Climate Engineering through injection of aerosol particles into the atmosphere: physical insights into the possibilities and risks

Transcription

1 Climate Engineering through injection of aerosol particles into the atmosphere: physical insights into the possibilities and risks PD Dr. Mark G. Lawrence Director: Sustainable Interactions with the Atmosphere (SIWA) Institute for Advanced Sustainability Studies (IASS) Potsdam Uni-Frankfurt,

2 Observed Climate Change 159 Years 50 warmest Years * Anomaly relative to the mean for [Bull. Am. Meteorol. Soc., 2009]

3 Starting points IPCC (2007): Global warming is unequivocal, humans play a major role Major future consequences, including tipping points heat waves droughts + floods sea level rise melting glaciers and ice sheets Mitigation and/or Adaptation necessary but difficult Sustainability: reducing emissions or recycling carbon Will take time and excess CO 2 still there Civil society, industry, commerce and policy-makers: eager to find quick fixes Viability? Desirability as a 3 rd component?

4 Quick Fixes MANY quick fixes being discussed Various names: Climate Engineering (CE) Geoengineering Climate Intervention (CI) or Climate System Intervention (CSI) Novel Options (EU FP7) Targeted Environmental Modification Role of Scientists and Engineers? Provide valuable information to help assess effectiveness and be aware of side effects (analogy: medicine) Science + Economics + Ethics + Regulation + (here focus only on scientific aspects) Near-future and far-future contexts

5 The Climate Engineering Twist to the Climate Change Discourse What Climate Change?? There s no climate change!! Okay, so there is a Climate Change but no need to worry we can fix it easily with climate engineering!! Geoengineering holds forth the promise of addressing global warming concerns for just a few billion dollars a year. Instead of penalizing ordinary Americans, we would have an option to address global warming by rewarding scientific innovation Bring on the American Ingenuity. Stop the green pig. -- Newt Gingrich Diverting money into controlling carbon emissions and away from geoengineering is probably morally irresponsible. -- Julian Morris 5 (quotes from Retooling the Planet, report prepared by the ETC Group)

6 The Climate Engineering Twist to the Climate Change Discourse What Climate Change?? There s no climate change!! Okay, so there is a Climate Change but no need to worry we can fix it easily with climate engineering!! Geoengineering holds forth the promise of addressing global warming concerns for just a few billion dollars a year. Instead of penalizing ordinary Americans, we would have an option to address global warming by rewarding scientific innovation Bring on the American Ingenuity. Stop the green pig. -- Newt Gingrich Diverting money into controlling carbon emissions and away from geoengineering is probably morally irresponsible. -- Julian Morris 6 (quotes from Retooling the Planet, report prepared by the ETC Group)

7 Iterative Interdisciplinary Information exchange: Complex! 2b) + 6) Human Rights: Aspects and Indications 3a) Research Programs, Resolutions und Regulations Law / Politics + Research Funding Regulations + International Action 5) Economic Implications of Climate Engineering Ethics, Morality, Philosophy 1) + 5) Economic Implications of Climate Engineering Economics 3b) Information Requests 2a) Scientific Responsibility and Self-Regulation 4) Revised / Specified Scientific Conclusions 0) Initial Studies of Effects and Side Effects Natural Sciences, Engineering 3c) Information Requests Communication Research 7

8 Climate Engineering: Historical Perspective Weather Modification From ancient magic to modern cloud seeding via silver iodide injections [Graphics from Wikimedia Commons]

9 Climate Engineering: Historical Perspective Weather Modification Short-term (weather) modification regulated under ENMOD (UN, 1977)

10 Climate Engineering: Long-Term Targeted Influence Serious but limited high-level discussions since ~mid-1960 s The possibilities of deliberately bringing about countervailing climatic changes therefore need to be thoroughly explored. A change in the radiation balance could be produced by raising the albedo, or reflectivity, of the earth. Research explosion since ~2006 MANY proposed techniques (and MANY noted problems)

11 Classes of Climate Engineering SRM: solar radiation management acts on the short wave (solar) contribution to the energy balance ( band-aid approach) CDR: carbon dioxide removal acts on the infrared (terrestrial) contribution to the energy balance ( treats cause, but likely slow) (Kiehl and Trenberth, 1997)

