Lecture „Climate Engineering“

1. Introduction

Ulrich Platt

Institut für Umweltphysik

Lecture Program of „Climate Engineering

2

Part 1: Introduction to the Climate System (4 sessions)1. Introduction and scope of the lecture2. The Climate System – Radiation Balance 3. Elements of the Climate System - Greenhouse Gases, Clouds, Aerosol4. Dynamics of the Climate System - Sensitivity, PredictionsPart 2: Climate Engineering Methods - Solar Radiation Management, SRM1. SRM – Reflectors in space 2. SRM – Aerosol in the Stratosphere3. SRM – Cloud Whitening4. SRM – Anything elsePart 3: Climate Engineering Methods – Carbon Dioxide Removal, CDR1. Direct CO2 removal from air2. Alkalinity to the ocean (enhanced weathering)3. Ocean fertilization4. Removal of other greenhouse gasesPart 4: CE – Effectiveness, Side Effects (3 sessions) 1. Comparison of Techniques, characterisation of side effects2. Other parameters than temperature3. Summary

Contents of Today's Lecture

• Global Warming - „Climate Change“

• What is Climate Engineering

• Why Climate Engineering?

• Physics of Climate – which knobs to turn?

• „Leverage“ of CE-Techniques

• Techniques to influence the climate, examples

• Even stranger ideas

• Conclusion

Literature

Bodansky, D. (1996), 'May we Engineer the Climate?', Climatic Change 33, 309-321.

Boyd, P. W. (2008), 'Ranking geo-engineering schemes', Nature Geoscience 1, 722-724.

Cicerone, R. J. (2006), Geoengineering: Encouraging research and overseeing implementation, National Academy of Sciences, Washington DC, chapter Climatic Change, pp. 221-226.

Crutzen, P. J. (2006), 'Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolve a Policy Dilemma?', Climatic Change 77(3-4), 211--220.

Feichter, J. & Leisner, T. (2009), 'Climate engineering: A critical review of approaches to modify the global energy balance', The European Physical Journal - Special Topics 176(1), 81--92

Hegerl, G. C. & Solomon, S. (2009), 'Risks of Climate Engineering', Science 325, 955-956.

IPCC Climate Change 2014 Synthesis Report: https://www.ipcc.ch/site/assets/uploads/2018/02/SYR_AR5_FINAL_full.pdfLamb, H. H. (1971), 'Climate-Engineering Schemes to meet a Climatic Emergency', Earth-Science Reviews 7, 87-95.

Lenton, T. M. & Vaughan, N. E. (2009), 'The radiative forcing potential of different climate geoengineeringoptions', Atmos. Chem. Phys. 9, 5539-5561.

Robock, A. (2008), '20 reasons why geoengineeringmay be a bad idea', Bulletin of the Atomic Scientists 64(2), 14-18.

Society, The Royal (2009), Geoengineering the climate: Science, governance and uncertainty', Technical report, The Royal Society (RS Policy Document 10/09 ).

Wood, L.; Hyde, R. & Teller, E. (1997), 'Global Warming and Ice Ages: I. Prospects for Physics-Based Modulation of Global Change'.

Ross A & Matthews HD (2009) Climate engineering and the riskof rapid climate change. Environmental Research Letters 4, 045103 doi: 10.1088/1748-9326/4/4/045103

Web – Pages of Interest

Heidelberg Marsilius Project on Climate Engineering:http://www.climate-engineering.uni-hd.de/projects/

Asilomar Conference on Climate Intervention Techniques:http://www.climateresponsefund.org/

Report: Climate Engineering Responses to Climate Emergencies:http://arxiv.org/ftp/arxiv/papers/0907/0907.5140.pdf

Report of the Britischen Royal Society on CE:http://royalsociety.org/policy/publications/2009/geoengineering-climate/

