RE: [geo] RE: Aluminum particles as a replacement for sulfate aerosols?
A lot of the health and ecosystems effects particularly may be affected by the size and shape. Think asbestos and pm2.5s for comparisons Have you compared these parameters to natural dust? I prefer sulphur because it is natural in the stratosphere and predictable. It is safe on rain out, too. A On 12 Jul 2011 04:05, David Keith ke...@ucalgary.ca wrote: Answers: 1) Particles raining out and causing respiratory problems in dry deposition, especially in Inuit communities who live pretty much at the end of the Brewer-Dobson circulation The particle density involved is orders of magnitude below the levels that cause air pollution risk. Similar arguments apply to sulfate aerosols. Someone should write a paper or two on this. There are, however, several back-of-the-envelope arguments that show this. 2) Particles staying up for longer than wanted, thus reducing control. Yes. It's interesting to ask what lifetime one might want. Too short and control is hard. Too long and you can't stop. 3) Particles drifting or thermally levitating far higher than intended. Needs some more modeling. Don't know. But the particle sizes we are talking about are 0.1 micron or larger, so would be very similar to sulfates. 4) Particles getting entrained in precip and causing problems for water ecosystems or the human gut. Needs to get looked at, but remember that aluminum oxide is one of the most common consituents of the earth's crust and the total flux is much, MUCH, smaller that global dust deposition rates. 5) Surface chemistry with substances other than chlorine Not sure what you mean, Br? 6) Particles melting or clumping onto jet engines like volcanic ash Look at that section in the Aurora report. Density just not in the right range. Also, Al2O3, will not be melted. 7) Particles interfering with wavelengths vital for comms or astronomy Look at index of refraction of alumina. Think about optical depths. There will no doubt be some effects, but, contrary to assertions by Robock, the big issue with strat particles likely to be in the infrared. Here the much lower emissivity of alumina should help but not eliminate the issue. 8) Cloud seeding from descending particles This needs serious work for alumina or other particles. If we drive upper tropospheric clouds then we have a warming effect, opposite effect also possible. Can you reassure us you've covered all these potential issues? I'm aware that most if not all items in the above list may not be problems whatsoever, but far better to include something that's not a problem than to miss something which is. Of course we have not covered all these issues. We had thought of them all before. They have not been covered for sulfate either. This is early research. Doing this in a comprehensive way will require many peoples involvement with papers and critiques by different scientific groups in some cases lab or small scale testing. A On 12 July 2011 02:30, David Keith ke...@ucalgary.camailto: ke...@ucalgary.ca wrote: Folks Building on the work we did on the direct formation of small aerosols in the stratosphere, see paper link below, Jeff Peirce, Debra Weisenstein and I are beginning work looking at alumina aerosol. This is motivated by the fact that one could, in principle, form alumina aerosol using similar methods to the ones we examined in the previous paper. The benefits of using alumina might be: 1. Lower potential for chlorine activation per unit surface area. (Maybe, we are reviewing the old lit.) 2. Higher index of refraction à less particles needed for a given radiative forcing à smaller coalescence rate à slower growth àlonger lifetime à even less particles needed. This effect might be quite large. 3. Lower IR emissivity. 4. Smaller aerosols à less forward scattering problem. Of course this is all preliminary, but this gives us a sense that it might be that alumina aerosols would have less side effects per unit radiative forcing. Yours, David Paper: Jeffrey R. Pierce, Debra K. Weisenstein, Patricia Heckendorn, Thomas Peter and David W. Keith. (2010). Efficient formation of stratospheric aerosol for geoengineering by emission of condensable vapor from aircraft. Geophysical Research Letters, 37, L18805, doi:10.1029/2010GL043975, http://www.agu.org/pubs/crossref/2010/2010GL043975.shtml From: John Nissen [mailto:j...