Skip to main content


Log in

The cost of stratospheric climate engineering revisited

  • Original Article
  • Published:
Mitigation and Adaptation Strategies for Global Change Aims and scope Submit manuscript

An Erratum to this article was published on 23 December 2016

This article has been updated


Stratospheric aerosol injection (SAI) has been receiving increasing attention as a possible option for climate engineering. Its direct cost is perceived to be low, which has implications for international governance of this emerging technology. Here, we critically synthesize previous estimates of the underlying parameters and examine the total costs of SAI. It is evident that there have been inconsistencies in some assumptions and the application of overly optimistic parameter values in previous studies, which have led to an overall underestimation of the cost of aircraft-based SAI with sulfate aerosols. The annual cost of SAI to achieve cooling of 2 W/m2 could reach US$10 billion with newly designed aircraft, which contrasts with the oft-quoted estimate of “a few billion dollars.” If existing aircraft were used, the cost would be expected to increase further. An SAI operation would be a large-scale engineering undertaking, possibly requiring a fleet of approximately 1,000 aircraft, because of the required high altitude of the injection. Therefore, because of its significance, a more thorough investigation of the engineering aspects of SAI and the associated uncertainties is warranted.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Subscribe and save

Springer+ Basic
EUR 32.99 /Month
  • Get 10 units per month
  • Download Article/Chapter or Ebook
  • 1 Unit = 1 Article or 1 Chapter
  • Cancel anytime
Subscribe now

Buy Now

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6

Similar content being viewed by others

Change history

  • 23 December 2016

    An erratum to this article has been published.


  • Barrett S (2008) The incredible economics of geoengineering. Environ Resour Econ 39(1):45–54

    Article  Google Scholar 

  • Barrett S (2014) Solar Geoengineering’s brave new world: thoughts on the governance of an unprecedented technology. Rev Environ Econ Policy 8(2):249–269. doi:10.1093/reep/reu011

    Article  Google Scholar 

  • Blackstock J, Steinbruner J, Cohen A (2013) Climate change series: the geoengineering debate.

  • Blackstock JJ, Battisti D, Caldeira K et al (2009) Climate engineering responses to climate emergencies. Novim, archived online at:

  • Bodansky D (2011) Governing climate engineering: scenarios for analysis. Discussion Paper 2011–47, Cambridge, Mass.: Harvard Project on Climate Agreements

  • Boeing Defense Space & Security (2013) Backgrounder: F-15E Strike Eagle.

  • Budyko MI (1977) Climatic changes. American Geophysical Union, Washington DC

  • Caldeira K, Keith DW (2010) The need for climate engineering research. Issues Sci Technol Fall 2010:57–62

    Google Scholar 

  • Caviezel C, Revermann C (2014) Climate engineering: Kann und soll man die Erderwarmung technisch eindammen? Statew Agric L Use Baseline 2015. doi:10.1017/CBO9781107415324.004

  • Collins A (2014) Andrew Parker: uncertainties and implications of geoengineering. In: Belfer Cent.

  • Crutzen PJ (2006) Albedo enhancement by stratospheric sulfur injections: a contribution to resolve a policy dilemma? Clim Chang 77:211–219. doi:10.1007/s10584-006-9101-y

    Article  Google Scholar 

  • Davidson P, Burgoyne C, Hunt H, Causier M (2012) Lifting options for stratospheric aerosol geoengineering: advantages of tethered balloon systems. Philos Trans A Math Phys Eng Sci 370:4263–4300. doi:10.1098/rsta.2011.0639

    Article  Google Scholar 

  • Davies S, Dildy D (2007) F-15 eagle engaged: the world’s most successful jet fighter. Osprey Publishing Limited, Oxford, UK

    Google Scholar 

  • Dykema JA, Keith DW, Keutsch FN (2016) Improved aerosol radiative properties as a foundation for solar geoengineering risk assessment. Gephys Res Lett 43(14):7758–7766. doi:10.1002/2016GL069258

    Article  Google Scholar 

  • English JM, Toon OB, Mills MJ (2012) Microphysical simulations of sulfur burdens from stratospheric sulfur geoengineering. Atmos Chem Phys 12:4775–4793. doi:10.5194/acp-12-4775-2012

    Article  Google Scholar 

  • Flyvbjerg B, Skamris Holm MK, Buhl SL (2004) What causes cost overrun in transport infrastructure projects? Transp Rev 24:3–18. doi:10.1080/0144164032000080494a

    Article  Google Scholar 

  • Forbes (2015) The world’s billionaires.

