India’s first Covid-19 lockdown significantly improved air quality and lowered land surface temperatures, according to researchers from the University of Southampton and the Central University of Jharkhand.
Like neighboring China, India has long had major problems with air pollution: according to the air quality index, both Kolkata and Delhi are in the top ten most polluted cities in the world.
The new study found that travel and work restrictions imposed early in the pandemic resulted in significant environmental improvements, resulting from an abrupt reduction in industrial activities and a large decrease in the use of land and air transport.
The team used data from a range of Earth observation sensors, including those from the European Space Agency’s Sentinel-5p and NASA’s MODIS sensors, to measure changes in surface temperature and air pollutants and aerosols.
They focused on six major metropolitan areas: Delhi, Mumbai, Kolkata, Chennai, Bangalore and Hyderabad, comparing data from the March to May 2020 lockdown with the years before the pandemic.
Their findings revealed a significant reduction in nitrogen dioxide (NO2), a greenhouse gas emitted from the combustion of fossil fuels, representing an average reduction of 12 percent across India and 31.5 percent in the six cities.
There was a 40 percent reduction from the national capital New Delhi. In India alone, about 16,000 premature deaths occur each year due to exposure to poor air quality.
The study also found that land surface temperatures over major cities in India dropped significantly compared to the previous five-year average (2015-2019) with daytime temperatures up to 1°C cooler and nighttime temperatures up to 2°C cooler.Co-author Professor Jadu Dash, from the University of Southampton, said:
“The lockdown provided a natural experiment to understand the link between urbanization and local microclimate.
“We clearly established that reduction of air pollutants (by reducing anthropogenic activity during lockdown) resulted in a drop in local day and night temperatures, which is an important finding to take into account when planning for sustainable urban development.
” Along with surface temperature, atmospheric fluxes at the surface and top of the atmosphere also decreased significantly in much of India.
The reduction in greenhouse gas concentration, higher water vapor content in the atmosphere and meteorological conditions played a complex role in the reduction in temperature on land and near the surface.
Dr Gareth Roberts from the University of Southampton added: “Satellite instruments play a vital role in providing timely information about the Earth’s environment.
This study has illustrated the importance of Earth observation data for monitoring changes in air pollutants, which pose a significant health risk, and for highlighting the impact that anthropogenic activities have on regional air quality.
” OpenAQ that the average level of air pollution in the world’s largest cities is nearly four times higher than the maximum levels recommended by the WHO.