What is carbon trading?
The effects of CO2 pollution are increased by aviation
Carbon trading, which began in 1989, is a way of tackling global warming using the theory that the country carbon dioxide (CO2) comes from is less important than total amounts released into the atmosphere.
However it received its main impetus after the Kyoto treaty - which came into force in February 2005 - where industrialised countries have to cut greenhouse gas emissions from their 1990 levels by an average 5.2% between 2008-2012.
Carbon trading creates a choice where either the polluter pays to cover the costs of emissions or pays someone else to cut their pollution.
Why is air travel a particular concern?
Because planes fly in the upper atmosphere the effects of CO2 pollution are increased by about a factor of three. One short haul flight produces roughly the same amount of the global warming gas as three months worth of driving a 1.4 litre car.
What is personal carbon trading?
Some economists believe that in the future our lifestyles should be based on a form of rationing where every person is given a carbon quota.
For example with flying, anybody who wants to fly more than their quota would have to buy credits from people who rarely or never fly.
How does it work?
It is argued carbon should be divided equally amongst the population to give everyone a virtual share of the air. Those using less could sell the surplus to people or businesses using above their share.
Some economists suggest it would help poor people, who are said to emit below average levels of carbon dioxide, and anyone who has a low energy use lifestyle. This could work on a global basis too to help the poorest societies.
How else can we offset carbon emissions?
One idea is to plant trees in relation to the carbon impact of your flight.
For example someone on a short haul flight could plant one tree in a new native forest - a mature tree is estimated to soak up a tonne of C02.
Another idea is to fund projects with a cash equivalent to the carbon used to back such ideas as energy efficiency, conservation or reforestation in developing countries or invest in eco-friendly technology.
What about the future?
Some campaigners argue that just as we have labels on clothing giving its size and material, or labels showing the fat in food, we should have the carbon load or carbon offset on a product label. Some manufacturers have already started assigning a 'carbon rating' to everything it sells such as Tesco.
It is said this would be useful to calculate carbon emissions, as most products have a CO2 load.
Designer Katharine Hamnett has already created a range of clothes that have been sustainably produced using organic cotton and recycled metal zips and shipped via sea rather than air freight.
Marks and Spencer aims to be carbon neutral in five years time.