SSiRC Home Page

Activity Leaders

Landon Rieger, University of Saskatchewan, Saskatoon, SA, Canada

Anja Schmidt, Deutsches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen-Wessling, Germany, and Meteorological Institute, Ludwig Maximilian University of Munich, Munich, Germany

Marc von Hobe, Forschungszentrum Jülich GmbH, Jülich, Germany

Scientific Steering Group

Juan Carlos, Antuña-Marrero, Departamento de Física Teórica, Atómica y Óptica, Universidad de Valladolid, España,

Terry Deshler, University of Colorado, Boulder, USA,

Suvarna Fadnavis. Indian Institute of Tropical Meteorology, Pune, India ,

Corinna Kloss, Le Centre National de la Recherche Scientifique, Orléans, France

Mahesh Kovilakam, SSAI, Hampton, VA USA

Eduardo Landulfo, Instituto de Pesquisas Energéticas e Nucleares (IPEN), São Paulo, Brazil

Graham Mann, School of Earth and Environment, University of Leeds, Leeds, UK

Andrew Rollins, NOAA, Boulder, CO USA

Jean-Paul Vernier, National Institute of Aerospace, Hampton VA USA

Yunqian Zhu, University of Colorado, Boulder, CO, USA

About SSiRC

SSiRC is an established SPARC (Stratosphere-Troposphere Processes and their role in Climate) activity, with SPARC being a core project within the World Climate Research Program (WCRP). SSiRC aims to foster collaboration across observational and modelling groups to better understand the stratospheric aerosol layer and the drivers for its observed variations. The abrupt volcanic enhancements of the stratospheric aerosol concentrations cause strong solar dimming and thereby surface cooling with important changes in circulation and atmospheric composition in response. SSiRC key science questions link with several foci of the WCRP grand challenges. The stratospheric aerosol layer was discovered 60 years ago, but it still poses us riddles. Aerosol above 15 km forms an optically thin veil with a small well characterized impact on climate, but then, in explosive episodes, it can intensify dramatically due to massive, aperiodic volcanic eruptions. Following such events, the stratospheric aerosol influences Earth's climate by cooling the planet as a whole and creates potentially devastating changes to regional weather patterns, such as winter warming in the Northern Hemisphere and reducing summer monsoon rainfall over Africa and Asia. It also increases the probability of an El Niño in the following Northern Hemisphere winter. In the modern era, large volcanic events can temporarily slow the pace of anthropogenic global warming. While much is understood about the impact of stratospheric aerosol on climate, there are a number of open questions relevant to SSiRC, SPARC and the WCRP:

What is the uncertainty associated with estimates of aerosol properties such as aerosol optical depth over the satellite era, and what are the uncertainties at scales from the 1991 Pinatubo eruption to background levels?
What is the contribution from non-sulfate components and how important is the contribution?
How do anthropogenic emissions stratospheric aerosol precursors affect stratospheric aerosol variability?
How does the tropospheric sulfur cycle respond to climate change, and how does it affect stratospheric aerosol levels?
How does variability in stratospheric aerosol affect surface temperature and precipitation?
How does co-emitted ultra-fine ash influence the volcanic SO₂ radiative forcing from major volcanic eruptions?
What are the major uncertainties in calculating stratospheric aerosol radiative forcing?

By addressing these questions, SSiRC aims at better constraining the pathways of stratospheric aerosol and its precursors from emission to radiative forcing. By raising these questions and highlighting their importance, SSiRC stimulates research in this area, research that is relevant to WCRP's mission. SSiRC enables the assessment of our understanding the role of stratospheric aerosol in climate including the potential for catastrophic climate impacts following a major volcanic event, and decoupling more moderate climate changes in the stratospheric aerosol burden from those attributable to human activities. SSiRC builds a community from different fields of study and fosters collaboration. SSiRC connects to other WCRP/SPARC activities including ACAM, OCTV-UTLS and CCMI.

SSiRC activities

SSiRC is currently supporting a number of endeavors, such as:

ISAMIP compares interactive stratospheric aerosol models using a range of satellite and in situ observations to constrain and improve climate models,
GloSSAC to improve stratospheric aerosol data sets used by climate models to prescribe aerosols,
Data Rescue to secure historical data into archival facilities,
Observed sulfur burden paper to review and consolidate observations of the sulfur burden over the post Pinatubo era,
Define a new volcanic climate index that is based on the characteristics that make a major volcanic eruption major, and
VolRes to articulate a scientific response plan in the event of a large volcanic eruption.
- Atmospheric impacts of the 2022 Hunga Tonga-Honga Ha'apai eruption

SSiRC is linked to:

VolMIP is a CMIP6 endorsed project with the aim to coordinate the activities of different research institutes involved in numerical climate modelling focused on a multi-model assessment of climate model performance under strong volcanic forcing conditions,
GeoMIP serves to organize geoengineering simulations by prescribing the experiments which all participating climate models will perform, and
PAGES VICS supports research focused on reconstructing the history of past explosive volcanism, and research using this knowledge to better understand how the climate system responds to changes in radiative forcing, and how societies have been impacted by and responded to the resulting climatic changes.