Earth Syst. Dynam., 5, 43–53, 2014 Open Access www.earth-syst-dynam.net/5/43/2014/ Earth System doi:10.5194/esd-5-43-2014 © Author(s) 2014. CC Attribution 3.0 License. Dynamics Applying the concept of “energy return on investment” to desert greening of the Sahara/Sahel using a global climate model S. P. K. Bowring1, L. M. Miller2, L. Ganzeveld1, and A. Kleidon2 1Earth System Science Group, Wageningen University and Research Centre, Wageningen, the Netherlands 2Max Planck Institute for Biogeochemistry, Jena, Germany Correspondence to: S. P. K. Bowring (
[email protected]) Received: 30 July 2013 – Published in Earth Syst. Dynam. Discuss.: 8 August 2013 Revised: 9 December 2013 – Accepted: 21 December 2013 – Published: 30 January 2014 Abstract. Altering the large-scale dynamics of the Earth 1 Introduction system through continual and deliberate human intervention now seems possible. In doing so, one should question the en- ergetic sustainability of such interventions. Here, from the Numerous human activities revolve around the capture and basis that a region might be unnaturally vegetated by em- use of energy. The potential now exists for humans to ap- ploying technological means, we apply the metric of “en- propriate additional energy (e.g., renewable technologies), ergy return on investment” (EROI) to benchmark the ener- which on a large scale may alter the underlying dynamics getic sustainability of such a scenario. We do this by apply- of Earth system processes (e.g., via land-use change). Yet ing EROI to a series of global climate model simulations energy on Earth is limited by the flow of incoming solar ra- where the entire Sahara/Sahel region is irrigated with in- diation, its “heat of formation”, gravitational attraction by ce- creased rates of desalinated water to produce biomass.