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Comments 33801 to 33850:

33801. michael sweet at 11:27 AM on 1 October 2014
       How did the UK grid respond to losing a few nuclear reactors?
       

       Keith,

       According to your first link, wind costs 61.4$/MWh while nuclear is 71.4$/MWh.  Nuclear is over 10% more expensive. 

       It is interesting that the Lazard report for investors shows decrease in wind costs but your sources show flat costs, hopefully someone more informed than I will tell us the difference.  Certainly  much more wind is being installed now than was installed in the past.  Presumably that is because costs went down.

       I am not going to post again, it is my experience that nuclear discussions are a waste of time and clutter up the comments board.   

33802. michael sweet at 10:59 AM on 1 October 2014
       How did the UK grid respond to losing a few nuclear reactors?
       

       Ed,

       Please provide data on a nuclear power plant that is economic when it load follows.  It is the responsibillity of nuclear supporters to provide their data, not mine to look for it.  If France, a government agency that has no public budget, is your best example I think you have made my case.

       Load following and economic are two completely different matters.  Some nuclear can theoretically follow load a little, but all are uneconomic when they are not working all out all the time.  They are currently uneconomic when they are running all out all the time.  It will lower their cost benefit if they run only part of the time.

       Reading more in the Lazard report I linked before (an investment white paper that is presumably unbiased), I see that the most expensive wind in the USA is cheaper than the cheapest nuclear. Unsubsidized wind: $37-81/kwh, unsubsidized nuclear 92-132 $/kwh (page 2) (load following nuclear would be much more expensive).   

       Cheap wind is about 1/3 the cost of cheap nuclear.  Wind is dropping in price at 10% plus per year.  Nuclear's price keeps going up.  Please provide economic numbers that show nuclear can produce power as cheap as renewables.  I have provided data to support my argument, it is your responsibility to provide data to support your argument.

33803. keithpickering at 10:46 AM on 1 October 2014
       How did the UK grid respond to losing a few nuclear reactors?
       

       @michael sweet.

       If you've heard the "too cheap to meter" claim your entire life, then you've been misled your entire life. That quote, from Lewis Strauss, refers to fusion power, not fission.

       Regarding the cost of nuclear energy, see EIA's LCOE here:

       http://www.eia.gov/forecasts/aeo/electricity_generation.cfm

       ... which shows nuclear comparable to wind, even under the (false) assumption that both generator types have identical lifetimes. 

       Or see a composite of LCOE studies collected by the Open IE project's Transparent Cost Database here: 

       http://en.openei.org/apps/TCDB/transparent%20cost%20database

       ... which again shows nuclear comparable to wind, and is based on literally dozens of peer-reviewed sources. So if nuclear is too expensive, so is wind, by the same token.

       For actual historical costs of wind, as installed, here's the National Renewable Energy Lab:

       

       ... and here's Lawrence Berkeley Lab:

       

       ... and also see IPCC 2011, figure 7.20, confirming these sources for both Denmark and the US:

       http://srren.ipcc-wg3.de/report/IPCC_SRREN_Ch07.pdf

       ... and also see also IPCC 2011 figure SPM.6, which confirms that the learning curve for wind has hit bottom and bounced:

       http://www.ipcc.ch/pdf/special-reports/srren/SRREN_FD_SPM_final.pdf

       All of these peer-reviewed sources agree that wind has hit bottom some years ago.

       The lack of interest in new nuclear build in the US is due to regulatory uncertainty and high entry cost. Nuclear plants cost billions to build, which effectively closes off entry to all but a handful of the largest utilities. The enormous amounts of energy produced will eventually make up for that and more, but I agree that a move toward small modular reactors is needed. It's incorrect, however, that there are no private investors for nuclear: all five nuclear reactors currently under construction in the US obtained private financing, and there are a number of VCs (including Bill Gates, for one) who are funding leading-edge startups in the nuclear industry.

       You ask, "Where is the utility scale nuclear plant that can load follow?" and the answer is, every nuclear plant that has ever been built can load follow. In France, which has a mostly-nuclear grid, nuclear plants load follow routinely. In the US they don't, but that's an economic decision, not a technilogical requirement. It's simply cheaper to operate the grid when nuclear plants are in baseload mode (and it's also better for the climate too, because it avoids the maximum amount of GHG emissions that way).

       Moderator Response:

       [RH] Adjusted image size down to 550 px wide.

33804. ed leaver at 10:25 AM on 1 October 2014
       How did the UK grid respond to losing a few nuclear reactors?
       

       Michael, Google is your friend. Try "load following nuclear". See Responding to System Demand. Things are indeed a bit complicated with Pressurized Water Reactors, but in practice quite doable. See Nuclear Power in France and scroll to "Load-following with PWR nuclear plants". Boiling Water Reactors are inherently easy load followers as moderator density may be moderated by pumped recirculation rate. They are usually designed specifically for load following although of course are still most economic as base load providers. Canadian CANDU reactors also do rather well. 

33805. Paul W at 10:12 AM on 1 October 2014
       How did the UK grid respond to losing a few nuclear reactors?
       

       While this argument is interesting it seems to be a bit circular.

       Currently we are playing "lower fossil fuels". Current renewables can do that.

       There is a greater game however which gets seen when you consider that at 400 ppm CO2 3 million years ago we did not have ice sheets.

       Given that Greenland now has reported a doubling time of ice loss of less than 5 years and that an end to the world economy happens at 1 metre of sea level rise, Hansen 2012 has reported 1 metre sea level rise at sooner than 2050.

       At that point the cost of adaption will exceed what we can spend on mitigation and we have lost control and are headed towards an end to civilisation.

       It seems to me that the anti nukes see nuclear power as a greater threat than fossil fuels.

       What can be said about the cost of nukes in the western world is that a very large part is due to extreme regulations due to the anti nuke emotions. 

       I think we need to be playing end fossil fuels which will needs nukes both 3rd and 4th gen as well as an enormous push for renewables.

33806. Rob Honeycutt at 09:39 AM on 1 October 2014
       People's Climate March NYC photos
       

       Russ...  You're leaving out all the other information in the article. That was just the conclusion of one estimate. Why do you leave out (or invalidate) all the other estimates in the article?

33807. Russ R. at 09:07 AM on 1 October 2014
       People's Climate March NYC photos
       

       How many people really showed up to the People's Climate March?

       "about 125,000"

       But what's the harm in a bit of exaggeration for the cause?

33808. michael sweet at 08:42 AM on 1 October 2014
       How did the UK grid respond to losing a few nuclear reactors?
       

