What is carbon offsetting?
Carbon offsetting is a way to counter damage done through the release of carbon emissions (CO2), from activities such as driving a car, flying or heating a building.
For every tonne of CO2 emitted, an equivalent tonne is supposedly removed elsewhere.
Carbon offset schemes set a price on the amount it costs to mitigate the harm from emissions.
Offsetting does not undo the environmental harm caused but does cut the total amount of CO2 released.
How long has carbon offsetting been around?
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Offsetting has been around for over a decade but it has taken off in the past few years, amid a growing awareness of climate change.
Numerous providers have sprung up, allowing people and companies to offset often simply by joining schemes online.
What types of schemes exist?
Forestry schemes, including tree planting, were some of the earliest projects. Many have now been discredited for their temporary benefits.
More recently, energy efficiency projects in developing countries have sprung up.
These projects provide anything from energy efficient light bulbs or cookers to wind farms. Some of these are included in offsetting measures set out under the Kyoto protocol on climate change.
Who can pay to offset and at what cost?
Anyone can offset emissions, but it tends to be people in developed countries investing in poorer countries. Providers can be found in the UK, Germany and the US.
The prices vary depending on the amount of CO2 in question.
Offsetting flights has been especially popular, in part because of the relative ease of knowing how much CO2 has been released.
It can cost £10 or less to offset a return flight from London to New York, while a return trip to Australia could cost around £30.
How are carbon offsetting projects regulated?
Most schemes are part of a voluntary and unregulated market, which has been criticised for its lack of transparency. Verifying that projects deliver the promised cuts is far from an exact science.
Prices are set depending on the provider - but there are no rules on how much must be spent on the scheme as opposed to administration.
How effective is carbon offsetting in tackling climate change?
Taken alone, it is not the answer.
Offsetting accounts for a fraction of all emissions produced. Long term we need to radically cut our emissions rather than mitigate them, the government says.
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There is no precise way to assess the effectiveness of carbon offsetting schemes
Environmentalists say such offsetting sends the wrong signal by allowing people to think we can continue business as usual.
Others argue that making people aware of their carbon footprint is beneficial.