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Critics Say Carbon Offsets Are Inaccurate

August 22, 2008

An expert in aircraft performance models said that inaccurate calculation of greenhouse gas emissions from air travel is undermining the method of using carbon offsetting to combat climate change.  

As a result, critics of the system say that those who travel by air may be deceiving themselves that their offsets are having their intended effect. 

Carbon offset supporters maintain the system allow air travelers to fight climate change without altering their behavior through compensating others to reduce emissions of greenhouse gases on their behalf.

Online travel company Expedia Inc. threw its support behind carbon offsetting on Thursday, allowing its customers to continue traveling exotic destinations with a clearer conscience.

But the airlines use a different method to calculate carbon emissions, casting doubt about the credibility of current offset calculators.  In June, The United Nation’s International Civil Aviation Organization (ICAO) unveiled a carbon calculator aimed at standardizing emission calculations by various airlines. However, the model can nevertheless provide misleading results, according to Dimitri Simos, director at Lissys Limited, who provided the aircraft performance model that was the basis for the ICAO estimate. The model was also previously used by the British government.

“Producing a single number is crude,” Simos told Reuters.

“If you go from Heathrow to Athens, ICAO gives 217 kilograms (kg) of CO2. That hides huge variations – fly in a full (Boeing) B767 and it’s nearer to 160 kg per person, or fly in a half-empty (Airbus) A340 and it’s more like 360 kg.”

“It’s the variations that are missing and that are important.”

For example, a carbon calculator on the British Airways website found 314kg per person of CO2 emissions for a trip from London Heathrow to Athens, whereas a Lufthansa calculation found 260kg per person of CO2 from London Stansted.

Critics of carbon offsetting say the system creates a false impression of fighting climate change, focusing on insignificant efforts such as building wind turbines or planting trees instead of addressing the underlying problem by flying less or burning less coal.

Expedia published a survey on Thursday that revealed the public’s ignorance of carbon offsetting.  Ten percent of the 2,000 British survey participants believed offsetting meant walking to work instead of driving, with one percent of men believing it meant properly putting out a barbeque.  Just one in three understood the true meaning of the term.




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