Environmental Change Institute, University of Oxford

World Weather Attribution (WWA) is an initiative of international climate scientists co-led by ECI’s acting director Dr Fredi Otto and Dr Geert Jan van Oldenborgh at KNMI in the Netherlands.

The project is the first of its kind and answers the question: whether and to what extent does anthropogenic climate change alter the likelihood and intensity of extreme weather events? It does this around the world in real-time, while the event is still unfolding.

WWA has been instrumental in developing an emerging field of climate research: event attribution and the public discourse on the events analysed.

Why is this research important?

In times when the impact of climate change is hugely debated, the importance of WWA cannot be underestimated. It provides crucial scientific evidence to a debate that has often been driven by values and opinions alone.

WWA has paved the way towards a best-practice of event attribution vetted by the scientific community. It will also form the basis for an operational European attribution service, to be implemented in 2020/2021.

Models and methods

The basic idea behind the WWA methodology is to simulate possible weather in the present climate (with anthropogenic climate change), with possible weather in the climate as it would be without man-made climate change. Subsequently, the probability of the investigating extreme event in both worlds is compared.

A priori there are always four possible outcomes of an attribution study:

  1. the event could have been made more likely/intense
  2. the event could have been made less likely/intense
  3. the likelihood/intensity could have been unaltered by human-induced climate change
  4. with the current available models and observations an investigation is not possible.

In WWA the researchers always use a multi-method approach, combining observational data, analysis of a range of models (like weather@home, CIMP5) and on-site reports.

Depending on the type of event and region in the world, the team of researchers varies with the expertise required.


For more information and assessments of individual extreme weather events, please visit worldweatherattribution.org.


Project details