David Keith‘s Home Page:http://keith.seas.harvard.edu/

Alan Robock‘s Home Page:http://www.envsci.rutgers.edu/~robock/

Intergovernmental Panel on Climate Change, IPCC:https://www.ipcc.ch/

YouTube CE-Playlist (CE-Related Video Clips):

http://www.youtube.com/playlist?list=PLF8369A27273314D8

Provided by: Andrew Lockley

Editors:Wilfried Rickels, Gernot Klepper, and Jonas DovernAuthors: Gregor Betz, Nadine Brachatzek, Sebastian Cacean, Kerstin Güssow, Jost Heintzenberg, Sylvia Hiller, Corinna Hoose, Gernot Klepper, Thomas Leisner, Andreas Oschlies, Ulrich Platt, Alexander Proelß, Ortwin Renn, Wilfried Rickels, Stefan Schäfer, Michael Zürn

From the Preface: …. Climate engineering raises numerous questions of fundamental importance: Which proposals are scientifically realistic? Can they be technically implemented, and how effective are they likely to be? What interactions and side-effects (e.g., in the climate system) are to be expected? How far do the efficiency advantages of individual measures go in a comprehensive macro-economic consideration? Will climate engineering become an endurance test for society and international relations? Is selective intervention in the Earth system ethically acceptable or justifiable?…

Dr. Georg SchütteState Secretary at the Federal Ministry of Education and Research (BMBF)

Interventions into the Climate

System?Assessing the Climate Engineering Debate

2011

Climate Engineering(frequently also called „Geoengineering“)

Intentional, large scale manipulation of the environment to counteract the unintended effects of anthropogenic climate change (D. Keith, 2000).

Absichtliche, großskalige Manipulation der Umwelt, um unerwünschten Effekten des anthropogenen Klimawandelsentgegenzuwirken (D. Keith, 2000)

Questions:

1) Is it actually possible and (if yes) affordable?

2) If 1) should be true, should we actually do it?

3) What are the side effects?

Geoengineering

Blasphemous - How can we dare to interfere with nature (or God)?

Hubris - How can we think that everything can beaccomplished by technology?

yet

We are modifying our climate already – not intentionally though - e.g. by releasing greenhouse gases to the atmosphere

The History of Weather Control

http://www.terraforminginc.com/weather-control/

Modifying Weather and Climate?

History of CE-Proposals (1)

Source: Climate engineering, Technical status, future directions, and potential responsesCenter for Science, Technology, and EngineeringUnited States Government Accountability Office, GAO, July 2011, GAO-11-71

September 29, 1921:End Of Iceberg Menace!

Nuke theArctic

Professor Julian Huxley. “Can We Atomize the Arctic?”, Jan. 1945

Wallace W. Ashley and Elmer V. Swan. According to them, Professor Julian Huxley had proposed the ideaof using nuclear bombs to melt thepolar ice caps. This would moderate our northern climate, eliminatingpesky cold snaps and opening up shipping across the top of the world.

History of CE-Proposals (2)

Source: Climate engineering, Technical status, future directions, and potential responses, GAO, July 2011, GAO-11-71

History of CE-Proposals (3)

Source: Climate engineering, Technical status, future directions, and potential responses, GAO, July 2011, GAO-11-71

0.8 ppm/Yr.

2.4 ppm/Yr.CO2-fraction in dry air, µmole/mole or ppm 400

320

340

360

380

The Atmospheric CO2 – Mixing Ratio During the last 60 Years

Scripps

Charles D. Keeling (1928-2005)

Mauna Loa, Hawaii, USA, 3397m a.s.l.

Source: World Meteorological Organization (WMO)

Cumulative Anthropogenic Carbon Emission to the Atmosphere 1850-2006 (in units of 109 tC)

Source: Carbon Dioxide Information Analysis Center (CDIAC.com) and values of atmospheric CO2 concentrations from Mauna Loa, as well as other locations.Carbon emissions from land use change and deforestation not included.