@cloudworld.co.uk] Sent: Wednesday, May 25, 2011 4:18 PM To: Mark Massmann Cc: Ken Caldeira; David Keith; karolyn massmann; Kevin Layton; Mike MacCracken; Andrew Lockley; P. Wadhams; John Gorman; Geoengineering Subject: Re: Aluminum particles as a replacement for sulfate aerosols? Hi Mark, You might be interested in this work [1] - I attended the presentation at the EGU 2011 geoengineering session, and they were talking about producing engineered
Re: [geo] Wind and wave energies are not renewable after all
Hi David, Couple of questions. Generation of wind energy would increase the KE dissipation rate but this is not an external forcing to the climate system. I agree there would be local and regional climate changes but there should be no global mean warming. Right? The current KE dissipation rate is about 2 watts/m^2. Over land, this translates to about 300 TW. Suppose wind farms extract 150 TW (which may be impractical), the dissipation rate over land will increase to 3 Wm^2. Don't you think the KE (or available PE) generation rate in the atmosphere would correspondingly increase? Of course these would be large regional climate changes. Bala On Tue, Jul 12, 2011 at 8:37 AM, David Keith ke...@ucalgary.ca wrote: Responding to a VERY old thread on wind power: ** ** *The only link to geoengineering here is that there is a possibility of manipulating wind turbine drag for weather control, see: * ** ** At 10’s TW scale extraction of wind does begin to be constrained by the generation of kinetic energy. I led the a joint NCAR-GFDL group that published the first paper on this topic see: David W. Keith et al, The influence of large-scale wind-power on global climate. *Proceedings of the National* *Academy* *of Sciences*, *101*, p. 16115-16120. http://people.ucalgary.ca/~keith/papers/66.Keith.2004.WindAndClimate.e.pdf ** ** See http://people.ucalgary.ca/~keith/papers/94.Kirk-Davidoff.SurfaceRoughnessJAS.p.pdffor a paper that says a bit about why it happens. ** ** The following web page gives and overview but it’s now out of date: http://people.ucalgary.ca/~keith/wind.html ** ** Alvia’s comment that about “kinetic energy, i.e. the motion of molecules”, confuses the physics. Kinetic energy is *macroscopic* velocity, random motion of molecules is just heat. It is true that large scale production and dissipation of kinetic energy must balance, have a look at Peixoto and Oort’s the *Physics of Climate* or a short encyclopedia article I one wrote on atmospheric energetics: http://people.ucalgary.ca/~keith/papers/15.Keith.1996.Energetics.s.pdf *** * ** ** Bottom lines: ** ** 1. Commonly cited estimates for global wind power potential are too large. On cannot get to 100 TW in any practical scheme I know about. ** ** 2. At even a few TW large scale climate effects will begin to be important. But, this does not say we should not make a few TW of wind, just that--like any energy technology—there are tradeoffs. ** ** David ** ** *From:* geoengineering@googlegroups.com [mailto: geoengineering@googlegroups.com] *On Behalf Of *Nando *Sent:* Saturday, April 02, 2011 8:25 AM *To:* agask...@nc.rr.com *Cc:* andrew.lock...@gmail.com; geoengineering *Subject:* Re: [geo] Wind and wave energies are not renewable after all*** * ** ** My reading of the article suggested that the authors of the study were principally claiming that wind has an impact on climate, so it is already being used. What wasn't clear from the article was *what type* of impact reducing the energy level of winds all over the globe through the prolific use of wind turbines might have. In a warming world, I understand we should expect stronger winds. On a simplistic generalized level that might not be relevant to local climate, slowing those stronger winds down might have an ameliorating effect on climate change. Hence the claim that *The magnitude of the changes was comparable to the changes to the climate caused by doubling atmospheric concentrations of carbon dioxide* might not be as bad as it is made to seem. ** ** As usually, I'm grasping at straws, but as a layman, that's what stood out for me. ** ** Nando On Sat, Apr 2, 2011 at 3:15 PM, Alvia Gaskill agask...