<p>Satellite images by NASA and the European Space Agency have shown a significant decline in pollution levels over China, partly due to the economic slowdown following the deadly coronavirus outbreak, the US space agency has said.</p>.<p>The pollution monitoring satellites of the space agencies detected significant decreases over China in nitrogen dioxide (NO2), a noxious gas emitted by motor vehicles, power plants, and industrial facilities, NASA said in a statement.</p>.<p>In January, Chinese authorities had shut down transportation going into and out of Wuhan, as well as local businesses, in order to reduce the spread of the new coronavirus (COVID-19).</p>.<p>It was the first of several quarantines set up in the country and around the world, according to NASA.</p>.<p>The virus has so far killed over 3,000 people and infected more than 88,000 globally after the outbreak in China in December last year.</p>.<p>Maps created using data from NASA and ESA satellites show NO2 values across China from January 1-20 (before the quarantine) and February 10-25 (during the quarantine).</p>.<p>The data were collected by the Tropospheric Monitoring Instrument (TROPOMI) on ESA's Sentinel-5 satellite.</p>.<p>A related sensor, the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite, has been making similar measurements.</p>.<p>According to NASA scientists, the reduction in NO2 pollution was first apparent near Wuhan but eventually spread across the country.</p>.<p>"This is the first time I have seen such a dramatic drop-off over such a wide area for a specific event," said Fei Liu, an air quality researcher at NASA's Goddard Space Flight Center.</p>.<p>Liu recalls seeing a drop in NO2 over several countries during the economic recession that began in 2008, but the decrease was gradual.</p>.<p>Scientists also observed a significant reduction around Beijing during the 2008 Olympics, but the effect was mostly localised around that city, and pollution levels rose again once the Olympics ended.</p>.<p>The drop in nitrogen dioxide in 2020 also coincided with Lunar New Year celebrations in China, and much of Asia, according to NASA.</p>.<p>Generally, businesses and factories close from the last week in January into early February to celebrate the festival.</p>.<p>Past observations have shown that air pollution usually decreases during this period and then increases once the celebration is over, NASA said.</p>.<p>"There is always this general slowdown around this time of the year," said Barry Lefer, an air quality scientist at NASA.</p>.<p>"Our long-term OMI data allows us to see if these amounts are abnormal and why,"Lefer said.</p>.<p>Launched in 2004, OMI has been collecting global data on NO2 and various air pollutants for more than 15 years.</p>.<p>The maps show NO2 values over three periods in 2020: January 1-20 (before Lunar New Year), January 28-February 9 (around New Year celebrations), and February 10-25 (after the event).</p>.<p>The 2020 values were compared to the same periods in 2019 for reference.</p>.<p>Lefer noted that the overall values in 2020 were lower than 2019 due to new environmental regulations that China has enforced over the past few years.</p>.<p>While the Lunar New Year may have played a role in the recent dropoff, researchers believe the decrease is more than a holiday effect or weather-related variation.</p>.<p>In a preliminary analysis, NASA researchers compared NO2 values detected by OMI in 2020 with the average amounts detected at this time of year from 2005-2019.</p>.<p>In 2020, NO2 values in eastern and central China were significantly lower -- from 10 to 30 per cent lower -- than what is normally observed for this time period.</p>.<p>Liu and colleagues have not seen a rebound in NO2 after the holiday.</p>.<p>"This year, the reduction rate is more significant than in past years and it has lasted longer," she said.</p>.<p>"I am not surprised because many cities nationwide have taken measures to minimise the spread of the virus," Liu added.</p>
<p>Satellite images by NASA and the European Space Agency have shown a significant decline in pollution levels over China, partly due to the economic slowdown following the deadly coronavirus outbreak, the US space agency has said.</p>.<p>The pollution monitoring satellites of the space agencies detected significant decreases over China in nitrogen dioxide (NO2), a noxious gas emitted by motor vehicles, power plants, and industrial facilities, NASA said in a statement.</p>.<p>In January, Chinese authorities had shut down transportation going into and out of Wuhan, as well as local businesses, in order to reduce the spread of the new coronavirus (COVID-19).</p>.<p>It was the first of several quarantines set up in the country and around the world, according to NASA.</p>.<p>The virus has so far killed over 3,000 people and infected more than 88,000 globally after the outbreak in China in December last year.</p>.<p>Maps created using data from NASA and ESA satellites show NO2 values across China from January 1-20 (before the quarantine) and February 10-25 (during the quarantine).</p>.<p>The data were collected by the Tropospheric Monitoring Instrument (TROPOMI) on ESA's Sentinel-5 satellite.</p>.<p>A related sensor, the Ozone Monitoring Instrument (OMI) on NASA's Aura satellite, has been making similar measurements.</p>.<p>According to NASA scientists, the reduction in NO2 pollution was first apparent near Wuhan but eventually spread across the country.</p>.<p>"This is the first time I have seen such a dramatic drop-off over such a wide area for a specific event," said Fei Liu, an air quality researcher at NASA's Goddard Space Flight Center.</p>.<p>Liu recalls seeing a drop in NO2 over several countries during the economic recession that began in 2008, but the decrease was gradual.</p>.<p>Scientists also observed a significant reduction around Beijing during the 2008 Olympics, but the effect was mostly localised around that city, and pollution levels rose again once the Olympics ended.</p>.<p>The drop in nitrogen dioxide in 2020 also coincided with Lunar New Year celebrations in China, and much of Asia, according to NASA.</p>.<p>Generally, businesses and factories close from the last week in January into early February to celebrate the festival.</p>.<p>Past observations have shown that air pollution usually decreases during this period and then increases once the celebration is over, NASA said.</p>.<p>"There is always this general slowdown around this time of the year," said Barry Lefer, an air quality scientist at NASA.</p>.<p>"Our long-term OMI data allows us to see if these amounts are abnormal and why,"Lefer said.</p>.<p>Launched in 2004, OMI has been collecting global data on NO2 and various air pollutants for more than 15 years.</p>.<p>The maps show NO2 values over three periods in 2020: January 1-20 (before Lunar New Year), January 28-February 9 (around New Year celebrations), and February 10-25 (after the event).</p>.<p>The 2020 values were compared to the same periods in 2019 for reference.</p>.<p>Lefer noted that the overall values in 2020 were lower than 2019 due to new environmental regulations that China has enforced over the past few years.</p>.<p>While the Lunar New Year may have played a role in the recent dropoff, researchers believe the decrease is more than a holiday effect or weather-related variation.</p>.<p>In a preliminary analysis, NASA researchers compared NO2 values detected by OMI in 2020 with the average amounts detected at this time of year from 2005-2019.</p>.<p>In 2020, NO2 values in eastern and central China were significantly lower -- from 10 to 30 per cent lower -- than what is normally observed for this time period.</p>.<p>Liu and colleagues have not seen a rebound in NO2 after the holiday.</p>.<p>"This year, the reduction rate is more significant than in past years and it has lasted longer," she said.</p>.<p>"I am not surprised because many cities nationwide have taken measures to minimise the spread of the virus," Liu added.</p>