  • Foundation Center (2014) Top 100 U.S. foundations by asset size.

  • Fuss S, Canadell JG, Peters GP, et al. (2014) Betting on negative emissions. Nat Clim Chang 4:850–853

    Article  Google Scholar 

  • Gingrich N (2008) Stop the green pig: defeat the Boxer–Warner–Lieberman Green Pork Bill capping American jobs and trading America’s future (Newt Direct Blog, June 3, 2008).

  • (2011) F15 Eagle production/inventory.

  • Gregory JM, Ingram WJ, Palmer MA, et al. (2004) A new method for diagnosing radiative forcing and climate sensitivity. Geophys Res Lett 31:L03205. doi:10.1029/2003GL018747

    Google Scholar 

  • Hamilton C (2013) Earthmasters: the dawn of the age of climate engineering. Yale University Press, New Haven and London

    Google Scholar 

  • Heckendorn P, Weisenstein D, Fueglistaler S, et al. (2009) The impact of geoengineering aerosols on stratospheric temperature and ozone. Environ Res Lett 4:045108. doi:10.1088/1748-9326/4/4/045108

    Article  Google Scholar 

  • Holton JR, Haynes PH, McIntyre ME, et al. (1995) Stratosphere–troposhere exchange. Rev Geophys 33:403–439

    Article  Google Scholar 

  • Horton JB (2011) Geoengineering and the myth of unilateralism: pressures and prospects for international cooperation. Stanford J Law Sci Policy IV:56–69

  • Hulme M (2014) Can science fix climate change?: a case against climate engineering. Polity Press, Cambridge, UK

    Google Scholar 

  • International Civil Aviation Organization (1993) Manual of the ICAO standard atmosphere: extended to 80 kilometres (262 500 feet). Int. Civil Aviation Org, Montreal, Quebec

    Google Scholar 

  • Irvine PJ, Kravitz B, Lawrence MG, Muri H (2016) An overview of the earth system science of solar geoengineering. WIREs Clim Change. doi:10.1002/wcc.423

    Google Scholar 

  • Jahren CT, Ashe AM (1990) Predictors of cost-overrun rates. J Constr Eng Manag 116:548–552. doi:10.1061/(ASCE)0733-9364(1990)116:3(548)

    Article  Google Scholar 

  • Jones A, Haywood J, Boucher O, et al. (2010) Geoengineering by stratospheric SO2 injection: results from the Met Office HadGEM2 climate model and comparison with the Goddard Institute for Space Studies ModelE. Atmos Chem Phys 10:5999–6006. doi:10.5194/acp-10-5999-2010

    Article  Google Scholar 

  • Jones A, Haywood J, Jones A (2016) Climatic impacts of stratospheric geoengineering with sulfate, black carbon and titania injection. Atmos Chem Phys 16:2843–2862. doi:10.5194/acp-16-2843-2016

    Article  Google Scholar 

  • Katz JI (2010) Stratospheric albedo modification. Energy Environ Sci 3:1634–1644. doi:10.1039/c002441d

    Article  Google Scholar 

  • Keith DW (2000) Geoengineering the climate: history and prospect. Annu Rev Energy Environ 25:245–284

    Article  Google Scholar 

  • Keith DW (2010) Photophoretic levitation of engineered aerosols for geoengineering. Proc Natl Acad Sci U S A 107:16428–16431. doi:10.1073/pnas.1009519107

    Article  Google Scholar 

  • Keith DW (2013) A case for climate engineering. The MIT Press, Cambridge, MA

    Google Scholar 

  • Keith DW, MacMartin DG (2015) A temporary, moderate and responsive scenario for solar geoengineering. Nat Clim Chang 5:201–206. doi:10.1038/nclimate2493

    Article  Google Scholar 

  • Keith DW, Parson E, Morgan MG (2010) Research on global sun block needed now. Nature 463:426–427. doi:10.1038/463426a

    Article  Google Scholar 

  • Klepper G, Rickels W (2011) Climate engineering, Wirtschaftliche Aspekte

  • Klepper G, Rickels W (2014) Climate engineering: economic considerations and research challenges. Rev Environ Econ Policy 8:270–289. doi:10.1093/reep/reu010

