Alvia's comments aren't the whole picture, and neither is the report. It's not a cost benefit analysis! OIF may be limited in it's capacity but it's cheap as chips (as it's a leveraged effect). There are lots of other techniques they didn't consider, such as using dust aerosols and adding powdered rock to oceans - both of which are promising.
However, I think the analysis that cloud machines and sulfur aerosols are 'right now' technologies that could save use from runaway climate change. However, it's notable that when you add up ALL the radiative forcing, it's not enough to offset the radiative forcing from a methane-rich atmosphere. The inescapable conclusion is that if we leave it too late then not even geoengineering will save us. A 2009/1/28 Alvia Gaskill <[email protected]>: > OIF gets an F, while others do less well than advertised (UK spelling). > Puts the urban albedo idea into perspective also. Comments solicited by the > authors. Thanks to Oliver Morton for the link from the less well attended > Climate Intervention group. Never heard of the desert cover idea Oliver? > Must not read the NY Times. Or the Geoengineering Group. Or the DEFRA > response to Parliament. Or the EU website for post Kyoto. Or the recent > article I panned where they confused a year with a century (other > assumptions were about the same). > > Lots to discuss on this one. It is interesting to see a side-by-side > comparison. Haven't read it all the way through, but the tree planting idea > must be wrong and doesn't take into account albedo feedback effects. I also > don't think biochar has a chance. Need to look into BAP (benzo-a-pyrene) > produced. It IS a human carcinogen and EPA has spent millions getting rid > of it from town gas and other Superfund type sites. > > http://www.atmos-chem-phys-discuss.net/9/2559/2009/acpd-9-2559-2009.pdf > > > http://www.atmos-chem-phys-discuss.net/9/2559/2009/acpd-9-2559-2009.html > > > Atmos. Chem. Phys. Discuss., 9, 2559-2608, 2009 > www.atmos-chem-phys-discuss.net/9/2559/2009/ > (c) Author(s) 2009. This work is distributed > under the Creative Commons Attribution 3.0 License. > > The radiative forcing potential of different climate geoengineering options > > T. M. Lenton1,2 and N. E. Vaughan1,2 > 1School of Environmental Sciences, University of East Anglia, Norwich NR4 > 7TJ, UK > 2Tyndall Centre for Climate Change Research, UK > > Abstract. Climate geoengineering proposals seek to rectify the Earth's > current radiative imbalance, either by reducing the absorption of incoming > solar (shortwave) radiation, or by removing CO2 from the atmosphere and > transferring it to long-lived reservoirs, thus increasing outgoing longwave > radiation. A fundamental criterion for evaluating geoengineering options is > their climate cooling effectiveness, which we quantify here in terms of > radiative forcing potential. We use a simple analytical approach, based on > the global energy balance and pulse response functions for the decay of CO2 > perturbations. This aids transparency compared to calculations with complex > numerical models, but is not intended to be definitive. Already it reveals > some significant errors in existing calculations, and it allows us to > compare the relative effectiveness of a range of proposals. By 2050, only > stratospheric aerosol injections or sunshades in space have the potential to > cool the climate back toward its pre-industrial state, but some land carbon > cycle geoengineering options are of comparable magnitude to mitigation > "wedges". Strong mitigation, i.e. large reductions in CO2 emissions, > combined with global-scale air capture and storage, afforestation, and > bio-char production, i.e. enhanced CO2 sinks, might be able to bring CO2 > back to its pre-industrial level by 2100, thus removing the need for other > geoengineering. Alternatively, strong mitigation stabilising CO2 at 500 ppm, > combined with geoengineered increases in the albedo of marine stratiform > clouds, grasslands, croplands and human settlements might achieve a patchy > cancellation of radiative forcing. Ocean fertilisation options are only > worthwhile if sustained on a millennial timescale and phosphorus addition > probably has greater long-term potential than iron or nitrogen > fertilisation. Enhancing ocean upwelling or downwelling have trivial effects > on any meaningful timescale. Our approach provides a common framework for > the evaluation of climate geoengineering proposals, and our results should > help inform the prioritisation of further research into them. > > Discussion Paper (PDF, 771 KB) Interactive Discussion (Open, 0 Comments) > > Citation: Lenton, T. M. and Vaughan, N. E.: The radiative forcing potential > of different climate geoengineering options, Atmos. Chem. Phys. Discuss., 9, > 2559-2608, 2009. Bibtex EndNote Reference Manager > > ----- Original Message ----- > From: "Oliver Morton" <[email protected]> > To: "Climate Intervention" <[email protected]> > Sent: Tuesday, January 27, 2009 7:57 PM > Subject: [clim] Lenton and Vaughan paper comparing potential of different > geoengineering approaches > > I just posted this at Heliophage (and if anyone known how to get html > into posts here could they