       Keithpickering,

       I have heard promises of nuclear energy too cheap to meter my entire life, and that is starting to be a long time.  Please cite some peer reviewed data to support your claims.  I currently have only your unsupported word. Meanwhile, we see daily that investors are putting up money for wind farms all around the world.  Solar is currently cheaper for me to install on my house than grid.  Utility scale solar plants are being built. 

       According to Lazard (click link half way down the page), from 2009 to 2014 the cost of wind energy went down 58%.  Please cite data to support your wild claim that wind costs have been constant since 2004.  Widespread investor interest demonstrates your claim is false.

       Where are the investors who want to build your nuclear plants?  Only governments are building nuclear and their track record is bad.  In Florida, where I live, Nuclear plants can be billed ten years before they generate any power.  We are currently paying $1.5 billion dollars for a plant where they never broke ground (it has been decided it is uneconomic to build).  Where is the utility scale nuclear plant that can load follow?  What did it cost to build and run?  Oh wait, it has never been built and exists only in your imagination.  Come back when you have built a pilot plant.  That will take at least ten years, which is too long to help.  Wind and solar are being built now.

33809. Tom Curtis at 08:36 AM on 1 October 2014
       Your questions on climate sensitivity answered
       

       MA Rodger @20, did you downscale the ocean heat content by 0.6 to match L&C's method?

33810. Ken in Oz at 08:06 AM on 1 October 2014
       How did the UK grid respond to losing a few nuclear reactors?
       

       Increasing penetration of intermittent renewables requires increasing intermittency of generation from fossil fuels; whatever inability to respond - and with improved weather forecasting it's not all blind, moment by moment responding - needs to be recognised as inadequacies of existing fossil fuel plant at least as much as an inadequacy of intermittent generation.  With a transition to low emissions as a clear goal the shift of fossil fuel plant from being the principle supply into the role of backup to low emissions alternatives needs to be recognised and facilitated, not used as an excuse to fail to continue with that transition. The burden of costs of replacing or updating infrastructure that is outdated and inadequate to the task of being backup to low emissions should land primarily upon the operators of obsolete fossil fuel plant and, if necessary, become a defacto carbon price. In this case the low emissions supply intermittency that fossil fuels are responding to is not that of wind generation but that of nuclear generation. 

33811. keithpickering at 07:12 AM on 1 October 2014
       How did the UK grid respond to losing a few nuclear reactors?
       

       @michael sweet.

       I cite Budischak only to point out that even the most wind-friendly source possible admits that an all-renewable grid would be very expensive. They support my overall point. And please point out where Budischak et al. say that nuclear is too expensive? Because I'm not seeing it. What I see is Budischak et al. rejecting nuclear out-of-hand for technical reasons that do not stand up to scrutiny. 

       There is probably a hidden reason Budischak et al. reject nuclear, and it's not because nuclear is too expensive — it's because the nuclear gid is too cheap. Certainly anyone truly concerned for the climate would admit that a non-fossil backup for wind is superior to a fossil-fuel backup for wind. So then, why not back up wind with fast ramping open-cycle nuclear rather than fast ramping open-cycle gas? And thinking about this solution, it becomes obvious: if you have the nuclear plant, why do you even need the wind turbine? Why not just run the nuclear plant for peaking, and avoid the cost of the wind turbine entirely? Thus the nuclear-allowed grid will therefore always be cheaper than the nuclear-banned grid, because it avoids the excess cost of renewables. And if you're on the only-renewables-can-save-us bandwagon, that's a politically unacceptable outcome, regardless of the technical and financial merits.

       The price of wind power hit bottom in 2004, well before Budischak was published, and has been going essentially sideways since then. As turbines get bigger, costs scale with the mass, which scales with the cube of the rotor diameter. But wind energy scales with the square of the rotor diameter. Therefore economies of scale are running up against the laws of physics and they are fighting to a draw.

       And solar continues to be one of the most expensive energy sources out there, and will continue to be. Even as the price of modules continues to decline, the balance-of-system costs alone will not allow solar to compete with wind, much less fossil fuel.

33812. ed leaver at 06:57 AM on 1 October 2014
       How did the UK grid respond to losing a few nuclear reactors?
       

       Well said, Michael. However, one might also respect the time-honored tradition in scientific, medical, economic, and legal discourse of citing an author's own data to refute his stated conclusions.

33813. michael sweet at 05:51 AM on 1 October 2014
       How did the UK grid respond to losing a few nuclear reactors?
       

       Kiethpickering:

       If you think Budischak et al are wrong you should not cite them.   If you do not like their conclusions cite a peer reviewed source to support your objections.  The key point is that your peer reviewed source thinks nuclear is too expensive. I note the OP does not cite any peer reviewed sources of information, it is an opinion piece. 

       Wind and solar have dropped dramatically in price since Budischak et al was published.  Up to date figures would show wind and solar are even more cost effective now than they were then.

33814. Richard Hampton at 04:59 AM on 1 October 2014
       It hasn't warmed since 1998
       

       M. A. Rodger @287

       You are absolutely correct that the moderating effect of energy absorption by the oceans is much greater than the effect of melting glacial ice. However the ocean effect has been continuous and is reflected in the historical atmospheric temperature record. My point is that the newly active heat sink effect of arctic/antarctic net land ice melting coincides with the inflection in the atmospheric temperature record curve in both timing and energy balance. Direct cause and effect must be examined in the context of energy transfer mechamisms to develop a full understanding of the process. Nevertheless, whenever a continuing process (atmospheric warming) shows an inflection there has to be a coincidental cause. Here with arctic/antarctic ice melting we have a good fit in the data and therefore a strong candidate for a cause of the "pause".

33815. keithpickering at 04:13 AM on 1 October 2014
       How did the UK grid respond to losing a few nuclear reactors?
       

       @michael sweet

       Yes, that's what Budischak et al. said. But they're wrong. The ability of any thermal power plant to ramp quickly depends on the design of the turbine and has nothing to do with the heat source. Current nuclear plants ramp up and down just as quickly as combined-cycle gas turbines. And, just as with natural gas, it is entirely possible to build a nuclear plant to ramp faster, if you're willing to accept a lower-efficiency turbine. Nuclear submarines and ships do that routinely right now.

       Budischak et al. reached that conclusion only because they refused to consider nuclear from the get-go, for highly dubious reasons. That decision seems to have had a lot more to do with reaching a "desirable" outcome than it did with an honest appraisal of technology.

33816. ubrew12 at 03:58 AM on 1 October 2014
       How did the UK grid respond to losing a few nuclear reactors?
       

       The UK has abundant access to wave power.  Perhaps one reason this resource goes untapped today is the nuclear power industry there, which sabotaged their access to research funds in 1982.

33817. michael sweet at 03:10 AM on 1 October 2014
       How did the UK grid respond to losing a few nuclear reactors?
       

