cop15_blueYou are going to start having to be a skilled mathematician and serious spinwatcher to wade through the political commitments being made before Copenhagen.

Take China’s announcement –which is being hailed as significant as it is the country’s first ever carbon reduction commitment. The country’s Cabinet has pledged to reduce CO2 per unit of gross domestic product by 40 to 45 per cent by 2020 compared with 2005 levels.

But this is not a straight reduction it is a reduction in CO2 per unit of gross domestic product. China claims that, unlike developed countries, it does not need to set a target for cutting its overall emissions because its per capita emissions are much lower.

So what does this actually mean? It “does not mean that China will actually cut its carbon emissions by 2020,” argues the Times, but “given the expected huge increases in its economy over the next decade, its global warming emissions should increase at a much slower pace than if China had made no changes.”

The paper argues that the target is not as ambitious as it sounds. “China has chosen 2005 as a starting point for measuring its cut in carbon intensity because it has already reduced its emissions per unit of GDP sharply in the past four years. To meet the target of a 40-45 per cent reduction, it merely has to continue cutting at the same rate.”

The figure “is unlikely to be high enough to satisfy European and US negotiators, who have indicated that anything below 50% would represent a less ambitious target than its current efforts to improve energy efficiency,” argues the Guardian.

Even then, China’s commitment is purely voluntary and incredibly hard to measure and monitor, or in the jargon to make sure it is “Measurable, reportable and verifiable.”

As Reuters points out: these three “little letters – MRV – could spell big trouble for global climate change negotiations even after China, the world’s biggest emitter of greenhouse gases, announced its first firm goals to curb emissions … How will the world know if it is telling the truth about any emissions reductions?”

It is unlikey that the Copenhagen talks will finalise what is considered to fall under MRV, with an agreement supposed to be sometime next year.

But until that gets nailed down, you know how politicians like to leave themselves wriggle room.

It is not the only areas they will be wriggling on. Huge diplomatic rows remain over rich nations’ emissions cuts, the cash promised to developing nations and how to tie down a legal treaty.

As one environmentalist said last week “The White House … was noticeably silent about finance”.

And the “politically binding agreement” that people are now talking about has been described by Tom Burke, of the E3G think-tank in London as “a meaningless term”.