Goodbye carbon offsets...

And, good riddance...

As millions of Britons jet off to foreign climes for their holiday this month, the more environmentally minded travellers will have salved their consciences by paying for trees to be planted to compensate for the carbon emissions caused by their flight.

But a ground-breaking study has now called into question the effectiveness of using trees to "offset" emissions, suggesting that their ability to "lock-up" carbon dioxide has been greatly exaggerated.

Forests have long been seen as an effective way of absorbing the greenhouse gases, such as carbon dioxide, which are thought to trap the sun's heat in the atmosphere, causing global warming.

Celebrities, including the Rolling Stones and Leonardo DiCaprio, the film actor, have signed up to schemes to plant trees to offset their own emissions.

However, the new research found that trees bathed in extra carbon dioxide grew more tissue, but did not necessarily store significant extra quantities of carbon. Instead, the tree's capacity to absorb the gas depended on water and nutrient leve

The news will come as a blow to the carbon-offsetting industry, which has expanded rapidly as individuals and companies try to atone for their carbon dioxide emissions by paying companies to plant trees for them.

In 2003, the Rolling Stones held a "carbon neutral" tour, planting one tree for every 60 tickets sold.