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GREENCYCLES Biogeochemistry and Climate Change Research and Training Network


Helena van der Merwe

Phone: +44 1223 339775

Postal Address:

University of Cambridge
Department of Geography,
Downing Place,


current research | curriculum vitae | publications | carrer development plan (internal)

Current Research: Quantifying the Effect of Biogeochemical Feedbacks on Global Climate Change.

The purpose of this project is to quantify the spatial distribution and uncertainties related to the effect biological feedbacks have on the growth rate of anthropogenic gasses in the atmosphere. Large increases in CO2 and other greenhouse gasses over the last 250 years due to anthropogenic activities have had a measurable effect on the earth’s global mean surface temperature. Natural terrestrial and marine processes have reabsorbed large proportions of the anthropogenic CO2, however the future role that these negative feedbacks will be able to play remains uncertain.

As a first step towards developing a spatially explicit global reduced-complexity model of coupled biogeochemical-climate feedbacks, a zero-dimensional model will be developed to determine the change in global mean temperature with respect to a change in CO2 concentration over time. The change in CO2 concentration is a function of various processes. In this study we will focus on industrial and land use emissions, terrestrial uptake, and marine uptake. The change in CO2 concentration will be related to its radiatively equivalent change in solar irradiance and used in calculating the global mean temperature change. The model will be tested by comparing the output temperature and atmospheric CO2 values to historical data. Predictions of variation in global mean temperatures over the next 200 years will be made under various assumptions concerning emission rates and sink activities.

Once this model has been thoroughly tested, it will be expanded. The contribution of different regions to the terrestrial and oceanic sinks will be made explicit. This allows analyses of the effect and relative importance of a variation in CO2 exchanges in each region on the global climate feedback. The climate response to variation and relative contribution of each of the processes involved in the feedback cycle will be investigated. Processes such as respiration, permafrost melt, fire, seawater stratification, etc. can be included. Feedbacks occur due to surface fluxes of different gasses, not only CO2. Changes in concentrations of various gasses in the atmosphere can be investigated, as well as the interaction between them. The consequences of different assumptions concerning the responses of greenhouse gas fluxes to climate and the responses of climate to GHG forcing will be investigated. A key source of knowledge for these parameterisations will be the various projects taking place across the GREENCYCLES network. These analyses will quantify the climate response to a range of biogeochemical feedback processes, and their contributions to uncertainties in the evolution of the earth system over the next couple of decades.

This project (ESRXIII) contributes to the science objective 1 (Quantify feedbacks in the global carbon cycle) of GREENCYCLES.

Curriculum Vitae

Dec 2007 - present Research Assistant (within Greencycles project) at the Department of Geography, University of Cambridge, UK.
2005 - 2006 MSc(Med) in Computational Biomechanics, University of Cape Town, South Africa.
Funded by Medronic Research Scholarship (Medtronic Inc, Minneapolis, USA)
2004 BSc(Hons) in Applied Mathematics at the Nelson Mandela Metropolitan University, South Africa
Dec. 2003 - Jan. 2004 Vacation Scholarship in Neuro Physics, University of Sydney, Australia
2000 - 2003 BSc at the University of Port Elizabeth, South Africa.


P.A. Robinson, P.M. Drysdale, H. Van der Merwe, E. Kyriakou, M.K. Rigozzi, B. Germanoska and C.J. Rennie. BOLD responses to stimuli: Dependence on frequency, stimulus form, amplitude, and repetition. NeuroImage, Volume 31, Issue 2, June 2006.