Computer models of Earth's atmosphere can tell us a lot.
Trained on how the atmosphere typically operates, the models
take in data about temperature, wind speed, humidity, and more
to give us important insights into the world around us.
Computer models like NASA's GEOS model can help us study how
chemicals move through the atmosphere, how the ocean
circulates, and where air quality might be affected by fires and
pollution. These models can also provide a look at what might
have been if circumstances were different. For instance, climate
models can forecast how temperatures might change with
different levels of carbon emissions. In 2020, the world
threw the models a new test when people began behaving very,
very differently with almost no warning, a global pandemic
set in. Around the globe, people stopped driving and
flying in large numbers, started staying home, and completely
changed their pollution patterns. In particular
emissions of nitrogen dioxide, a common air pollutant released by
cars, airplanes and many factories, declined
significantly. But just how much did the shutdown change our
emissions? NASA\'92s GEOS atmospheric composition model offers an
answer. The model run functions by assuming that nothing was
different in 2020, that people continued behaving roughly the
same as they would have with no activity shutdowns, adding the
same number of atmospheric pollutants to the air. It's then
a matter of subtraction. Comparing those models to real
world observations made by satellites during the shutdowns
shows how significant the decrease in pollution was in
various cities. Activity shutdowns started in Wuhan,
China. And in January, observed emissions of nitrogen dioxide
began to diverge from what models predicted, about 60% less
than predicted, that is. As the virus and the associated
shutdowns moved west, European cities began to experience
decreased levels of nitrogen dioxide emissions as well. in
Madrid, Spain, nitrogen dioxide emissions were also 60%
less than modeled. Shortly after, cities in the United States
began to follow suit. In March, New York City shut down all but
essential activities and emissions dropped by 45%. 50 of
the 61 analyzed cities show nitrogen dioxide reductions
between 20 and 50% \'97 clearly linking lower NO2 emissions
to pandemic related restrictions, and therefore
human activity. This sudden change in human behavior gives
us new insights into the relationship between human
activities and air pollution, which still has many unanswered
scientific questions. The only way we can fully understand air
pollution is by combining surface observations, satellite
data and computer models. With NASA's satellite monitoring system
and computing capabilities, it's uniquely positioned to provide
detailed information about air quality everywhere in the world.