By 2011: 360 GtCequiv. to 1.31022JHeat Air by 3K Average Power: 510-3W

Global Annual Mean Surface Air Temperature Change

Recovery from volcanic eruptions dominates

Tropospheric aerosols mask

warming(global dimming)

Greenhouse gases dominate

http://data.giss.nasa.gov/gistemp/graphs/Fig.A2.pdf

The Challenge: Limit CO2-Growth

From: Klaus Lackner

Constant emissions at 2010 rate

10% of 2010 rate

0% of 2010 rate

33% of 2010 rate

Will We Manage to Reduce CO2 –Emissions?

Will We Manage to Reduce CO2 – Emissions?Example: Germany

Emission of greenhouse gases regulated by UNFCC

Mt CO2equiv.

100%

-31%

-40%

-55%

-70%

-95%

Radiative Climate Forcing Components

Source: IPCC-AR5, Fig. SPM.5

Problem beyond Gradual Changes: „TippingElements“

Timothy M. Lenton, Hermann Held, Elmar Kriegler, Jim W. Hall, Wolfgang Lucht, Stefan Rahmstorf, and Hans Joachim Schellnhuber(2008), Tippingelements in the Earth’sclimate system, PNAS 105(6), 1786–1793.

Climate subsystems where anthropogenic climate forcing could cause threshold-type behavior. small perturbation at a critical point qualitatively alters the future fate of the system. They could be triggered this century and would undergo a qualitative change within this millennium. (“Tipping Elements” in colour, overlain on global population density)

Climate Change – what to do?

Mitigation (Abwendung )

Rapid reduction of greenhouse gas emissions

Adaptation (Anpassung )

Relocate population, change structure of

agriculture, higher levies...

Climate Engineering

Reduction of solar radiation, removal of greenhouse gases

from the atmosphere, …

From: nature reports climate change, Vol. 4, p. 5, Jan. 2010,

Climate Engineering

• Serious discussions sinceabout the mid-1960ties (basic ideas shade sun, raise Earth‘salbedo)

• Increasing number of publications since about 2006

• Today there are manyproposed techniques, moreand more problems are noticed

- Geoforming, GeoengineeringBering straight - dam or diversion of large sibirian rivers forirrigation of central asia make the North Polar See ice-freeP.M. Borisov, Bulletin of the Atomic Scientists, March, 1969, pp. 43-48

- Weather and precipitation control for commercial andmilitary purposes (USA, UdSSR, China, 1950 ~ 1980)

As our civilization steadily becomes more mechanized and as ourpopulation density grows the impact of weather will become evermore serious. ...The solution lies in ... intelligent use of more preciseweather forecasts and, ideally, by taking the offensive throughcontrol of weather... I shudder to think of the consequences of a priorRussian discovery of a feasible method for weather control.Henry Houghton, MIT, 1957

Historical Background

- “Can We Atomize the Arctic?”, Jan. 1945, Prof. Julian HuxleyIdea of using nuclear bombs to melt the polar ice caps. This would moderate the northern climate, eliminating pesky cold snaps and opening up shippingacross the top of the world.

Geo-EngineeringIntentional change of climate parameters (to compensate forthe consequences of the antropogenic greenhouse effect)

P. CrutzenClimatic Change, 2006

34

Save The

World?

Forget about a future filled with wind farms and hydrogen cars. The Pentagon's top weaponeer

says he has a radical solution that would stop global warming now --no matter how much oil we burn.

Jeff GoodellRolling Stone

November 3, 2006

Attempting to Modifying the Climate -Why?

• Annual anthropogenic emissions: 9 Gt of carbon (equivalent to 33 Gt of CO2)

• It is clear that our climate is changing and will even more rapidlychange in the coming decades (if projections are correct).

• Stabilizing the atmmospheric CO2 level would require about 80% cutin global emissions.

