Research to Evaluate Climate Engineering

The German Research Foundation's Priority Program 1689, coordinated at GEOMAR, ran from 2013 – 2020 with the participation of 20 universities and research institutes from German-speaking countries. In SPP 1689, different climate engineering approaches were evaluated in an interdisciplinary way in order to create a basis for a responsible use of climate engineering methods. In addition to the scientific-technical dimension, social, political, legal and ethical aspects have also been investigated.

The work within SPP 1689 has shown that solar radiation management methods would be extremely problematic globally, could also have significant regional effects on neighboring regions, and would not be responsible in principle without an accompanying effort to remove CO2 from the atmosphere (CDR). The focus of further research is therefore on CDR methods.

A major concern of SPP 1689 was also the transparency of the research (see contributions Knowledge Transfer).

The news portal which has been established in SPP 1689 will continue to be operated by the research mission CDRmare at

Brochure SPP 1689

Climate engineering and our climate targets – a long-overdue debate

This publication was produced in 2019 as part of the public outreach work under the DFG Priority Programme, with only minor changes made for the English-language edition compared with the German edition. Its aim is to promote open social and political debate that is informed by the best available knowledge about the possibilities and risks of the various climate engineering ideas.

Animation film on youtube: Ambitious climate targets – the role of negative emissions

SPP 1689 Publication 2021

  • Burt DJ, Fröb F and Ilyina T (2021) The Sensitivity of the Marine Carbonate System to Regional Ocean Alkalinity Enhancement. Front. Clim. 3:624075. doi: 10.3389/fclim.2021.624075 /
  • Stenzel, F., Gerten, D., Hanasaki, N. (2021): Global scenarios of irrigation water abstractions for bioenergy production: a systematic review. In Hydrol. Earth Syst. Sci. 25 (4), pp. 1711–1726. DOI: 10.5194/hess-25-1711-2021.
  • Stenzel, F., Greve, P., Lucht, W., Tramberend, S., Wada, Y. and Gerten, D.  Irrigation of biomass plantations may globally increase water stress more than climate change. Nat Commun 12, 1512 (2021).
  • Klaus, G., Oswald, L., Ernst, A. and Merk, C. (2021) Effects of opinion statements on laypeople's acceptance of a climate engineering technology. Comparing the source credibility of researchers, politicians and a citizens' jury. doi:10.22323/2.20010203
  • Robrecht, S., Vogel, B., Tilmes, S., Müller, R. Potential of future stratospheric ozone loss in the midlatitudes under global warming and sulfate geoengineering. doi:10.5194/acp-21-2427-2021 /

Digitale Woche Kiel 2020

Wie können wir das 1,5-Grad-Ziel noch erreichen?

Interaktiver Vortrag von Prof. Dr. Andreas Oschlies, GEOMAR Kiel, 09.09.20

New Publications 2020

SPP 1689 in Oxford Research Encyclopedias: Geoengineering

Publications 2020

  • Kreuter, J., Matzner, N., Baatz, C., Keller, D.P., Markus, T., Wittstock, F., Bernitt, U. and Mengis, N. Unveiling assumptions through interdisciplinary scrutiny: Observations from the German Priority Program on Climate Engineering (SPP 1689). Climatic Change (2020).
  • Neuber, F. and Ott, K. The Buying Time Argument within the Solar Radiation Management Discourse. Appl. Sci. 2020, 10, 4637.
  • Amann, T., Hartmann, J., Struyf, E., de Oliveira Garcia, W., Fischer, E. K., Janssens, I., Meire, P. and Schoelynck, J. (2020) Enhanced Weathering and related element fluxes – a cropland mesocosm approach.
  • Matzner, N. and Barben, D. (2020): Climate Engineering as a Communication Challenge: Contested Notions of Responsibility Across Expert Arenas of Science and Policy.

Das Klima retten - aber wie? // Tagesschau 24 // THEMA

ARD // 22.12.2019

New Publications

  • Merk, C., Klaus, G., Pohlers, J., Ernst, A., Ott, K., and Rehdanz, K. (2019): Public Perceptions of Climate Engineering: Laypersons’ Acceptance at Different Levels of Knowledge and Intensities of Deliberation.
  • Klaus, G., A. Ernst, L. Oswald (2019) Psychological factors influencing laypersons’ acceptance of climate engineering, climate change mitigation and business as usual scenarios.