    Article  Google Scholar 

  • Kravitz B (2013) Climate engineering with stratospheric aerosols and associated engineering parameters. In: Frontiers of engineering: reports on leading-edge engineering from the 2012 symposium. The National Academies Press, Washington DC

    Google Scholar 

  • Kravitz B, Caldeira K, Boucher O, et al. (2013) Climate model response from the Geoengineering Model Intercomparison Project (GeoMIP). J Geophys Res Atmos 118:8320–8332. doi:10.1002/jgrd.50646

    Article  Google Scholar 

  • Kravitz B, Robock A, Boucher O, et al. (2011a) The Geoengineering Model Intercomparison Project (GeoMIP). Atmos Sci Lett 12:162–167. doi:10.1002/asl.316

    Article  Google Scholar 

  • Kravitz B, Robock A, Boucher O et al (2011b) Specifications for GeoMIP experiments G1 through G4. Version 1.0

  • Lenton TM, Vaughan NE (2009) The radiative forcing potential of different climate geoengineering options. Atmos Chem Phys 9:5539–5561. doi:10.5194/acp-9-5539-2009

    Article  Google Scholar 

  • MacMartin DG, Caldeira K, Keith DW (2014) Solar geoengineering to limit the rate of temperature change. Philos Trans R Soc A 372:20140134. doi:10.1098/rsta.2014.0134

    Article  Google Scholar 

  • McClellan J, Keith DW, Apt J (2012) Cost analysis of stratospheric albedo modification delivery systems. Environ Res Lett 7:034019. doi:10.1088/1748-9326/7/3/034019

    Article  Google Scholar 

  • Michaelson J (2013) Geoengineering and climate management: from marginality to inevitability. In: Climate change geoengineering: philosophical perspectives, legal issues, and governance frameworks. Cambridge University Press, Cambridge, UK

  • Morton O (2008) AGU: Geoengineering costs.

  • Moss RH, Edmonds JA, Hibbard KA, et al. (2010) The next generation of scenarios for climate change research and assessment. Nature 463:747–756. doi:10.1038/nature08823

    Article  Google Scholar 

  • Myhre G, Shindell D, Bréon F-M et al (2013) Anthropogenic and natural radiative forcing. In: Stocker TF, Dahe Q, Plattner, G-K, et al (eds) Clim. Chang. 2013 Phys. Sci. Basis. Contrib. Work. Gr. I to Fifth Assess. Rep. Intergov. Panel Clim. Chang. Cambridge University Press, Cambridge, UK, pp 659–740

  • National Research Council (2015) Climate intervention: reflecting sunlight to cool earth. The National Academies Press, Washington DC

    Google Scholar 

  • Nemet GF, Kammen DM (2007) U.S. energy research and development: declining investment, increasing need, and the feasibility of expansion. Energy Policy 35:746–755. doi:10.1016/j.enpol.2005.12.012

    Article  Google Scholar 

  • Niemeier U, Timmreck C (2015) What is the limit of climate engineering by stratospheric injection of SO2? Atmos Chem Phys 15:9129–9141. doi:10.5194/acp-15-9129-2015

    Article  Google Scholar 

  • Niemeier U, Schmidt H, Timmreck C (2011) The dependency of geoengineered sulfate aerosol on the emission strategy. Atmos Sci Lett 12:189–194. doi:10.1002/asl.304

    Article  Google Scholar 

  • Panel on Policy Implications of Greenhouse Warming (1992) Policy implications of greenhouse warming: mitigation, adaptation, and the science base. Press, Washington DC, Natl. Acad

    Google Scholar 

  • Parson EA, Ernst LN (2013) International governance of climate engineering. Theor Inq Law 14:307–337. doi:10.1515/til-2013-015

    Google Scholar 

  • Pierce JR, Weisenstein DK, Heckendorn P, et al. (2010) Efficient formation of stratospheric aerosol for climate engineering by emission of condensible vapor from aircraft. Geophys Res Lett 37:L18805. doi:10.1029/2010GL043975

    Article  Google Scholar 

  • Pope FD, Braesicke P, Grainger RG, et al. (2012) Stratospheric aerosol particles and solar-radiation management. Nat Clim Chang 2:713–719. doi:10.1038/NCLIMATE1528