@nc.rr.com wrote:* *** Wind and wave energy are the result of the conversion of solar energy into kinetic energy, i.e. the motion of molecules. Once converted into kinetic energy it's a use it or lose it proposition. Extracting kinetic energy from the atmosphere or the ocean doesn't mean it won't be replaced by more energy from sunlight. Planting more trees will also intercept winds, albeit without the electricity generation. Who funded this research? The same people who want to prevent contact with alien civilizations? I note that the Royal Society was also a party to that one too. Note to Royal Society. When you actually find something under the bed I should be afraid of, wake me up. - Original Message - *From:* Andrew Lockley and...@andrewlockley.com *To:* geoengineering geoengineering@googlegroups.com *Sent:* Friday, April 01, 2011 8:10 *Subject:* [geo] Wind and wave energies are not renewable after all ** ** Wind and wave energies are not renewable after all **· **30 March 2011 by *Mark Buchanan*http://www.newscientist.com/search?rbauthors=Mark+Buchanan **·
Re: [geo] Wind and wave energies are not renewable after all
Dear David--I was going to ask a similar question to Bala¹s‹as this has actually been an ongoing argument in some circles of the energy community, with a scientific study by a Royal Society lead physicist in their energy analysis talking about a limit based on extracting a share of the existing atmospheric KE and Mark Jacobson at Stanford saying there is plenty of KE as it will be restored. It seems to me that the KE pulled out will be replaced‹if not, the atmosphere would eventually not be moving and so a huge equator-pole temperature gradient would build up. With solar energy concentrated at the low latitudes and IR loss in excess at high latitudes, the atmosphere will be seeking balance; take some energy out and the atmosphere will try to restore it, rather like what happens when one puts a rock in a stream, maybe with a bit different flow, but I would not think significantly less KE. Right? Mike On 7/12/11 7:25 AM, Govindasamy Bala bala@gmail.com wrote: Hi David, Couple of questions. Generation of wind energy would increase the KE dissipation rate but this is not an external forcing to the climate system. I agree there would be local and regional climate changes but there should be no global mean warming. Right? The current KE dissipation rate is about 2 watts/m^2. Over land, this translates to about 300 TW. Suppose wind farms extract 150 TW (which may be impractical), the dissipation rate over land will increase to 3 Wm^2. Don't you think the KE (or available PE) generation rate in the atmosphere would correspondingly increase? Of course these would be large regional climate changes. Bala On Tue, Jul 12, 2011 at 8:37 AM, David Keith ke...@ucalgary.ca wrote: Responding to a VERY old thread on wind power: The only link to geoengineering here is that there is a possibility of manipulating wind turbine drag for weather control, see: At 10¹s TW scale extraction of wind does begin to be constrained by the generation of kinetic energy. I led the a joint NCAR-GFDL group that published the first paper on this topic see: David W. Keith et al, The influence of large-scale wind-power on global climate. Proceedings of the National Academy of Sciences, 101, p. 16115-16120. http://people.ucalgary.ca/~keith/papers/66.Keith.2004.WindAndClimate.e.pdf http://people.ucalgary.ca/%7Ekeith/papers/66.Keith.2004.WindAndClimate.e.pdf See http://people.ucalgary.ca/~keith/papers/94.Kirk-Davidoff.SurfaceRoughnessJAS. p.pdf http://people.ucalgary.ca/%7Ekeith/papers/94.Kirk-Davidoff.SurfaceRoughnessJ AS.p.pdf for a paper that says a bit about why it happens. The following web page gives and overview but it¹s now out of date: http://people.ucalgary.ca/~keith/wind.html http://people.ucalgary.ca/%7Ekeith/wind.html