Mark Lynas's Copenhagen Notebook

Very few people seem to realise this, but the Kyoto protocol divided the world. With its strict definitions of haves and have-nots, developed and developing, the divisions between rich and poor enshrined in the 1997 treaty are almost as rigid as those between the West and the Eastern bloc in the Cold War. Except that instead of an Iron Curtain, what lies between the two sets of countries is known rather cryptically as "the firewall".

Industrialised countries are not all rich; their ranks include the likes of Ukraine and Croatia. Nor are all developing countries poor: Singapore and the United Arab Emirates, for example, hardly need to beg for aid. But the distinction matters because under Kyoto only "rich" countries had to make cuts in their carbon emissions. Poor nations, in recognition of their lower per-person emissions and their smaller historical responsibility for causing global warming, were expected to follow suit only when they attained industrialised status.

This all makes sense from an equity perspective – but is shaping up to be extremely bad news for the planet. For if we are to keep temperature rise within tolerable bounds (1.5C is the upper limit, according to front-line vulnerable states like Bangladesh and Tuvalu) then global emissions need to peak about now and start coming rapidly down again, eventually reaching zero by about mid-century. This in turn means that big developing countries like China, India and Brazil, who are expected to account for almost all emissions rises in future, must also take on targets here at Copenhagen – thereby breaching the Kyoto firewall.

In fairness, India and China have both come to this meeting offering targets – but only to cut their emissions intensity (carbon emitted per unit of GDP) not their absolute levels of carbon output. Using this metric, a Chinese CO2 "cut" of 45 per cent translates into a real-world rise of about 100 per cent. By any reasonable scientific measure, this is a recipe for climate chaos.

So Kyoto's two big power blocs – rich and poor – are beginning to break down here in Copenhagen. In particular, the Maldives (who I am helping to advise) is causing a stir by offering to cut its emissions by 100 per cent in a decade, without preconditions. Ironically, however, it is legally prevented from doing so under Kyoto. To take on a mandatory emissions target, the Maldives must first declare itself "industrialised", thereby assuming a potential financial liability for the adaptation and mitigation costs of other "poor" countries, like India and China.

This is an obvious absurdity, and one which a growing number of developing countries – many of whom also recognise the pressing need for low-carbon growth – are trying to tackle. As a result, the traditional G77 group of developing countries is split down the middle and barely functioning.

Copenhagen is beginning to enter the end-game. In five more days we will know if the two most important and highest-emitting countries – the United States and China – are serious about tackling climate change. Everything else, indeed the future of us all, depends on what they decide.

Mark Lynas, one of Britain's leading climate change experts and author of 'Six Degrees', the Royal Society's Science Book of the Year, will be writing for 'The Independent' throughout the final stages of the Copenhagen negotiations. He is attending as an adviser to the Maldives.