase to cause pronounced natural response over large areas. Arctic sea ice is an easy to visualize indicator but as Sks and others have shown there are numerouse others. For me as a layman the point is that  the flatish average annual surface temperatures mislead the willing-to-be-misled into thinking that no damage is being done between up-ticks in avg. surface temperature.

46021. John Hartz at 01:43 AM on 23 April 2013
       2013 SkS Weekly News Roundup #16B
       

       @jyushchyshyn:

       If Canadians are truly concerned about the global environmnet, they will demand that the mining of the tar sands bitumen be stopped.  

46022. Glenn Tamblyn at 20:47 PM on 22 April 2013
       The science isn't settled
       

       engineer

       There are a range of potential feedbacks that are hard to quantify because each one of them is an entire field of study in its own right. For example:

       Vegetation response. Will the Amazon for example remain a rainforest? Become a drier forest? Grassland? Each has different implications for carbon cycle sinks and sources, surface albedo and evapotranspiratioin patterns.

       Ice sheet retreat. What are the dynamics of any decline in Greenland ice sheet cover, WAIS, EAIS? Timing and extent of this for any particular level of GHG forcing again has significant impacts on albedo.

       Ocean Circulation. Major ice sheet melt might impact on the Thermo-Haline circulation that drives ocean currents - there is some evidence this was a part of what happened during the warming from the last Glacial Maximum. If ocean currents change, this can alter the distribution of where heat is transported to. Thus cloud patterns, climate zones, all sorts of things.

       Methane release from Permafrost. How fast will permafrost melt and where? Will this produce more aerobic or anaerobic decomposition of the defrosted organic matter, influencing whether carbon outgasses as Methane or CO2. Higher rates of methane release will have a greater short term warming effect than if it is released as CO2 even though the longer term impact will be the same as ultimately the methane is oxidised to CO2

       This stuff is too hard to do at a theoretical level and even modelling involves stacking models on models. Thats why paleo climate studies are an important reference point. That is what climate has actually done in other circumstances.

46023. Miriam O'Brien (Sou) at 17:09 PM on 22 April 2013
       Major PAGES 2k Network Paper Confirms the Hockey Stick
       

       It's great that we are now getting more detailed information about past conditions at the regional level within the context of the whole world.  Paleo research seems to be progressing exponentially.  It will help us better understand what humanity is facing now, even though we've never faced conditions like this before.

46024. engineer8516 at 14:17 PM on 22 April 2013
       The science isn't settled
       

       @ Bob, It's just a miscommunication on my part. I couldn't think of how to word my question that's why I ended up asking that subjective question in the beginning.

       I'm not questioning the reliability of models...models are used all the time like CFD. The limitations in CFD is due to budget and computer power. I was wondering where the uncertainty in climate was mainly coming from like the uncertainty in equilibrium climate sensitivity from double co2. was it because of theory or tech? but you guys already answered my questions that the it's due to limits on current tech. thanks.

46025. jyushchyshyn at 14:04 PM on 22 April 2013
       2013 SkS Weekly News Roundup #16B
       

       If Canada wants people to accept Keystone XL and the oil sands, it must show the world that it takes the environment seriously. The carbon pricing deadlock is indeed hurting Canada's economy.

46026. Maggnum at 13:46 PM on 22 April 2013
       Major PAGES 2k Network Paper Confirms the Hockey Stick
       

       I look forward to seeing the results of the ocean temperature recreations. I hope they are able to include and take into account the deep ocean warming, especially as it relates to the paleo-climate of the past 2000 or so years.

46027. scaddenp at 13:39 PM on 22 April 2013
       The science isn't settled
       

       There can be quite a gap between a qualitiive description of a process (eg think ENSO) and a computer model able to capture it, but a big factor is limitations on the measurement system and time length of good data. (eg for Argo we have only 10 years so far). If you want quantitive models, you need accurate measurements. As far as I know, aerosol measurements are still short of modellers hopes.

46028. Bob Loblaw at 13:36 PM on 22 April 2013
       The science isn't settled
       

       engineer:

       ...it is odd that you interpret my somewhat-rhetorical questions as "defensive", when you yourself began with somewhat-rhetorical questions. Granted, it can be difficult to read tone into a written comment, but you started off with what semed like a "gee, this should be so simple if it is well-understood" sort of comment. It reminded me of the following XKCD comic:

       

        

       Perhaps a better start would have been to pose the question something like "What part are understood, and where does uncertainty in this value come from?" (as you are beginning to ask now) rather than implying it can't be "well understood" because it can't be predicted as easily or accurately as the simple examples you gave. The question relates to the How reliable are climate models? discussion, where you can find out much more about how the reliability is examined.

