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n this essay, Professor David S. Jenkinson discusses the paper ranked at #8 in our Special Topics analysis of global warming research over the past decade. The paper, "Model estimates of CO2 emissions from soil in response to global warming," (D.S. Jenkinson, D.E. Adams and A. Wild, Nature 351[6324]: 304-6, 23 May 1991), was cited 190 times at the time of the analysis, and presently has 206 citations. Professor Jenkinson’s work can be found in the field of Agricultural Sciences in ISI Essential Science Indicators Web product. Professor Jenkinson is the Lawes Trust Senior Fellow at the Institute of Arable Crops Research (IACR) - Rothamsted in the United Kingdom.

Why we did the work.

This paper is about the effects of global warming on the decomposition of soil organic matter—often known as humus. Carbon dioxide from the combustion of fossil fuels is one of the key drivers behind global warming. But global warming will also warm terrestrial soils—and there is about twice as much carbon in the top meter of soil than there is in the atmosphere as CO2. If global warming accelerates the decomposition of this soil carbon, more CO2 will be released to the atmosphere, further enhancing the warming trend. Positive feedbacks like this are always worrying in a dynamic system, since they destabilise the system still more. Towards the end of the 1980s, several people realised the importance of feedback from soil warming and produced various estimates of its size, some extremely disturbing.

Some years earlier, James Rayner and I had developed a model for the turnover of organic matter in soil that operated over the decades-to-centuries time scale (RothC)1,2. This model, originally designed for use on agricultural soils, was based on changes in soil carbon in the Rothamsted long-term field experiments, which have been running for more than 150 years. It contained modules that relate decomposition to temperature and soil water...