Alvia¹s comment that about ³kinetic energy, i.e. the motion of molecules², confuses the physics. Kinetic energy is macroscopic velocity, random motion of molecules is just heat. It is true that large scale production and dissipation of kinetic energy must balance, have a look at Peixoto and Oort¹s the Physics of Climate or a short encyclopedia article I one wrote on atmospheric energetics: http://people.ucalgary.ca/~keith/papers/15.Keith.1996.Energetics.s.pdf http://people.ucalgary.ca/%7Ekeith/papers/15.Keith.1996.Energetics.s.pdf Bottom lines: 1. Commonly cited estimates for global wind power potential are too large. On cannot get to 100 TW in any practical scheme I know about. 2. At even a few TW large scale climate effects will begin to be important. But, this does not say we should not make a few TW of wind, just that--like any energy technology‹there are tradeoffs. David From: geoengineering@googlegroups.com [mailto:geoengineering@googlegroups.com] On Behalf Of Nando Sent: Saturday, April 02, 2011 8:25 AM To: agask...@nc.rr.com Cc: andrew.lock...@gmail.com; geoengineering Subject: Re: [geo] Wind and wave energies are not renewable after all My reading of the article suggested that the authors of the study were principally claiming that wind has an impact on climate, so it is already being used. What wasn't clear from the article was what type of impact reducing the energy level of winds all over the globe through the prolific use of wind turbines might have. In a warming world, I understand we should expect stronger winds. On a simplistic generalized level that might not be relevant to local climate, slowing those stronger winds down might have an ameliorating effect on climate change. Hence the claim that The magnitude of the changes was comparable to the changes to the climate caused by doubling atmospheric concentrations of carbon dioxide might not be as bad as it is made to seem. As usually, I'm grasping at straws, but as a layman, that's what stood out for me. Nando On Sat, Apr 2, 2011 at 3:15 PM, Alvia Gaskill agask...@nc.rr.com wrote: Wind and wave energy are the
Re: [geo] Wind and wave energies are not renewable after all
If anything, an obstruction or impediment to fluid flows resulting from wind energy extraction will tend to reduce heat redistribution, and that will help restore the temperature differential between tropics and poles which has been harmed by the polar amplification of global warming Logically, it will help to restore the polar ice, or at least prevent it from retreating further as fast. It could even help maintain ocean circulation, and help prevent an anoxic event. A On 12 Jul 2011 13:22, Mike MacCracken mmacc...@comcast.net wrote: Dear David--I was going to ask a similar question to Bala¹s‹as this has actually been an ongoing argument in some circles of the energy community, with a scientific study by a Royal Society lead physicist in their energy analysis talking about a limit based on extracting a share of the existing atmospheric KE and Mark Jacobson at Stanford saying there is plenty of KE as it will be restored. It seems to me that the KE pulled out will be replaced‹if not, the atmosphere would eventually not be moving and so a huge equator-pole temperature gradient would build up. With solar energy concentrated at the low latitudes and IR loss in excess at high latitudes, the atmosphere will be seeking balance; take some energy out and the atmosphere will try to restore it, rather like what happens when one puts a rock in a stream, maybe with a bit different flow, but I would not think significantly less KE. Right? Mike On 7/12/11 7:25 AM, Govindasamy Bala bala@gmail.com wrote: Hi David, Couple of questions. Generation of wind energy would increase the KE dissipation rate but this is not an external forcing to the climate system. I agree there would be local and regional climate changes but there should be no global mean warming. Right? The current KE dissipation rate is about 2 watts/m^2. Over land, this translates to about 300 TW. Suppose wind farms extract 150 TW (which may be impractical), the dissipation rate over land will increase to 3 Wm^2. Don't you think the KE (or available PE) generation rate in the atmosphere would correspondingly increase? Of course these would be large regional climate changes. Bala On Tue, Jul 12, 2011 at 8:37 AM, David Keith ke...