12 Examples of Climate Engineering Approaches SRM CDR [Keith, Nature, 2001]

13 Examples of Climate Engineering Approaches SRM CDR [Keith, Nature, 2001]

14 Sunshade Climate Engineering: Mirrors, Particles, Clouds, Surface Albedo, How much shading would be needed??

15 Simple Temperature Estimate Solar Constant at Earth Orbit: I s 1372 W m 2 I I 4 2, = k s gm 343W m

16 Simple Temperature Estimate Solar Constant at Earth Orbit: I s 1372 W m 2 I I 4 2, = k s gm 343W m Via Stefan-Boltzmann Law, compute Earth s equiv. blackbody Temperature: σ T 4 E = I s, gm 343W m 2 => T E 279 K

17 Simple Temperature Estimate Solar Constant at Earth Orbit: I s 1372 W m 2 I I 4 2, = k s gm 343W m Via Stefan-Boltzmann Law, compute Earth s equiv. blackbody Temperature: σ T 4 E = I s, gm 343W m 2 => T E 279 K But clouds and the Earth s surface reflect about 30% of solar radiation: σ T 4 E = 0.7 I s, gm 240 W m 2 => T E 255K 18 C

18 Simple Temperature Estimate Solar Constant at Earth Orbit: I s 1372 W m 2 I I 4 2, = k s gm 343W m Via Stefan-Boltzmann Law, compute Earth s equiv. blackbody Temperature: σ T 4 E = I s, gm 343W m 2 => T E 279 K But clouds and the Earth s surface reflect about 30% of solar radiation: σ T 4 E = 0.7 I s, gm 240 W m 2 => T E 255K 18 C a bit cold! Need to account for Greenhouse Gases (H 2 O, CO 2, etc.)!

19 Simple Temperature Estimate Solar Constant at Earth Orbit: I s 1372 W m 2 I I 4 2, = k s gm 343W m Approximate the Earth-Atmosphere system with a simple 2-layer model: Earth s surface Atmosphere Single absorbing gray-body layer Radiates evenly in both directions (up and down)

20 Simple Temperature Estimate Solar Constant at Earth Orbit: I s 1372 W m 2 I I 4 2, = k s gm 343W m Approximate the Earth-Atmosphere system with a simple 2-layer model: Earth s surface Atmosphere Single absorbing gray-body layer Radiates evenly in both directions (up and down) Apply Kirchhoff s Law (emissivity = absorptivity) to the atmosphere (with ε 0.77):

21 Simple Temperature Estimate Solar Constant at Earth Orbit: I s 1372 W m 2 I I 4 2, = k s gm 343W m Approximate the Earth-Atmosphere system with a simple 2-layer model: Earth s surface Atmosphere Single absorbing gray-body layer Radiates evenly in both directions (up and down) Apply Kirchhoff s Law (emissivity = absorptivity) to the atmosphere (with ε 0.77): σt 4 S = 0.7 I s, gm => T 0.77 S K 15 C

22 Simple Temperature Estimate Solar Constant at Earth Orbit: I s 1372 W m 2 I I 4 2, = k s gm 343W m Approximate the Earth-Atmosphere system with a simple 2-layer model: Earth s surface Atmosphere Single absorbing gray-body layer Radiates evenly in both directions (up and down) Apply Kirchhoff s Law (emissivity = absorptivity) to the atmosphere (with ε 0.77): σt 4 S = 0.7 I s, gm => T 0.77 S K 15 C Reduce by 1% => ~0.7 C cooling

23 Examples of Climate Engineering Approaches SRM CDR [Keith, Nature, 2001]

24 Stratospheric Particle Injections Inspired by Volcanic Eruptions Budyko, Michail: Climatic Changes. American Geophysical Society, Washington, DC, 1977 (translated from original 1974 publication in Russian). Pinatubo, June 1991 Paul Crutzen (Nobel Prize in Chemistry, 1995): Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolve a Policy Dilemma? Climatic Change, Nevertheless, again I must stress here that the albedo enhancement scheme should only be deployed when there are proven net advantages and in particular when rapid climate warming is developing, paradoxically, in part due to improvements in worldwide air quality.

