Summary/Abstract
Climate impact of transportation can vary over time because of competing cooling and warming effects. For example, aerosol emissions from maritime shipping cool the atmosphere in the short term by reflecting sunlight, whereas greenhouse gas emissions from the same source exhibit a warming effect in the long-term that outweighs the cooling. In order to reduce overall atmospheric warming, policy makers must be aware of the long-term and “lag” effects of transportation emissions, some of which may not be apparent for decades. This study uses climate modeling to compare the net climate effect of several methods of transportation: aviation, cars, buses, 2-wheel vehicles, and rail. Although aviation produces by far the greatest short-term warming effect, this effect decreases over time, making its long-term effect roughly equivalent to transportation by car over the 50-year range. This may indicate that reducing transportation by aviation is an effective strategy to reduce warming in the short term, while reducing transportation by fossil-fuel powered car is an effective way to reduce long-term warming.