@ucalgary.ca wrote: Responding to a VERY old thread on wind power: The only link to geoengineering here is that there is a possibility of manipulating wind turbine drag for weather control, see: At 10¹s TW scale extraction of wind does begin to be constrained by the generation of kinetic energy. I led the a joint NCAR-GFDL group that published the first paper on this topic see: David W. Keith et al, The influence of large-scale wind-power on global climate. Proceedings of the National Academy of Sciences, 101, p. 16115-16120. http://people.ucalgary.ca/~keith/papers/66.Keith.2004.WindAndClimate.e.pdf http://people.ucalgary.ca/%7Ekeith/papers/66.Keith.2004.WindAndClimate.e.pdf See http://people.ucalgary.ca/~keith/papers/94.Kirk-Davidoff.SurfaceRoughnessJAS . p.pdf http://people.ucalgary.ca/%7Ekeith/papers/94.Kirk-Davidoff.SurfaceRoughnessJ AS.p.pdf for a paper that says a bit about why it happens. The following web page gives and overview but it¹s now out of date: http://people.ucalgary.ca/~keith/wind.html http://people.ucalgary.ca/%7Ekeith/wind.html Alvia¹s comment that about ³kinetic energy, i.e. the motion of molecules², confuses the physics. Kinetic energy is macroscopic velocity, random motion of molecules is just heat. It is true that large scale production and dissipation of kinetic energy must balance, have a look at Peixoto and Oort¹s the Physics of Climate or a short encyclopedia article I one wrote on atmospheric energetics: http://people.ucalgary.ca/~keith/papers/15.Keith.1996.Energetics.s.pdf http://people.ucalgary.ca/%7Ekeith/papers/15.Keith.1996.Energetics.s.pdf Bottom lines: 1. Commonly cited estimates for global wind power potential are too large. On cannot get to 100 TW in any practical scheme I know about. 2. At even a few TW large scale climate effects will begin to be important. But, this does not say we should not make a few TW of wind, just that--like any energy technology‹there are tradeoffs. David From: geoengineering@googlegroups.com [mailto:geoengineering@googlegroups.com] On Behalf Of Nando Sent: Saturday, April 02, 2011 8:25 AM To: agask...@nc.rr.com Cc: andrew.lock...@gmail.com; geoengineering Subject: Re: [geo] Wind and wave energies are not renewable after all My reading of the article suggested that the authors of the study were principally claiming that wind has an impact on climate, so it is already being used. What wasn't clear from the article was what type of impact reducing the energy level of winds all over the globe through the prolific use of wind turbines might have. In a warming world, I understand we should expect stronger winds. On a simplistic generalized level that might not be
[geo] Re: HOME/ETC Group Targets IPCC: Data on public perception
David, Thanks for making this available. Note some earlier public opinion focus group work on geoengineering done by UK NERC - http://www.nerc.ac.uk/about/consult/geoengineering-dialogue-final-report.pdf. This contains some very interesting results, particularly on the moral hazard issue. Josh On Jul 11, 9:35 pm, David Keith ke...@ucalgary.ca wrote: Folks Earlier comments on this thread contained lots of speculation about what people think about SRM/geo. We recently submitted a paper that has some of the first results from a high-quality surveys of public perception. (Where for a survey, high-quality=that is big numbers, good demographic sampling, and well tested questions.) The paper is athttp://people.ucalgary.ca/~keith/Preprints.html. You need a username password which you can get (quickly) from the Hollie Roberts see email link on the page (and I don't change it). Yours, David -- You received this message because you are subscribed to the Google Groups geoengineering group. To post to this group, send email to geoengineering@googlegroups.com. To unsubscribe from this group, send email to geoengineering+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en.