       Keithpickering,

       Citing Budischak et al. 2013 to support nuclear is a contradiction of the paper.  They say:

       We do not simulate nuclear for backup because it cannot be ramped up and down quickly and its high capital costs make it economically inefficient for occasional use.

       In fact, Budischak states that renewables are the cheapest way to generate electricity.  The question that needs to be answered is what to do with the excess energy generated when the wind blows hard.  Budischak just wastes this electricity.  It seems to me that someone will be able to use this energy profitably.

       This article seems to me to be an attack on renewables without significant data to support it.  The original articles supporting renewables were not published on SkS.  This article does not include peer reviewed data, it is an opinion piece.

33818. John Hartz at 02:59 AM on 1 October 2014
       The Wall Street Journal downplays global warming risks once again
       

       Readers of this comment thread will also want to check out:

       The Climate Deniers’ Newest Argument, an Op-ed by Jeffrey Kluger posted by Time magazine yesterday, Sep 29, 2014.

       Like Dana,  Kruger critiques Koonin’s recent piece in the Wall Street Journal:

       The lede of Kluger’s op-ed:

       "It’s a lot easier to attack environmental scientists when you make up something they didn’t say—and then criticize them for saying it"

33819. WRyan at 02:46 AM on 1 October 2014
       How did the UK grid respond to losing a few nuclear reactors?
       

       I'm pretty sure that gas is a fossil fuel. So if wind power is displacing gas-fired power then wind power is "taking the place of fossil fuels."

       Figure 1 shows that the average value of wind-generated power was 2 GW higher from the Sunday night to the Wednesday night when compared with the pre-shutdown value. This is approximately equal to the reduction in nuclear power during this period. This is undoubtedly what the authors of the articles criticised in this piece were referring to when they wrote that an increase in wind power had replaced the lost nuclear generation. Thursday was the only day when the wind power value was lower than its pre-shutdown value.

33820. keithpickering at 02:32 AM on 1 October 2014
       How did the UK grid respond to losing a few nuclear reactors?
       

       The problem with wind (and solar, for that matter) has always been how to back it up when the wind dies. Currently that's almost entirely gas, making wind a crypto-fossil energy source. While it's true that wind-plus-gas is better than gas alone, it's also true that getting to zero fossil fuels on a wind-based system would be hugely expensive.

       The reason for that is that for geographically remote wind to back up local wind, distant regions must overbuild wind to meet their own demands AND potential demand from out-of-region. And each region must do this, to allow for the possibility that exports will be needed on windy days. But if those exports are not needed on windy days, those overbuilt wind turbines must then stand idle as the wind blows: a situation known as curtailment. Since curtailment reduces wind's capacity factor, it drives up the price of wind generated electricity. One recent study (Budischak et al. 2013) estimated that an all-renewable grid would nearly triple the price of electricity because of this issue. 

       We have reached the point where the only way to prevent a looming climate catastrophe is to deploy, deploy, deploy non-fossil energy sources as rapidly as possible. Given limited resources, the way to deploy the most non-fossil the fastest is to deploy the lowest-cost options. Those technologies are (1) shallow geothermal, where available; (2) hydro, where available; and (3) nuclear. Wind is almost as cheap as nuclear, but only as long as grid penetration remains low; once wind reaches the curtailment point (about 25% of total generation) its costs begin to escalate rapidly. 

       Jurisdictions that have already adopted this strategy have already decarbonized their grids: Sweden, Norway, France, Ontario. 

33821. MA Rodger at 23:41 PM on 30 September 2014
       It hasn't warmed since 1998
       

       Richard Hampton @286.

       I usually trot out the following levels of current annual ice loss - Arctic Ocean 300Gt, Greenland 450Gt, Antarctica 150Gt, Other 300Gt. Thise are far bigger numbers than last decade with today a total latent energy gain of 0.4 Zj pa. However that figure is a lot smaller than the extra annual increase in OHC which would be something like an extra 3Zj pa in just the measured bit of the oceans 0-2000m.

       So it is correct that more energy is being used melting ice but a whole lot more of the extra energy is ending up in the oceans. Further, if the atmosphere had been warmed significantly, most of that energy entering the oceans would be required to keep the atmosphere at the higher temperature and thus be radiating back into space.

33822. MA Rodger at 23:24 PM on 30 September 2014
       Your questions on climate sensitivity answered
       

       Tom Curtis @18.

       Thanks for pointing out my use of the wrong Gregory graph. It is as you say figure 1 that was used. I had assumed it was in figure 2 somewhere as I couldn't see how L&C14 obtained such low numbers from figure 1. But I had failed to account for the 60% adjustment used by L&C14.

       For the record repeating the exercise @17 with the figure 1 numbers yields ECS=2.13ºC.

33823. kmalpede at 22:38 PM on 30 September 2014
       People's Climate March NYC photos
       

       It was a great Day in NYC. and now what is next?www.theaterthreecollaborative.org/extreme-whether a play about the battle of Climate Scientists to speak truth to power. Oct. 2-Oct 26, Theater for the New City, NY, NY, with a Festival of Conscience including climate scientists: Jim Hansen, Jennifer Francis, Radley Horton,

33824. mancan18 at 09:08 AM on 30 September 2014
       The Wall Street Journal downplays global warming risks once again
       

       I don't know how relevant this is and, although rhetorical, it is certainly not very scientific.

       However, I have read, with great interest, all the threads in relation to this article, particularly Tom Curtis who is always informative. With some of the threads here questioning the veracity of the 97% of scientists who agree that AGW is real, there is a line from the movie "Ronin" which might be relevant to those who wish to cast doubt. It is "When there is doubt there is no doubt". It seems to me that uncertainty is doubt. So does that mean that the 3% of scientists who are uncertain have doubt which means they have no doubt. But what does this mean about their doubt? Does this mean they have no doubt that increasing greenhouse gases from anthropogenic sources WILL warm the planet OR mean that they have no doubt that increasing greenhouse gases from anthropogenic sources WON'T warm the planet. Now the first proposition is believed by 97% of climate scientists and there is plenty of evidence to support their position. However, if those arguing uncertainty have no doubt about proposition two, i.e. increasing greenhouse gases from anthropogenic sources WON'T warm the planet, then they haven't proven their case, which most certainly, doesn't provide a sufficient reason to delay taking positive action to alleviate anthropogenic greenhouse gas emissions.

       Moderator Response:

       [RH] Please watch it with the all caps.

