The Sustainable Development Commission's attitude to wind power (Letters, May 2) is based on thorough analysis of all data over several years. Our report concluded that while wind, of course, blows at variable speed, this variability "is not a problem for the electricity grid. Wind is accurately forecast over the timeframes relevant to network operators . . . Increasingly, the proportion of wind power in the electricity system does not require back up' capacity as is often believed, but it does slightly increase the cost."

We believe that wind power, along with other sources of renewable energy, has a vital role to play in decarbonising our energy system - an important aim if we are to avoid the worst effects of climate change in the coming decades. It is simply untrue for A R Nelson to state that our membership largely consists of wind farm company representatives. We have no membership, as we are an independent adviser to government, run by 18 commissioners whose interests are all published on our website - www.sd-commission.org.uk.

Prof Jan Bebbington, Vice-chair, Scotland, Sustainable Development Commission, Osborne House, 1 Osborne Terrace, Edinburgh.