From today our blog becomes daily in the countdown to Copenhagen, and we will discuss the issues as well as the shifting positions as leaders try to converge to an agreement.

Today China has announced that it will reduce its "carbon intensity" by 40-45% by 2020. What this means is not that it will reduce carbon emissions. We will see much of this kind of game of words, that is the staple of politicians, in the following days.

"Carbon intensity" is amount of emissions produced per unit of GDP, typically measured in metric tons of CO2 per $1m of wealth creation. At the moment China emits 1,046 tons of CO2 per $1m of GDP, compared to 475 tons by the United States and 285 by the United Kingdom. This means its economy is vastly reliant on dirty energy and is so inefficient that it emits twice as much as the US and more than 3 1/2 times as the UK to create the same amount of economic output.

China's commitment to cut its carbon intensity by 40-45% means that by 2020 it will emit about 420 tons per $1m of GDP, which is just a touch below the US but still 50% more inefficient than the UK at the present time.

In terms of real emissions, China has yet to state when its emissions will peak (it's expected it will be around 2020, though it could be later), and what rate of cuts will follow thereafter. It is impossible to predict what will be China's position in 2050 and the rate of cuts from 2020 to 2050 unless we have some idea of the magnitude of the peak of emissions that will be reached. At its current rate of growth, it's predicted that China's economy will double by 2020, so if we extrapolate emissions and then subtract 40% in reduction in carbon intensity, then it would be expected that from 2009 to 2020 China's emissions will grow by 10%. That is 6bn tons of CO2 too many (and soon to become 7bn) that are emitted to the atmosphere every year.

It's not particularly what I call an express route to decarbonisation.

Brunella