The G8 summit agreed that they would aspire to 50 percent cuts in carbon emissions over the coming decades and try to keep the mean temperature rise to 2 degree centigrade or so. This is the level at which we could start to lose the Greenland ice cap, which would mean a seven-meter rise in sea levels. Goodbye Manhattan, London, Holland, Shanghai, Mumbai, etc, etc.

In the final G8 statement this week, Japan's Prime Minister Fukuda said Australia, South Korea and Indonesia had expressed support for the 50 percent cuts agreed by the G8.

But China, India, Brazil, Mexico and South Africa issued a separate statement which argued that rich countries needed to slash carbon emission levels by 80-95 percent from 1990 levels.

From one point of view, this is entirely fair. The current industrialized countries of the G8 are responsible for the existing stock of carbon deposits in the atmosphere. They should cut more and faster.

The developing countries are going to be responsible for the next wave of emissions, which may well put us over the top of what the planet can stand. So the obvious solution is for the maximum amount of technology sharing to help the developing countries develop as cleanly and as carbon-free as possible.

Given the time frame involved, it is very nearly impossible to see any way of achieving this without a massive investment in nuclear power. Much of the Green movement is understandably against this but the best available evidence suggests that they are deeply, deeply mistaken.

It is remarkable how many leading scientists, including James Lovelock, father of the Gaia theory of earth, and Greenpeace founder Patrick Moore, take this view. They have now been joined by Professor David J. C. MacKay of the Cambridge University Department of Physics holds a PhD in computation from Cal Tech and a starred first in Physics from Cambridge. His new book, "Sustainable Energy Without the Hot Air" is the clearest and most judicious analysis of why nuclear may be the only interim solution. It can be downloaded at http://www.withouthotair.com.

MacKay's key point, using Great Britain as an example, is that even if it installs more than all the wind and wave and tidal power currently deployed worldwide, devotes all the current arable land used to grow crop to biofuels and modernizes the grid and all electrical appliances for load sharing, Britain would still need to quadruple its nuclear energy supply to keep running.

Iran has a point. No matter how much oil and gas a country has, the world is going to need peaceful nuclear power.