Mike Raupach’s contribution to global change research has been exceptional. Trained in physical sciences, Mike first contributed extensively to the field of micro-meteorology, after his PhD adviser discouraged him from studying climate change because at that time – the early 1970s – it was a speculative theory. Instead, Mike focused on understanding the effects of vegetation on wind and turbulence. He tested his theories by modelling those effects at the local scale, then at the global scale, looking also at the exchanges of carbon and energy. He then expanded his work further to consider the role of humans, including understanding the drivers of human-driven global environmental change.
Mike contributed to building international cooperation through global change programmes, and to improving the science-policy interface. He provided intellectual leadership for research and for making scientific research more relevant for society. His journey exemplifies the co-evolution of science and society that took place during the 1980s and 1990s and led to the development of interdisciplinary global change research. It also highlights the importance of fundamental sciences in addressing global change issues.
Contribution to carbon cycle research
How land and ocean carbon sinks are responding to a changing climate is one of the most important questions in carbon cycle research. For decades this question had been informed by the so-called ‘airborne fraction’, the fraction of CO2 emissions that remained in the atmosphere. However, trends in the airborne fraction are influenced by a number of factors that are difficult to untangle, in particular the natural climate variability, the uncertain size of the emissions from land-use change, and the influence of emissions trajectory on growth in atmospheric CO2. In Raupach et al. (2014a), Mike provided a formal decomposition of the contribution of each factor and could quantify that the land and ocean carbon sinks have already responded to climate change in a way that reduces their capacity to take up CO2. This paper reconciled the views of several researchers who had published conflicting evidence in recent years. It is thanks to Mike’s desire to reach a scientific consensus on the issue that advances could be made on the drivers of change.
One of Mike’s most important contributions to carbon cycle research was as co-founder of the Global Carbon Project in the early 2000s, which he co-Chaired between 2000 and 2008, designing and implementing its science framework. Mike also edited (with Chris Field) the book The Global Carbon Cycle: Integrating Humans, Climate, and the Natural World (2004), which provided at the time a new, more extensive, interdisciplinary framework to align research on the natural carbon cycle in the context of its human drivers.
Working on the Australian terrestrial biosphere, Mike quickly recognized the great constraints that could come from coupling the carbon and water cycles, which he subsequently did, leading to the recognition of the role of semiarid regions in the inter-annual variability of atmospheric CO2.
Contribution to global change research
Raupach et al. (PNAS 2007) is one of Mike’s most influential papers. It highlighted and explained a discontinuity in the rate of growth of global CO2 emissions around the year 2000. Whereas emissions had been growing by 1% per year in the 1990s, the rate jumped to 3% per year from 2000. Mike’s examination of this discontinuity highlighted that the drivers of CO2 emissions were changing at a fundamental level. Whereas population growth had played an important role prior to 2000, this was no longer the case. Instead, growth in Gross Domestic Product (GDP) was now the main driver, with a shift in global distribution of emissions towards emerging economies, and a slowdown in the energy efficiency improvements that had persisted for two decades. The paper also highlighted that fossil fuel emissions were following the most carbon-intensive emissions scenarios used by the IPCC to project climate change, a situation that has persisted since then.
In a follow up study published last September, Raupach et al. (2014b) tackled one of the most difficult questions for climate policy now: how to share a finite quota of cumulative carbon emissions in order to limit average global warming to 2°C. The paper quantifies the sharing options available to inform practical policy decisions with, on the one hand, a full equity world, and on the other hand, continuation of the status quo. The paper thus provides a framework for the policymaker to ask: ‘if others acted consistently with our proposed share of the carbon quota (i.e. in the same way as us), would the global outcome be acceptable to us?’ It also contributed to make explicit the gap between the cumulative carbon quota available and fossil fuel reserves at the global and local scale.
Contribution to informing climate policy
Mike was among the leading minds that realised the importance of making research results widely accessible to policymakers and the public, and the importance of understanding the public’s concerns and need for information. He led a number of important reports that have informed the Australian government of the implications of climate change for Australia, many co-designed with government officers. This included the booklet of the Australian Academy of Science on “The Science of Climate Change: Questions and Answers” (2010); a report for the Prime Minister’s Science, Engineering and Innovation Council on “Challenges at Energy-Water-Carbon Intersections” (2010); that of the Australian Academy of Science on “Negotiating our future: Living scenarios for Australia to 2050” (2012); and a number of articles on the widely read The Conversation website. These extensive contributions – along with Mike’s efforts to disseminate results far beyond scientific circles and encourage and support others to do the same – will have a long-lasting effect. Mike was a keen communicator and contributed to public forums and climate change debates, and to a broad range of television, radio and written media.
Raupach, M. R., M. Gloor, J.L. Sarmiento, J.G. Canadell, T.L. Frölicher, T. Gasser, R.A. Houghton, C. Le Quéré, and C.M. Trudinger, The declining uptake rate of atmospheric CO2 by land and ocean sinks (2014a), Biogeosciences, 11, 3453-3475. doi:10.5194/bg-11-3453-2014
Raupach, M.R., S. J. Davis, G. P. Peters, R. M. Andrew, J. G. Canadell, P. Ciais, P. Friedlingstein, F. Jotzo, D. P. van Vuuren, and C. Le Quéré (2014b). Sharing a quota on cumulative carbon emissions, Nature Climate Change. doi:10.1038/nclimate2384
Raupach, M.R., G. Marland, P. Ciais, C. Le Quéré, J.G. Canadell, G. Klepper and C.B. Field (2007). Global and regional drivers of accelerating CO2 emissions. PNAS, 104, 10288-10293. doi: 10.1073/pnas.0700609104
Raupach, M.R., J.J. Finnigan, and Y. Brunet (1996). Coherent eddies and turbulence in vegetation canopies: the mixing-layer analogy. Boundary-Layer Meteorology, 78, 351-382. doi:10.1007/BF00120941