We’ve Been Promised That EVs Will Lead To Cleaner Air. This Bay Area Study Just Proved It
Source: Fast Company, Kristen Toussaint
Photo: Justin Sullivan/Getty Images
A new study from UC Berkeley was able to correlate the rise in EV adoption with a decrease in emissions.
Electric vehicles have long been lauded as a key part of our transition to a low-carbon future. But the impact of EVs remains, admittedly, a little intangible. Conversations around electric vehicles often point to the future: How, if every new car and truck were electric, climate pollution would drop by 35%, and prevent thousands of premature deaths from air pollution. But are EVs having any impact now—and if so, how much?
Researchers from the University of California, Berkeley, finally have some answers: Between 2018 and 2022, CO2 emissions from all sources across the San Francisco Bay Area dropped about 1.8% annually, a decrease the researchers attribute to the rise in EVs, according to a study published today in the journal Environmental Science & Technology. Vehicle emission rates specifically dropped 2.6% annually. The Bay Area has the highest EV adoption rate in the country: last year, electric cars, pickup trucks, and SUVs made up nearly 40% of new auto registrations in San Jose and 34% in San Francisco.
That insight came via a network of sensors around the San Francisco Bay Area, which monitor both CO2 and air pollution—made up of particulate matter, nitrogen oxides, ozone, and carbon monoxide. Ronald Cohen, a chemistry professor at UC Berkeley, began setting up the sensors, which make up the Berkeley Environmental Air Quality & CO2 Network (BEACO2N), in 2012.
By looking at both air pollution and CO2, the sensors can help identify emission sources. “Different sources of combustion have different ratios of air pollutants to CO2,” he says. Heavy duty trucks, for example, emit lots of nitrogen oxides while cars emit almost none; conversely, cars emit lots of CO2, while heavy duty trucks don’t. These sensors are also unique compared to others; air quality sensors from the Environmental Protection Agency don’t monitor CO2, because it’s not a pollutant regulated by the Clean Air Act. (The EPA does track CO2 in some places, but it’s separate from their air pollution efforts.)
There are about 50 active sensors in the Bay Area, and researchers are able to divide the emissions those sensors monitor into three categories: steady emissions from industry, like refineries; seasonally varying emissions, mostly from home and commercial heating; and emissions tied to traffic. By looking at those separate buckets, they saw the traffic category decreasing, and lined that up with the progress made on EVs, hybrid electric vehicles, and better fuel efficiency. “It’s a consistent story to say the drop we’re seeing is associated with both the increase in EVs and more fuel-efficient cars,” Cohen says.
Though the sensors have been in place for years, analyzing their findings has taken time; separate from the hardware of the sensors, the team had to develop software to analyze their readings. Researchers were able to report a drop in vehicle emissions during the COVID-19 shelter in place, which was “a proof of principle” for this work, Cohen says. That allowed them to tease out the more subtle change of that 1.8% annual decrease.
It’s notable that a rise in EV adoption correlates with a detectable drop in vehicle emissions: It turns the abstract climate promise of EVs, and the push for individuals to change their behavior, into something tangible. “This is a direct measure from the atmosphere that we’ve made a change,” Cohen says.
It also points to Cohen’s larger ambitions for the BEACO2N project: “My fantasy about this project is that we would be the moral support that leaders need to say ‘my policy is working,’” he says, “and that we can tell feel-good stories like this, because there is so much action happening in trying to reduce emissions, but so little observations showing that we actually are.” If these monitors were in every city, politicians who commit to lowering their city’s CO2 footprint could have direct evidence that they accomplished their goals. Data from the monitors could also bolster environmental justice work by showing the difference in emissions by location.
It’s good news that emissions across the Bay Area are dropping, but it’s also true that emissions need to decrease more. California has a goal to reach net-zero emissions by 2045. To get there “smoothly,” Cohen says, emissions should be dropping 3.7% per year. The 1.8% annual drop was only related to vehicle emissions—which account for about a third of local emissions. To reach the broader goal, home and industry emissions have to drop, too, which will require new policies.
But there’s still room for optimism. “Nobody thought we would get [to net-zero] smoothly. They thought we would start slow and it would have to accelerate,” Cohen says. “So I take heart that at the beginning of that, we’re at half of what we need, on average.”