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computer models of earth's atmosphere

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can tell us a lot trained on how the

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atmosphere typically operates the models

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take in data about temperature wind

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speed humidity and more to give us

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important insights into the world around

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us computer models like nasa's geos

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model can help us study how chemicals

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move through the atmosphere how the

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oceans circulate and where air quality

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might be affected by fires and pollution

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these models can also provide a look at

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what might have been if circumstances

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were different for instance climate

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models can forecast how temperatures

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might change with different levels of

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carbon emissions

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in 2020 the world through the models a

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new test when people began behaving very

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very differently with almost no warning

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a global pandemic set in

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around the globe people stopped driving

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and flying in large numbers started

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staying home and completely changed

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their pollution patterns in particular

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emissions of nitrogen dioxide a common

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air pollutant released by cars airplanes

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and many factories declined

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significantly

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but just how much did the shutdown

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change our emissions

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nasa's geos atmospheric composition

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model offers an answer

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the model run functions by assuming that

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nothing was different in 2020 the people

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continued behaving roughly the same as

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they would have with no activity

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shutdowns adding the same number of

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atmospheric pollutants to the air

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it's then a matter of subtraction

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comparing those models to real-world

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observations made by satellites during

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the shutdowns shows how significant the

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decrease in pollution was in various

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cities

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activity shutdowns started in wuhan

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china and in january observed emissions

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of nitrogen dioxide began to diverge

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from what models predicted about 60

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percent less than predicted that is as

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the virus and the associated shutdowns

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moved west european cities began to

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experience decreased levels of nitrogen

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dioxide emissions as well

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in madrid spain

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nitrogen dioxide emissions were also 60

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percent less than modeled

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shortly after cities in the united

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states began to follow suit

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in march new york city shut down all but

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essential activities and emissions

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dropped by 45

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50 of the 61 analyzed cities show

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nitrogen dioxide reductions between 20

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and 50 percent

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clearly linking lower no2 emissions to

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pandemic-related restrictions and

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therefore human activity

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this sudden change in human behavior

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gives us new insights into the

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relationship between human activities

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and air pollution

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which still has many unanswered

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scientific questions

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the only way we can fully understand air

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pollution is by combining surface

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observations satellite data and computer

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models

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with nasa's satellite monitoring system

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and computing capabilities it's uniquely

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positioned to provide detailed

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information about air quality everywhere