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Clear Skies for Earth Day 2020

Clear Skies for Earth Day 2020

For the first time in two generations, citizens of New Delhi and other cities in India can see the Himalayas as the air quickly clears from a slowdown in industrial manufacturing and traffic.

@Deewalia. This is Dhauladhar mountain range of Himachal (lesser Himalayas) seen from New Delhi for the first time in 30 years. According to a WHO survey, New Delhi typically has the worst air quality of any major city in the world.

As communities and whole countries shelter in place, the atmosphere is also getting a breather from human activities. Observed from space, China and Italy saw similar improvement in pollution levels. This is a rare opportunity for scientists who study the atmosphere to continue their work measuring carbon emissions and pollution and watching for patterns that can guide policy and actions to improve our future climate and air quality.

On a global scale, scientists are measuring an unprecedented drop in air pollution, particulates, and, on local scales, carbon dioxide emissions. While there are no silver linings to a tragedy, scientists and urban planners are documenting the welcome changes and drawing attention to some lessons we can draw from this pause—including how we might tread more lightly on earth and create the kind of future where global citizens can enjoy healthy air and we can circumvent the more extreme consequences of climate change.

Locally, Ron Cohen from UC Berkeley has been documenting the sharpest drop in air pollution and emissions that he’s ever seen in the Bay Area. Using data from the Sentinel 5 earth observation satellite, his lab analyzed NO2 data (a measure of air pollution detectable from space). By comparing the same time period last year with this year, it’s clear to see that NO2 levels (depicted by the bright yellow color) drop off the week of March 17 in 2020, after the shelter-in-place, but not in 2019.

Data from the Sentinel 5 satellite shows how levels of air pollution, represented by NO2 concentrations, dropped after March 16, 2020 but stayed level in the same time period in 2019.

For measuring changes within neighborhoods, Dr. Cohen’s lab has worked with schools, the Exploratorium, and other partners to install air quality sensors on rooftops in the East Bay and San Francisco. This research helps pinpoint differences in carbon emissions and pollution on a neighborhood scale, and detective work helps the scientists pinpoint sources. His team noticed right away that carbon dioxide and aerosol particulates dropped after March 17, shown by the much lower peaks in pollution levels. These changes are driven by reduced traffic, especially near the Bay Bridge.

Data from Beacon2 network showing carbon dioxide (CO2) and aerosol (exhaust particulate) levels before and after the shelter-in-place order on March 16, 2020. Six locations, including the two Exploratorium sensors are shown here

You can also explore Beacon data from the Exploratorium’s Wired Pier, along with an array of other weather and water quality instruments. A video tutorial shows how to use the data explorer tool; a good place to start is by graphing CO2 data from the two Beacon instruments on the Embarcadero and Bay ends of the Exploratorium building.

Like most of the Wired Pier sensors, these instruments usually operate without human intervention (until they need servicing or replacement). For other environmental measurements, scientists gather samples and analyze them in a lab.  NOAA’s Global Monitoring Laboratory (GML) in Boulder, Colorado conducts atmospheric research on planet-warming gases and other climate challenges using remote satellite sensing and field instruments and by collecting air samples from all over the world. On Earth Day in 2015, GML director Jim Butler traced the history of carbon on earth and why it matters, ending with some thoughts on how we can reduce our impact on climate. Watch the video here. In a recent discussion with Jim, I asked whether the lab has seen a global decrease in carbon emissions like we’ve seen on a local level. “Not yet,” he said. “It’s just been a month, and normally, those short-term records have a lot of noise." He said that he'd expect to see a signal when they look back at the year, but it's not likely to be significant on a global level.  "The amount of carbon we put in the atmosphere on a yearly basis is just massive," Dr. Butler said, "so it’ll be more significant if we can emerge from this with strategies to reduce carbon emissions in the long run.”

The good news is that if we reduce the fossil fuel emissions that drive climate change in the long run, we’ll also reduce harmful particulates and pollution and reap some of the human health and air quality benefits we’ve been seeing for the last few weeks.