"If nuclear power is the answer, it must have been a pretty stupid question," went an oft-cited slogan of the 1970s environmental movement. But the question was not stupid, and it is even less so today when the challenge is even blunter: how are we going to provide for our energy needs in a way that does not destroy, via global warming, the capacity of our planet to support life? The hard truth is that if nuclear power is not at least part of the answer, then answering that challenge is going to be very difficult indeed.

Unfortunately, just by writing the sentence above, I will already have prompted many readers to switch off. Being anti-nuclear is an article of faith (and I use that word intentionally) for many people in today's environmental movement and beyond, just as it was during the 1970s. That the Green Party, Friends of the Earth and Greenpeace have held the same position on the subject for 30 years could show admirable consistency - but it could also be evidence of dogmatic closed-mindedness.

When I first broached the issue in these pages three years ago, the reaction was extraordinary. A close acquaintance sent me a tearful email saying that I had "destroyed" her motivation for environmental campaigning. Other friends here in Oxford accused me - jokingly, of course - of having formed a romantic liaison with BNFL's spokeswoman. Just last week, after tackling the subject once again, I received a one-line email from a well-known environmentalist accusing me of having "done a considerable disservice to the cause of combating climate change".

So why does the nuclear issue evoke such strong reactions? For answers, I think we need to look to nuclear's past, when today's entrenched positions were first formed. Civil nuclear power began life as a heavily state-subsidised industry largely designed to produce plutonium for bombs. Civil nuclear power was part of the military-industrial complex and shrouded in secrecy. An association with the mushroom cloud has tainted the nuclear industry ever since - and clearly continues to be an issue in countries such as Iran, North Korea and Pakistan.

Then there is radiation. Most people are terrified of radiation precisely because it is invisible, making it all the more threatening, and because of its potential to cause cancer and genetic deformities. (Many other cancer-causing agents such as food or smoke seem innocuous by comparison.) Nuclear accidents and near-meltdowns - such as Three Mile Island in 1979 - provoke scary headlines throughout the media, as did popular treatments such as the film The China Syndrome (released, by an extraordinary stroke of luck for the film-makers, just 12 days before Three Mile Island), in which a sinister nuclear cabal covers up evidence of an accident.

It is undeniable that nuclear fission generates radioactive by-products, some of which will inevitably enter the environment. It is also undeniable that exposure to radiation increases the risk of cancer (though radiation can also be employed to treat cancers). But it is the level of risk that counts, and here the story is less fearsome than many would have us believe. Take Three Mile Island, which exposed local populations to one millirem of radiation on average. This equates to roughly what we all receive from natural sources (cosmic rays and naturally occurring radioactive elements in the ground) every four days. The number of deaths from Three Mile Island - the worst civil nuclear accident ever in a western country, and one that ended the US nuclear programme (not a single reactor has been built since) - is therefore officially estimated to be zero.

Even Chernobyl, surely the worst-imaginable case for a nuclear disaster, was far less deadly than most people think. In the immediate aftermath of the explosion, 28 people died due to acute radiation sickness - all firemen and power plant workers, some of whom had been exposed to radiation doses as high as one million millirems. By comparison, 167 men were killed during the Piper Alpha disaster on a North Sea oil rig in 1988. But it is the long-term effects from Chernobyl that tend to scare people most. In a 2006 report, Greenpeace claimed that "60,000 people have additionally died in Russia because of the Chernobyl accident, and estimates of the total death toll for the Ukraine and Belarus could reach another 140,000".

These figures, if correct, would make Chernobyl one of the worst single man-made disasters of the last century. But are they correct? The United Nations Scientific Committee on the Effects of Atomic Radiation reports 4,000 cases of thyroid cancer in children and young people in Belarus, Russia and Ukraine, but very few deaths (thyroid cancer is mostly treatable). Indeed, it concludes, "There is no evidence of a major public health impact attributable to radiation exposure 20 years after the accident", and no evidence of any increase in cancer or leukaemia among exposed populations. The World Health Organisation concludes that while a few thousand deaths may be caused over the next 70 years by Chernobyl's radioactive release, this number "will be indiscernible from the background of overall deaths in the large population group". Without wishing to downplay the tragedy for the victims - especially the 300,000 people who were evacuated permanently - the explosion has even been good for wildlife, which has thrived in the 30km exclusion zone.

A plentiful supply of free fuel

One way of statistically assessing the safety of nuclear power versus other technologies is to use the measure of deaths per gigawatt-year. This technique is cited by Cambridge University's Professor David MacKay in his book Sustainable Energy - Without the Hot Air (available free on the web), and shows that in Europe, nuclear and wind power are the safest technologies (about 0.1 death per GWy), while oil, coal and biomass the most dangerous (above 1 per GWy).

A focus on statistics is also useful when assessing the financial costs of nuclear power. The high price for nuclear waste disposal and decommissioning - with a hefty chunk always payable from public funds - is surely one of the environmental lobby's strongest arguments, particularly if any subsidy from taxpayers means taking money away from investment in renewables. Helen Caldicott's book Nuclear Power is Not the Answer discusses the finances of nuclear under a chapter subheaded "Socialised Electricity", quoting figures for nuclear's subsidy in the US over recent decades of $70bn. To make a direct cost comparison, the International Energy Agency in a 2005 study looked at life-cycle costs for all power sources - including construction costs, operations, fuel and decommissioning - and concluded that nuclear was the cheapest option, followed by coal, wind and gas.

