Science

Air quality briefly improved in 2020 due to COVID lockdowns, UN agency confirms

The UN weather agency says the world — and especially urban areas — experienced a brief, sharp drop in emissions of air pollutants last year amid lockdown measures and related travel restrictions put in place over the coronavirus pandemic.

But World Meteorological Organization said pollutant levels still exceeded guidelines in many places

This combination of photos from Nov. 1, 2019, top, and April 20, 2020 shows New Delhi's skyline. India's air quality improved drastically during a nationwide lockdown to curb the COVID-19 coronavirus. The World Meteorological Organization said there was a brief, sharp drop in air pollution due to lockdowns around the world. (Manish Swarup/The Associated Press)

The UN weather agency says the world — and especially urban areas — experienced a brief, sharp drop in emissions of air pollutants last year amid lockdown measures and related travel restrictions put in place over the coronavirus pandemic.

The World Meteorological Organization, releasing its first ever Air Quality and Climate Bulletin on Friday, cautioned that the reductions in pollution were patchy — and many parts of the world showed levels that outpaced air quality guidelines. Some types of pollutants continued to emerge at regular or even higher levels.

"COVID-19 proved to be an unplanned air-quality experiment, and it did lead to temporary localized improvements," said Petteri Taalas, the WMO secretary-general. "But a pandemic is not a substitute for sustained and systematic action to tackle major drivers of both population and climate change and so safeguard the health of both people and planet."

WATCH | Before and after video shows impact of coronavirus lockdown on air quality in cities around the world:

Before and after video shows the impact of the coronavirus lockdown on air quality in various cities around the world

2 years ago
1:10
An unintended consequence of the coronavirus lockdown has been a noticeable improvement in air quality. Here's a look before and after the lockdown began in various cities around the world. 1:10

The WMO study analyzed changes in air quality around the main pollutants, including sulfur dioxide, nitrogen oxides, carbon monoxide and ozone. The Geneva-based agency noted an "unprecedented decrease" in pollutant emissions as many governments restricted gatherings, closed schools, and imposed lockdowns.

Oksana Tarasova, head of WMO's atmospheric environment research division, said the impact of such measures on major pollutants was short-lived. When measures to reduce mobility mean "there are no cars on the street, you see the improvement in air quality immediately. And of course, as soon as the cars go back on the street, you get the worsening back."

That compared to "long-lead greenhouse gases" behind global warming like carbon dioxide, whose atmospheric levels can take many years to change.

Nitrogen oxides, particulates see big drops

WMO cited declines of up to nearly 70 per cent in average levels of nitrogen oxides, which are largely emitted through transportation and burning of fossil fuels. It also noted up to 40 per cent drops — the biggest ones recorded in southeast Asia — of average levels of tiny particulate matter in the air during full lockdown measures last year, compared to the same periods from 2015 to 2019.

Mount Everest is viewed from Kathmandu Valley during the pandemic lockdown in 2020. Normally, it can't be seen due to smog. (Submitted by Abhusan Gautam)

Nitrogen oxides also destroy ozone in the air. Partially as a result of the drop in nitrogen oxides, ozone levels — which vary depending on location — remained flat or slightly increased in some places. Carbon monoxide levels fell in all regions, especially South America.

One conundrum for policy makers is that some pollutants like sulfur dioxide in the air actually help to cool the atmosphere, partially offsetting the impacts of climate change.

Tarasova said air quality was "very complex" and noted that events like wildfires in Australia, smoke from biomass burning in Siberia and the United States, and the "Godzilla effect" — in which sand and dust drift from the Sahara Desert across the Atlantic to North America — also had effects on air quality last year.

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