NASA Studies How COVID-19 Shutdowns Affect Emissions

Narration: Kathleen Gaeta

Transcript:

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Computer models of Earth's

atmosphere can tell us a lot.

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Trained on how the atmosphere

typically operates, the models

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take in data about temperature,

wind speed, humidity, and more

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to give us important insights

into the world around us.

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Computer models like NASA's GEOS

model can help us study how

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chemicals move through the

atmosphere, how the ocean

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circulates, and where air quality

might be affected by fires and

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pollution. These models can also

provide a look at what might

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have been if circumstances were

different. For instance, climate

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models can forecast how

temperatures might change with

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different levels of carbon

emissions. In 2020, the world

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threw the models a new test

when people began behaving very,

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very differently with almost no

warning, a global pandemic

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set in. Around the globe,

people stopped driving and

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flying in large numbers, started

staying home, and completely

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changed their pollution

patterns. In particular

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emissions of nitrogen dioxide, a

common air pollutant released by

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cars, airplanes and many

factories, declined

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significantly. But just how much

did the shutdown change our

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emissions? NASA’s GEOS atmospheric

composition model offers an

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answer. The model run functions

by assuming that nothing was

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different in 2020, that people

continued behaving roughly the

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same as they would have with no

activity shutdowns, adding the

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same number of atmospheric

pollutants to the air. It's then

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a matter of subtraction.

Comparing those models to real

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world observations made by

satellites during the shutdowns

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shows how significant the

decrease in pollution was in

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various cities. Activity

shutdowns started in Wuhan,

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China. And in January, observed

emissions of nitrogen dioxide

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began to diverge from what

models predicted, about 60% less

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than predicted, that is. As the

virus and the associated

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shutdowns moved west, European

cities began to experience

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decreased levels of nitrogen

dioxide emissions as well. in

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Madrid, Spain, nitrogen

dioxide emissions were also 60%

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less than modeled. Shortly after,

cities in the United States

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began to follow suit. In March,

New York City shut down all but

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essential activities and

emissions dropped by 45%. 50 of

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the 61 analyzed cities show

nitrogen dioxide reductions

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between 20 and 50% — clearly

linking lower NO2 emissions

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to pandemic related

restrictions, and therefore

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human activity. This sudden

change in human behavior gives

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us new insights into the

relationship between human

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activities and air pollution,

which still has many unanswered

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scientific questions. The only

way we can fully understand air

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pollution is by combining

surface observations, satellite

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data and computer models. With

NASA's satellite monitoring system

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and computing capabilities, it's

uniquely positioned to provide

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detailed information about air

quality everywhere in the world.