In The Guardian Ken Livingstone writes: Whatever happens over the next few years, our children and grandchildren are going to live in a world in which the climate is very different from the one we grew up with.

A climatic time lag means that we are already locked into a further half-century of global warming. The concern is that if we keep on increasing carbon emissions then climate change will become irreversible and the long-term consequences catastrophic.

As Britain is one of the world's largest economies, the government's current review of energy policy will determine whether we have a progressive role to play in preventing this. For 200 years our economy has been based on the assumption of an unlimited supply of fossil fuels.

Two-thirds of the energy inputted into our power stations is simply wasted - either as heat ejected through the cooling towers, or in transmitting electricity from rural power stations to cities and towns. Only a third, or less, of your household fuel bill reflects the cost of the energy you have used - the rest is subsidising waste.

So far, the debate has centred on whether or not we should replace fossil fuel and nuclear power stations with new large, centralised nuclear power generation. But that's the wrong question. The first thing we need to grapple with is how to reduce total energy use.

The answer is decentralise. This means generating energy closer to where it's needed and reusing heat created as a byproduct of electricity generation to warm and cool buildings, instead of pumping it out into the atmosphere. Carbon emissions are cut, as are fuel bills. Decentralised energy systems can be small or large, and can use pretty much any energy source. But, crucially for the long term, they make the use of renewable energy much more economic.

The energy-conscious Scandinavians already employ decentralised energy widely. Ninety-six per cent of Copenhagen's energy needs are provided in this way. A recent study by Parsons Brinkerhoff construction management, commissioned by my office and Greenpeace, showed that by adopting the decentralised energy approach in London we can cut emissions by up to 32% by 2025, putting us on track to achieve the government's target of a 60% cut by 2050.

We have set up a London Climate Change Agency to do just this. In contrast, the report found that new centralised nuclear power stations could not achieve such emissions cuts, despite my stipulation that all the assumptions be weighted in favour of nuclear in order to be as robust as possible.

A decentralised energy solution would also be cheaper and quicker to implement. As someone who has campaigned against nuclear power for 30 years, it won't surprise many people that I have come out against nuclear power again now. But even I would have been prepared to back a nuclear gamble if it could have been demonstrated that it was the best or only solution to tackling global warming.

The truth is that, if you ask the question properly, nuclear power is definitively not the answer.


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