explain it to me?) Meanwhile, to see links > go to > http://heliophage.wordpress.com/2009/01/28/geoengineering-by-the-numbers/ > > A very useful paper comes out today in Atmospheric Chemistry and > Physics by Tim Lenton and his student Naomi Vaughan. Tim told me when > I was reporting the Andy Ridgwell paper on leaf albedo (Nature story| > blog entry) that he'd become pretty interested in evaluating > geoengineering schemes, and was setting up a group at the University > of East Anglia to assess them. This paper presumably represents the > first fruits of that interest, providing a ranking of most of the > geoengineering schemes proposed in the literature in terms of the > amount of radiative forcing they can provide. > > Radiative forcing is, more or less, the difference in terms of energy > per square metre that's associated with any given action that changes > the climate; it's a pretty routine way of expressing things in IPCC- > land. The IPCC puts the radiative forcing associated with the > greenhouse gas industrial and industrialising societies pumped into > the atmosphere from 1800 to 2005 at about 1.6W/m², and the forcing > for a doubling of CO2 at about 3.7W/m². > > Lenton and Vaughan first divide geoengineering proposals into two > sorts: shortwave and longwave. Shortwave schemes seek to reduce the > amount of energy that gets into the earth system by reflecting away > incoming sunlight. Longwave schemes seek to increase the amount of > energy leaving the earth system by making the atmosphere more > transparent to outgoing infrared radiation -- that is, by reducing the > greenhouse effect. Then they assess the two with some very simple > modelling (well, for the longwave there are some wrinkles, but it's > all in principle pretty simple). They don't claim that the figures > they come up with are the best available in any particular case, just > that they are all derived the same way, and so allow fairly > straightforward comparisons. By standardising the techniques they also > show up a few errors in previous analyses: for example, if you > increase the total amount of light reflected back into space by > clouds, you reduce the amount reflected by the surface, simply because > less light gets there in the first place. > > The first and most striking conclusion is that if you want to have a > big effect, go shortwave. Sulphate aerosols in the stratosphere (which > were the main topic of this piece and these Climate Feedback posts) > and mirrors/refractors in space (also in that piece, and in this paper > by Roger Angel) both have the potential to provide as much by way of > negative forcing as a doubling of CO2 provides by way of positive > forcing. Not surprising; if you're not constrained by money or by > concerns about environmental side effects, you can put mirrors in the > sky and particles in the stratosphere until it's darkness at noon. > > When you leave these global technologies behind, the other shortwave > interventions rank, unsurprisingly, more or less according to the area > they affect. Increasing the brightness of marine stratocumulus clouds, > as proposed by John Latham, would affect about 17% of the earth's > surface, and the Lenton-Vaughan analysis suggests that the whitening > effect would have to be considerably more marked than previous work > has assumed; but if that brightening could be achieved then a negative > forcing that averages more than 3W/m² should be possible. Covering non- > sandy deserts with aluminium and polyethylene (not an idea I had come > across before, and a pretty silly one as far as I can see: more here > if you want it) makes 2% of the surface a lot brighter, and gets you > an average 1.7W/m² of negative forcing, obviously very unevenly > spread. Increasing the brightness of the planet's grassland as Robert > Hamwey has discussed (pdf) gets you 0.64W/m², and the Ridgwell et al > idea of planting brighter crops gets you 0.44W/m² at best, croplands > being smaller than grasslands. Lightening everywhere that people > actually live (another idea from the Hamwey paper) gets you 0.19W/m²; > increasing the area of plankton blooms that seed the creation of > clouds in parts of the southern ocean gives you just 0.016W/m² (and > that may be an overestimate) and restricting yourself to just creating > shinier cities gives you no more than 0.01W/m². > > What of the longwave? In principle, capturing carbon dioxide from the > air (pdf of the Keith et al paper) and burying it in the ground could > give you whatever radiative forcing you wanted; the limits to such a > scheme are entirely economic, rather than being imposed on the earth > system. All the other schemes, though, which involve making changes in > the natural carbon cycle, are quite constrained, with none able to > counter a doubling of carbon dioxide, even given the most extreme > assumptions. > > The biggest effect comes from really aggressive planting of forests, > as described in an essay (pdf) by Peter Read on his global gardening > plans. This involves growing enough plant material in the next 50 > years to more than completely make up for all the arbon dioxide lost > through deforestation and land use change over the past few