But how about nuclear power's potential contribution to mitigating global warming? One persistent myth is that once construction and uranium mining are taken into account, nuclear is no better than fossil fuels. However, according to the Intergovernmental Panel on Climate Change (IPCC), total life-cycle greenhouse-gas emission per unit of electricity is about 40g CO2-equivalent per kilowatt-hour, "similar to those for renewable energy sources".

But why not ditch nuclear and focus only on renewables, as the greens suggest? MacKay calculates that even if we covered the windiest 10 per cent of the UK with wind turbines, put solar panels on all south-facing roofs, implemented strong energy efficiency measures across the economy, built offshore wind turbines across an area of sea two-thirds the size of Wales, and fully exploited every other conceivable source of renewables (including wave and tidal power), energy production would still not match current consumption.

This is rather different to Britain being the "Saudi Arabia of wind power" as many in the environmental movement are fond of asserting. Indeed, MacKay concludes that we will need to import renewable electricity from other countries - primarily from solar farms in the North African desert - or choose nuclear, or both. Indeed, it is vital to stress the neither I nor MacKay nor any credible expert suggests a choice between renewables and nuclear: the sensible conclusion is that we need both, soon, and on a large scale if we are to phase out coal and other fossil fuels as rapidly as the climate needs. As MacKay told me: "We need to get building."

The UK's Sustainable Development Commission, in its 2006 report on nuclear power, argued that new plants should be ruled out until the existing waste problem could be solved. But what if a new generation of nuclear plants could be designed that, instead of producing more waste to leave as a toxic legacy for our grandchildren, actually generated energy by burning up existing waste stockpiles? This is the solution proposed by Tom Blees, a US-based writer, in his upcoming book Prescription for the Planet. Blees focuses particularly on so-called fourth-generation nuclear technology - better known as fast-breeder reactors. While conventional thermal reactors use less than 1 per cent of the potential energy in their uranium fuel, fast-breeders are 60 times more efficient, and can burn virtually all of the energy available in the uranium ore.

This gives these fourth-generation reactors a big advantage. As Blees puts it: "Thus we have a prodigious supply of free fuel that is actually even better than free, for it is material that we are quite desperate to get rid of." Moreover, fast-breeder reactors can also run on the "depleted" uranium left behind by conventional reactors, and help reduce the proliferation threat by burning up plutonium stockpiles left over from decommissioned nuclear weapons. Blees estimates that supplies of nuclear waste and depleted uranium are sufficient to "provide all the power needs of the entire planet for hundreds of years before we need to mine any more uranium". Although these reactors produce plutonium - which might be used for nuclear weapons, and could therefore pose a proliferation threat - weapons-grade material is never isolated in the fuel-cycle process, making fast-breeders less dangerous to international stability than conventional reactors, and relatively simple to inspect.

But what about the waste these reactors themselves produce? Since the by-products of fast-breeder reactors are highly radioactive, they have much shorter half-lives - rendering them inert in a couple of centuries, instead of the longer time over which conventional nuclear waste remains dangerous. (Once again there is a powerful myth here - that high-level waste from reactors remains dangerous for enormous lengths of time. Greenpeace states that "waste will remain dangerous for up to a million years". In fact, almost all waste will have decayed back to a level of radio activity less than the original uranium ore in less than a thousand years.) Fourth-generation nu clear technology is also inherently safer than earlier designs. The Integral Fast Reactor (IFR), discussed at length by Blees, operates at atmospheric pressure, reducing the possibility of leaks and loss-of-coolant accidents. It is also designed to be "walk-away safe", meaning that if all operators stood up and left, the reactor would shut itself down automatically rather than overheat and suffer a meltdown.

So why, given the purported advantages in safety and fuel use, have fast-breeders not been developed commercially? The US Integral Fast Reactor programme was shut down in 1994, possibly - Blees suggests - because of political pressure levied on the Clinton administration by anti-nuclear campaigners. (Even so, fourth-generation nuclear power plants are being built in India, Russia, Japan and China.) Ironically, the Clinton administration may have inadvertently killed off one of the most promising solutions to global warming in an attempt to please environmentalists. Even if the decision were to be reversed immediately, 20 years has been lost.

It is worth remembering the contribution that nuclear power has already made to offsetting global warming: the world's 442 operating nuclear reactors, which produce 16 per cent of global electricity, save 2.2 billion tonnes of carbon dioxide per year compared to coal, according to the IPCC. Blees agrees that "the most pressing issue is to shut down all coal-fired power plants" and urges a "Manhattan Project-like" effort to convert the world's non-renewable power to IFRs by the thousand. This sounds daunting but it is not unprecedented: France converted its power supply to 80 per cent nuclear in the space of just 25 years by building about six reactors a year.

An anti-nuclear report published by the Oxford Research Group in 2007 concluded that an additional 2,500 reactors would need to be built by 2075 to significantly mitigate global warming. The report's authors suggested that this was a "pipe-dream". But it sounds eminently achievable to me, given that it is only a five-times increase from today. The question is this: are those who care about global warming prepared to reconsider their opposition to nuclear power in this new era? We are no longer living in the 1970s. Today, the world is more threatened even than it was during the Cold War. Only this time nuclear power - instead of being part of the problem - can be part of the solution.