An article of Aljazeera - the topic says everything...

You're buying an airplane ticket online. Scroll to the bottom of the website, and there's an option to "buy carbon credits" to "offset" the climate change-inducing emissions you are about to produce during your flight.

It sounds like an attractive, market-based way to appease your environmental conscience - and quite affordably, too. But what are you actually buying? And how much - if any - difference can it really make in the fight against global warming?

In effect, you're paying someone else to exercise carbon emission restraint. It may be a tech factory reducing their pollution, or a Third World forester leaving a jungle tract unlogged.

But many questions surround the viability and potential negative consequences of carbon trading.

Can the carbon market attain enough credits to help halt global climate change? How, with its diversity of climate mitigation efforts, can carbon contracts be kept feasible enough for the markets to grow? And are there costs to biodiversity and indigenous people living in or near forests?

Under the 1997 Kyoto Protocol, 193 countries committed to reduce their annual rate of greenhouse gas emissions by four per cent compared to 1990 levels. One of their suggested methods for implementing the goal was a "cap-and-trade" market.

The premise of the scheme was to put a value or price tag on carbon held in trees in developing countries, then get people and governments in the developed world to pay for "carbon offsets", or forests left standing.

Conservationists have challenged the effectiveness of basing these rewards on sheer tree tallies, or on the tonnage of carbon sequestered. Diverse carbon-absorbing forests can all too easily be wiped out and replaced with mono-cropped oil-palm or rubber tree plantations, they say.

Read further here...