By Dane Gambrell
In the past three decades, greenhouse gas emissions have risen in metropolitan areas across the United States. How does your city stack up?
“The Most Detailed Map of Auto Emissions in America”, created by Nadja Popovich and Denise Lu and published in the New York Times, is an interactive web map of auto emissions for metropolitan areas across the country.
The map was created using data from Boston University’s Database of Road Transportation Emissions (DARTE), which provides transportation emissions data at a 1-km resolution for the contiguous United States from 1980 – 2017.
The Times analysis then combined this data with population data from the Census Bureau and National Institutes of Health to determine the 100 metropolitan areas with the highest total on-road emissions. Selecting a metropolitan area from the drop-down list updates the map to show a pop-up showing the percentage change in total and per capita auto emissions from 1990 – 2017 for that city.
Since 1990, total auto emissions have increased across the board, despite a temporary dip in certain areas during the late 2000s recession. In a majority of areas, per capita auto emissions have also increased, indicating that emissions have grown faster than population. This is particularly true for cities with sprawling suburbs where a large percentage of the population drives. The Chicago, Illinois metropolitan area, for instance, has seen a 66% increase in total auto emissions and a 43% increase in per capita auto emissions since 1990.
In addition to federal fuel economy standards, cities have sought to reduce emissions by encouraging the adoption of hybrid and electric vehicles as well as increasing transportation options such as public transit and carpooling. Metropolitan areas that have also seen a drop in per capita emissions include Atlanta, Georgia; Las Vegas, Nevada; Orlando, Florida; Portland, Oregon; and Rochester, New York, among others.
Many metropolitan areas in California have also seen success in curbing emissions growth. Under a waiver from the Environmental Protection Agency (EPA), the state sets pollution and fuel economy standards for vehicles that are stricter than the federal regulations, which twelve other states also follow. Per capita emissions have fallen in the metropolitan areas of Bakersfield, Fresno, Los Angeles, Sacramento, and San Francisco, while total emissions in San Jose have actually dropped by 13%.
As the authors note, transportation is “the largest source of planet-warming greenhouse gas emissions today.” In 2017, the transportation sector surpassed electricity production in emissions for the first time; an EPA estimate in that year placed transportation at 29% of overall emissions, accounting for roughly 1,866 million metric tons of carbon dioxide equivalent. Emissions from electricity production, meanwhile, dropped due to the ongoing shift from coal toward natural gas and renewables (as well as mild weather compared to the previous year), which contributed to a decrease in total emissions compared to 2016.
A similar shift would be needed to reduce emissions in the transportation sector, where over 90% of fuel is still petroleum-based. While the adoption of alternative fuel sources such as biodiesel may be a natural first step, policies aimed at improving the efficiency of vehicles, such as fuel economy regulation, could also provide a way forward. Regardless, emissions from transportation will need to play a role in ongoing conversations about curbing climate change.