centuries, > which is really remarkably ambitious, especially if people are still > going to have some space to grow food. By 2050 this strategy gets you > an effective 0.49W/m² of negative forcing thanks to 88 gigatonnes of > carbon dioxide being stored away. A variant of the idea in which you > grow the biomass and burn it in power stations fitted out for carbon > capture and storage does even better: 0.69W/m² by 2050 and almost 2W/ > m² by 2100 (For the longwave calculations, the radiative forcing > depends on how long the programme has been going on. It also depends > on what assumptions you make about how effective carbon-emissions > control is; Lenton and Vaughan calculate all the forcings in terms of > what extra relief the carbon-dioxide drawdown provides in a world that > is already making serious cuts in emissions). > > A lower tech idea that Read is fond of, as for that matter am I, is > turning biomass into biochar and ploughing it into the ground. Jim > Lovelock, Lenton's mentor and friend, was extolling this as a possible > way of making things better in New Scientist last week, speaking to > the in-this-case-aptly-named Gaia Vince. This may make sense for all > sorts of reasons, and the fact that making the charcoal also provides > you with fuel (see Johannes Lehmann's commentary in Nature a few years > ago) is obviously a plus, but even a really aggressive campaign along > these lines gives ou a negative forcing of only 0.40W/m² by 2100. > > After that come a bunch of ocean fertilization schemes, using > phosphorous, nitrogen and iron, all of which offer something in the > region of 0.1-0.2W/m². A system of pumping nutrient-rich water up to > the ocean surface sketched out by Lovelock and Chris Rapley (earlier > blog entry) delivers a truly meagre 0.003W/m² by 2100. > > None of this, as Lenton and Vaughan are at pains to make clear, counts > as an endorsement; all the schemes have side effects and risks, as > well as in some cases (ahoy there, vast fleet of space parasols) > quite remarkable costs. But looking at the options this way does allow > a sense of what might be possible, and a way of seeing what might be > done in a mix and match sort of way. And the fact that the paper is > published in the discussion section of ACPD means that the various > researchers whose work is discussed will have a chance to answer back, > correct any poor assumptions, and carry the debate forward. > > Cross-posted to Climate Feedback > > http://heliophage.wordpress.com/2009/01/28/geoengineering-by-the-numbers/ > > Here it is with the links. To add links to posts, simply copy the link and > paste it into the post. Always glad to help the working professional. > Geoengineering by the numbers > January 28, 2009, 12:34 am > Filed under: Geoengineering, Global change, Interventions in the > carbon/climate crisis > > A very useful paper (abstract|pdf|discussion space) comes out today in > Atmospheric Chemistry and Physics by Tim Lenton and his student Naomi > Vaughan. Tim told me when I was reporting the Andy Ridgwell paper on leaf > albedo (Nature story|blog entry) that he'd become pretty interested in > evaluating geoengineering schemes, and was setting up a group at the > University of East Anglia to assess them. This paper presumably represents > the first fruits of that interest, providing a ranking of most of the > geoengineering schemes proposed in the literature in terms of the amount of > radiative forcing they can provide. > > Radiative forcing is, more or less, the difference in terms of energy per > square metre that's associated with any given action that changes the > climate; it's a pretty routine way of expressing things in IPCC-land. The > IPCC puts the radiative forcing associated with the greenhouse gas > industrial and industrialising societies pumped into the atmosphere from > 1800 to 2005 at about 1.6W/m², and the forcing for a doubling of CO2 at > about 3.7W/m². > > Lenton and Vaughan first divide geoengineering proposals into two sorts: > shortwave and longwave. Shortwave schemes seek to reduce the amount of > energy that gets into the earth system by reflecting away incoming sunlight. > Longwave schemes seek to increase the amount of energy leaving the earth > system by making the atmosphere more transparent to outgoing infrared > radiation — that is, by reducing the greenhouse effect. Then they assess the > two with some very simple modelling (well, for the longwave there are some > wrinkles, but it's all in principle pretty simple). They don't claim that > the figures they come up with are the best available in any particular case, > just that they are all derived the same way, and so allow fairly > straightforward comparisons. By standardising the techniques they also show > up a few errors in previous analyses: for example, if you increase the total > amount of light reflected back into space by clouds, you reduce the amount > reflected by the surface, simply because less light gets there in the first > place. > > The first and most striking conclusion is that if you want to have a big > effect, go shortwave. Sulphate aerosols in the stratosphere (which were the > main topic of this piece and these Climate Feedback posts) and > mirrors/refractors in space (also in that piece, and in this paper by Roger > Angel) both have the potential to provide as much by way of negative forcing > as a doubling of CO2 provides by way of positive forcing. Not surprising; if > you're not constrained by money or by concerns about environmental side > effects, you can put mirrors in the sky and particles in the stratosphere > until it's darkness at noon. > > When you leave these global technologies behind, the other shortwave > interventions rank, unsurprisingly, more or less according to the area they > affect. Increasing the brightness of marine stratocumulus clouds, as > proposed by John Latham, would affect about 17% of the earth's surface, and > the Lenton-Vaughan analysis suggests that the whitening effect would have to > be considerably more marked than previous work has assumed; but if that > brightening could be achieved then a negative forcing that averages more > than 3W/m² should be possible. Covering non-sandy deserts with aluminium and > polyethylene (not an idea I had come across before, and a pretty silly one > as far as I can see: more here if you want it) makes 2% of the surface a lot > brighter, and gets you an average 1.7W/m² of negative forcing, obviously > very unevenly spread. Increasing the brightness of the planet's grassland > as Robert Hamwey has discussed (pdf) gets you 0.64W/m², and the Ridgwell et > al idea of planting brighter crops gets you 0.44W/m² at best, croplands > being smaller than grasslands. Lightening everywhere that people actually > live (another idea from the Hamwey paper) gets you 0.19W/m²; increasing the > area of plankton blooms that seed the creation of clouds in parts of the > southern ocean gives you just 0.016W/m² (and that may be an overestimate) > and restricting yourself to just creating shinier cities gives you no more > than 0.01W/m². > > What of the longwave? In principle, capturing carbon dioxide from the air > (pdf of the Keith et al paper) and burying it in the ground could give you > whatever radiative forcing you wanted; the limits to such a scheme are > entirely economic, rather than being imposed on the earth system. All the > other schemes, though, which involve making changes in the natural carbon > cycle, are quite constrained, with none able to counter a doubling of carbon > dioxide, even given the most extreme assumptions. > > The biggest effect comes from really aggressive planting of forests, as > described in an essay (pdf) by Peter Read on his global gardening plans. > This involves growing enough plant material in the next 50 years to more > than completely make up for all the arbon dioxide lost through deforestation > and land use change over the past few centuries, which is really remarkably > ambitious, especially if people are still going to have some space to grow > food. By 2050 this strategy gets you an effective 0.49W/m² of negative > forcing thanks to 88 gigatonnes of carbon dioxide being stored away. A > variant of the idea in which you grow the biomass and burn it in power > stations fitted out for carbon capture and storage does even better: > 0.69W/m² by 2050 and almost 2W/m² by 2100 (For the longwave calculations, > the radiative forcing depends on how long the programme has been going on. > It also depends on what assumptions you make about how effective > carbon-emissions control is; Lenton and Vaughan calculate all the forcings > in terms of what extra relief the carbon-dioxide drawdown provides in a > world that is already making serious cuts in emissions). > > A lower tech idea that Read is fond of, as for that matter am I, is turning > biomass into biochar and ploughing it into the ground. Jim Lovelock, > Lenton's mentor and friend, was extolling this as a possible way of making > things better in New Scientist last week, speaking to the > in-this-case-aptly-named Gaia Vince. This may make sense for all sorts of > reasons, and the fact that making the charcoal also provides you with fuel > (see Johannes Lehmann's commentary in Nature a few years ago) is obviously > a plus, but even a really aggressive campaign along these lines gives ou a > negative forcing of only 0.40W/m² by 2100. > > After that come a bunch of ocean fertilization schemes, using phosphorous, > nitrogen and iron, all of which offer something in the region of > 0.1-0.2W/m². A system of pumping nutrient-rich water up to the ocean surface > sketched out by Lovelock and Chris Rapley (earlier blog entry) delivers a > truly meagre 0.003W/m² by 2100. > > None of this, as Lenton and Vaughan are at pains to make clear, counts as an > endorsement; all the schemes have side effects and risks, as well as in some > cases (ahoy there, vast fleet of space parasols) quite remarkable costs. > But looking at the options this way does allow a sense of what might be > possible, and a way of seeing what might be done in a mix and match sort of > way. And the fact that the paper is published in the discussion section of > ACPD means that the various researchers whose work is discussed will have a > chance to answer back, correct any poor assumptions, and carry the debate > forward. > > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