Unsere Klimaziele – die Rolle negativer Emissionen: SPP 1689 beim Tag der offenen Tür des GEOMARs

Sonntag, 18. August 2019, 11 - 17 Uhr.

GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Wischhofstr. 1-3, 24148 Kiel.

New Publication

Unsere Klimaziele – die Rolle negativer Emissionen: Trickfilm auf der Kieler Woche 2019

Zu sehen auf der Kieler Woche im Zelt auf der "Schlaumachwiese" vor dem GEOMAR.

Podiumsdiskussion im Museum für Naturkunde

MITTWOCH 15. MAI 2019 // 19:30 – 22:30


Das Schwerpunktprogramm der Deutschen Forschungsgemeinschaft
zu Climate Engineering und das Museum für Naturkunde luden zur
öffentlichen Podiumsdiskussion ein. 

Weitere Informationen und Impressionen hier.

SPP 1689 Workshop

Climate Engineering: Opportunities and Challenges for Responsible Research and Anticipatory Governance 

May 14-16, 2019 in Berlin

Read more

New Publications

Öffentlicher Vortrag in der GEOMAR-Reihe »Wissen Schaffen«: Wie wir das 1.5 Grad Ziel noch erreichen könnten

Prof. Dr. Andreas Oschlies  // Mittwoch, 16. Januar 2019

Sehen und hören Sie den Vortag auf youtube:

Klar Soweit? No.59 – Dr. Greenhouse

Comic der Helmholtz Gemeinschaft zum Thema Climate Engineering:

Workshop Detection and Attribution of Climate Engineering

3 – 5 December 2018, Hamburg, Elsa-Brandström-Haus (

More information and some impressions here ...

Debatte zu Geoengineering vom 28. November ab 18 Uhr im Spreepalais in Berlin: (deutsch)

Auf dem Podium zu Gast waren die Geographin Lili Fuhr von der Heinrich-Böll-Stiftung, der Ökonom Prof. Jan Christoph Minx, PhD vom Mercator Research Institute on Global Commons and Climate Change und der Physiker Prof. Dr. Andreas Oschlies vom Helmholtz-Zentrum für Ozeanforschung in Kiel und Sprecher des SPP 1689. Christoph Koch (Stern) und Dr. Mai Thi Nguyen-Kim (freie Wissenschaftsjournalistin) moderierten die Veranstaltung.

Wissenschaft, natürlich!

Zum Thema: Climate Engineering – mit gezielten technischen Eingriffen das Klima verändern. Hilft uns das weiter?


Prof. Dr. Andreas Oschlies vom GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel und Prof. Dr. Alexander Proelß, Rechtswissenschaftler der Universität Hamburg diskutieren mit dem Publikum.

Eine Veranstaltung des Naturkundemuseums Berlin in Zusammenarbeit mit dem SPP 1689 im Rahmenprogramm zur Sonderausstellung ARTEFAKTE im Naturkundemuseum.

Weitere Informationen und Anmeldung:

„Klimaforschung und Handlungsoptionen im globalen Wandel – Hintergründe, Möglichkeiten und Ideen für den naturwissenschaftlichen Unterricht“

Eine Kooperation des SPP 1689 mit dem Pädagogischen Landesinstitut Rheinland-Pfalz:
Lehrerfortbildung am 26.10.2018 in Trier mit einem aktivierenden Vortag von Ulrike Bernitt und dem Climate engineering Rollenspiel „Globaler Krisenstab zum Klimawandel“.

Mehr zum Rollenspiel für Schüler finden Sie hier ...