33825. Richard Hampton at 05:13 AM on 30 September 2014
       It hasn't warmed since 1998
       

        

       COMMENT TO SKEPTICALSCIENCE re PAUSE IN GLOBAL WARMING

        (snip)

       I wonder if the so-called pause in global warming as expressed by surface atmospheric temperature can be quite easily explained as follows? The measured net atmospheric temperature was increasing at an annual rate of about 0.025º C prior to the late 90's. It then leveled off rather abruptly and increased at a much slower pace. Climate change deniers have been celebrating this as evidence that global warming has stopped and there's nothing to worry about. But what really happened? If increased atmospheric CO₂ is trapping more energy, where is it going? What has changed? Andrew Shephard et al. in(Science, 2012, 338: 1183-1189 ), document a new phenomenon which began in the late 90's: significant net melting of arctic and antarctic land based ice. Greenland in particular and West Antarctica are losing about 400 gigatonnes per year (including allowances for increases of ice from increased snowfall in East Antarctica) as net ice melt. Prior to the late 90's there was no significant loss of land based ice mass. Their paper discusses the effect in terms of sea level rise (also measurable). But let's do the energy balance math. It appears that this recently arrived phenomenon of net ice melting coincides well with the abrupt change in the rate of atmospheric temperature increase. So, the energy required to melt 400 Gt of ice (its latent heat of fusion) is quite close to the amount of energy required to warm the earth's atmosphere by 0.025 º C. Wouldn’t such a newly arrived heat sink be taking up the so called missing energy? As has been widely reported, this “missing” energy is going into the oceans in the form of liquid water. So global warming has not paused at all! The earth is continuing to gain energy because of the increased energy absorption caused by the increased level of atmospheric CO₂. Ice melting is accelerating and the atmosphere is still showing signs of warming. Thus we could rightly assume that global warming and its effects on climate are continuing and even accelerating as more and more energy is embedded in our global environment as we burn our way into a high risk future. Short term greed, instant gratification, discounting the future, delusional economics, and denial of reality are the hallmarks of humanity's dis-function and abuse of our only home.

        

       Moderator Response:

       [RH] Snipped all caps (per policy) and resized font to standard size.

33826. Tom Curtis at 01:36 AM on 30 September 2014
       Your questions on climate sensitivity answered
       

       An ammendment to my post @18.  At ATTP, Paul S has pointed out an error I made in my use of the Ocean Uptake Efficiency.  Correcting for it, and allowing for non-ocean heat storage results in a slightly lower ECS than just making the error corrections already noted.  That would count as concurrence between the L&W estimate and an alternative reasonable approach.

33827. KR at 01:11 AM on 30 September 2014
       2014 SkS Weekly Digest #39
       

       This isn't the first time that a climate-related satirical cartoon has been criticized for not portraying every incidental part of the drawing in a photo-realistic manner. Such complaints are, properly speaking, whinging. IMO they are attempts to dismiss, denigrate, or distract from what said cartoon is actually saying. 

       Perhaps the cartoons are effectively making their points... hmm. 

33828. Tom Curtis at 00:39 AM on 30 September 2014
       2014 SkS Weekly Digest #39
       

       Russ R, perhaps you failed to notice the heavy satire.  Everybody knows that cartoons aren't science, and distort not only faces, profiles, submarine designs, and architecture but even science for humorous impact.  Somebody who thinks that noticing that fact informs others of something new, or is worthy of comment really needs to get a grip.

33829. Tom Curtis at 00:36 AM on 30 September 2014
       CO2 effect is saturated
       

       rational being @286, the increased warmth of the atmosphere from the increased greenhouse effect does in fact raise the tropopause, but it does so by increased convection due to the surface warming.  The change in radiative forcing would occur whether or not that happened.  I have explained the actual method of warming in greater detail and clarity than I can in a comment here.  I recommend you read it and comment further on that thread if you want to explore the issue in detail.

       I agree that averageing across the Earth's surface creates a multitude of problems.  They are not as large as often imagined, however, because at the effective altitude of radiation to space, temperatures are far more similar over a range of latitudes than they are at the surface (in part because of the higher tropopause in the tropics).  However, the alternative to using globally averaged values is (more or less) to develop a full scale AOGCM, which is a bit much for blog comments.  As it is, observations and AOGCM's show that globally averaged values give good back of the envelope estimates, though not accurate enough for detailed prediction (obviously).

33830. Russ R. at 00:35 AM on 30 September 2014
       2014 SkS Weekly Digest #39
       

       Tom Curtis,\

       Sticking to climate change related matters, you failed to notice the implied timeline... "a generation ago" implies < 50 years.

       Even the most dire predictions of sea level rise for the next 50 years are in the order of centimeters.

       Moderator Response:

       [JH] Your concerns have been duely noted.

33831. KR at 00:26 AM on 30 September 2014
       CO2 effect is saturated
       

       rational being - That's correct, increased GHGs (not just CO2) raise the tropopause, the slope of the lapse rate remains constant, and the entire atmosphere and surface are warmer as a result of increased effective radiating altitude. There's a fair bit of literature on that (see Google Scholar here), for example Santer et al 2003 states:

       Observations indicate that the height of the tropopause—the boundary between the stratosphere and troposphere—has increased by several hundred meters since 1979. Comparable increases are evident in climate model experiments. The latter show that human-induced changes in ozone and well-mixed greenhouse gases account for
       80% of the simulated rise in tropopause height over 1979 –1999. (emphasis added)

33832. Tom Curtis at 00:26 AM on 30 September 2014
       Your questions on climate sensitivity answered
       

       MA Rodger @17, my take was that they used the CCSM4 spun up from 850 AD as shown in figure 1 (red line) for pre-1950 ocean heat fluxes.  Certainly, based on a pixel count, it gives the same values over 1859-1882.  VarNVarN in figure 2c (solid blue line) is similar, but smoother and drops much lower around the turn of last century, which would allow much higher climate sensitivity.  I am not sure that woud be the case with the figure 1 values.

       For an alternate approach, I used the Ocean Uptake Efficiency from Gregory and Forster, along with HadCRUT4 to determine Q in the 19th century.  The result is a mean ECS of 1.98 K per doubling of CO2, inline with Otto et al 2012.  I discuss it in detail at ATTP.  I do not claim, of course, that that is the best approach, although I think it is significantly better than L&C's method as applied (ie, using a single run on a single ensemble member and an incorrect downscaling).  But the factor of 23 difference in the resulting estimated Q means L&C need to seriously justify their choice at a minimum, something they have not done.

33833. Tom Curtis at 00:08 AM on 30 September 2014
       2014 SkS Weekly Digest #39
       

       Russ R @2, you're right.  What a travesty.  Even worse:

       1. profiles of human heads look nothing like those shown;
       2. heads are not a third of body length as shown;
       3. the capitol building is shorter than the Washington Monument;
       4. fish don't blow bubbles;
       5. cavitation bubbles are not so persistent; and
       6. water currents do not show up as lines underwater.

