The tragedy of less bad.

• Author: Kusano, Keita
• Position: Automobile energy efficiency - Report

The biggest and perhaps most misleading or problematic fact about today's movement to stop climate change is what superficially sounds good: increased energy efficiency. Increasing energy efficiency (say, miles per gallon) would be an excellent way to reduce energy use or emissions. It is great, absolutely. But it is great only if it leads to a decrease in total energy consumption. If you increase your car's miles per gallon (mpg) from 10 to 20 but drive twice as far as you used to, you achieve nothing. What if the population grows? If you increase the mpg of all types of cars from 10 to 20 and drive as much as you used to, but population doubles, you also achieve nothing.

It can be difficult to calculate these factors. Therefore, it is very unlikely to achieve an 80% reduction, which has to be achieved by 2050 to stop climate change, by focusing on energy efficiency. Data regarding carbon intensity decreases, energy efficiency increases and total carbon dioxide emission increases over the last few decades show the impossibility of achieving an 80% reduction.

Case 1: Carbon intensity decrease. Over the last 30 years, technological advances, associated with changes in the sources of energy supply, have caused carbon emissions to grow only half as fast as the gross world product (1.5% versus 3% per year). (1) As a consequence, global carbon intensity--the ratio of global carbon emissions to gross world product--has been consistently falling.

So, is this good news? Not necessarily. The in-crease in total emissions is more critical than the decrease of carbon intensity. The impact of each product on the environment became less bad, but total impact became worse. In fact, atmospheric concentrations of carbon dioxide, the single most important indicator of global warming, have increased more in the last 25 years than ever before.

Case 2: Miles per gallon increase. In the US, transportation accounts for 30% of total carbon emissions and, within the transportation sector, motor gasoline accounts for 60% of total carbon emissions. (2) That is, about one billion metric tons of carbon dioxide is emitted from car use. In the last 20 years, fuel efficiency has also increased dramatically. In 1980, the fuel economy average of all 1980 model cars used in the US was only 24.3 miles per gallon. (3) Twenty years later, it went up to 28.5 mpg. (3) An additional four miles can be driven on the same amount of gasoline. This seems to be good news.

Unfortunately...