Mehr zum Thema Climate Engineering als Thema im Schulunterricht hier …

Our animation film is now available on youtube: Ambitious climate targets – the role of negative emissions

3rd SPP 1689 Retreat / September 2018

3rd & last annual retreat of the SPP1689/2
26. - 28. September Schloss Buchenau

Some Impressions

New SPP 1689 Publications

Video Impression from the SPP 1689 & ISOS Workshop on Science Communication

A video by Zhihong Zho // July 2018 // Travemünde

Updated versions of our information graphics on Climate Engineering ideas

The infographics are licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License.

Contrails vs Chemtrails

Young Scientist Retreat & Workshop 2018

The SPP 1689 Young Scientist Retreat & Workshop on Interdisciplinary Exchange took place in the Landhaus Lenzener ElbtalaueApril 23-25.

Some impressions

SPP 1689 citizen's jury

The DFG project TOMACE, one of the projects within the SPP 1689 »Climate Engineering«, started in January his citizen's jury. Participation was only possible by invitation.

More informations
Some impressions

New SPP 1689 Publications

  • Ferrer González, Miriam, Tatiana Ilyina, Sebastian Sonntag, Hauke Schmidt (2018): Enhanced Rates of Regional Warming and Ocean Acidification after Termination of Large‐scale Ocean Alkalinization, Geophysical Research Letters, doi: 10.1029/2018gl077847
  • Keller, D.P., Lenton, A., Littleton, E.W. et al. (2018): The Effects of Carbon Dioxide Removal on the Carbon Cycle, Curr Clim Change Rep, 1-16,
  • Kriegler, M., G. LudererN. BauerL. BaumstarkS. FujimoriA. PoppJ. RogeljJ. Strefler, . P. van Vuuren (2018): Pathways limiting warming to 1.5°C: a tale of turning around in no time?, 
  • Oliveira-Garcia, W., T. Amann, J. Hartmann (2018): Increasing biomass demand enlarges negative forest nutrient budget areas in wood export regions, Scientific Reports 8 (5280), doi:10.1038/s41598-018-22728-5
  • Ott, K. K. (2018): On the Political Economy of Solar Radiation Management, Frontiers in Environmental Science 6, 43,
  • Rickels, W., Reith, F., Keller, D., Oschlies, A., & Quaas, M. F. (2018): Integrated Assessment of Carbon Dioxide Removal, Earth’s Future, 6.
  • Roshan, E., M. M. Khabbazan & H. Held (2018): Cost-Risk Trade-Off of Mitigation and Solar Geoengineering: Considering Regional Disparities Under Probabilistic Climate Sensitivity,  Environ. Resource Econ., 1-17,
  • Strefler, Jessica; et al. (2018): Between Scylla and Charybdis: Delayed mitigation narrows the passage between large-scale CDR and high costs, Environmental Research Letters, 13. 044015.
  • Werner, C., H-P. SchmidtD. GertenW. Lucht and C. Kammann (2018): Biogeochemical potential of biomass pyrolysis systems for limiting global warming to 1.5 °C, Environmental Research Letters 13 (4),

CDRMIP has been endorsed by CMIP6

The Coupled Model Intercomparison Project (CMIP; currently in it's 6th phase) is organized under the auspices of the World Climate Research Programme (WCRP) and designed to better understand past, present, and future climate change through coordinated international multi-model experiments that have become a central element of national and international assessments of climate change, e.g., IPCC reports.  The Carbon Dioxide Removal Model Intercomparison Project (CDRMIP), which has just been endorsed by CMIP6, brings together models of the Earth system in a common framework to explore the potential, impacts, and challenges of Carbon Dioxide Removal (CDR).  CDRMIP experiments are designed to address questions concerning CDR-induced climate "reversibility", the response of the Earth system to direct atmospheric CO2 removal (direct air capture and storage), and the CDR potential of proposed schemes such as afforestation/reforestation and ocean alkalinization.    

