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Thursday, September 24, 2020

Explained: To what extent did the Covid-19 lockdown affect global temperatures?

The researchers said a reduction in GHG emissions and air pollutants was observed as countries started imposing lockdowns on their residents and restricting their movement.

Written by Mehr Gill , Edited by Explained Desk | New Delhi | Updated: August 11, 2020 9:38:47 am
covid-19 pandemic, coronavirus latest news, covid impact on climate, covid-19 lockdown affect global temperatures, greenhouse gas emissions, nature climate change, express explained, indian express Researchers claimed that the dip is expected to be temporary since pollution levels are already returning back to normal levels in many parts of Asia. (File Photo)

It is well known that Covid-19 enforced lockdowns in several countries has led to a dip in greenhouse gas (GHG) emissions and air pollution. Now, in a study published in Nature Climate Change on August 6, researchers from University of Leeds and University of York have analysed global emissions reductions from February-June 2020 and made a prediction of the change in global temperatures.

What does the study say?

The researchers said a reduction in GHG emissions and air pollutants was observed as countries started imposing lockdowns on their residents and restricting their movement.

Referring to mobility data from Google and Apple, they maintained that a drop in mobility of about 10 per cent was observed in all but one among the 125 countries tracked by them. They observed a mobility reduction of as much as 80 per cent in five or more nations.

Further, mobility data from Google and Apple points out that more than 50 per cent of the world’s population reduced travel by more than half during April 2020. In fact, Google mobility trends indicate that more than 80 per cent of the population in 114 countries (approximately 4 billion people) reduced their travel by more than 50 per cent.

So are the dips in pollution levels permanent?

That does not seem to be the case. Researchers claimed that the dip is expected to be temporary since pollution levels are already returning back to normal levels in many parts of Asia.

However, considering that social distancing measures will be the new normal for another two years, the researchers assume that decrease in emissions may remain at about 66 per cent of their June 2020 levels by the end of 2021.

A study published in late June said while Covid-19 lockdowns cleaned up the air as a plethora of economic activities were brought to a standstill, pollution from ozone shot up during this time. This is because ozone pollution is known to increase in the warmer months and builds up in cleaner areas.

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How does this affect temperatures?

As per the study, a decline in nitrogen oxide (NOx) levels by as much as 30 per cent will contribute to a short-term cooling of up to 0.01 degrees Celsius over the period 2020-2025 “almost exclusively from reductions in tropospheric ozone”.

But overall, the effect of the immediate Covid-19 related restrictions is close to “negligible and lasting effects, if any, will only arise from the recovery strategy adopted in the medium term”, the study said.

“These results highlight that without underlying long-term system-wide decarbonization of economies, even massive shifts in behaviour, only lead to modest reductions in the rate of warming,” it said.

What are the limitations of using Google and Apple mobility data?

One limitation is of how representative this data is of wider national behaviour, since the usage and penetration of phones will vary across countries and regions.

For instance, the study mentions that while more than an 80 per cent decline was observed in Apple driving mobility in India, this may not be the whole picture since it probably represents that section of the population that is able to work from home. Therefore, the estimates based on this data should be seen as an overestimation of the Covid-19 induced emissions change.

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