       Clearly we need a new community standards board to eliminate all inaccuracies from cartoons.  The exageration of facts or features for humorous delivery is not to be tolerated.

33834. rational being at 00:05 AM on 30 September 2014
       CO2 effect is saturated
       

       Thank you Tom Curtis and KR for taking the time to reply.

       Are we saying that increasing upper atmosphere CO2 raises the altitude of the tropopause? And is the warming argument, then, that the temperature of the tropopause is fixed by the needs of radiative balance, so that a higher tropopause implies a warmer surface?

       The altitude of the tropopause varies over the globe from around 9km at the poles to almost double in the tropics. I suppose it is where convective heat transport gives way to radiation as the dominant mode. The details are complex enough that I am not sure simple averaging arguments work well.

33835. Russ R. at 23:54 PM on 29 September 2014
       2014 SkS Weekly Digest #39
       

       Re the toon:

       1. If all the ice melted, sea level would be 216 feet higher.
       2. The Washington monument is more than 555 feet tall.
33836. MA Rodger at 22:31 PM on 29 September 2014
       Your questions on climate sensitivity answered
       

       Tom Curtis @16.

       You say "their method of determining the Heat Content Flux for 1859-1882  ... is highly dubious." Coincidently for other reasons, I recently extracted the thermosteric SLR data from Gregory et al (2013) by scaling their Fig 2c. This is apparently what L&C2014 did to obtain thermoSLR data which they then used to infer OHC for years prior to the earliest OHC data. I must say, the resulting numbers do have a rather dubious feel. The Base Periods centred on 1870 & 1940 used by L&C2014 turn out to be the best choice possible for reducing Δ(F-Q) and thus for reducing ECS/TCR estimates. But I can now pick my own Base & End Periods and using the first half decade and last half dozen years of the Gregory et al thermoSLR data (this length of period to avoid volcanos) to infer Δ(F-Q), IPCC Appendix 2 for ΔF and HadCRUT(C&W) for temperature I get ECS=2.4ºC.

33837. Tom Curtis at 15:45 PM on 29 September 2014
       Your questions on climate sensitivity answered
       

       MA Rodger @12, even taken as a hypothetical excercise to determine the values of TCR and ECS using IPCC values, Lewis and Curry (hereafter L&C) is seriously flawed.  I explained part of the reasons in a comment at And Then There's Physics.  Further to that comment (quoted below), their method of determining the Heat Content Flux for 1859-1882 is not grounded in the IPCC, is highly dubious and likely further deflates their headline results.  In addition, more recent findings since the IPCC was published suggest a higher effective radiative forcing of aerosols is in order, which would increase the result still further.  So, as an attempt to determine ECS based on IPCC assumptions, the result is flawed - and even more flawed as an attempt to find the actual value of ECS.  (The determination of the value of the TCR is also flawed, but the problems are of little consequence given how close their value is to the IPCC values).

        

       "I downloaded the AR5 forcing data from Annexe 2, HadCRUT4 from the Hadley Center, Domingues et al OHC data from the CSIRO and Levitus et al forcing data from the NODC. I then proceeded to calculate ΔT, ΔF, and ΔQ from that data. Using C&L value for Q over the period 1859-1892(which I also dispute). The result was that L&C incorrectly estimated ΔT by 0.57% (small enough to be a rounding error), ΔF by 2.68%, and ΔQ by 17.03%. The later two are too large to be rounding errors. All errors favour lower values for TCR and ECS. Combined, the errors deflated TCR by 3.16% and ECS by 8.27%.

       The “error” in ΔT is just a rounding error as noted. That in ΔF may be due to an adjustment to the aerosol forcing. If so, it means Lewis and Curry are not, after all, trying to show what is obtained from the IPCC data, and need to independently justify their choices of data. If they were trying to show the results of the IPCC data, and also obtain the difference when the forcing data is modified as Lewis claims it ought, then they should have shown both.

       The difference in ΔQ is the most interesting. I obtained the most recent values by downloading the 0-2000 meter pentadal record, and using the difference between successive values to determine the difference between individual years six years apart. I then used the the 2005-2012 annual data as an anchor point from which annual values were reconstructed back to 1955. Comparison of rolling 5 year averages with the pentadal values showed a constant offset over the reconstructed period, which because constant has no effect on trends. I then deducted the 0-700 meter annual OHC, added in the Domingues 0-700 meter OHC and the Purkey and Johnson trend from 1992 (as per box 3.1) and dividing by 0.93 to account for the heat content of ice loss, into the ground and into the atmosphere.

       Interestingly, my figures and L&C’s figures agree within 1% if I neither add in the Purkey and Johnson trend for OHC below 2000 m, nor apply a modifier for non-ocean heat storage. This looks like a likely source for the error.

       Resolving the errors results in a mean TCR of 1.37 C, and a mean ECS of 1.79 C per doubling of CO2. These are still low values, but well within the IPCC range. Further, at this stage the errors amount to errors in arithmetic rather than errors in assumptions (of which I believe there are plenty)."

       (Bolding added to draw attention to key points.)

33838. Bob Loblaw at 11:57 AM on 29 September 2014
       The Wall Street Journal downplays global warming risks once again
       

       Joe:

       In addition to the material provided by Tom, take a look at Hansen et al (1981) "Climate Impact of Increasing Atmospheric Carbon Dioxide", Science 213, 957-966. A copy is available on this NASA page.

       Figure 4 in that paper provides a result from a 1-d radiative-convective model, showing the first initial (instantaneous) response to doubling CO2, the changes a few months later, and the final changes many years later.

       • In the instantaneous case, increasing CO2 does cause a change in back radiation at the surface (+1.1 W/m²), but that is not what leads to warming. The key element is the change at the top of the atmosphere: a decrease of 2.4 W/m² (a reduction of 0.8 from the surface, and 1.6 from the atmosphere). There are also changes in the surface-->atmosphere convective fluxes. If there was no top-of-atmosphere (TOA) change, then we'd just see shifts within the system, not necessarily an overall warming.
       • After a few months, the atmosphere has had a chance to adjust, but the surface has not - the ocean heat capacity is the key here, At this point, the TOA imbalance is actually greater - a net change from 1xCO2 of -3.8 W/m².
       • Only after many years is the imbalance removed, after the entire system has time to warm. The net changes for the atmosphere, surface, and TOA (whole system) have re-equilibrated at 0.

       Koonin's mistake is to look at initial changes at the top of the atmosphere, and compare them to magnitudes at the surface. It's not the magnitudes that matter: it's the changes, and how the system reacts to counteract those changes (re-equilibrate).