    Article  Google Scholar 

  • Preston CJ (2013) Ethics and geoengineering: reviewing the moral issues raised by solar radiation management and carbon dioxide removal. WIREs Clim Change 4(1):23–37. doi:10.1002/wcc.198

    Article  Google Scholar 

  • Rasch PJ, Crutzen PJ, Coleman DB (2008) Exploring the geoengineering of climate using stratospheric sulfate aerosols: the role of particle size. Geophys Res Lett 35:L02809. doi:10.1029/2007GL032179

    Article  Google Scholar 

  • Rickels W, Klepper G, Dovern J et al (2011) Large-scale intentional interventions into the climate system? Assessing the climate engineering debate. Scoping report conducted on behalf of the German Federal Ministry of Education and Research (BMBF), Kiel Earth Institute, Kiel

  • Robock A (2000) Volcanic eruptions and climate. Rev Geophys 38:191–219

    Article  Google Scholar 

  • Robock A (2008) 20 Reasons why geoengineering may be a bad idea. Bull At Sci 64:14–18. doi:10.2968/064002006

    Article  Google Scholar 

  • Robock A (2014) A case against climate engineering. In: Huffpost Sci.

  • Robock A, Marquardt A, Kravitz B, Stenchikov G (2009) Benefits, risks, and costs of stratospheric geoengineering. Geophys Res Lett 36:L19703. doi:10.1029/2009GL039209

    Article  Google Scholar 

  • Robock A, Oman L, Stenchikov GL (2008) Regional climate responses to geoengineering with tropical and Arctic SO2 injections. J Geophys Res 113:D16101. doi:10.1029/2008JD010050

    Article  Google Scholar 

  • Royal Society (2009) Geoengineering the climate: science, governance and uncertainty. Royal Society, London

    Google Scholar 

  • Salter S, Sortino G, Latham J (2008) Sea-going hardware for the cloud albedo method of reversing global warming. Philos Trans A Math Phys Eng Sci 366:3989–4006. doi:10.1098/rsta.2008.0136

    Article  Google Scholar 

  • Sanderson BM, O’Neill B, Tebaldi C (2016) What would it take to achieve the Paris temperature targets? Geophys Res Lett:1–10. doi:10.1002/2016GL069563

  • Smith P, Davis SJ, Creutzig F, et al. (2016) Biophysical and economic limits to negative CO2 emissions. Nat Clim Chang 6:42–50 10.1038/nclimate2870\r

    Article  Google Scholar 

  • Stilgoe J (2015) Experiment earth: responsible innovation in geoengineering. Routledge, Abingdon, Oxon and New York, NY

    Google Scholar 

  • Stocker T et al. (2013) IPCC 2013: Summary for policy makers. Climate change 2013: The physical science basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK and New York

  • Stockholm International Peace Research Institute (SIPRI) (2014) SIPRI Military Expenditure Database.

  • Teller E, Wood L, Hyde R (1997) Global warming and ice ages: I. Prospects for physics-based modulation of global change. UCRL-231636/UCRL JC 128715. Lawrence Livermore National Laboratory, Livermore, CA

  • Thomason L, Peter T (2006) Assessment of stratospheric aerosol properties (ASAP), WCRP-124 WMO/TD- No. 1295/SPARC Report No. 4. Toronto, Ontario

  • Tilmes S, Sanderson BM, O’Neill B (2016) Climate impacts of geoengineering in a delayed mitigation scenario. Geophys Res Lett. doi:10.1002/2016GL070122

    Google Scholar 

  • United Kingdom Treasury (2003) The Green Book: appraisal and evaluation in central government.

  • United States Government Accountability Office (2011) Climate engineering: technical status, future directions, and potential responses

  • Victor DG, Morgan MG, Apt J, et al. (2009) The geoengineering option—a last resort against global warming? Foreign Aff 88:64–76

    Google Scholar 

  • Weisenstein DK, Keith DW, Dykema JA (2015) Solar geoengineering using solid aerosol in the stratosphere. Atmos Chem Phys 15:11835–11859. doi:10.5194/acp-15-11835-2015

    Article  Google Scholar 

  • Weitzman ML (2015) A voting architecture for the governance of free-driver externalities, with application to geoengineering. Scand J Econ 117(4):1049–1068. doi:10.1111/sjoe.12120

