Decomposition of factors determining the trend of CO 2 emissions from car travel in Great Britain (1970–2000)

Abstract

Carbon dioxide (CO 2) is the most important of the greenhouse gases that are causing global warming. The transport sector currently accounts for more than one-quarter of CO 2 emissions and more importantly its share in total emissions is increasing in most countries. This paper investigates the key factors in the change in CO 2 emissions from car travel in Great Britain over the last 30 years. It attempts to disentangle determinants of growth in CO 2 emissions from car travel, which has the largest share of emissions in road transport. The study is based on various decomposition analyses, starting from the IPAT identity. As summarised in the IPAT identity, the degree of the Impact of human activity on the environment is determined by changes in Population, Affluence (per-capita consumption) and Technology (environmental impact per quantity of consumption). In the case of CO 2 emissions from car travel in Great Britain, the affluence ( A) factor (car driving distance per person) was a dominant force for the growth of emissions over the last 30 years. Not only do people travel longer distances by cars than 30 years ago, but car occupancy rates have also decreased, contributing to the growth of car driving distance per person. Although technology ( T) factors such as fuel efficiency and fuel substitution to diesel fuel partly cancelled out these growth effects of affluence factors, this contribution was relatively small. However, in the 1990s there emerged a different pattern in the trend. Of the affluence ( A) factors, the growth rate of car trip distance per person weakened considerably. As for the technology ( T) effect, the carbon intensity of car driving kept decreasing over this period. Therefore, although CO 2 emissions from car travel ( I) continued to increase, the growth rate became substantially lower than in the earlier periods. More detailed investigation into the determinants of both affluence ( A) factors and technology ( T) factors is needed to confirm whether the trend in the 1990s indicates that carbon dioxide emission from car travel in Great Britain reached the turning point of the Environmental Kuznets Curve.