For the past few weeks, Jen Morse and a colleague have had to ski 6 kilometers to a snow-buried shack on Niwot Ridge to collect data.
Once at this remote, windswept spot on the Front Range of the southern Rocky Mountains of Colorado, Morse, a climate technician at the University of Colorado Boulder, fills four heavy flasks of mountain air, which she carries down in her backpack. Skiing the full distance isn’t the norm, “but it’s hard to social distance in the cab of a snowcat,” Morse said.
Hundreds of such carefully collected flasks get shipped to the National Oceanic and Atmospheric Administration’s (NOAA) Global Monitoring Laboratory in Boulder each week from such remote locations as Hawaii, Mongolia, and Antarctica. In Boulder, scientists analyze the flasks’ contents to determine how the levels of trace and greenhouse gases, such as carbon dioxide and methane, are fluctuating or increasing.
But over the past few weeks, many countries have implemented strict measures to curb the spread of the coronavirus disease (COVID-19), placing cities and even entire countries on lockdown, and NOAA researchers have scrambled to keep the flask collection going. “We’ve never had a situation where we’ve had the potential to lose the flask data from so many sites at the same time,” said Arlyn Andrews, who manages NOAA’s Global Greenhouse Gas Reference Network.
So far, more than 90% of the flask sites are still sampling, and automated measurements made at in situ sites continue to provide data for carbon dioxide and methane. Doing whatever is safely possible during the pandemic to sustain monitoring is important, not least for maintaining records, scientists assert. “There are some very specific things that we can learn right now that are going to turn out to be valuable in the long run,” said Prof. Joost de Gouw at the University of Colorado Boulder.
When news of the impending lockdown reached de Gouw on 11 March, he knew he had to act fast. With his group, he physically moved a mass spectrometer to a prime site on the university campus where it could measure the changing levels of organic gas compounds in the background ambient air. “It was hectic, but we got it done in time,” de Gouw said. “And now our instrument is happily chugging away.”
The instrument measures organic compounds, in the form of gases, that emanate from transportation, agriculture, vegetation, oil and gas production, and personal care products such as cleaning materials. De Gouw hopes that the measurements will help researchers discriminate how much air pollution comes from individual sources.
“In normal times, all of these compounds are emitted where people live and where they drive, so they come from similar locations at the same times, and it is difficult to decide what the relative contributions are,” de Gouw said. “Now we are taking one important source away—cars—so then what do we see?”
Already, de Gouw’s data have revealed several improved air quality days in the Boulder region. “There is a wow factor of the level of pollution that all of us combined put into the atmosphere, and that is now no longer present,” de Gouw said.
A Big-Picture Perspective
While de Gouw’s mass spectrometer is revealing changes in local air quality, the Dutch/European Space Agency (ESA) Tropospheric Monitoring Instrument (TROPOMI), which is on the ESA’s Copernicus Sentinel-5P satellite, has enabled researchers to observe the changes in air pollution at a global level.
Observations from TROPOMI have shown that on average, across China, levels of nitrogen dioxide have dropped by 35% from the day that lockdown measures went into effect, compared with the same time period in 2019. The TROPOMI data also reveal reduced concentrations of nitrogen dioxide in the major cities of Europe, such as Milan, Paris, and Madrid, in the past couple of weeks.
“It is something that we have never seen before, such a big change in air pollution levels in such a short time frame,” said Pieternel Levelt from the Royal Netherlands Meteorological Institute and Delft University of Technology in the Netherlands.
To fully understand the impacts of the lockdowns on nitrogen dioxide concentrations, scientists are starting to investigate a combination of satellite, meteorological, and ground data. “We are testing our knowledge in the extremes,” Levelt said.
Unlike the scenario with nitrogen dioxide, it will take some time before scientists begin to see changes in the rate of greenhouse gas emissions, Andrews said. Their network, which includes in situ monitoring and flask samples taken on planes in addition to the ground-based flask data, was designed to look at changes on continental to global scales, and large reductions in emissions will register only a small signal at remote sites, such as the long-running Mauna Loa Observatory in Hawaii.
“But if we have a slowdown that lasts for 5 or 6 months, the signal will start to stand out even at these remote sites,” Andrews said.
Regional signals over the United States and Europe will likely be larger, but it’s too early to see anything yet, Andrews said. “Signals of the economic slowdown will be larger than what we see at remote sites, but the economic impacts are only just starting.”
Factors such as photosynthesis and respiration play a larger role in emissions at the continental sites, meaning that it can be even more difficult to find a clear signal of reduced emissions in the data, Andrews said.
The scientific questions that the lockdowns present are interesting but are secondary to concerns about global health and the economic impacts of coronavirus and the safety of colleagues locally and around the world. The logistics of trying to manage the network via telework while also homeschooling children are challenging, Andrews said.
Levelt concurs. Despite the scientific possibilities, it’s still a difficult situation for scientists, Levelt said. “Everyone has someone in their family that they are worried about, and that is also true for us scientists,” Levelt said. “That is our main concern—we are just human beings like everyone else.”
—Jane Palmer (@JanePalmerComms), Science Writer