       In a system as complex as global climate, you can have uncertainty in predictions due to uncertainty in the measurement of input variables, even if the physics of those portions of the system are well understood at a theoretical level. For example, consider the effect of aerosols. The radiative effect of a specific aerosol can be modelled quite well, given sufficient data about the size distribution, physical, and optical properties of the aerosol, etc., but getting detailed measurements of those physical properties over huge swaths of the atmosphere over sufficient time can be extremely difficult. Even if the technology exists (e.g AERONET), budgets aren't infinite and measured data is incomplete.

       Then take that difficulty into the future, and try to predict exactly what the future aerosol state will be. It's not that it's hard to predict what a particular aerosol will do - it's hard to predict exactly what will be up there.

46029. engineer8516 at 13:23 PM on 22 April 2013
       The science isn't settled
       

       scaddenp, last question. when you say "a lot less confidence quantifying some of those processes accurately" is that due to technology limitations (computing power) or theory? thanks

46030. engineer8516 at 13:05 PM on 22 April 2013
       The science isn't settled
       

       thank you. that explained a lot.

46031. scaddenp at 13:04 PM on 22 April 2013
       Climate's changed before
       

       Kristjan, I think it is expected to be more or less constant within a particular range of temperature/states. Ie once all the ice is melted, then the albedo feedback becomes a lot more subtle. Ditto, on an iceball earth, you would expect sensitivity to be high at point where ice melts at tropic.

46032. scaddenp at 13:00 PM on 22 April 2013
       The science isn't settled
       

       Good question. As far as know, for ECS you need to know where feedbacks will stabilize. Ie if you perturb CO2, where does T settle when all feedbacks are in equilibrium. Now I think you could say there is a lot of confidence about what the feedbacks are, a lot of confidence about how the feedbacks work, but a lot less confidence about quantifying some of those processes accurately. (eg the complex dance of aerosol, water vapour, temperature and clouds).

46033. engineer8516 at 12:36 PM on 22 April 2013
       The science isn't settled
       

       @ bob, relax man. I'm not sure why you're so defensive.

46034. engineer8516 at 12:33 PM on 22 April 2013
       The science isn't settled
       

       so is the uncertainty mainly the result of the lack of theoretical understanding or the lack of more sophisticated technology (e.g. better satellites)? How much of the uncertainty in equilibrium climate sensitivity is from a lack of theoretical understanding?

46035. Kristjan at 12:16 PM on 22 April 2013
       Climate's changed before
       

       Is climate sensitivity a constant or dependant on other variables? Meaning, as the earth gets warmer (or cooler) does the climate sensitivity stay the same or increase/decrease (or maybe it's dependant on some other variables as well)?

46036. Bob Loblaw at 12:15 PM on 22 April 2013
       The science isn't settled
       

       engineer:

       I will answer the question with more questions.

       1) you are selecting some very simple examples from heat transfer (mixing two different quantities, at two temperatures, of the same fluid) and the properties of materials (a single Hookian spring). They are high-school "engineering", not engineering school engineering. How simple is it to calculate the peak spark plug tip temperature in an F-1 racing engine at the end of a straight-away on the 72nd lap of the race at [pick a course] on a hot summer afternoon - from first principles? Would you consider the design of racing engines to be an area that is not well understood?

       2) I would think that brige-building, slope stability calculations, etc. would be considered well understood engineering areas. Why does standard design practice often  use relatively large (e.g. 2 or greater) factors of safety? Surely any factor of safety greater than one will do? (For those not familar with the term, a design factor of safety of 2 means that the design strength is twice the needed strength.)

       3) a standard physics example of things that are difficult to calculate is the n-body problem. Does this difficulty in calcuating an exact answer mean that our understanding of gravity is not well understood?

       4) If you wish to continue the discussion, would it be better if we did so without rhetorical questions?

46037. scaddenp at 11:39 AM on 22 April 2013
       The science isn't settled
       

       Understanding the feedback processes well does not necessarily mean that crucial numbers can be extracted easily. Things like - amount of aerosol, full thermal description of ocean, cloud vapour response etc. The Argo network, better satellite measurement, GRACE and so on eventually allow for more precision.