• Negotiations to reduce CO2-emissions have had dissapointingresults

• In addition there is the danger of „Tipping Elements“

So our options appear to be:

• Adapt to climate warming or

• Actively change the climate

Some Question

s:

• Is CE technologicallyfeasible?

• Do we actually need to apply CE?

• Who decides on application of CE?

• Who decides on theglobal temperature?

Reasons why Geoengineering may be a Good Idea

1. Cool the planet

2. Reduce or reverse ice melting

3. Reduce or reverse land ice sheetmelting

4. Reduce or reverse sea level rise

5. Increase plant productivity

6. Increase terrestrial CO2 sink

Robock et al. 2009, GRL

Reasons why Geoengineering may be a Bad Idea

1. Effects on regional climate (temperature, precipitation, other para.)2. Continued ocean acidification3. Rapid warming when CE stops 4. Stratospheric Ozone depletion5. Effects on plants (less solar radiation and lower direct/diffuse ratio)6. Enhanced acid precipitation7. Whitening of the sky (but nice sunsets)8. Effects on cirrus clouds as aerosols fall into the troposphere9. Less solar radiation for solar power (especially less direct radiation)10. Environmental impacts of aerosol injection (production and delivery)11. There’s no going back (how rapidly could effects be stopped?)12. Human error13. Undermining emissions mitigation. 14. Cost15. Commercial control of technology16. Military use of technology17. Conflict with current treaties18. Control of the thermostat?19. Question of moral authority20. Unexpected consequences

Robock, Alan, 2008: 20 reasons why geoengineering may be a bad idea. Bull. Atomic

Scientists, 64, No. 2, 14-18, 59, doi:10.2968/064002006.

Two Types of „Climate Engineering“

2) Carbon cycle engineering (CDR)• Direct capture of CO2 from air• Ocean fertilization• Alkaline material into the ocean• bury charcoal „Bio-char“• Alkaline material into the soil

Slow and expensive,But the cause (the CO2) is actuallyremoved from the air

1) Solar radiation management (SRM)• Sulfate aerosol in the stratosphere• Cloud whitening• Change surface albedo of Earth

and/or ocean• Special particles in the mesosphere• Scatterers in space

Fast, cheap, imperfect and unsafe, littleinfluence on atmospheric CO2

Greenhousegases reduceIR-emission

The „Leverage“ of CE - Techniques

Leverage Ratio:

Lev

Mass of Greenhouse Gas the effect of which is neutralizedR

Mass of material needed for the measure

Examples:1) Mankind emitted about 370 Gt carbon (1357 Gt CO2) since 1750. About 1 Mt of sulfur would be required to offset the warming effect of that much CO2 (for one year) Rlev 1.4106

2) In order to induce ocean uptake of the same amount of CO2 about 3100 Gt of CaCO3 (carbonate) would be required Rlev 0.44

(CO2 + CaCO3 + H2O Ca(HCO3)2)

3) Iron Fertilization of the ocean requires 1 atom of Fe for 105 atoms of C in algalbiomass (Redfield ratio) mass ratio Rlev 2.5104

Climate-Engineering (Geo-Engineering)

Adapted from Thomas Leisner42

04 4S A

A A

S 2 1 A2LT 2 T

2 2

Simple Global Radiation Balance:

• Scattering surfaces in space

Change of Solar constant (S0)Increase of Planetary Albedo (A) Reduction of atmospheric (IR) absorption (A)

• Scattering surfaces in thestratosphere(e.g. sulfate aerosol)

• Absorber in the Stratosphere

• Scattering surfaces in theTroposphere(e.g. whiter clouds)

• Change of Albedo of Land-and Ocean – surfaces

• Geochemical CO2 –sequestration in the ocean

• Ocean Fertilization

• CO2 – sequestration from theair (air capture)

• CO2 – uptake by terrestrialecosystems(new forests, biochar)

Climate-Engineering

Climate Engineering Techniques ...