    Article  Google Scholar 

Download references


We thank Mr. K. Funato and Mr. S. Fujimoto of Tokyo Dylec Corp. for useful comments on liquid-atomization technologies. We also thank Dr. Jeffrey Pierce, Dr. David Keith, Dr. Ben Kravitz, Mr. Justin McClellan, and Dr. Ulrike Niemeier for sharing their data with us, and we thank Dr. Wilfried Rickels for helpful discussions. The constructive comments by Dr. Keith on an earlier version of this manuscript helped us improve the content considerably. This research was supported by the Environment Research and Technology Development Fund (S-10) of the Ministry of the Environment, Japan (

Author information

Authors and Affiliations


Corresponding authors

Correspondence to Ryo Moriyama or Masahiro Sugiyama.

Ethics declarations

Conflict of interest

The authors declare that they have no conflict of interest.

Additional information

An erratum to this article is available at


Appendix 1: References to the SAI cost of “a few billion dollars”

Here, we document those references made to “a few billion dollars” as being the cost required to geoengineer the climate using SAI. We acknowledge that the range of costs found in the literature is large. For example, the estimate of ~US$0.2 billion/year/(W/m2) by The Royal Society (2009) is one of the cheapest, while the estimates of ~US$50 billion by Crutzen (2006) is at the upper end of the scale. The United States Government Accountability Office (2011) and Rickels et al. (2011) also reported high estimates, although these were not original analyses. Some sources have referred to costs at the higher end of the scale (listed below); however, estimates at the lower end of the spectrum have drawn a disproportionately large response from various circles.

We searched for references to SAI costs in online sources, books, and opinion pieces and we identified sentences mentioning the cost of geoengineering. No formal systematic screening was performed, although efforts have been made to look at important sources.

For newspapers, a query of geoengineering AND (price OR cost OR million OR billion) with the LexisNexis Academic database identified a number of articles (inquiry conducted on May 13, 2014). Note that the query was constructed with the operand OR, and that the addition of the qualifiers million and billion did not narrow the range of identified newspaper articles. For the top 10 outlets listed in the results of this query, we document all articles mentioning the cost of SAI. As described below, many sources refer to low-cost estimates but some do cite high costs. For brevity, we only provide a sentence from each source referring to the SAI cost. Readers are encouraged to consult the original material to understand the context fully.

1.1 Online sources

Collins (2014): “It’s been said that it would be so cheap—in the order of a few billion dollars per year—that most countries could deploy this if they wanted to.”

Robock (2014): “I have calculated that it would only cost a few billion dollars per year to lift enough sulfur into the stratosphere with airplanes to create a cloud to reflect enough sunlight to counteract the global warming we will experience in the next several decades, but with a big ‘if’.” [The “if” is a question on the size of aerosol particles.]

Blackstock et al. (2013): “For just a few billion dollars a year, it appears possible for a fleet of a couple dozen aircraft to spray enough sulfur particles into the stratosphere to lower temperatures by a couple degrees Celsius.”

Gingrich (2008): “Instead of imposing an estimated $1 trillion cost on the economy by Boxer–Warner–Lieberman, geoengineering holds forth the promise of addressing global warming concerns for just a few billion dollars a year.” [This statement by a former Republican congressman of the United States was originally posted on his blog and reproduced in full in a book chapter by Michaelson (2013).]

Morton (2008): “That’s a purchase cost of about $6 billion, and an ops cost more like a billion a year.”

1.2 Book

Keith (2013): “Taking the estimate of one dollar per kilogram delivered to 75,000 ft and assuming one million tons of material per year, the total cost of large-scale geoengineering would be about one billion dollars a year.” [Unlike many other experts, Keith explicitly talks about a new type of aircraft in the same book and thus, his comment should be carefully interpreted, although those quoting him may not realize such nuances.]

1.3 Opinion article

Keith et al. (2010): “At about US$1,000 a tonne for aerosol delivery, [the solar radiation management cost] adds up to just billions of dollars per year.”

1.4 Newspapers

“Annually, it could cost somewhat less than $8 billion—about the price of a major oil pipeline.” (“Arctic thaw could be reversed. Theoretically feasible, but other issues arise” by Bob Weber, The Calgary Herald, December 26, 2012).

“According to Justin McClellan of Aurora Flight Sciences in Cambridge, Mass., whose team evaluated several ways to deliver the sulfates, this would cost about $10 billion per year.” (“Can we engineer a fix to our climate problems?” by Stephen Battersby, The New York Times, November 6, 2012, Health Section, p. E01).