World Climate Research Program:



New SPP 1689 Publications

  • Keller, D. P., Lenton, A., Scott, V., Vaughan, N. E., Bauer, N., Ji, D., Jones, C. D., Kravitz, B., Muri, H., and Zickfeld, K.: The Carbon Dioxide Removal Model Intercomparison Project (CDR-MIP): Rationale and experimental protocol for CMIP6, Geosci. Model Dev.,, 2018
  • Kleinschmitt, C., Boucher, O., and Platt, U. (2018): Sensitivity of the radiative forcing by stratospheric sulfur geoengineering to the amount and strategy of the SO2injection studied with the LMDZ-S3A model, Atmos. Chem. Phys., 18, 2769-2786,
  • Oschlies, Andreas (2018): Solar engineering must take temperature debt into account, Nature 554, 423,
  • Mengis, N., Keller, D. P., and Oschlies, A. (2018): Systematic Correlation Matrix Evaluation (SCoMaE) – a bottom–up, science-led approach to identifying indicators, Earth Syst. Dynam., 9, 15-31,
  • Keller D.P. (2018) Marine Climate Engineering. In: Salomon M., Markus T. (eds) Handbook on Marine Environment Protection. Springer, Cham, doi:10.1007/978-3-319-60156-4_13
  • Strefler, Jessica; et al. (2018): Potential and costs of carbon dioxide removal by enhanced weathering of rocks
  • Sonntag, Sebastian; et al. (2018): Quantifying and comparing effects of climate engineering methods on the Earth system, Earth's Future, doi:10.1002/2017EF000620
  • Heck, Vera; et al. (2018): Biomass-based negative emissions difficult to reconcile with planetary boundaries, Nature Climate Change (2018), doi:10.1038/s41558-017-0064-y

SPP 1689 Workshop Terrestrial CO2 Removal

SPP 1689 WORKSHOP // 22 – 23 Jan 2018 // Potsdam Institute for Climate Impact Research, A56

Terrestrial CO2 Removal: Potentials and tradeoffs in the SDG context

This workshop will look into a set of pertinent questions related to potentials of tCDR methods and their interaction with SDGs. It will bring together SPP 1689 researchers and external experts to increase our holistic understanding of global and regional potentials and side-effects of tCDR as well as to identify future research priorities.
read more and find the agenda here ...

New Publications

Niemeier, U. and Schmidt, H. (2017): Changing transport processes in the stratosphere by radiative heating of sulfate aerosols, Atmos. Chem. Phys., 17, 14871-14886,

Feng, E. Y.; Koeve, W.; Keller, D. P. and Oschlies, A. (2017): Model-based Assessment of the CO2 Sequestration Potential of Coastal Ocean Alkalinization. In Earth's Future. DOI: 10.1002/2017EF000659.

New Publication

Ferrer-Gonzalez, M. (2017). Climate engineering by enhancement of ocean alkalinity: impacts on the Earth system and a comparison with solar radiation management. PhD Thesis, Universität Hamburg, Hamburg. doi:10.17617/2.2472753.

German Science Hour im Deutschen Pavillion auf der COP 23

Andreas Oschlies, Mark Lawrence, Oliver Geden and Lilly Fuhr: “Failing the carbon budget - what's next?” (Photo)

SPP 1689 Workshop Climate Engineering Regulation and Liability

16 – 18 October 2017, KIEL

Some photographs, more information and the agenda here (english only) ...

New SPP 1689 Publications

  • Kemena,Tronje Peer; Matthes, Katja; Martin, Thomas; Wahl, Sebastian; Oschlies, Andreas: Atmospheric feedbacks in North Africa from an irrigated, afforested Sahara, Clim Dyn (2017).
  • Keller, D. P., Lenton, A., Scott, V., Vaughan, N. E., Bauer, N., Ji, D., Jones, C. D., Kravitz, B., Muri, H., and Zickfeld, K.: The Carbon Dioxide Removal Model Intercomparison Project (CDR-MIP): Rationale and experimental design, Geosci. Model Dev. Discuss.,, in review, 2017.

