Recent news show evidence that the global state of public health emergency associated with COVID 19 may have contributed to a decrease in air pollution. Satellite images from India, China, Italy and other countries show steep declines in the concentration of atmospheric pollutants. Yet, these data should be analyzed with caution since it mainly refers to nitrogen oxides (NOx – gases produced through combustion of fuels such as gasoline).
These pollutants, whose atmospheric concentrations have declined since the beginning of the lockdown, are short-lived, that is, they stay in the atmosphere for a short period of time and influence the local weather in a city or urban area where they are released. Once in the atmosphere, NOx contribute to acid rain and the formation of ground-level ozone. This type of ozone should not be confused with the ozone layer in the stratosphere that protects us against UV radiation. In lower regions of the atmosphere, ozone is a highly oxidative gas that can react with other particles forming a toxic cloud known as smog.
Particles in suspension in the atmosphere, such as dust, soot and volatile compounds, are small, less than PM10 or even PM2.5 (i.e. particles of less than 10 or 2.5 micrometers per cubic meter) and consequently can be inhaled through the respiratory system. According to State of Flobal Air 2018, more than four million deaths per year at a global scale are related to respiratory issues associated with these particles.
What about carbon dioxide CO2?
In contrast with short-lived pollutants, CO2, methane CH4 and nitrous oxide N2O can remain in the atmosphere for decades or more. Approximately 2.4 trillions of tones of CO2 were released to the atmosphere between 1850 and 2019, after the industrial revolution. Of these, 40% accumulated in the atmosphere and the remaining 60% were sequestrated in the oceans and by biosphere. According to Carbon Brief, just the year of 2019 corresponded to 45 Gton of CO2 releases.
What can we expect from 2020 taking into account COVID 19 lockdown?
Not a large difference from previous years regarding CO2. Instead of the predicted 43 Gton, this year the releases will be around 40 Gton, corresponding to 5 to 7% decline comparing to 2019.
As expected, the lockdown has not been enough to stop the loss of sea ice in the poles, according to a study published in Geophysical Research Letters, where scientists examined the sea ice loss in the Arctic based on 40 climate models. They concluded that the Arctic might be completely sea ice free in September before 2050, because as discussed, persistent gases will remain in the atmosphere.
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Author: Ricardo Ramos