46038. Bob Lacatena at 11:30 AM on 22 April 2013
       The science isn't settled
       

       engineer,

       I think that the problem is that you are trying to compare climate science with the hardest of hard sciences -- engineering sciences, like classical physics.  Many other sciences are not nearly so precise, including quantum physics, biology, neuroscience, medicine and more difficult chemistry (especially the state of chemistry before the development of the electron microscope).

       Would you consider all of these fields to be "not well understood?"

46039. barry1487 at 10:30 AM on 22 April 2013
       Climate Sensitivity Single Study Syndrome, Nic Lewis Edition
       

       Albatross,

       I often point out to people ('skeptics', usually) the error of relying on a single study, and most often it is with climate sensitivity estimates. It's good to see that caution explained here. I'm not trying to bait anyone. After reading at several places in the article that one should not lean on a single study, it simply leapt out at me that this had been done to make a point about uncertainty on climate sensitivity estimates from intermediate complexity models. Is it inappropriate to apply the same standard to this question as it is to climate sensitivity estimates?

46040. John Hartz at 09:00 AM on 22 April 2013
       2013 SkS News Bulletin #8: Alberta Tar Sands and Keystone XL Pipeline
       

       @jyushchyshyn:

       If the Keystone XL were to be approved, the refined product would be sold to the highest bidder -- most likely China.

       The primary cause of manmade climate change is the burning of fossil fuels. Keeping the reamaining deposits of fossil fuels in the ground ensures that they will not be burned. 

46041. engineer8516 at 08:50 AM on 22 April 2013
       The science isn't settled
       

       I have some questions related to this that have been bothering me for a while.

       This article isn't about equilibrium climate sensitivity from double co2, but I'll use that for my point. the IPCC report gives a value of 2 to 4.5 C with a likely value of 3C and confidence level of greater than 66%. Less than 1.5C has a confidence level of less than 10%.

       This is where I'm confused, for very well understood fields, such as heat transfer, equilibrium values can be calculated with a high degree of accuracy. For example, we can calculate the equilibrium temperature that a mixture of 1lb of 80F water and 1lb of 60F water would reach. Or in vibrations, how much a spring would stretch when it reaches rest from a hanging mass.

       Obviously these are simple examples, but the point is that equilibrium values can be calculated with a high degree of accuracy in well understood fields certainly. The 5% not understood in climate looks like it has a pretty significant impact on the calculation of an equilibrium value. So why is the topic of climate considered well understood? Thanks

46042. scaddenp at 08:45 AM on 22 April 2013
       The science isn't settled
       

       Thinking on this further - that statement is not "an essential part of AGW theory". It is an outcome of the current theory of climate. Falsifying climate theory is same as for any other theory - the theory must change if predictions derived from the theory do not match observation with both the limits of prediction and limits on observation. One of the problems with claims to  falsify climate theory is that they falsify predictions that climate theory does not make.

46043. jyushchyshyn at 07:29 AM on 22 April 2013
       2013 SkS News Bulletin #8: Alberta Tar Sands and Keystone XL Pipeline
       

       If you have a plan not to use the oil which Keystone would deliver, why do you need Obama to reject it? Why not let the market stop it. Global warming is caused by consumers, not suppliers.

46044. sidd at 06:56 AM on 22 April 2013
       Global Warming: Not Reversible, But Stoppable
       

       1)Byalko (2012) get the formula from a regression of T and CO2 for last 780Kyr

       2)The reference [19] to Byalko (2010)

       "...climate perturbations increase proportionally to the time derivative of temperature [19] ..." is a very general discussion of basins of stability, and does not convince me yet.
       

       That said, i do like Byalko (2012) teasing the 40Kyr periodicity out of a simple model.
       

       sidd
       

       
       

46045. scaddenp at 06:00 AM on 22 April 2013
       The science isn't settled
       

       Further to 6 - measure the change in surface radiation or OLR and then find that is inconsistent with calculated change due to increased GHG.

       You could also add - models based on AGW forcing would not reproduce past climate within the errors of model and forcing. You might think from arguments about paleo that this isnt a strong argument, but note that you can use this method to disprove alternative hypotheses like "the sun explains it all". "GHG changes have no effect".

       I think that the easy practical ways to disprove AGW were all tried long ago and failed with explains your problem with find them.