25 Stratospheric Particle Injections Inspired by Volcanic Eruptions => ca. 20 Million Tons of SO 2 injected into the stratosphere Pinatubo, June 1991 SO 2 H 2 SO 4

26 Brewer-Dobson Circulation (Middle-Atmosphere) Particle Residence Times: Stratosphere: ~1-3 Years Troposphere: ~1-10 Days

27 Mt. Pinatubo: ~ C Cooling over the Following Year (GISS Analysis, based on Hansen et al., 2006)

28 Mt. Pinatubo: ~ C Cooling over the Following Year Quantitative interpretation made difficult by El Niño in (Robock and Mao, J. Clim., 1995)

29 Mt. Pinatubo: ~ C Cooling over the Following Year Quantitative interpretation made difficult by El Niño in (Soden et al., Science, 2002)

30 But how do WE get the stuff up there? Costs? Safety? Sustainability? Robock et al., GRL, 2009

31 And how much sulfate would we actually need to inject into the stratosphere? Strong dependence on the assumed or calculated effective radii (r e ). Pinatubo-like r e may overestimate the cooling potential (but microphysical aerosol models have large uncertainties). /year] Pinatubo ~10 Mt(S) (Niemeier, Schmidt and Timmreck, ASL, 2010) 31

32 And what would it do IF we were to put it up there?? Many Uncertainties and Unknowns! Examples: Self-limiting effects (large particles sediment faster) Uneven meridional distribution of cooling Side Effects: Ozone loss? Sky and sunset colors? O 2 + hν O + O O + O 2 + M O 3 + M O + O 3 2O 2 O 3 + hν O + O 2 First studies indicate potential losses of 5% (equatorial) to 15% (polar) [Tilmes et al., 2009; Heckendorn et al., 2009]

33 Stratospheric sulfur injections: Global temperature effects Very rapid temperature increase if sulfate injections were stopped. (Robock et al., JGR, 2008)

34 Different Models Different Answers: Coordinated Activities Underway IMPLICC EU FP7 project, 5 partners, coordinated at MPI-Met (Hamburg),

35 GeoMIP/IMPLICC Simulations Setup Solar Constant at Earth Orbit: I s 1372 W m 2 (Kravitz et al., 2011)

36 GeoMIP/IMPLICC Simulations Setup 0 (Kravitz et al., 2011)

37 Examples of Climate Engineering Approaches SRM CDR [Keith, Nature, 2001]

38 Cloud Brightening Inspired by Ship Tracks South of Alaska West of California (Photos: NASA)

39 Cloud Brightening Inspired by Ship Tracks Coast of Washington Atlantic Coast of Europe (Photos: NASA)

40 Cloud Brightening Inspired by Ship Tracks Coast of Washington Atlantic Coast of Europe John MacNeill (Photos: NASA)

41 Cloud Brightening First proposed by Latham (Nature, 1990) Twomey effect: smaller droplets brighter clouds Sea salt spray more cloud condensation nuclei (CCN) smaller droplets Effectiveness? Side Effects? (Very inhomogeneous radiative forcing!) First results from model simulations John MacNeill

42 Primary Susceptible Regions Simulated mean cloud cover fractions [Jones et al., 2009]

43 Impact of Cloud Brightening on Global Mean Temperatures IPCC future CO 2 increase scenario Cloud brightening in all 3 regions [Jones et al., 2009]

44 Mean Surface Temperature Change due to Cloud Brightening (in all regions) Unclear if Cooling or Warming! T ALL T A1B [ C] [Jones et al., 2009]

45 Mean Precipitation Change due to Cloud Brightening (in all regions) mean Precip ALL Precip A1B [mm/day] [Jones et al., 2009]

46 Mean Precipitation Change due to Basic Climate Change Scenario Precip (A1B: ) Precip ( ) [mm/day] [Jones et al., 2009]

47 First Major Assessments Already Done

48 First Comparative Assessments of Various Proposed Techniques Multi-model studies like GeoMIP/IMPLICC not considered in assessments so far! (Royal Society Report, 2009)

49 Conclusions / Outlook First assessments already done, basic impressions but: LARGE uncertainties Incomplete (new ideas proposed frequently) Focus on global balances (not yet much on regional level) Disconnected from other aspects of targeted environmental modification More research urgently needed; focal points: effectiveness, costs, timing, uncertainties, side effects, Particularly important: Coordinated multi-model activities (e.g., GeoMIP, IMPLICC) Interdisciplinary collaboration ( e.g., IASS-Potsdam): Natural sciences (atmosphere, land, ocean) Economics Ethics Psychology Law and Political Sciences

50 Further Information Climate Engineering Webseite: EU Forschungsprojekt IMPLICC : BMBF Sondierungsstudie: ondierungsstudie-climateengineering/ UBA Geoengineering Bericht: -info-medien/4125.html/ Royal Society Geoengineering Bericht blications/2009/geoengineeringclimate/