The growing popularity of electric vehicles has helped drive an almost 2 per cent annual decrease in carbon emissions for the San Francisco Bay Area in recent years.
鈥淩eally, it鈥檚 both electric vehicles and more fuel-efficient cars,鈥� says at the University of California, Berkeley. 鈥淭here have been some efficiency gains in the gasoline-powered fleet, and not just the hybrid-electric ones.鈥�
Cohen and his colleagues calculated the emissions impact of electric cars in the Bay Area by using a network of 80 sensors that measure carbon dioxide and five air pollutants: carbon monoxide, two types of nitrous oxides, ozone and fine particulate pollution (PM 2.5). The sensor network covers both the city of San Francisco and nearby areas such as Sonoma county with its wineries and vineyards.
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The researchers combined the sensor measurements with a meteorological model to calculate ground-level emissions and predict their source. They also used mathematical modelling to help distinguish vehicle emissions from other emissions relating to industrial refineries and natural gas heating for homes and commercial buildings.
Their findings showed a 2.6 per cent annual reduction in vehicle emissions along with a 1.8 per cent annual reduction in the Bay Area鈥檚 overall carbon footprint between 2018 and 2022. But that is still just halfway to the annual reduction in emissions needed for California鈥檚 state-wide goal of reaching net-zero emissions by 2045.
More cities could use such sensors to track regional emissions, says at Carnegie Mellon University in Pennsylvania. But he cautioned that 鈥渕easuring trends in emissions released where people drive tells an important but incomplete part of the story鈥�, because Bay Area drivers charge electric vehicles using a power grid that draws electricity from power plants outside the Bay Area 鈥� and those power plants include some that run on carbon-emitting fossil fuels.
There needs to be both greater adoption of electric vehicles and increased renewable energy sources for the power grid, says Cohen. 鈥淲e [also] need to electrify industry and we need to electrify our homes,鈥� he says.
Environmental Science & Technology
