LONDON (Reuters) – Carbon offsetting, already a multi-billion dollar industry, will get a major boost from the launch of an international scheme to offset aviation emissions, called CORSIA, in 2021. FILE PHOTO: EasyJet airplanes are pictured at Tegel airport in Berlin, Germany, November 14, 2019. REUTERS/Fabrizio Bensch British budget carrier easyJet said on Tuesday it would go further than the scheme by offsetting all of its flights. The global market for offsets of economy flights alone is set to reach $3.8 billion a year by 2025, analysts at Citi say. Aviation already accounts for some 2% of global greenhouse gas emissions and green groups have accused the sector of using offsets to try to buy out of the problem cheaply. WHAT IS OFFSETTING AND HOW LONG HAS IT BEEN GOING ON? Carbon offset schemes involve compensating for emissions of the gases which cause global warming by paying for emissions cuts elsewhere. They are measured in terms of carbon dioxide equivalent and can be awarded carbon credits. The U.N.’s clean development mechanism (CDM), the first major offsetting scheme, was set up under the 1997 Kyoto Protocol, in which 190 countries agreed country-by-country emission reduction targets. The scheme was designed to help…