On Thursday, the aviation agency of UN, the International Civil Aviation Organization (ICAO), introduced a standard to calculate how much air travellers should pay to offset the carbon emissions produced by the their travel, deciding to pay no attention to an area of hot discussion on the environmental impact of the industry.

Enno Harders, a senior official at Germany's emissions trading authority which calculates national greenhouse gas emissions, said, "It's a race to the bottom",

Harders also said that the proposed calculator underestimated the contribution airlines are making to warming.

Air travel sector is under the public attention from environmental agencies as it is one of the most speedily growing sources of greenhouse gases emissions.

Some of the airline companies have taken action by offering their customers the option to offset their air travel, by contributing some amount of money towards some projects initiated for the benefit of environment, for example by making payments towards the setting up of a wind turbine in India.

But before making any payments, passengers need to know that how much impact their air travel is causing on the environment, which is where carbon calculators works.

While referring to carriers including British Airways and Lufthansa, which all introduced different measures, Jane Hupe, the chair of ICAO's environmental unit, said, "We were very concerned with the proliferation of offsetting schemes. We (think) this will become a reference. We really want everyone to link to our site. We have signs from IATA (the International Air Transport Association) that they'll use our calculator".