Air travellers who feel racked with guilt for spewing carbon dioxide into the atmosphere and speeding up global warming can now rest easy. For a small fee a not-for-profit company, Climate Care, will offset the environmental damage of your holiday, making it CO2-neutral, and helping keep the globe cool.

Climate Care sets up and invests in projects that reduce CO2 emissions in less developed parts of the world, including reforestation in Uganda, a hydroelectric generator in Bulgaria, and distributing low-energy light bulbs in Mauritius. The projects also aim to provide jobs in depressed areas.

Air travel is the fastest growing source of emissions in the world, accounting for 3.5 per cent of the total, and because planes fly in the sensitive upper atmosphere, their exhaust gases cause between two and four times the amount of global warming than the CO2 alone. It costs 81p to offset the emissions from one hour's air travel, so if a family of four fly return to Cyprus (around nine hours each) you can pay Climate Care just £29.16 to neutralise your 'environmental footprint'.

The need for projects such as this was outlined by the government's chief adviser on environmental issues, Jonathon Porritt, last week at the Association of British Travel Agents conference in Cairo. Citing the effects of global warming - this summer's flooding in central Europe, predictions that some Italian ski resorts could be without snow by 2008 and the planned evacuation of the 11,000 residents of 'sinking' South Pacific island Tuvalu - Porritt stressed that responsible behaviour was no longer 'an optional add on, but a necessary component of travel.' However, he also praised travel as offering 'huge social and environmental benefits to developing countries', and being 'the most fascinating way of breaking down our peculiar isolation from the natural world and poorer people'.

Climate Care (01865 777770) has a carbon calculator on its website where you can tot up the cost of neutralising the energy consumption of your entire life. Jonathon Porritt's Forum for the Future (020 7251 6070).