       I know squat about plasma physics, so I can't come up with an analogy there. Perhaps a chemistry example? You have a chemical system that is in equilibrium, but it's highly active - mega reactions in both directions, at matching rates. You toss in a catalyst that slightly alters the reaction rate in one direction only. What happens?

       • It's not the change in reaction rate versus the original reaction rate that matters.
       • concentrations will change until the two rates balance again.
       • the new concentrations can only be predicted if you know how the two rates respond to the changing concentrations. If the rates change slowly with concentration, you need a large change. If the rates change rapidly, equilibrium is reached more quickly.

       [But I"m not a chemist, either, so this may be a crummy analogy.]

33839. chriskoz at 11:40 AM on 29 September 2014
       2014 SkS Weekly Digest #39
       

       Re the toon: a good reminder to anyone that "uniting against existential threat of ISIS" as the western coalition is doing right now is like treating the symptom rather than the cause. The cause is twofold:

       - the increasing impact of climate change related events, like drought in Syria as reportewd by Tom Friedman in Years of Living Dangerously,

       - the constqant military presense of western forces infringing the soveregnity of middle eastern countries (as you can read e.x. in other reports, i.e. "Hot Flat & Crowded" by the same Tom Friedman)

       Obviously the recent strikes on ISIS in Iraq only exacerbated the second cause while nothing is being done on the first cause. So while past & current symptoms (Saddam, Al-Qaeda, ISIS) may be extinguished, new symptoms will soon resurface.

33840. Tom Curtis at 11:12 AM on 29 September 2014
       The Wall Street Journal downplays global warming risks once again
       

       JoeT @37, first, for ease of discussion, here is the IPCC Fig 2.11 (which is discussed in Chapter 2 of IPCC AR5 WG1:

       

       It is an update of previous images by Fasullo and Trenberth, inferior in not showing the size of the atmospheric window (40 W/m^2 in the latest Fasullo and Trenberth image), but superior in showing the 95% confidence interval in brackets.  Not including the data for the atmospheric window means the energy balance cannot be determined for the atmosphere, but only for the surface and the Top Of the Atmosphere (TOA).  The legend of the image informs us that:

       "Numbers state magnitudes of the individual energy fluxes in W m^–2, adjusted within their uncertainty ranges to close the energy budgets. Numbers in parentheses attached to the energy fluxes cover the range of values in line with observational constraints."

       (My emphasis)

       The important thing about figure 2.11 is that it only shows the energy balances.  It in no way shows the change in radiative forcing, and is in no way intended to show the greenhouse effect.  You can determine what is called the "total greenhouse effect" from it, that being the difference between the upward IR radiation at the surface and the upward IR radiation at the TOA.  That total effect, however, includes the effect of feedbacks that effect IR radiation (including WV, lapse rate, and cloud thermal feedbacks) as well as the direct effect of the total concentration of Well Mixed Greenhouse Gases, stratospheric water vapour, and ozone.

       To properly understand Koonin's error, it is helpfull to look at Fig 8.1 (from Chapter 8 of the WG1 report):

       

       "Figure 8.1 | Cartoon comparing (a) instantaneous RF, (b) RF, which allows stratospheric temperature to adjust, (c) flux change when the surface temperature is fixed over the whole Earth (a method of calculating ERF), (d) the ERF calculated allowing atmospheric and land temperature to adjust while ocean conditions are fixed and (e) the equilibrium response to the climate forcing agent. The methodology for calculation of each type of forcing is also outlined. DTo represents the land temperature response, while DTs is the full surface temperature response. (Updated from Hansen et al., 2005.)"

       The important thing here is to understand what is meant by radiative forcing, which is illustrated in Fig 8.1b.  It is the change in net upward radiation at the tropopause following a change in atmospheric composition or incoming radiation etc, after allowing the stratosphere to adjust temperature.  With a doubling of CO2 (approximately the situation Koonin considers), that change is 3.7 W/m^2.  To determine the percentage of that effect, you need to compare it to the net radiative forcing of relative to the situation with no greenhouse effect.  

       The total greenhouse effect is given by the difference between surface and TOA upward IR radiation, or 159 W/m^2.  However, 75% of that is due to clouds and water vapour, ie, due to feedbacks, and are not a "forcing".  The reason for that is that a change in those values will simply revert to equilibrium values in a short time.  So, the change in greenhouse forcing due to doubling CO2 is 3.7/(0.25*159), or 9.3%.  If the response of temperature to changes in forcing were linear (which they are not), that would result in an increase of temperature of 3.55 K before feedbacks (9.3% of 33K).

       Alternatively, we can see that increase is 1.6% of the TOA energy budget, leading to an linear 'expected' increase of 4.08 K; or a 0.9% of the net solar plus total greenhouse effect, leading to an linear 'expected' increase of  2.59 K.  

       Importantly, these are all TOA comparisons.  Because the radiative forcing is a TOA value (technically top of stratosphere, but the numerical difference with TOA is sufficiently small that it can be neglected), it can only meaningfully be compared to TOA values.  Koonin tries to compare a TOA value with a surface value, he is comparing apples to oranges, and demonstrating his complete failure to understand even basic theory of the science he criticizes.

       If Koonin wanted to make legitimate comparisons, he should really be making comparisons of temperature response.  The expected temperature response of doubling CO2 ignoring feedbacks is only 1.2C (+/-0.12 C).  That is only 0.4% of Global Mean Surface Temperature (GMST), but 3% of the temperature range consistent with the existence of human civilization.  Annual average temperatures below 0 C or above 40 C don't really concern us, because they are inconsistent with human flourishing.  It is the percentage change within that range that matters.  With feedbacks, that doubling pushes the response up to 6-12% of that temperature range.  With a GMST we currently have a small part of the Earth below that range (the poles), and no part of the Earth above it but nearly a third of the Earth is within 25% of the upper limit.  One doubling could push sizable portions of the Earth to the limit or beyond; while two doublings may make as much as a third of the Earth unsuitable for human civilization.  These are the percentages that matter.

       Moderator Response:

       [TD] The second figure in Tom's comment has gone missing (only the caption shows).  Will somebody please fix it?

33841. Tom Curtis at 08:55 AM on 29 September 2014
       Your questions on climate sensitivity answered
       

       For additional information, the often mentioned trillion tonnes of carbon limit on human emissions to avoid dangerous impacts of global warming amounts to a 540 ppmv limit.  That view, above all others, represents the scientific consensus on safe levels of emissions.  There are scientists who believe that even it overstates the necessary level of concern, but at least equally many who thinks it overstates the safe limits, including Hansen.  

