The current program partnership team includes the University of Oxford Environmental Change Institute, the Royal Netherlands Meteorological Institute, the University of Melbourne, the Red Cross Red Crescent Climate Centre, and Climate Central. Our science partners at KNMI and the University of Melbourne will utilize established peer- reviewed methods to perform their attribution assessments. The Oxford team is currently building on their well-known weather@home methodology to develop the capacity to perform more rapid event assessment. Over time, we will expand the team with additional international partners to develop greater regional capacity and geographic reach.

Climate Central. In addition to serving as “secretariat” and coordinator of the World Weather Attribution partnership, the Climate Central team — led by Heidi Cullen — is also providing the interface to the science and outreach teams, coordinating Science Oversight Committee activities and peer review and leveraging its network of partners to disseminate World Weather Attribution findings. In particular, Climate Central is coordinating with communications experts and conducting social science research to identify and employ the most effective ways to communicate the science of severe weather event attribution, including the levels of certainty and uncertainty involved in such an endeavor.

University of Oxford Environmental Change Institute. The Oxford team is led by Friederike Otto.

Their unique approach uses very large ensembles of simulations of regional climate models to run two different analyses: one to represent the current climate as it was observed, and one to represent the same events in the world that might have been without human-induced climate change. The soundness of this methodological approach is supported by its widespread use in submissions to the annual Bulletin of the American Meteorological Society Special Issue on Explaining Extreme Events from a Climate Perspective (e.g., Rupp et al., 2013,  Añel et al., 2014, Massey et al., 2012. This analysis used very large ensembles of a regional climate model over Europe embedded in a global circulation model to assess the change in risk of extreme precipitation under two very distinct versions of the event: 1) the observed extreme weather event itself, and 2) a model of the extreme weather event with the impact of anthropogenic greenhouse gas emissions removed. Using a distributed computing framework — weather@home (Massey et al., 2014) — members of the public facilitate multi-thousand-member ensemble weather simulation experiments at both global and regional resolution scales.

In order to accelerate the attribution analysis, the Oxford team has developed a novel approach based on using forecast sea surface temperatures (SSTs) instead of observed SSTs. The team is currently performing a proof of concept using the 2014 United Kingdom floods as a case study to demonstrate the robustness of this approach.

Royal Netherlands Meteorological Institute. The KNMI team, led by Geert Jan van Oldenborgh, focuses on empirical event attribution using historical data records and follows the methodology described in van Oldenborgh (2012). It consists of looking for a trend in the observed extremes before the event to be studied has occurred. If there is a trend, a physical model is used to connect it with the temperature rises that have been attributed to human influences in a multi-step attribution. The method is complementary to model-based methods (which are used most often for large-scale weather and climate events) as it is most sensitive when used to attribute the causes of small-scale events; it is also a useful cross-check on model results for large-scale events. These routines are being developed as part of the KNMI Climate Explorer — a research tool built by van Oldenborgh to investigate climate variability and change.

University of Melbourne. The Melbourne team is led by David Karoly. Their approach utilizes a suite of climate model simulations undertaken as part of the Coupled Model Intercomparison Project phase 5 (CMIP5) (Taylor et al., 2012). After an extreme weather event has been identified and defined, the team first assesses the capability of global climate models to simulate this type of extreme event. Different from the Oxford regional model approach, the Melbourne method relies on existing simulations from global coupled ocean-atmosphere climate models. These global models have coarser spatial resolution, but they include the effects of coupling the atmosphere to the ocean in the models and the uncertainties associated with using multiple different climate models to simulate the extreme events. This approach was used in the analysis of the record summer temperature averaged across Australia in 2012-13 (Lewis and Karoly, 2013), which showed that human-caused climate change had very likely led to at least a five-fold increase in the frequency of similar extreme summer temperatures across Australia.

Note: As new ensembles become available, they will be integrated into our analyses. Working with multiple climate models and data sets provides additional analytical power.

Red Cross Red Crescent Climate Centre. The Climate Centre team is led by Dr. Maarten van Aalst and Erin Coughlan. The Climate Centre is a specialist reference center for the International Federation of Red Cross and Red Crescent Societies (IFRC) and helps the Red Cross and Red Crescent Movement and other partners reduce the impacts of climate change and extreme-weather events on vulnerable people. It will use its humanitarian network to identify disasters that will be analyzed by the WWA initiative. Further analysis will help place the event in the larger context of patterns of changing risk, including trends in vulnerability and exposure. The Climate Centre team is also helping develop an index of published articles relevant to specific events and geographical regions that will be consulted when WWA assesses a specific event. This “living database” includes peer-reviewed studies on regional trends in extremes, and in hydrology, decadal variability, future projections, and other published attribution studies that will allow us to more quickly assess the state of the science.

Science Oversight Committee.
 The World Weather Attribution Program benefits from the expertise of its Science Oversight Committee, which represents the collective scientific voice of the climate attribution and risk community. The committee provides advice and feedback on approaches, methodologies, and procedures, including the core program strategy. Science Oversight Committee members include:

  • Gabi Hegerl (Chair, University of Edinburgh)
  • Michael Wehner (Deputy Chair, Lawrence Berkeley National Lab)
  • Stephane Hallegatte (World Bank)
  • Alexis Hannart (CNRS – UMI IFAECI)
  • Reto Knutti (ETH Zurich)
  • Sophie Lewis (Australia National University, Canberra)
  • Ben Santer (Lawrence Livermore National Lab)
  • Sonia Seneviratne (ETH Zurich)
  • Hideo Shiogama (NIES, Japan)
  • Peter Stott (UK Met Office)
  • Francis Zwiers (University of Victoria)