Targets are the easiest things in the world to set. The act of setting one costs you nothing. You've got a target? OK, I'll set a bigger one. But delivering them is a different matter entirely.

Yesterday the Government unveiled the world's first delivery system for the targets involved in radically cutting back the gases that are causing global warming. It is based on two simple principles: make the targets legally binding, and map out the road towards them in detail. The system is enshrined in the Climate Change Bill, unveiled by the Environment Secretary, David Miliband, which proposes to set into law the crucial aim of cutting the UK's CO2 emissions by 60 per cent, on 1990 levels, by 2050, and lays out a statutory path towards that from which it will be very hard, if not impossible, for any future government to stray.

The 60 per cent figure is one that might once have appeared very ambitious, but recent estimates of just how quickly climate change is now progressing ­ the world's ice is melting everywhere before our very eyes ­ have made it seem the very least that will have to be done, by Britain and other countries, if the earth is to escape the catastrophic consequences of runaway atmospheric warming, from mass agricultural failure to world-wide sea level rise. Yet until now that 60 per cent has just been a target ­ first suggested by the Royal Commission on Environmental Pollution and subsequently adopted with enthusiasm by Tony Blair. And targets to cut CO2, in the climate change business have been bandied about for nearly 20 years in many countries, with very few of them being achieved. Indeed, hovering in the background to the Government's initiative yesterday was its own chastening experience of setting a target for cutting Britain's CO2 emissions by 20 per cent by 2010. It was solemnly repeated in three separate election manifestos, one after the other, yet is not now going to be met.