Michael R. Raupach. Credit: Australian National University
Michael R. Raupach. Credit: Australian National University

Michael Robin Raupach, a gifted climate scientist and micrometeorologist, passed away on 10 January 2015, in Canberra, Australia. Michael devoted his life to science. He breathed it, dreamed it, and talked about it until days before his passing. His research early in his career served as a foundation for modern micrometeorology, and he later led groundbreaking studies on human perturbations to the global carbon cycle.

Always quick to praise his colleagues, Michael himself received many awards over his career. He was a fellow of the American Geophysical Union, the Australian Academy of Science, and the Australian Academy of Technological Sciences and Engineering.

Michael received his B.Sc. in mathematical physics from the University of Adelaide in 1971. He then moved to Flinders University, where he earned a Ph.D. studying turbulent exchange processes between vegetation and the atmosphere. He gained postdoctoral experience at the University of Edinburgh and, upon returning to Australia in 1979, took a position with the Commonwealth Scientific and Industrial Research Organization (CSIRO). He remained with CSIRO until 2014, when he moved to the Australian National University.

Vegetation Canopies

Michael’s early work focused on understanding turbulent flows in vegetation canopies and the transport of heat, water, carbon dioxide, and trace gases. This work included the development of one of the first infrared hygrometers, which he used to take pioneering eddy covariance measurements of evaporation. Among his most significant contributions, Michael identified the roughness sublayer just above the canopy and showed why heat and momentum eddy diffusivities in this layer are similar.

He also formulated the mixing layer hypothesis that explained for the first time the fundamental differences between coherent structures dominating canopy and rough-wall boundary layer flows. Michael created the “localized near-field Lagrangian” turbulence model, which explained the failure of the widely used gradient-diffusion theory and how to correct it. The model is now commonly used to describe canopy scalar transport.

These breakthroughs in the field of biosphere-atmosphere interactions were as profound as the acceptance of continental drift and plate tectonics to geologists.

Michael’s continued research in this area led to the development of inverse Lagrangian methods that were routinely used for determining scalar sources and sinks in canopies from measured mean concentration profiles instead of gradient-diffusion theories. This body of research transformed modern micrometeorology. As a colleague of Michael’s put it, these breakthroughs in the field of biosphere-atmosphere interactions were as profound as the acceptance of continental drift and plate tectonics to geologists.

As his career progressed, Michael became interested in mass and energy exchange at increasing spatial and temporal scales. Using fluid-mechanical scaling principles, he developed averaging rules that span local- (or canopy-scale) to regional-scale exchanges of energy and matter between land and atmosphere. He generalized the thermodynamic constraints on regional-scale energy balances to describe heterogeneous landscapes and formulated upscaling principles, which rationalized the description of surface-atmosphere interactions at scales from leaves to regions and beyond.

The Global Carbon Project

Later in his career, Michael cofounded the Global Carbon Project, initiating a global research program engaging hundreds of scientists, practitioners, and policy makers. During this period, his interests grew from purely biophysical analyses of carbon cycle fluxes to studies that measured human impacts as well.

Along with colleagues in the Global Carbon Project, Michael described changes in the dynamics of natural carbon sinks on land and in the oceans, which together remove about half of all anthropogenic atmospheric carbon dioxide (CO2) and, in consequence, slow the progression of human-induced climate change. He initially detected an increase in the “airborne fraction,” the proportion of anthropogenic CO2 emissions that remain in the atmosphere, suggesting that carbon sinks were losing the race against the rapid increase in carbon emissions.

Michael excelled at integrative research, and he developed the “sink rate,” a diagnostic that relates carbon uptake in oceans and on land with the amount of excess atmospheric CO2, and an attribution approach to assign rate changes to underlying causes. He showed that the efficiency of sinks was declining because of the trajectories of extrinsic factors, including the CO2 emissions growth and volcanic eruptions, and, more concerning, intrinsic feedback responses such as sink responses to climate change and nonlinear responses to increasing CO2, mainly in the oceans. His critical contribution was to assemble these disparate factors into a single modeling framework.

Michael pioneered research showing how global carbon emissions were tracking the most carbon-intensive scenarios of the Intergovernmental Panel on Climate Change. He also identified how a century-old declining trend—an improvement—in the carbon intensity of the global economy had ceased as emerging economies took center stage in the growth of the global economy.

Societally Relevant Research

During his last decade of research, Michael was a strong advocate for the scientific community to combine first-class and societally relevant research. He examined relationships between emissions and economic development, the contributions of urbanization to the global carbon fluxes, drivers of present and future greenhouse emissions, and ways to explore the responsibilities of nations to address mitigation and their commitments.

Michael also led numerous groups in Australia on behalf of the Australian Academy of Science to explore the implications of the Australian population trajectory for economic, social, and ecological sustainability. One important example was a report to the prime minister’s Science, Engineering and Innovation Council on the need for an integrative approach to managing energy, water, and carbon.

Michael was an example of integrity, clarity of purpose, and humility, from which we all benefited.

His commitment to the relevance of research also led him to become interested in climate change narratives as a way to engage with stakeholders in the climate change debate, from policy makers to the public, who wanted to be active in climate mitigation.

Beyond his scientific contributions, Michael was an example of integrity, clarity of purpose, and humility, from which we all benefited. His kindness and approachability made him a wonderful person to work and be with; he inspired and touched many colleagues and friends.

Michael’s greatest joy was his family—his wife, Hilary, and their three children, Anna, Tim, and Alex. While we all miss him dearly, his personal and professional legacy will continue to influence scientists and science for decades to come.

—Josep G. Canadell, Global Carbon Project, CSIRO Oceans and Atmosphere, Canberra, Australia; email: pep.canadell@csiro.au; and Robert B. Jackson, School of Earth, Energy, and Environmental Sciences, Woods Institute for the Environment, and Precourt Institute for Energy, Stanford University, Stanford, Calif.

Citation: Canadell, J. G., and R. B. Jackson (2015), Michael R. Raupach (1950–2015), Eos, 96, doi:10.1029/2015EO040845. Published on 7 December 2015.

Text © 2015. The authors. CC BY 3.0
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