       The later takes the view expressed by 350.org, ie, that 350 ppmv is the upper limit on safe greenhouse concentrations.  I have a problem with 350.org that they appear to over-egg the data.  Hansen, for example (and no doubt sincerely), considers the possibility of runaway global warming real, even though the science is very firmly against him on that point.

       My biggest problem with the 350.org point of view is a failure to take into account the fact that, given zero net human emissions, CO2 levels will fall substantially if slowly; and that the full impacts of ECS will occur slowly and on approximately the same timescale as the initial natural draw down of CO2.  These are very important facts, and make an otherwise impossible task plausible.  That is, there is an economic cost in reducing CO2 emissions at least in the short term, and reducing emissions to net negative values in the very short term as advocated by 350.org makes that economic cost sufficient that it could plausible cause as much damage as 550 or even 650 ppmv of CO2.  In constrast, limiting net emissions to 0.75 to 1 trillion tonnes (475-540 ppmv) in the short term will have an initial short term economic cost substantially less than (for example) the cold war.  That is, it is achievable while retaining the economic ability to achieve other major ends.  

       Developing the technology to limit CO2 emissions by that amount will also develop the technology to go the further and necessary step to achieve net zero anthropogenic emissions.  In particular, zero gross anthropogenic emissions will be impossible to achieve for a variety of reasons, and gross emissions above 5% of current emissions may result in either no natural draw down, or a long term slow build up of CO2 concentration.  Therefore, as with 350.org, I agree that we will need to develop a cost effective technology for carbon sequestration.  I disagree about the scale to which that is necessary, and the time period in which it is necessary.  

       (Apologies to the moderators for the extensive off topic post.)

33842. sidd at 08:54 AM on 29 September 2014
       The Wall Street Journal downplays global warming risks once again
       Koonin is doing exactly what he has been commissioned to do, influence the APS/AIP climate change statement. I urge those of you who are APS or AIP members to write (paper/snailmail is much better than email) to pointing out his underhanded elisions and demanding a strong statement on climate change. The op ed is directed toward that smallish fraction of physicists who yet engage in denial. As for the rest, he is at a disadvantage, they are scientifically literate, can calculate and look up citations ...

       Note though, there is actually mention of a revenue neutral tax on fossil carbon. That, coupled with the Goldman Sachs downgrade of Peabody Coal indicates to me that the oligarchs are looking for an exit.

33843. Tom Curtis at 08:29 AM on 29 September 2014
       Your questions on climate sensitivity answered
       

       ranyl @13, it would be helpfull to myself, and presumably other readers if you distinguish quotation from your own words.  At a minimum, you should use quotation marks (on your keyboard next to the enter key).  It would also be helpful if you used the indent function from the wysiwyg panel in the comments screen, indicated by the quotation mark signal.

       Trivial points aside, it is very easy to get a long list of papers which indicate models may (there is disagreement on the point among relevant scientists) overestimate CO2 drawdown (or climate sensitivity).  It is equally easy to get long lists of papers which indicate models may overestimate the same.  Climate change deniers continually refer to the later and ignore the former, in a process that is called pseudoscience.  It is no more scientific to continually refer to the former and ignore the later.  The climate scientists who actually device the models, such as David Archer, keep track of both; and revise the models on the basis of the balance of evidence.

       So:

       • While you can list a series of reasons to think the models underestimate draw down, it has recently been shown that volcanic emissions are significantly larger than previously thought, which implies a larger draw down rate, and hence that models underestimate the draw down.
       • The models in question have with reasonable accuracy retrodicted the Earth's carbon budget over the last 600,000 years.  While they are likely to be wrong in detail (as with all models), they are therefore unlikely to be wrong about the basic picture.
       • The higher temperatures and sea levels in the pliocene where in a near full equilbrium condition.  That is, they were achieved as the Earth achieved its Earth System Climate Sensitivity, which is noticably higher than the Equilibrium Climate Sensitivity or the more relevant (over the coming two centuries) Transient Climate Response.
       • Finally, anybody who knows me knows I am not sanguine about about even 500 ppmv, let along 650.  As a matter of urgency we need to stop net anthropogenic emissions before atmospheric CO2 tops 450 ppmv.  Not, however, due to some panicked forecasts about the effect of a current 400 ppmv 500 plus years down the track.
33844. ranyl at 07:23 AM on 29 September 2014
       Your questions on climate sensitivity answered
       

       ranyl & Rob P @8, with a slug of CO2 of a trillion tonnes or more, approximately 25% remains in the atmosphere in the long term. About 50% has human emissions have already been drawn down, so another 50% remains to be drawn down. That means to get a long term 400 ppmv CO2 concentration, in the short term CO2 concentrations need to rise to 620 ppmv. For 460 ppmv CO2e, you need 640 ppmv of CO2 (as other WMGHG decay in the short term). The upshot is that long term concentrations of 400 ppmv plus, along with the effects of such concentrations evident from the paleo record, are likely long term consequences of BAU (RCP 8.5 or even RCP 6) scenarios. They are still very avoidable, however, if we get serious attempts to mitigate climate change.

       Sorry Tom that is using models with many CO2 feedbacks not included, presuming a strogner fertilization effect than being seen, not including forest fire feedbacks, and several others despite the complexity of the models. And don't forget the widespread fertilization effect of nitrogen fertilisers, that has been more than enough to offset all the NO2 emissions from them, stop using the industrial fertilizers as is necesary for biodiversities sake and well that fertilizer effects goes. And si has been shown that ecosystem disrupton releases carbon (not included in those optimistic carbon withdrawal nodels),  adn extrem weather event sand increased erosion is releasign soil carbon, and then there si the frozen sea bed stoes of permafrost of siberia that are releases stuff also not included.

       We are already committed to be above 400ppm (and think 470ppn CO2e) for at the very best least another 200 years or so, so that is at least 80% of the warming of full equilibrium.

       Stiff the roses.

       350-400ppm it was 3-5C hotter and that was not including the extra heat recetnyl found in the western pacific recently reported, the WPAC was 3C hotter than thought and that is a reasonable chunk of ocean to increase, and thus 5C is the much more likely.

       There is no more room for any more carbon emissions, yet we are going to have lots more for nothing stops overnight.

       Now I get all the papers and many more to prove these points.

       Including several recent papers that match climate models to reality in temr so fo wate vapour and cloud fomrations when only the models with a climate sensitivity of 3C or above do the trick,  and it is more likel yto be 4C as many are now realising.

       We have a huge carbon debt not a budget.

       But anyway apparently WWW3 has kicked off in papal terms so that wil a whole load carbon emssions and habitat destruction with millions of people sufferign on top, so let su be sure 400ppm will soon be a distant target everyone wishes we could back to, but gettign any CO2 out the atmosphere any time soon will a transformation of everything to acheive.

