Michael J. Prather
The 2020 Vilhelm Bjerknes Medal is awarded to Michael J. Prather for groundbreaking developments in chemistry-transport modelling, establishing a theoretical framework to elucidate the role of reactive species in climate forcing, and improving environmental policy.
Michael Prather holds the position of UCI Distinguished Professor in the Earth System Science Department, University of California, Irvine. He is an exceptional scientist who applies fundamental concepts in atmospheric science to questions of societal importance.
Prather’s work centres on understanding the time scales and magnitudes of the environmental impacts of changes in atmospheric composition. His primary tools are numerical atmospheric models, with an approach based on mathematical abstraction of the complex problem of modelling the highly heterogeneous but tightly coupled system of atmospheric constituents. Prather’s fundamental scientific contributions have been to develop accurate numerical algorithms to describe atmospheric transport in the models; improve the representation of photochemistry and atmospheric radiation; and then to couple these into global models that describe ozone and other reactive and greenhouse gases.
Prather pioneered many of the algorithms and tools that are used today in international ozone and climate assessments to evaluate policy options for limiting ozone depletion and climate change. For example, he started the use of atmospheric chlorine loading (timeline of future levels of the ozone-depleting chlorocarbons) to evaluate policy options for stratospheric ozone recovery. This new approach dramatically shifted international policy under the Montreal Protocol: previously the Protocol was based on a single static measure of the ozone-depleting potential of a particular species, but following Prather’s work, this changed to an interactive timeline examining various phase-out options to limit the overall chlorine loading (and ozone depletion).
In some of the earliest model realisations used for assessments, Prather developed a simple method for the accurate determination of the atmospheric lifetimes of many ozone-depleting and greenhouse gases that remain in use today. In the climate-change arena, he pioneered the use of a mathematical formalism to deconstruct chemical interactions in the atmosphere. This work identified the methane chemical feedbacks that effectively lengthen the estimated lifetime for this greenhouse gas in the atmosphere, thereby increasing its estimated climate impact by 40%.
Prather has led or co-authored a large number of congressional reports in the US and served as a Jefferson Science Fellow in Washington, DC. He has also contributed to international assessments on questions related to stratospheric ozone depletion (World Meteorological Organisation Ozone/United Nations Environment Programme), the impacts of human activity on air pollution, and the role of reactive species as short-lived forcers in the climate system (Intergovernmental Panel on Climate Change).