“Hockey Sticks” Made of Carbon

Personal transportation accounts for the majority of greenhouse gas emissions from the transportation sector, in particular, when international aviation is included, yet relatively little is known about the composition and socioeconomic makeup of travel emissions at the household and individual levels. Do they vary by choice of transportation mode, geographical location, socioeconomic factors, vehicle technology choice, and other personal characteristics and if so, by how much? This paper aims to shed some light on the profile of greenhouse gas emissions at the disaggregate level. It presents the results of a substantive case study, performed in the United Kingdom, based on a newly developed greenhouse gas emissions evaluation tool. When all known climate effects are accounted for, however uncertain they may be, air travel dominates overall as the source of greenhouse gas emissions from personal travel. There is a huge range in emissions, with the highest 20% of emitters producing 61% of emissions. This 61% to 20% emission rule is mirrored in the “hockey-stick” shape of the curves ranking respondents by their emissions levels, which is surprisingly similar when transportation modes, location, and unit of analysis (individual, household) are compared. Although income, working status, age, and car ownership are significantly related to overall emissions, factors related to accessibility, household location, and gender are not. The paper concludes by discussing methodological considerations and policy implications.

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