T.M. Lenton and N.E. Vaughan, The radiative forcingpotential of different climate geoengineering options, Atmos. Chem. Phys., 9, 5539–5561, 2009

Are there no better ideas?

Keith, David, 2001: Geoengineering, Nature, 409, 420. 45

SRM

CDR

r

rE

ME

1. Site: 1. Lagrange-point (L1-point) (unstable)

2. Implementation: Cloud of many thin discs, stabilised by

modulation of radiation pressure, disk size: ~1 m,

Weight: 1g, Number: 1.61013

3. Optical Design: Transparen refracting material, low areal

density, total mass: 20 Mt

4. Transport: elektromagnetic accelerator,

Ionen thrusters, Cost: 50 $/kg (zur Zeit 20000 $/kg)

Total cost several Trillion $

(100 billion $/a)

Change of the Solar constant: (Angel, PNAS, 2006)

How much shading is Needed?

Example: We whish to offset temp. change due to 2xCO:

Primary forcing: 3.7 W (there will be little or no feedback if wecompensate primary forcing)

Incident Radiation on Earth: 1372 W/m2

minus reflection (A=0.7): 960 W/m2

We need to shade an area of: 3.7/960 x cross section of Earth (πR2)

0.0038 x 1.29108 km2 5105 Km2

Assumin a sheet of 0.1 mm thickness would have a volume of 5107

m3

Stratospheric Particle Injection – Inspired by VolcanicEruptions

Explosive

NET COOLING

Stratospheric aerosols

(Lifetime 1-3 years)

Ash

Effectson cirrusclouds

absorption (IR)

IR

Heating

emission

emission

IR Cooling

More

Downward

IR Flux

Less

Upward

IR Flux

forward scatter

Enhanced

Diffuse

FluxReduced

Direct

Flux

Less TotalSolar Flux

Heterogeneous LessO3 depletion Solar Heating

H2S

SO2

NET HEATING

Tropospheric aerosols

(Lifetime 1-3 weeks)

Quiescent SO2 H2SO4

H2SO4

CO2

H2O

backscatter

absorption

(near IR)Solar Heating

More Reflected

Solar Flux

Indirect Effects on

Clouds

Stratospheric Sulfate Aerosol

from a presentation by Alan Robock, Heidelberg 2010 49

Mount Pinatubo (1)Eruption June 1991

before

after

Photo: NASA

WMO (2003)

NASA

Mount Pinatubo (2)

Effects of Mount Pinatubo, Philipines volcanic eruption (June 1991) on the radiation balance and on the hydrological cycle as an analog of geoengineering

Trenberth and Dai (2007)Geophys. Res. Lett.

from a presentation by Alan Robock, Heidelberg 2010

Mount Pinatubo (3)

52

Reflection

Surface

Optimal Particle Size?

Small Particles More Surface/Mass (less mass needed)

But at size parameter x < 1 rapidlydecreasing scattering efficiency

But more scattering in backward direction

also: particles settle less rapidly

However, the useful lifetime of particles is also limitedby the stratospheric circulation

1 large particle, 8 small particles, radius r/2, same total volumeradius r but twice the total surface area

Why Endanger Particles the Ozone Layer? (1)

Katalytic Ozone destruction:

X + O3 XO + O2

XO + O X + O2

net: O + O3

2O2

X/XO: „Katalyst“(e.g. OH/HO2, NO/NO2, Cl/ClO, Br/BrO)

HOX (Bates and Nicolet, 1950)NOX (Crutzen, 1970)ClOX (Stolarski and Cicerone, 1974;

Molina and Rowland, 1974)

Katalytic ozone destruction explainsdifference between measured (lower) and calcualted (ca. 3x higher) O3 –concentrations and their dependence on.

Particles?

How could Particle Sedimentation be prevented?

Prinziple of the „Light-Mill“(Lichtmühle)?