RE: [geo] Wind and wave energies are not renewable after all
Mike Bala A few answers: First there is almost no link to geo here so we should probably take this off this list. The only (weak link) is weather control, see: http://www.atmos-chem-phys.org/10/769/2010/acp-10-769-2010.html 1. Bala said Generation of wind energy would increase the KE dissipation rate but this is not an external forcing to the climate system. And The current KE dissipation rate is about 2 watts/m^2. Over land, this translates to about 300 TW. Suppose wind farms extract 150 TW (which may be impractical), the dissipation rate over land will increase to 3 Wm^2. Don't you think the KE (or available PE) generation rate in the atmosphere would correspondingly increase? Of course these would be large regional climate changes. Answer: As the surface drag is increased the total dissipation does not change much. That is, as you increase the KE sink in some locations with wind turbines the dissipation decreases elsewhere keeping total about constant. See Figure 2 of our 2004 PNAS where we tried this. This is what one would expect because dissipation of KE must balance its creation from APE (see pexoto and ort or my encyclopedia article cited below for an overview of atmo energetics). Going a bit deeper one might think that with more to push against the APE generation rate would go up and the atmo heat engine get more efficient, Kerry Emanuel have suggested to me that this should not be true because of a maximum entropy principle that I do not fully understand. Bottom line: very likely Bala's assumption is wrong. 2. Bala said: I agree there would be local and regional climate changes but there should be no global mean warming. Right? Answer: mostly. One can see either warming or cooling depending on where the wind drag is applied. The point is that (a) climate changes due to drag are non-local, and (b) they can be large. 3. Mike asked about the Jacobsen paper that says no effect. Answer: I think this paper is just wrong. If it were true I could violate the first law by extracting power without altering KE and then using that power to increase APE generating infinite power with no input. Nice trick. There are now about 5 studies that confirm the broad results in our 2004 paper. The Jacobsen paper is an outlier. I expect a convincing critique will be published in the next few years. Yours, David From: geoengineering@googlegroups.com [mailto:geoengineering@googlegroups.com] On Behalf Of Mike MacCracken Sent: Tuesday, July 12, 2011 6:22 AM To: Govindasamy Bala; David Keith; Ken Caldeira Cc: Geoengineering Subject: Re: [geo] Wind and wave energies are not renewable after all Dear David--I was going to ask a similar question to Bala's-as this has actually been an ongoing argument in some circles of the energy community, with a scientific study by a Royal Society lead physicist in their energy analysis talking about a limit based on extracting a share of the existing atmospheric KE and Mark Jacobson at Stanford saying there is plenty of KE as it will be restored. It seems to me that the KE pulled out will be replaced-if not, the atmosphere would eventually not be moving and so a huge equator-pole temperature gradient would build up. With solar energy concentrated at the low latitudes and IR loss in excess at high latitudes, the atmosphere will be seeking balance; take some energy out and the atmosphere will try to restore it, rather like what happens when one puts a rock in a stream, maybe with a bit different flow, but I would not think significantly less KE. Right? Mike On 7/12/11 7:25 AM, Govindasamy Bala bala@gmail.com wrote: Hi David, Couple of questions. Generation of wind energy would increase the KE dissipation rate but this is not an external forcing to the climate system. I agree there would be local and regional climate changes but there should be no global mean warming. Right? The current KE dissipation rate is about 2 watts/m^2. Over land, this translates to about 300 TW. Suppose wind farms extract 150 TW (which may be impractical), the dissipation rate over land will increase to 3 Wm^2. Don't you think the KE (or available PE) generation rate in the atmosphere would correspondingly increase? Of course these would be large regional climate changes. Bala On Tue, Jul 12, 2011 at 8:37 AM, David Keith ke...@ucalgary.ca wrote: Responding to a VERY old thread on wind power: The only link to geoengineering here is that there is a possibility of manipulating wind turbine drag for weather control, see: At 10's TW scale extraction of wind does begin to be constrained by the generation of kinetic energy. I led the a joint NCAR-GFDL group that published the first paper on this topic see: David W. Keith et al, The influence of large-scale wind-power on global climate. Proceedings of the National Academy of Sciences, 101, p. 16115-16120. http://people.ucalgary.ca/~keith/papers/66.Keith.2004.WindAndClimate.e.pdf
