A woman with a dog looks out at the waterfront in Belfast on April 14.

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Next time you go outside in Maine, you may want to take a good look at the sky. Experts say that in the past few weeks, the air has become cleaner, and the atmosphere has become noticeably clearer.

These changes have been linked to the nationwide shutdown due to the COVID-19 pandemic, and more specifically to the significant decrease in emissions from transportation, such as airplanes and cars, and industrial operations.

[Our COVID-19 tracker contains the most recent information on Maine cases by county]

“Things are sharper, and in the night’s sky, you can see more stars,” said Paul Mayewski, director of the Climate Change Institute, which is based at the University of Maine in Orono. “The atmosphere is much cleaner.”

The Maine Department of Environmental Protection, which monitors air quality from dozens of stations scattered throughout the state, has yet to analyze air quality data from March, when the United States shut down began, and compare it to other months. But preliminary data collected by the department is showing a recent reduction in air pollution.

“There is data showing ozone levels are down noticeably in March 2020 over the same time period over the last 20 years,” said Don Darling, air monitoring section manager for the Maine Bureau of Air Quality of the DEP. “Other pollutants don’t show as noticeable a decline as ozone.”

In the months to come, the Maine Bureau of Air Quality will continue to look how air quality has changed in Maine during the shut down, Darling said.

On April 9, the National Aeronautics and Space Administration released a statement that satellite measurements revealed a significant reduction in air pollution over the major metropolitan areas of the Northeast in March. And the administration has observed similar reductions in other regions of the world during the pandemic.

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During a time of reduced emissions, it doesn’t take long for the atmosphere to become noticeably more clear as particulate matter settles to the ground, Mayewski said. Large, visible particles such as dust or soot, can settle in a matter of minutes or hours, while smaller particles can stay in the air for days or weeks.

“I’d hazard to guess our air quality will be improved by at least 25 percent if not 75 percent [in Maine], depending on how long the shutdown lasts,” Mayewski said. “But it’ll come back fast. If everything got turned on again tomorrow, we’d be back in the situation we were a month ago.”

The ‘tailpipe of the nation’

The most forested state in the nation, Maine is known for its fresh air and clean waterways.

“We are blessed to have good air quality generally speaking,” said Darling, who has been monitoring air quality in the state since the 1970s. “Overall in Maine, there are really no places you can go where air quality would be a meaningful concern, though there are instances during the summer during ozone season when we do have events where ozone is high.”

Ozone (O3) is a highly-reactive gas that occurs both in the Earth’s upper atmosphere and at ground level. When naturally produced in the upper atmosphere, it forms a protective layer against UV radiation. But at ground level, it’s considered a pollutant that’s harmful to breathe and damages crops, trees and other vegetation. It is a main ingredient of urban smog.

Ground-level ozone is created from certain chemicals found in emissions from industrial facilities, electric utilities, motor vehicle exhaust, gasoline vapors and chemical solvents. And while Maine may experience high ozone events, that doesn’t mean it originated in the state.

“Much of the pollutant events we experience have to do with pollutant materials that come in from out of state,” Darling said. “The wind patterns that bring the dirtiest air here either come up the coast or they come up from the Midwest or Ohio River Valley … and occasionally, in the summertime, there are forest fires in Canada [that Maine receives pollutants from]. Very little of the pollution we monitor actually originated here.”

For this reason, Maine is often referred to as “the tailpipe of the nation.” Therefore, during the pandemic, the shut down of big cities on the East Coast such as Boston and New York can have a big impact on the air quality in Maine.

Furthermore, changes in air quality rapidly produces changes in water quality, Mayewski said. Precipitation pulls down particles in the air and washes them into watersheds and the ocean.

“Water quality in surface waters should increase as a consequence of the increase in better air quality,” he said.

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What improved air quality means for climate change

The dramatic decrease in travel and industrial activities during the pandemic has resulted in lower greenhouse gas emissions throughout much of the world. So what does this mean for climate change?

The short answer is: not much, unless the world continues to reduce greenhouse gas emissions after it gets a handle on the novel coronavirus.

“Several months of reduced industrial activities and emission of greenhouse gases, or even a year, doesn’t have a large impact on the overall system,” said Maine State Climatologist Sean Birkel. “There’s a new climate baseline compared to say a century ago. The oceans are much warmer and the atmosphere as a whole is more humid. That’s not something that’s easily undone.”

Greenhouse gases are gases that trap heat in the atmosphere, resulting in climate change. These gases include carbon dioxide, methane, nitrous oxide and fluorinated gases — which are released into the atmosphere primarily through the burning of fossil fuels, solid waste and organic materials, as well as certain industrial and agricultural processes and the decaying of waste.

Unlike particulate matter, which can be washed from the atmosphere in a matter of hours or days, greenhouse gases remain in the atmosphere much longer — from a few years to thousands of years, according to the U.S. Environmental Protection Agency.

“Greenhouse gases have been accumulating in the atmosphere beyond natural levels for well over a century and a half now,” Birkel said. “Total emissions for this year during the pandemic will go down, but given the concentration in the atmosphere … it would likely be an amount that in the grand scheme of things has only a very minor impact.”

Among climatologists, there is a hope that the recent improvements in air and water quality around the world will serve as a wake up call, encouraging people to take greater measures to reduce pollution and greenhouse gas emissions in the future. But as is the case with most things these days, only time will tell.

Watch: Maine’s interstate traffic is down 53 percent

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Aislinn Sarnacki

Aislinn is a Bangor Daily News reporter for the Outdoors pages, focusing on outdoor recreation and Maine wildlife. Visit her main blog at actoutwithaislinn.bangordailynews.com.