Politicians should also set a personal green example

Tony Blair and the government should set a good example on climate change by adopting more sustainable personal behaviour and so Philip C James letter ('Government must lead by example', Bristol Evening Post, January 15) hit the nail on the head. We all need to do our bit because it all adds up - the Government are asking us all to contribute and it is hypocritical if they are not doing likewise.

Philip asks whether Labour are ready to offer leadership on this issue. The signs are far from good. Tony Blair first said he had no intention of cutting back on personal air travel but then quickly announced he would start to offset his carbon emissions. I cannot see why Tony Blair would not help to promote the country he leads by saying that he would take a holiday or two here instead of always flying. What does he not like about the UK?

Whilst his very sudden conversion to offsetting his carbon is welcome up to a point, there are also issues with the effectiveness of some offsetting schemes. Its also the case that committment to carbon offsetting varies considerably across the Cabinet! What's more the government's own advice to businesses considering carbon offsetting says that action to minimise emissions should be taken first, with only emissions that cannot be eliminated then offset. This is excellent advice to all trying to make carbon cuts and Tony Blair himself should follow it.

In a survey of government ministers only 5 out of 14 questioned by The Guardian currently offset their personal carbon from flights. This is very poor. Secretary of State for Culture Tessa Jowell was quoted as saying, 'I'll be working to plant trees to offset my carbon emissions'. This shows a real lack of awareness at the heart of government about what makes a reliable carbon offsetting scheme - in the week they are launching an offsetting standard! There is no way as yet to accurately measure how much carbon is absorbed and released by forests and woods as trees go through their lifecycle. One EU study estimated that Europes forests absorbed somewhere between 120 and 280 million tonnes of carbon per year, indicating massive measurement uncertainty.

There is growing interest in carbon offsetting but people considering it, Cabinet members included, should look closely at the particular schemes used and shop around for the best. Those that are heavily reliant on tree planting may not be reliable in terms of carbon absorbed - the error in measurement can be as high as 50% according to one New Scientist report! This is perhaps no surprise as carbon absorption by trees depends on many things: species; age; our increasingly uncertain climate, especially droughts and forest fires; diseases; canopy type; a range of pollutants and other factors.

Tree planting done properly is a very good thing and in optimum conditions a lot of carbon can be absorbed but such conditions seldom exist and its very hard to know with accuracy how much is absorbed. There are still fears that foresters might cut down existing forests to plant carbon guzzling trees. There are also many competing land uses for areas around the world that might be considered for trees, not least food production.

In any case carbon offsetting by trees is only a temporary 'solution'. Once trees are mature they begin emitting net amounts of carbon as they begin decomposing in whole or part. They must be removed or managed so that locked up carbon is not simply released again a few decades on.

Its important that we dont come to rely on carbon offsetting, especially by tree planting. Its tempting to put off the real task of cutting pollution or wriggle off the hook of emissions targets. However, the only guaranteed way to tackle climate change is to adopt sustainable lifestyles, which in any case would enhance our general wellbeing. So come on Tony Blair and company - show us how this is done!