46046. grindupBaker at 04:48 AM on 22 April 2013
       Global Warming: Not Reversible, But Stoppable
       

       Bill Everett @26 equilibrium temperature "Teq =0.98(C - 280)" must have some elements missed, in life haste possibly. I just readily found "http://www.oocities.org/marie.mitchell@rogers.com/Climate_Notes.html" with a bunch of familiar looking numbers and formulae I recall from Drs. Randall, Trenberth, Hansen & others video lectures the last few weeks like the Watts m**-2 forcing (no feedback) = 5.35*LN(CO2/CO2<base>). I'd suggest searching each of those to find the agreement from expert sources before using, but that site doesn't seem to be pushing an agenda, no diatribes just some related quoting after the numbers.

46047. Tom Curtis at 03:53 AM on 22 April 2013
       The science isn't settled
       

       h-j-m @61, each of the following methods states a condition which has been experimentally tested and is known to be false, but which would falsify the theory if true.

       Method 1:  Warming of land surfaces equal warming of oceans, showing the change in temperature is caused by changes of SST rather than forcing.

       Method 2:  Stratosphere warming as troposphere warm showing the warming to be dominated by changes in solar radiance.

       Method 3:  Meso-sphere and thermosphere increasing in volume (showing that they are warming) as troposphere warms.

       Method 4:  Warming exists even though anthropogenic forcing factors remain constant.

       Method 5:  Known natural forcings are larger than known anthropogenic forcings.

       Method 6:  Width of anthropogenic GHG absorption spectra in outgoing LW radiation  unchanged over time.

       I am sure the list can be extended substantially, particularly once we start applying statistical tests rather than the crude method of simple falsification.  It should be noted that if there were reasonable doubt about the theory, competing natural explanations would not have been falsified (they all have been).

       Now, here is the real challenge.  Find a theory that contradicts the claim that is both falsifiable and has not already been falsified.  It is a challenge "skeptics" seem to avoid like the plague.

46048. Albatross at 03:52 AM on 22 April 2013
       Climate Sensitivity Single Study Syndrome, Nic Lewis Edition
       

       Hi Tom @33,

       Either Dana or I will respond to your post, but I for one would like to investigate this more closely before doing so.  Thanks for your patience.

46049. Tom Curtis at 03:36 AM on 22 April 2013
       Climate Sensitivity Single Study Syndrome, Nic Lewis Edition
       

       Albatross @32, Dana correctly describes Lewis as claiming that the mode (most likely climate sensitivity) of his result is identical to the mode of Aldrin et al, but then incorrectly calls that claim a simple misrepresentation.  It is not a misrepresentation.  The modes of the two studies are identical to the first decimal point.  It is, however, misleading in that it is an apples and oranges comparison.  Given that other studies report the mean, in comparing with other studies the mean should be reported, or it should be made absolutely clear that not only are you reporting the mode, but that the authors you are reporting on reported the mean.

       Dana then engages in his own apples and oranges comparison, stating (correctly) that  Aldrin et al reported a climate sensitivity of 2 C, without stating that it was the mean.  As the preceding paragraph mentioned only modes of the climate sensitivities, contextually that indicates that Aldrin reported the mode, which is false.  It thereby creates a misleading impression.  It further misleads because the requirement to be responsive is ignored.  It appears that Dana is contradicting Lewis, whereas he is merely reporting a different value.  As it is his clear intention to rebut Lewis, readers should be able to reasonably expect that his counter evidence will be responsive.

       Further, the claim that the 1.6 C modal value appears nowhere in the paper is at best an evasion, and at worst directly untrue.  The figures are part of the paper, and the information in the figures therefore appears in the paper.  As such, the modal value of the main analysis, which is easilly identified from the figures, appears in the paper.  Dana is welcome to show that the figure does not show a modal value of 1.6 C if he likes, but simply pretending it is not part of the paper is not appropriate.

       It would be easy to correct the article by removing these flaws.  The discussion could be replaced with an informative discussion of the reason climate sensitivity studies report means (or central estimates) and why reporting only the mode in making those comparisons is misleading.

46050. h-j-m at 02:47 AM on 22 April 2013
       The science isn't settled
       

       I take that this sentence

       "anthropogenic greenhouse gases are causing most of the observed global warming"

       is an essential part of AGW theory.

       Can someone please offer a practical method of how to disprove it?

       Unfortunately so far I failed to find one.

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