Re: [geo] Wind and wave energies are not renewable after all
A few further thoughts. The driving force for atmospheric motions is the equator-pole temperature gradient‹energy continues to come in and decrease entropy (that is, enhancing the gradient), and then the motions tend to increase the entropy (trying to smooth out the gradient). I guess what wind power really does is create an alternate form of dissipation to small eddies moving vegetation and just dissipating heat. So, instead of local heat dissipation by the vegetation (entropy increase), the energy is drained by windmills and then the electricity is dissipated as heat, so it is an alternative pathway. And I gather what you find is that the atmosphere above does not really care if the dissipation is locally friction heat loss or goes through the wind power bypass, doing some useful work for humanity. I guess that is just sort of saying that having fully efficient wind power machines would be no different than having higher orography, as far as the atmospheric circulation is concerned. So, then the question is what fraction of the surface friction that one can replace with wind power machines. While you did the calculation for land areas, there is really no reason that one could not have floating windmills out over the ocean, diverting energy away from the wind driven currents and evaporation. If one could develop the optimal machine, one could potentially extract energy at the rate that it is created by the differences in energy being supplied and radiated away from low and high latitudes, not wasting any energy in wind, etc.--so there is a theoretical upper limit‹the supply is not infinite. But, the amount available could be pretty large using large windmills, tethered wind turbines in the jet stream, etc.--for an interim period, this would likely cause an increase in the gradient, but ultimately the limiting rate of removal of energy is the pole-equator difference (times some fractional potential efficiency). As for the Jacobson calculation, the US is a pretty small area and so I would think creating a stronger drag over it would tend to attract energy in from elsewhere as Nature likes to push down gradients. This can take time, but there surely will be some infilling, especially given large scale motions due to the atmospheric circulation. Interesting. Mike On 7/12/11 9:36 PM, David Keith ke...@ucalgary.ca wrote: Mike Bala A few answers: First there is almost no link to geo here so we should probably take this off this list. The only (weak link) is weather control, see: http://www.atmos-chem-phys.org/10/769/2010/acp-10-769-2010.html 1. Bala said ³Generation of wind energy would increase the KE dissipation rate but this is not an external forcing to the climate system.² And ³The current KE dissipation rate is about 2 watts/m^2. Over land, this translates to about 300 TW. Suppose wind farms extract 150 TW (which may be impractical), the dissipation rate over land will increase to 3 Wm^2. Don't you think the KE (or available PE) generation rate in the atmosphere would correspondingly increase? Of course these would be large regional climate changes.² Answer: As the surface drag is increased the total dissipation does not change much. That is, as you increase the KE sink in some locations with wind turbines the dissipation decreases elsewhere keeping total about constant. See Figure 2 of our 2004 PNAS where we tried this. This is what one would expect because dissipation of KE must balance its creation from APE (see pexoto and ort or my encyclopedia article cited below for an overview of atmo energetics). Going a bit deeper one might think that with more to ³push against² the APE generation rate would go up and the atmo heat engine get more efficient, Kerry Emanuel have suggested to me that this should not be true because of a maximum entropy principle that I do not fully understand. Bottom line: very likely Bala¹s assumption is wrong. 2. Bala said: ³I agree there would be local and regional climate changes but there should be no global mean warming. Right?² Answer: mostly. One can see either warming or cooling depending on where the wind drag is applied. The point is that (a) climate changes due to drag are non-local, and (b) they can be large. 3. Mike asked about the Jacobsen paper that says no effect. Answer: I think this paper is just wrong. If it were true I could violate the first law by extracting power without altering KE and then using that power to increase APE generating infinite power with no input. Nice trick. There are now about 5 studies that confirm the broad results in our 2004 paper. The Jacobsen paper is an outlier. I expect a convincing critique will be published in the next few years. Yours, David From: geoengineering@googlegroups.com [mailto:geoengineering@googlegroups.com] On Behalf Of Mike MacCracken Sent: Tuesday, July 12, 2011 6:22 AM To: Govindasamy Bala; David Keith; Ken Caldeira Cc:
