Pre-Industrial Revolution, the concentration of CO2 remained around 280 parts per million by volume (ppm). In 2009, the concentration increased to about 386 pmm. Including other greenhouse gases, the total effect was 464 ppm CO2 equivalents.
The impact of 'Cash for Clunkers” on greenhouse gas emissions: A life cycle perspective
One of the goals of the US Consumer Assistance to Recycle and Save (CARS) Act of 2009, more commonly known as ‘Cash for Clunkers’, was to improve the US vehicle fleet fuel efficiency. Previous studies of the program’s environmental impact have focused mainly on the effect of improved fuel economy, and the resulting reductions in fuel use and emissions during the vehicle use phase. We propose and apply a method for analyzing the net effect of CARS on greenhouse gas emissions from a full vehicle life cycle perspective, including the impact of premature production and retirement of vehicles. We find that CARS had a one-time effect of preventing 4.4 million metric tons of CO2-equivalent emissions, about 0.4% of US annual light-duty vehicle emissions. Of these, 3.7 million metric tons are avoided during the period of the expected remaining life of the inefficient ‘clunkers’. 1.5 million metric tons are avoided as consumers purchase vehicles that are more efficient than their next replacement vehicle would otherwise have been. An additional 0.8 million metric tons are emitted as a result of premature manufacturing and disposal of vehicles. These results are sensitive to the remaining lifetime of the ‘clunkers’ and to the fuel economy of new vehicles in the absence of CARS, suggesting important considerations for policymakers deliberating on the use of accelerated vehicle retirement programs as a part of the greenhouse gas emissions policy.