David Hookes (Letters, 2 July) argues that roughly 5% leakage would make methane leaking from fracking wells into a more potent greenhouse gas than carbon dioxide from coal burning. Is it possible to maintain leakage very much below 5%? A suitable target would be 0.5%. The proponents of fracking argue from existing technology that a company that leaked 5% of its methane would be in court. Although gas wells under the North Sea are not leak-free, leak detection of methane bubbling up from a high-volume underwater well is far easier than from an array of distributed fracking wells on land. The problem with fracking is that the production from any one borehole is much smaller than from a conventional North Sea well. However, there will be vast numbers of boreholes, only some of which will be commercially productive, but all with potential to leak. And leakage will matter whether during or after production, indeed for many decades into the future.
Dr Peter Harbour
Abingdon, Oxfordshire
• David Cameron cuts the ribbon on the biggest windfarm in the world (Report, 5 July) while his chancellor gives tax breaks to the fossil fuel companies preparing to extract Britain's shale gas. Any carbon saved by our new windfarm will be exported elsewhere and burnt anyway. The fossil fuel corporations have no plans to limit their production, and their known reserves are enough to fry the Earth five times over. Unless we manage to force the corporations to curtail production and leave 80% of their reserves in the ground, nothing will save us from disaster.
Ewa Barker
Manchester
