If the third and fourth biggest economies in the world believe they can cut their carbon emissions and keep the lights on without building nuclear power stations, then why can't the sixth? That's the question I am asking after Japan (3rd) yesterday followed Germany (4th) in

abandoning their plans for a new generation of nuclear reactors in the aftermath of the catastrophe at Fukushima. In contrast, the UK (6th) remains committed to building a new fleet of reactors.

The question may soon become even more stark if a referendum in Italy (7th) next month also cancels their future nuclear programme.

These are not small statements by Japan and Germany. About 30% of Japan's electricity comes from nuclear and a rise to 50% was projected by 2030. In Germany, up to 25% of electricity came from nuclear. Currently, the UK gets just 16% or so from nuclear and government plans only to replace - not expand - existing capacity.

Adding fuel to the fiery debate is Monday's report stating that 80% of the world's energy (not just electricity) can be provided from renewable from sources by 2050. The report, from the Intergovernmental Panel on Climate Change, was signed off by all the world's governments. It's worth noting the pie chart in the report showing that in 2008 just 2% of global energy came from nuclear power, with renewables (largely biomass) accounting for 12%. And don't forget improving energy efficiency, mentioned specifically by the already efficient Japanese as a way to compensate for lost nuclear power.

A different conclusion came, also on Monday, from the UK government's advisers, the Committee on Climate Change, who said that nuclear power could provide 40% of the UK's electricity by 2030. In particular, it says: "Nuclear generation appears likely to be the most cost-effective form of low-carbon power generation in the 2020s (i.e. before costs of other technologies have fallen), justifying significant investment if safety concerns can be addressed."

As regular readers will know, I have travelled in the opposite direction to my colleague George Monbiot, in moving from supporting nuclear power to opposing it, based on five key questions I drew up.

I believe there is a low-carbon, affordable and secure energy future without new nuclear power. But don't just listen to me, listen to prime minister Naoto Kan and chancellor Angela Merkel, the current stewards of two of the most successful economies on Earth.