Overview on modelling in the SPP 1689


Climate Engineering Conference 2017

October 9 -12, 2017, Berlin

Klimaschutz braucht mehr Forscher und Erfinder
// Weniger Emissionen allein reichen nicht: Der Atmosphäre muss CO2 entzogen werden / Von Andreas Mihm

Wilfried Rickels u.a. im Artikel auf (german):

New SPP 1689 Publications

  • Niemeier, Ulrike, Tilmes, Simone: Sulfur injections for a cooler planet, Science 21 Jul 2017, Vol. 357, Issue 6348, pp. 246-248, DOI: 10.1126/science.aan3317,

  • Lohmann, Ulrike, Gasparini, Blaž: A cirrus cloud climate dial?, Science 21 Jul 2017, Vol. 357, Issue 6348, pp. 248-249, DOI: 10.1126/science.aan3325,
  • Kleinschmitt, C., Boucher, O., and Platt, U.: Sensitivity of the radiative forcing by stratospheric sulfur geoengineering to the amount and strategy of the SO2 injection studied with the LMDZ-S3A model, Atmos. Chem. Phys. Discuss.,, in review, 2017.

  • Stelzer, Harald (2017): Justifying Climate Engineering?. In: Jahrbuch für Wissenschaft und Ethik. Band 21 (2016). Berlin: De Gruyter, 147–169.

2nd SPP 1689 Retreat / Summer 2017

July 5-7, 2017 at the Schloss Buchenau near Fulda/Bad Hersfeld.

Impressions of the Retreat here.

New SPP 1689 Publications

Radio Ecoshock

Lena Boysen about »green« climate engineering with trees:

New SPP 1689 Publications

First Young Scientist Retreat of the 2nd Phase

SPP 1689 Young Scientist Retreat in Malente

Impressions here …

New SPP 1689 Publications

Veröffentlichung der Deutschen Meteorologischen Gesellschaft

Die Deutsche Meteorologischen Gesellschaft (DMG) hat eine Stellungnahme und einen kurzen Erläuterungstext zu Climate Engineering in ihren »Mitteilungen« veröffentlicht:

New SPP 1689 Publications

  • Quaas, Martin F.; Quaas, Johannes; Rickels, Wilfried; Boucher, Olivier (2017): Are there reasons against open-ended research into solar radiation management? A model of intergenerational decision-making under uncertainty. In Journal of Environmental Economics and Management. DOI: 10.1016/j.jeem.2017.02.002.

New SPP 1689 Publications

SPP 1689 Workshop on the 1.5°C Target and Climate Engineering

24–25 November 2016 // Kiel // Germany

read more ...


Climate Engineering Ideas

More downloads for your information under DOWNLOADS

This infographic is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License.


Is Climate Engineering an option to prevent climate change?

There are many central open questions. More downloads for your information under DOWNLOADS

This infographic is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License.

Faltblatt Naturwissenschaftler antworten Journalisten

Einige Naturwissenschaftler aus dem Schwerpunktprogramm SPP 1689 antworten hier  professionellen WissenschaftsjournalistInnen vom „Nationalen Institut für Wissenschaftskommunikation“ (Karls­ruhe) auf konkrete Fragen zu ihrer Wissenschaft.

New SPP 1689 Publications

KlimaTaucher - Fernreisen mit gutem Gewissen? Wie wir das Klima beeinflussen können

DFG-Filmproduktion zu Climate Engineering mit Andreas Oschlies und Nadine Mengis

New SPP 1689 Publications

Ellias Y Feng (冯玉铭), David P Keller, Wolfgang Koeve and Andreas Oschlies (2016): Could artificial ocean alkalinization protect tropical coral ecosystems from ocean acidification? In: Environmental Research Letters, vol. 11, no. 7,

SPP 1689 Retreat Impressions

First SPP 1689 retreat of the 2nd phase.

See more impressions here ...

First SPP 1689 Retreat of the 2nd Phase

14-16 June 2016, Kloster Haydau / Morschen

(project presentations, discussion of action items for the 2nd phase, setting of cross-project topics)

New SPP 1689 Publications

Mengis, Nadine; et al. (2016): Assessing climate impacts and risks of ocean albedo modification in the Arctic. In Journal of Geophysical Research: Oceans, vol. 121, 3

Merk, Christine; Pönitzsch, Gert; Rehdanz, Katrin (2016): Knowledge about aerosol injection does not reduce individual mitigration efforts. In: Environmental Research Letters, vol. 11, no. 5

Start of 2nd phase

Start of 2nd phase of SPP 1689, May 2016.

Project composition here