“For well under a billion dollars, a ‘coalition of the willing,’ a single country, or even a wealthy individual could decide to take the climate into its own hands.” (“Geoengineering: Testing the Waters” by Naomi Klein, The New York Times, October 28, 2012).

“Especially the Pinatubo Option: We could scatter particles into the stratosphere with a fleet of high-altitude planes, for the (relatively) low price of a few billion dollars.” (“A high-tech tool kit to fight global warming” by Bill Gifford, June 13, 2010, The Washington Post).

“Keeping the planet cooled steadily (at least until carbon emissions declined) might cost $30 billion per year if the particles were fired from military artillery, or $8 billion annually if delivered by aircraft, according to the Novim report.” (“The Earth Is Warming? Adjust the Thermostat” by John Tierney, The New York Times, August 11, 2009, Section D, p. 1).

“[Cost of stratospheric aerosols] [e]stimated at $25-billion to $50-billion per year.” (“Ideas so crazy, they just might work (temporarily)” by Ivan Semeniuk, The Globe and Mail, December 5, 2009).

“The sulfur would have to be carried aloft by rockets or balloons—and every year or two, at a cost of untold billions of dollars.” (“Invent,” The New York Times, April 20, 2008).

“In a draft of his paper, Dr. Crutzen estimates the annual cost of his sulfur proposal at up to $50 billion, or about 5 % of the world’s annual military spending.” (“How to Cool a Planet (Maybe)” by William J. Broad, The New York Times, June 27, 2006, Section F, p. 1)

Appendix 2: Calculation of cooling efficiency from GeoMIP studies (Kravitz et al. 2011a, 2013)

GeoMIP is an abbreviation for Geoengineering Model Intercomparison Project, which is an international project with a standardized set of experiment protocols designed to analyze the climatic outcomes of geoengineering (Kravitz et al. 2011a, 2011b). The relevant scenarios are G3 and G4. Both of these scenarios envision situations where forcings according to the Representative Concentration Pathway (RCP)4.5 are countered with some form of SAI. In G4, SAI starts in 2020 and it is assumed to amount to a quarter of the material that resulted from the Mount Pinatubo eruption in 1991, injected at a rate of 5 Mt-SO2/year over an area of 16–25 km near the equator. In G3, SAI also begins in 2020 but it increases with time such that the surface temperature remains approximately constant.

Dr. Kravitz kindly computed the global averages of top of atmosphere (TOA) net total flux for RCP4.5 and G4 for the following models: BNU-ESM, CanESM2, GISS-E2-R, HadGEM2-ES, MIROC-ESM, and MIROC-ESM-CHEM (see (Kravitz et al. 2013) for general model descriptions). The first four models all incorporate bulk aerosol treatments, whereas the remaining two have prescribed aerosol optical depths for stratospheric sulfate aerosols. In the G4 simulations, the injection quantity of geoengineering sulfate aerosols was constant, and the TOA net flux difference between the G4 and RCP4.5 cases reduced with time.

We computed the cooling efficiency for the G4 scenario using a method similar to the diagnosis of effective radiative forcing by Gregory et al. (2004). In their method, the intercept of a temperature-flux line was taken to represent the effective radiative forcing (see their Fig. 1). In their paper, the data points were plotted in the first quadrant, whereas in our case, they plotted in the third quadrant because we considered cooling rather than warming.

We took RCP4.5 as a reference and computed the difference between G4 and RCP4.5 in the net TOA flux change. We compared that difference against the difference in surface air temperature and we regressed the flux change onto the temperature change. Unlike the usual method, which assumes a quadrupling of CO2, we were dealing with a very small change and thus, we took a decadal average.

Figure 7 shows the forcing changes versus temperature differences, averaged over decadal periods. The results of the two versions of MIROC do not show a simple dependence of temperature change on forcing change and thus, they were excluded in further analysis. Upon performing the regression, we obtained cooling efficiencies of 0.190–0.278.

Fig. 7
figure 7

Gregory-like diagnosis of effective radiative forcing for Geoengineering Model Intercomparison Project (GeoMIP) G4 scenario. The horizontal axis represents the decadal average of the surface air temperature difference, whereas the vertical axis denotes the net top-of-the-atmosphere flux change

In Fig. 2, we chose 2013 as the year of GeoMIP because the overview paper reporting the initial results was published in that year and because most of the papers on G4 were submitted in that year.

