Sir

Although the Letter by D. M. Jones and colleagues, 'Crude-oil biodegradation via methanogenesis in subsurface petroleum reservoirs' (Nature 451, 176–180; 2008), describes fascinating science, the progression of this research to a viable technology would represent a dangerous advance in humankind's ability to accelerate global warming.

The prospect of increasing the energy efficiency of hydrocarbon extraction from tar sands, as referred to in the Letter, is highly questionable. Any technology that will increase our capacity to free surface or sub-surface carbon is surely undesirable, and will reduce the imperative to migrate to non-carbon or closed-carbon energy cycles.