Exploring the Chemical and Climatic Impacts of Solid Particles for Stratospheric Solar Geoengineering

  • Awardees
  • Timofei Sukhodolov, Ph.D. Physical Meteorological Observatory Davos
  • Markus Ammann, Ph.D. Paul Scherrer Institute
  • Gabriel Chiodo, Ph.D. Spanish National Research Council
  • Beiping Luo, Ph.D. ETH Zurich
  • Arnold Müller, Ph.D. ETH Zurich
  • Krishnan Raghavan, Ph.D. Indian Institute of Tropical Meteorology
  • Christof Vockenhuber, Ph.D. ETH Zurich
Year Awarded


This project aims at investigating the chemical and climatic impacts of alternative materials for potential solar radiation management schemes through stratospheric aerosol injections (SAI). The project team will mainly focus on the alumina, calcite and diamond solid particles, which are hypothesized to produce fewer side effects compared to the traditionally considered SAI approach with sulfate aerosols. Such side effects include stratospheric ozone depletion and lower stratospheric heating, which has important implications for large-scale stratospheric and tropospheric circulation and regional climates, particularly in the high latitudes and in the regions affected by the Asian monsoon. The project will involve six institutes from three countries (Switzerland, Spain and India), three global models (the Solar Climate Ozone Links model, SOCOL; the Whole Atmosphere Community Climate model, WACCM; and the Indian Institute of Tropical Meteorology Earth System Model, IITM-ESM) and three chemical lab facilities (Ambient Pressure X-ray Photoelectron Spectroscopy, AP-XPS; Heavy Ion Elastic Recoil Detection Analysis, HI-ERDA; and Rutherford Backscattering Spectrometry, RBS). The lab measurements will be performed to get information about the surface and bulk chemistry processes associated with the solid particles, without which their effects on the ozone layer cannot be properly assessed. The project will thus establish a combination of laboratory and numerical multi-model results and experts in chemistry, aerosol microphysics, stratospheric dynamics and tropospheric circulation, which will provide a solid basis for an improved assessment of risks and benefits of SAI via alternative materials.

Timofei Sukhodolov is a head of the climate group at the Physical-Meteorological Observatory Davos / World Radiation Center (PMOD/WRC), Davos, Switzerland. He specializes in the fields of chemistry-climate modeling and the effects of various natural and anthropogenic forcings on the middle atmosphere and the ozone layer and their feedbacks with climate. He is the principal investigator of the SOCOLv4 atmosphere-ocean-aerosol-chemistry-climate model, which will be the main modeling tool of the project. Sukhodolov received his Ph.D. in environmental sciences in 2016 from ETH Zürich, and his thesis has been awarded the ETH Silver Medal. Sukhodolov is deeply integrated in international modeling communities focusing on stratospheric aerosol and ozone layers and is a member of the International Commission on the Middle Atmosphere.

Markus Ammann is head of the Multiphase Chemistry group of the Laboratory of Atmospheric Chemistry at Paul Scherrer Institute and an adjunct professor at ETH Zürich in the Institute of Atmospheric and Climate Sciences of the Department of Environmental Systems Sciences. He has received his Ph.D. from ETH Zürich in the field of volcanic aerosols. He has a long track record of activities related to the kinetics of trace gas-aerosol interactions in terms of experimental quantification but also of the further development of kinetics and thermodynamics concepts for multiphase atmospheric chemistry. Ammann is member of the Task Group on Atmospheric Chemical Kinetic Data Evaluation of the International Union of Pure and Applied Chemistry. Over the past decade, he has developed an in situ surface spectroscopy method, X-ray photoelectron spectroscopy, for the investigation of surface chemical composition, structure and reactivity on ice, mineral dust and aqueous solutions under atmospheric conditions. This has brought along unprecedented information about multiphase chemistry processes and allows better quantification of parameters essential for the description of import atmospheric chemical processes in models.

Gabriel Chiodo is a research scientist at ETH Zürich who will soon start a tenured junior research group leader position at the Spanish National Research Council. His research expertise is in the field of chemistry-climate modeling, with particular focus on ozone-climate interactions, stratosphere-troposphere coupling, radiative forcing and climate variability. He received his Ph.D. in 2014 at Complutense University in Madrid and was then a postdoctoral fellow at Columbia University from 2015 until 2018. He actively participated in a large National Science Foundation project on ozone depletion and its effects in the climate system. From 2019 until 2023, he has been leading a research group on ozone-climate interactions at ETH Zürich, funded via a competitive Swiss National Science Foundation (SNF) grant. His research has demonstrated, for the first time, the role of Arctic ozone in driving surface climate in the Northern Hemisphere. Chiodo is a steering committee member of the Chemistry-Climate Model Initiative and of the International Commission on the Middle Atmosphere. He was a co-author of the recent 2022 World Meteorological Organization and the United Nations Environment Programme Ozone Assessment report. Beginning in June 2024, he will be leading a new Horizon Europe project funded by the European Research Council to investigate the role of stratospheric composition in a changing climate.