Appendix 3: Regression analysis for lifting cost

To understand the general pattern, we performed a regression analysis in which we regressed the lifting cost onto altitude. We conducted sensitivity analyses by considering the effects of outliers, which we took to be the three data points with the maximum cost, minimum cost, and altitude of >40 km. We also examined the effect of including the estimates from Davidson et al. (2012) because their dataset had no variation in the independent variable because of their focus on the single altitude of 20 km. We also looked at two choices for the dependent variable: the logarithm of altitude and altitude itself. The results are shown in Figs. 8 and 9. The lower-left panel of Fig. 8 describes the regression lines in Fig. 3. The correlation coefficients are generally small for new technologies while those for existing technologies are >0.37. The impact of outliers is significant because their inclusion reduces the cost of existing technologies to such an extent that the order between the two lines becomes reversed for altitude > ~ 40 km. When we take the altitude (not its logarithm) as the dependent variable, the relationship generally degrades. When the data set of Davidson et al. (2012) is included, the slope for new technologies becomes even more negative.

Fig. 8
figure 8

Results of regression analysis of the lifting cost onto the logarithm of altitude

Fig. 9
figure 9

Results of regression analysis of the lifting cost onto altitude

Although this exercise is useful for highlighting the general pattern, we emphasize that each study took a distinct method of different quality. We therefore do not utilize the results of the regression analyses in estimating the total costs.

Appendix 4: Sensitivity to discount rates

Although we amortized the cost at a discount rate of 10 % over a 20-year period, the choice of discount rate is always subject to intensive debate in climate change economics. We therefore briefly explore the sensitivity of our results to discount rates. The total annual cost can be written as

$$ T(r)=I\cdot A(r)+O, $$

where T is the total annual cost (T = (L + P + D)F/E), I is the initial capital expenditure, and O is the cost of operation and maintenance. A is defined as A = r/{1 − (1 + r)N}, where r is the discount rate and N is the number of time periods (here N = 20). The percentage difference due to a change in the discount rate is

$$ \frac{\Delta T}{T}=\frac{T(r)-T\left({r}_0\right)}{T\left({r}_0\right)}=\frac{A(r)/A\left({r}_0\right)-1}{1+\left(O/I\right)/A\left({r}_0\right)}. $$

In the limit of O/I going to infinity, the difference vanishes, i.e., ΔT/T → 0. On the other hand, if O/I goes to zero, ΔT/T → A(r)/A(r 0) − 1. For r = 0.03 and r 0 = 0.10, ΔT/T →  ~  − 0.427..

Figure 10 shows the sensitivity of ΔT/T to O/I with r = 0.03 and r 0 = 0.10. The data from Davidson et al. (2012), for example, suggest that the range of O/I is 0 to ~200. Therefore, although a lower discount rate would lower the direct cost further, it would not change the order of magnitude.

Fig. 10
figure 10

Sensitivity of the percentage difference due to a change in the discount rate (∆T/T) to the relative cost of operation and initial capital expenditure (O/I)

Appendix 5: Cumulative production of F-15 fighter jets

This section documents the cumulative production of F-15s. In short, there are various numbers for the cumulative production depending on the variants covered. Boeing’s backgrounder (Boeing Defense Space & Security 2013) reports the cumulative production as in excess of 1,600. Davies and Dildy (2007) provide a detailed dataset of the past production for the F-15A/B/C/D/J/DJ, with a total production figure of 1,198., a website that documents numerous defense-related statistics, shows yet another value ( 2011). Their webpage on the F-15 lists the cumulative production as 1,712, including variants not covered by Davies and Dildy (2007). However, their data do not distinguish conversion from production.

In the main text, we take 1,600 as the value of cumulative production in Fig. 6. In the four decades since the initial production of the first F-15 in 1972, average production has been approximately 40, which is the number utilized in Fig. 6. The production numbers of 1,600 in total and 40 per annum do not differ appreciably from numbers quoted in other sources, at least for the purposes of order-of-magnitude comparisons.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Moriyama, R., Sugiyama, M., Kurosawa, A. et al. The cost of stratospheric climate engineering revisited. Mitig Adapt Strateg Glob Change 22, 1207–1228 (2017).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: