Pandemic restrictions reduced aerosols' 'masking' effect, led to more warming

A new research has found that Covid pandemic restrictions led to stronger climate warming.

The study from Stockholm University, Sweden, said that this was because the restrictions reduced the aerosol content in the air mass over South Asia, mainly Pakistan, India and Bangladesh, but had no effect on the concentrations of the longer-lived greenhouse gases.

A lower aerosol content meant less cooling, because of less reflection of incoming solar radiation back into space, and thus less 'masking' of the warming effect of the significantly longer-lived climate gases.

Measurements taken at the same time over the northern Indian Ocean revealed a 7 per cent increase in solar radiation reaching the Earth's surface, thus increasing temperatures. Measurements were taken at Hanimaadhoo, a measuring station in the northernmost Maldives off the coast of India.

The results published in NPJ Climate and Atmospheric Science showed that a complete phasing out of fossil fuel combustion in favour of renewable energy sources with zero emissions could result in rapid 'unmasking' of aerosols, while greenhouse gases linger.

In the spring of 2020, pandemic restrictions significantly reduced industrial activity and transportation worldwide, both of which are known to cause emissions of sulphur and nitrogen oxides and other air pollutants leading to aerosol formation.

The study said that the pandemic became a 'natural' experiment to examine what happens to the climate if gas and aerosol emissions were rapidly reduced.

"Through this large-scale geophysical experiment, we were able to demonstrate that while the sky became bluer and the air cleaner, climate warming increased when these cooling air particles were removed," said Orjan Gustafsson, professor at Stockholm University, lead researcher and responsible for the measurements in the Maldives.

"During a couple of decades, emission reductions risk leading to net climate warming due to the 'masking' effect of air particles, before the temperature reduction from reduced greenhouse gas emissions takes over. But despite an initial climate warming effect, we obviously still urgently need a powerful emission reduction," said Gustafsson.

The researchers said they have been measuring the atmospheric composition and radiation for soon two decades.

The measuring station is strategically placed to capture air masses from the Asian subcontinent and located in an area with few regional emission sources.