Radiation-source

Reflecting cold

Black warm

Wrong explanation 1:

Radiation pressure, Photons have momentum (p=E/c) but it is too small:

solar radiation: 10-4 W/cm2 3·1014 Photons/s, Momentum of a photon 10-27 kgm/s Force 3·10-13 Newtons (for 1 cm2)

Moreover: Momentum transfer to black surface: p, reflecting surface: 2p wrong rotational direction

Wrong explanation 2 (Wikipedia):

Warm layer of air at black surface provides larger pressure ...

low altitude Stratocumulus- clouds cover about 30% of the sea surface

A 2% enhancement of their albedo would provide a radiative forcing of -4 W/m². (Latham 2002)

Enhanced Cloud Reflectivity due to Ship Traffic

Scheme by John Latham (University of Manchester, NCAR) and SteveSalter (University of Edinburgh) to increasing cloud albedo by injecting more sea salt cloud condensation nuclei into marine stratus clouds.

from a presentation by Alan Robock, Heidelberg 2010

Cloud Whitening

57

more condensationnuclei same amount of condensing waterproduces more (and smaller) clouddroplets more surface area more scattering higher cloud

albedo Cools Earth

Primary Susceptible Regions for Cloud Whitening

Jones et al. 2009

Spatial and temporal distribution of forcing caused by x4 CO2

(negative) Radiation forcing due to stratospheric aerosol

Govindasamy et. al. Global and Planetary Change 37 (2003) 157–168

Problem: Side-Effects regarding the Spatial and Temporal Distribution of Climate Forcing

Govindasamy et. al. Global and Planetary Change 37 (2003) 157–168

Consequences of CE Offseting 2xCO2 on the Global Temperature Distribution

oC

Consequences of CE on Global Precipitation Patterns

Change in daily precipitation column, (mm), J. Feichter et al. submitted

Blackstock et al. 2009

CE-measuresoffsetting the meanglobal temperature risecaused by 2xCO2

Ocean (Iron) Fertilization: Enhance CO2-Uptake

Redfield Ratio: C:N:P:Fe 106:16:1:0.001 (e.g. Sarmiento&Gruber 2006)

5

C6.6

N

C1

P

C10

Fe

S.W. Chisholm, Nature 407, (2000)

CO2 – Uptake in the Ocean: The “Biological Pump”

Boyd, 2007

… it is difficult to see how ocean iron fertilization with such a low Csequestered: Feadded

export efficiency would easily scale up to solve our larger global C imbalance problems…

It would scale up to a region of 109 km²—more than an orderof magnitude larger than the entire area of the Southern Ocean.

K. O. Buesseler et al., Science 2002 and 2008

Side Effects:

enhanced production of greenhouse gases like DMS, COS, organic halogen species

M. Lawrence, Science, 2001

CO2 Sequestration by Fertilization of Suitable Ocean Areas

CO2 – Removal from theAtmosphere

Art: Stonehaven CCS, Montreal,

from Klaus Lackner, Columbia University

“Synthetic Tree”

Unconventional CE-Techniques

„Immaterial“ transport of Sulfur to the stratosphere

Terramobile – LASER: Make Aerosol out of Air

Bubbles in the ocean:Bright water

And more ...

Climate Engineering is based on innovative technology

Enhancing the Natural Sulfur Cycle to Slow Global Warming?

Wingenter O.W., Elliot S.M., Blake D.R. (2007),New Directions, Atmospheric Environment, 41 (34), 7373-7375, ISSN: 13522310, +Atmos. Env. 2008, 42, (19), 4806-4809, ISSN: 13522310.