Beiping Luo received his Ph.D. in physical chemistry at Free University of Berlin, with his thesis finished at the Fritz Haber Institute of the Max Planck Society in 1991. He is now a senior scientist at the Institute for Climate and Atmospheric Sciences of ETH Zürich. He is an expert in aerosol microphysics and aerosol optical properties, liquid, cirrus and polar stratospheric cloud formation and nucleation, heterogeneous aerosol chemistry and aerosol-radiation interaction. He was responsible for generating the stratospheric aerosol forcing data for the Coupled Model Intercomparison Project Phase 6 (CMIP6) and Chemistry-Climate Model Initiative (CCMI) model intercomparisons. He is the principal developer of ZOMM (Zürich Optical and Microphysical Model) and ReSAM (Respiratory Aerosol Model), and he contributed significantly to the implementation of the size-resolved (sectional, 40 bins) aerosol microphysics module in Solar Climate Ozone Links, version 4 (SOCOLv4), a unique feature of this Earth system model (ESM).

Arnold Müller is leading the ion beam analysis (IBA) activities at the Laboratory of Ion Beam Physics (LIP) at ETH Zürich. His main research area is the development of new instrumentation related to the analysis of materials with ion beams. He finished his Ph.D. in 2009 at ETH Zürich in the field of accelerator mass spectrometry (AMS), where he demonstrated the potential of compact multi-isotope AMS facilities. In the framework of the two EU infrastructure projects SPIRIT and SPRITE, he was involved in various R&D activities related to the implementation of novel ion beam detectors for IBA and AMS applications. In 2013, together with six other members of LIP, Müller was co-founder of the ETH Zürich spin-off company IONPLUS AG, commercializing the innovations made in the field of AMS. From 2016–2021, he worked at IONPLUS as senior researcher, where he was responsible for the Horizon 2020 project Radiate.

Krishnan Raghavan is the director of the Indian Institute of Tropical Meteorology (IITM) in Pune, India. He specializes in climate modeling to understand scientific issues relating to climate change, Asian monsoons and the water cycle. Under his leadership the Centre for Climate Change Research (CCCR) at IITM, he developed the first Earth system model from India that contributed to the CMIP6 and IPCC Sixth Assessment Report. He was a coordinating lead author in the Intergovernmental Panel on Climate Change Sixth Assessment Report of Working Group 1( IPCC AR6 WG1) report (Chapter-8: Water Cycle Changes) and is a member of the Joint Scientific Committee, World Climate Research Programme, World Meteorological Organisation. He and his team from CCCR-IITM published the First National Climate Change Assessment Report of the Ministry of Earth Sciences, Government of India in 2020. Raghavan is a fellow of the Indian National Science Academy, New Delhi and the Indian Academy of Sciences, Bengaluru, India. He received the National Award for Excellence in Atmospheric Science and Technology (2021) by the Ministry of Earth Sciences, Government of India.

Christof Vockenhuber is a senior scientist at ETH Zürich working in the field of ion beam analysis and accelerator mass spectrometry (AMS) at the Laboratory of Ion Beam Physics (LIP). He earned his Ph.D. from the University of Vienna in 2004, specializing in AMS of heavy radionuclides and the astrophysical application of Hf-182. From 2004 to 2008, he was a postdoctoral researcher at the radioactive ion beam facility Isotope Separator and Accelerator (ISAC) at TRIUMF, Canada’s national particle accelerator center in Vancouver, doing nuclear astrophysics with short-lived radionuclides. Since 2008, he has been responsible for measurements and applications of many cosmogenic and artificial radionuclides, which are used for dating applications and tracer studies in the environment. Since 2018, he has also been co-leading the ion beam analysis program at LIP including the installation of the new 1.7 MV Tandetron accelerator facility. He was involved in, and PI or co-PI of, several national and international projects, among others responsible for the LIP joint research activities and transnational access within the RADIATE project of 19 European partners funded by EU’s Horizon 2020 research and innovation program.

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