As soon as I have finished this column I will jump on the train to Kent. Last year Al Gore remarked: "I can't understand why there aren't rings of young people blocking bulldozers and preventing them from constructing coal-fired power plants." Like hundreds of honorary young people, I am casting my Zimmer frame aside to answer the call.

Everything now hinges on stopping coal. Whether we prevent runaway climate change largely depends on whether we keep using the most carbon-intensive fossil fuel. Unless we either leave it - or the carbon dioxide it produces - in the ground, human development will start spiralling backwards. The more coal is burnt, the smaller are our chances of future comfort and prosperity. The industrial revolution has gone into reverse.

It is not because of polar bears that I will be joining the climate camp outside the coal plant at Kingsnorth. It is not because of butterflies or frogs or penguins or rainforests, much as I love them all. It is because everything I have fought for and that all campaigners for social justice have ever fought for - food, clean water, shelter, security - is jeopardised by climate change. Those who claim to identify a conflict between environmentalism and humanitarianism have either failed to read the science or have refused to understand it.

Our government could lead the world in one of two directions. Roughly one third of our power stations will come to the end of their lives by 2020. It could replace them with low-carbon plants or it could repeat - this time in full knowledge of the consequences - the disastrous decisions of the past. E.ON's application to build a new coal-burning power station at Kingsnorth is the first for many years. At least five other such proposals hang on the outcome. Between them they would account for 54 million tonnes of carbon emissions a year: as much as the entire economy would produce if the UK, in line with current science, were to cut its emissions by 90%.

The government seems determined to make the wrong decision. It has inherited the party's traditional love for coal, but, being New Labour, now supports the bosses instead of the workers, and has colluded with them to make the case for a new generation of power stations. It has one justification for this policy: that one day dirty coal will be transformed into clean coal by means of carbon capture and storage (CCS). All that is needed to effect this transformation is a sprinkling of alchemical dust, in the form of the future price of carbon. The market, it claims, will automatically ensure that coal plants bury their carbon dioxide, as this will be cheaper than buying pollution permits.

Last month the House of Commons environmental audit committee examined this proposition and found that it was nonsense. It cited studies by the UK Energy Research Centre and Climate Change Capital which estimate that capturing carbon from existing coal plants will cost €90-155 (£71-£122) per tonne of CO2. Yet the government predicts that the likely price of carbon between 2013 to 2020 will be around €39 (£31) per tonne. Even E.ON believes that it won't rise above €50. "The gap between the carbon price and the cost of CCS," the committee finds, "is enormous." The energy minister, Malcolm Wicks, confessed to MPs: "I hope that the strengthening of carbon markets ... will bring forward a sufficiently good price for carbon that it will provide some of the financial incentive for CCS. Will it be enough? I do not know."

This is the sum of government policy: to cross its fingers and hope the market delivers. If it approves a new coal plant at Kingsnorth, it will do so on the grounds that the power station will be "CCS-ready". CCS-ready seems to mean nothing more than this: that there is enough space on the site for a carbon capture plant, should the developer deign one day to build it. The committee warns that this meaningless promise could be used "as a fig leaf to give unabated coal-fired power stations an appearance of environmental acceptability".

The government has already shown us what it wants to do. In January, Gary Mohammed, a civil servant at the Department for Business, emailed E.ON to ask whether he should include CCS as a condition for approving its new coal plant. (This gives a fascinating insight into how government works: companies are asked to write their own rules.) E.ON replied that the government "has no right to withhold approval for a conventional plant". Six minutes later Mohammed answered thus: "Thanks. I won't include. Hope to get the set of draft conditions out today or tomorrow."

There is a simple means by which the government could ensure that our future electricity supplies would not commit the UK to stoking runaway climate change. It would do as California has done and set, by a certain date, a maximum level for carbon pollution per megawatt-hour of electricity production. This would have to be a low one: perhaps 80kg of CO2. Then, in line with the government's precious principles (or absence thereof), it could leave the rest to the market. I have now reached the point at which I no longer care whether or not the answer is nuclear. Let it happen - as long as its total emissions are taken into account, we know exactly how and where the waste is to be buried, how much this will cost and who will pay, and there is a legal guarantee that no civil nuclear materials will be used by the military. We can no longer afford any rigid principle but one: that the harm done to people living now and in the future must be minimised by the most effective means, whatever they might be.

But I believe the likely response would be more interesting than this. Several recent studies have shown how, through maximising the diversity of renewable generators and by spreading them as far apart as possible, by using new techniques for balancing demand with supply and clever schemes for storing energy, between 80% and 100% of our electricity could be produced by renewables, without any loss in the reliability of power supplies. Unlike CCS, wind, wave, tidal, solar, hydro and geothermal power are proven technologies. Unlike nuclear power, they can be safely decommissioned as soon as they become redundant.

A policy like this requires both courage and vision. So look at the current cabinet - Brown, Straw, Darling, Hutton, Blears, Kelly, Hoon - and weep. Every man and woman with backbone was purged from this government years ago, leaving those who know how to appease the interests that might threaten them. These people won't stand up to business, even when the future prospects of mankind are at stake.

If fear is the only thing that moves them, we must present them with a greater threat than the companies planning new coal plants. We must show that this issue has become a political flashpoint; that the public revulsion towards new coal could help to eject them from office. You could do no better than joining us at Kingsnorth this week.

monbiot.com