The Idea:

Iron-fertilize about 5% of the southern ocean area (1nM, 3 x per week)(don‘t care about C-fixation)

Enhance dimethyl-slufide (DMS) concentration by 20%

Enhanced DMS leads to +10% CCN (since ½ of CCN are due to DMS-oxidation)

≈0.8% albedo increase due to „cloud whitening“ (from 46.0% to 46.4%)

Negative forcing of 3 W/m2 (summer)

See also: „The Iron CLAW“ (M. Harvey, Environmental Chemistry 4 (6), 396-399, 2007)

Conclusions (Unconventional Techniques)

• There are many new ideas to facilitate CE

• Some of them may actually work

• It is likely that more ideas will emerge ... We should not prematurely settle with the presently

discussed techniques

• In fact it could be that – should CE measures ever beimplemented – none of the presently discussedtechniques are actually used

Efficiency – Cost – Safety - Timeliness of CE-Measures

source: Geoengineering the climate: Science, Governance and Uncertainty,The Royal Society, 2009

Robock et al. JGR 2008

What Happens if we stop Climate Engineering Measures?

How to Test Climate Engineering Measures?

The Role of Field Trials

Sooner or later, the improvement of our understanding of CE technologies will necessitate large-scale field trials that come very close to an actual application of the technologies. Such field trials should be accompanied by comprehensive monitoring programs. Even if we assume the best possible design for large-scale trials, unequivocal identification and quantification of the effects and side-effects of particular technologies would take many years or even decades. In the course of a field trial extending over such a long period, apparent effects and side-effects unrelated to the application of the technology would also occur.

The conduct of such a large-scale trial without the occurrence of significant social and political impacts must be considered one of the major challenges of climate engineering.

Questions beyound Technological Feasibility and Cost of CE-Measures

CE in cases of severe emegency (Crutzen)?

CE could give a feeling of false scurity (we continue as usual, apply CE if thereshould be a problem)

CE could be used as excuse for neglecting mitigation and adapatation?

Some CE-measures appear to be very cheap in comparison to mitigation

Danger of unilateral application?

Ethics of CE?

Legal questions (precautionary principle, compensation for damages)

Political enforceability?

Who decides on termination or continuation of CE – measuresin case of problems?

Who can guarantee the continuation of CE-measures over centuries (or millennia)?

What happens if CE-measures are (or have to be) terminated?

Teilprojekte (Work Packages)

A: Umweltphysik: Profs. Leisner, Platt, Aeschbach, S. Müller-Klieser

B: Philosophie: Prof. M. Gessmann, H. Fernow

C: Humangeographie: Prof. H. Gebhardt, T. Wiertz

D: Umwelt-Ökonomie: Prof. T. Goeschl, D. Heyen

E: Psychologie: Prof. J. Funke, S. Wüstenberg

F: Internat. öffentl.Recht: Prof. R. Wolfrum, D. Reichwein

G: Politische Wissenschaft: Prof. S. Harnisch, S. Uther

H: Politische Ökonomie: Prof. S. Walter, W. Dietz

Marsilius Projekt der Univ. Heidelberg:„The Global Governance of Climate Engineering“ RNZ v. 1.12.2009

Really Roughly Estimated Cost of CE-measures(109 US$ per W/m2)

Reduction of CO2 Emission: 200 (forcomparison)

Urban albedo reduction: 2000

Desert albedo reduction: 1000

Cloud Whitening:0.135 (or more)

Stratospheric S-Aerosol: 2-67

Space Shades:1700 (L1)

Source: Rickels et al. 2011 (BMBF-Report)

Summary

• Climate modification measures are already being applied to our planet (Emission of greenhouse gases, deforestation, etc.) – although notdeliberate.

• The idea to add deliberate Climate Engineering to these measures mayappear blasphemic, however there might be emergency situationswhere CE may be the only solution (e.g. because of time scales).

• CE might not be feasible at all or much more difficult (and expensive) to implement than anticipated.

• There are great dangers associated with CE:- Moral dangers – less incentive for mitigation(„Climate Sceptics“: „Climate change is not a problem and CE is the solution“)

- Side effects and unwanted effects- Political disturbances

• However, research can answer some of these questions and reducesome of the uncertainties.

“Time Magazin24. 3. 2008