The issue of the benefits of carbon 'sinks' was a major talking point at the Bonn climate change summit. So, what exactly are they? And where do they exist?
Try to imagine every single football manager in the country (well, all but one) in the same room attempting to reach an agreement on who was the greatest player of all time.

Impossible, you might think. Yet the concept is strikingly similar to what occurred in Bonn recently at the latest climate change summit – because in what can only be described as a historic political event, 178 countries managed to agree on the how to best tackle global climate change.

The only country deciding that the deal was not acceptable enough was the United States – surprise, surprise. Yet, despite failing to win over President Bush and co the end result was one of elation as Japan and other big world polluters, such as eastern Europe and Russia agreed to a revised Kyoto protocol.

Following the agreement Michael Meacher, UK environment minister said: "This is a fantastic day for the environment. It's a huge leap to have achieved a result on this very complex international negotiation."

A problem shared..
Although the original figure of a 5·2% reduction in global emissions of greenhouses gases by 2012 now seems far less likely, the fact that so many countries have now agreed on a common strategy on tackling climate change must be hugely applauded.

Yet some of the concessions that led to the agreement seem highly contentious and are bound to leave many people confused as to how likely it will be that the reductions are met.

In particular, countries that profess to have carbon 'sinks' will be able to use them to help meet their pollution reduction targets set by Kyoto. But what exactly is a carbon sink and is it really effective?

A sink is a carbon-absorbing zone that literally sucks carbon out of the atmosphere and stores it in the land. It is believed to occur in densely forested areas when CO2 is absorbed by plants as they grow exceeds the level released by dead material when it decays. The Americans were one on the first to declare that they had evidence of the existence of a sink over ten years ago.

Following extensive studies of the global flow of CO2 in the early nineties, scientists found that carbon levels over North America were lower than expected. Researchers had anticipated a significant rise in CO2 levels over the continent, as the area was renowned for producing enormous levels of the gas from burning fossil fuels.

Scientists concluded the presence of the sink from this evidence. The latest figures declare that the United States is absorbing one to two-thirds of a billion metric tonnes of carbon each year as a result of carbon sinking.

There is little doubt that any help in the fight to reduce carbon dioxide levels is welcome, but does the supposed existence of sinks justify the special 'brownie points' being awarded to countries that can apparently prove they have one? Christine Pout, principle consultant from the BRE's energy division is unsure. She believes there are a number of arguments to suggest not: "Firstly, it is important to remember that the mechanism of sinking is only temporary," she explains. "When plants and trees stop growing rapidly and absorption levels of CO2 drop then the sink disappears."

So, what is the answer? Plant more trees? This would seem to be the most obvious solution, but as Christine Pout explains, with it comes a second problem: "Planting more trees will help decrease CO2 levels but it will also increase levels of other greenhouse gases, such as methane, that trees and plants emit."

Better late than never
The acceptance of the benefits of carbon sinks helped to persuade major CO2 producing countries such as Japan and Russia to agree to the deal, yet it appears to have weakened the original agreement by bringing an uncertainty as to its validity.

However, environmentalist and politicians (for once) appear to be united in the belief that the agreement is a great step forward. And in the absence of a more effective alternative surely is it better to have a weakened agreement than nothing at all.