       And how much carbon extra is it going to take to actual make all the new power generation, electric cars, etc, and just how toxic are batteries and the like?

       Oh I know lets pretend we put another 1/3 again of CO2 into the atmosphere because some computer models (that have underestimated lots so far (e.g. sea ice arctic), give a 2/3 chance of avoiding 2C by 2100, or to put it another way lets play russian roulette with 2 bullets in the 6 carousel with the future of humanity?

       Now what is the carbon budget that gives a 95% chance of avoiding 2C when the CS is 4C?

33845. JoeT at 05:06 AM on 29 September 2014
       The Wall Street Journal downplays global warming risks once again
       

       Tom or Bob,

       I think it's important for physicists such as myself (I'm a plasma physicist), who are essentially ignorant of climate science (but I'm trying to learn!) understand clearly what Koonin is saying. One more question if I may, just to make sure I have it right. The shocking thing to me from Figure 2.11 of the IPCC report is how huge the back radiation is, 342 w/m2 compared to the solar absorbed at the surface, 161 w/m2.  So if I look at a rough energy balance, then there is 159 w/m2 difference between the radiation output at the surface and that at the TOA. Now to get to 342, I need to add 84 for evaporation, 20 for sensible heat and 79 for solar that is absorbed in the atmosphere. That comes to 342 exactly. So, just to be pedantic about all this, the mistake Koonin is making is that he is including evaporation, sensible heat and solar as contributions to the greenhouse effect, rather than just the 159 w/m2. Am I saying that correctly? TIA.

33846. MA Rodger at 19:06 PM on 28 September 2014
       Your questions on climate sensitivity answered
       

       Lewis & Curry (2014) is pretty much what you'd expect from the title 'The implications for climate sensitivity of AR5 forcing and heat uptake estimates' and from its authors - a bean-counter meets a quasi-holistic climatologist. The thrust of the study is to take the numbers from AR5 WG1 Appendix2 and shove the implications of them back at the IPCC. This is easily done but there is quite a bit of cheese-paring required to get the desired result. For instance, note how the 'headline' 1859-2011 result when compared with Otto et al inc. Lewis (2013) loses 5% of the ∆T and gains 25% of the ∆(F-Q).

       And choosing a different temperature record than HadCRUT4 would gain 5-10% more ∆T. The comparing of peak temperatures from late-1800s & mid-1900s is potentially questionable unless you are signed up to a big constant-amplitude multi-decadal oscillation. There is certainly room for significantly higher sensitivity by taking different time periods if the Appendix 2 forcings are taken at face value (which is what the study is about). And as most of the warming has occurred recently, slow feedbacks will not have had time to act for 'most of the warming'. And the one natural wobbler of temperature that is beyond doubt, ENSO, is an unknown for the post-1850 period. ENSO could have elevated the 'headline' base temperatures just as it has mainly depressed the 'headline' end period. That could easily have clipped 10% off the ∆T used bt Lewis & Curry. (I note the MacDonald & Case (2005) PDO reconstruction (wiki-graph) looks a bit positive for 1859-82 suggesting ENSO will indeed have been warming.)

       So the headline low ECS provided by Lewis & Curry (2014) is at best controversial.

       And do note, if it is as Lewis & Curry suggest, it only works if we are now about to experience a repeat of the cooling cycle seen twice before over the last 160 years. So hold onto your hats. The Kara Sea will melt away (or is it 'ice over'?) plunging the whole Northern Hemisphere into two decades of cooling and priming a negative AMO ready for another round of Wyatt's Stadium Wave. This I will enjoy seeing.

33847. Rob Painting at 15:06 PM on 28 September 2014
       Your questions on climate sensitivity answered
       

       Tom @ 9 -  True, it depends how things pan out in the real world. If, for instance, carbon fertilisation of the atmosphere does indeed cause the stupendous growth of land-based plants, as the carbon cycle models predict, much of the excess carbon dioxide will be drawn down. The evidence for this is pretty equivocal so far.

       Also, once the ice sheets are committed to collapse, there's no turning back. If we haven't passed that point, and humanity were to get its act together, the collapse of the ice sheets may be averted. Trouble is that empty assurances are all we have so far. Fossil fuel emissions keep climbing, and will continue to do so for the foreseeable future.

       As you may have figured out, averting dramatic future sea level rise is not something I'm very optimistic about. 

33848. denisaf at 13:35 PM on 28 September 2014
       Your questions on climate sensitivity answered
       

       Sunlight is energy input that is absorbed in heating up the atmosphere and the oceans as well driving operations on the land. Energy is output by radiating out into space. The energy input and output had been roughly in balance for eons, so enabling the biological operations that organisms were dependent on. Then the emissions from fossil fuel usage rapidly upset that balance so heat has accumulated in the atmosphere, oceans and land. The emissions have effectively placed a blanket around the globe, so causing the warming. Cutting back the rate of emissions will do no more that slow down the heating. The energy input and output balance has been irrevocably degraded by the operations of industry. Natural forces will very slowly restore this balance after the demise of industrialed civilization.

33849. Tom Curtis at 12:45 PM on 28 September 2014
       Your questions on climate sensitivity answered
       

       ranyl & Rob P @8, with a slug of CO2 of a trillion tonnes or more, approximately 25% remains in the atmosphere in the long term.  About 50% has human emissions have already been drawn down, so another 50% remains to be drawn down.  That means to get a long term 400 ppmv CO2 concentration, in the short term CO2 concentrations need to rise to 620 ppmv.  For 460 ppmv CO2e, you need 640 ppmv of CO2 (as other WMGHG decay in the short term).  The upshot is that long term concentrations of 400 ppmv plus, along with the effects of such concentrations evident from the paleo record, are likely long term consequences of BAU (RCP 8.5 or even RCP 6) scenarios.  They are still very avoidable, however, if we get serious attempts to mitigate climate change.

33850. ranyl at 08:39 AM on 28 September 2014
       Your questions on climate sensitivity answered
       

       How hot was the earth the last CO2 was 400ppm?

       Or should we say 460ppm Co2e?

       And how high were sea levels?

       Moderator Response:

       [Rob P] - Based on the relationship between atmospheric CO₂ and sea level over the last 40 million years, we are likely committed to 24 metres (+7/-15 metres at 68% confidence) of future sea level rise.

       That seems to be supported by recent observations from the Antarctic showing that the West Antarctic ice sheet, and perhaps coastal sectors of the East Antarctic ice sheet, are beyond the point of no return. It will likely play out over millennia, but over a metre of sea level rise this century will cause widespread disruption and be extraordinarily expensive to deal with.

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