Menzies Campbell: My rivals offer nothing more than hot air

The world must plan for a low carbon economy and start making adjustments now

I welcome the conversion of David Cameron to the cause of environmentalism. But he will have to forgive a little cynicism on the part of those, such as the Liberal Democrats, who discovered green values and worked out ecological policies when his nanny was still tying his shoelaces.

There has been a flurry of green speeches in recent weeks from all quarters. But amid the wash of green words, it is important to recall that future generations will judge us by what we did not what we said. We are at a crucial moment in history. Climate change is happening. We are no longer in a position to stop some global warming.

But we can mitigate it and arrest its consequences. We have a window of opportunity within which we can affect the course of climate change. In ten years it may be too late. We must take urgent action now. The world must plan for a low-carbon economy and start making that adjustment now. The adjustment need not be painful. In fact in Britain with our twin assets of technology and talent we are well placed to be at the forefront of the coming green revolution.

But we must make the green switch in Britain for moral reasons as well as economic ones. We can lead the way in demonstrating the benefits of a low-carbon economy in terms of justice, well-being and innovation.

And we can also earn for ourselves moral capital to spend in persuading other countries to join us. This is why the timidity of our government on climate change is so damaging. If we have a role and responsibility in the world, it is to use our position of wealth and influence to lead.

Planning for a low-carbon economy at home is an essential part of winning the international argument on contraction and convergence of emissions. This is the only equitable way to deal with climate change. There is a finite amount of emissions that the world can take. We have to share out pollution judiciously, and ultimately, equally. Relative targets linked to GDP or how much a country feels it can reduce are not only unworkable, but our grandchildren may well view such political weakness as criminal.

The climate does not need more hot air - but that is what the Conservatives and the Labour Party are offering.

They have no serious proposals - they have not even committed to contraction and convergence as the basis for global targets after the Kyoto ones expire in 2012. Here are several things a responsible government should be doing right now:

Ruling out nuclear power. Nuclear power is not a panacea. New power stations will take years to build and hold uncertain financial, health and security risks for future generations. The taxpayer is facing a bill for £56bn to clean up the waste from the last round of decommissioning. We cannot afford another.

Planning for a decentralised energy system. Nuclear power will fossilize the inefficient centralised electricity distribution system we have at present and prevent investment in the large scale restructuring that needs to take place. A decentralised energy system that encouraged renewable energy, co-generation of heat and power and microgeneration in the home is the only sustainable option. Making the new Sustainable Building Code binding for all new build and aspects of it applicable to renovations and refurbishment. At present it is voluntary.

The Tories appear committed to the idea of using green taxes to change behaviour. If David Cameron is serious about the conversion to "green is good" rather than "greed is good", then the Conservatives will have no difficulty in agreeing to Lib Dem proposals on green taxes.

There are five simple things that Mr Cameron and Mr Brown could do to allay doubt about their green credentials.

First, commit to a rise in green taxes as a proportion of national income. The share of green taxes has in fact fallen under this government from 3.6 per cent in 1999 to 3 per cent today.

Second, promise to raise Vehicle Excise Duty substantially above the meagre £45 announced in the budget.

Third, commit to keep fuel duty in line with inflation. Since fuel duty was frozen it has declined in real terms while transport emissions have actually gone up.

Fourth, demonstrate a willingness to tax air travel, preferably through the Lib Dem idea of taxing aircraft movements instead of passengers.

Fifth, increase the climate change levy in line with inflation pending its reform into a carbon tax applicable across the economy - not just to business.

Of course, we all have a part to play in reducing energy consumption. But governments must lead. And any politician hoping to be taken seriously must fit rhetoric to action.

Sir Menzies Campbell MP is leader of the Liberal Democrats