Preface

On Today, the individually neutral words ‘global’ and ‘warming’ combine to provide an epithet whose consequences, already causing misery and premature death for millions, hold the prospect of unquantifiable change and potential disaster on a global scale for the decades to come. While the link between rising global temperatures and increasing atmospheric concentrations of CO2 has been known for more than a century, there is increasingly the sense that governments are failing to come to grips with the urgency of setting in place measures that will assuredly lead to our planet reaching a safe equilibrium. Today, the developed world is struggling to meet its (arguably inadequate) carbon-reduction targets while emissions by China and India have soared. Meanwhile, signs suggest that the climate is even more sensitive to atmospheric CO2 levels than had hitherto been thought. Alarmed by what are seen as inadequate responses by politicians, for a number of years some scientists and engineers have been proposing major ‘last-minute’ schemes that, if properly developed and assessed in advance, could be available for rapid deployment, should the present general concern about climate change be upgraded to a recognition of imminent, catastrophic and, possibly, irreversible increases in global temperatures with all their associated consequences. While such geoscale interventions may be risky, the time may well come when they are accepted as less risky than doing nothing. The above sets out the main elements that have led Phil. Trans. R. Soc. A to publish a Theme Issue on such macro-engineering options and to subject them to critical appraisal by acknowledged experts from around the world. In inviting contributors to this issue, we have turned especially to speakers at a workshop on Macro-Engineering Options for Climate Change Management and Mitigation organized by Prof. John Shepherd, FRS and Prof. Harry Elderfield, FRS in January 2004 on behalf of the Tyndall Centre for Climate Change Research. While that meeting at the Isaac Newton Institute for Mathematical Sciences in Cambridge provided stimulating exchanges among participants, no proceedings were published. Moreover, in the rather more than 4 years that have elapsed since that meeting, some of the current contributors have changed their views on the best strategy to adopt while others have developed them much further. It is our hope, therefore, that the present collection of articles will be seen as a timely and authoritative, though inevitably incomplete, statement of where the subject stands today. The Theme Issue is presented in three parts, the first of which, Scene Setting, provides over the four articles a historical and philosophical overview combined with projections of future CO2e levels and the foreseen capacity (or limitations) of conventional sequestration. The section Indirect Sequestration gives examples Phil. Trans. R. Soc. A (2008) 366, 3841–3842 doi:10.1098/rsta.2008.0151 Published online 29 August 2008