Lower air pollution has little effect on global warming: Study


With lockdowns around the world, road traffic had declined, leading to lower levels of pollution. PHOTO | FOTOSEARCH

The coronavirus, in relation to global climate, seemed like a blessing in disguise when lockdowns were imposed in most countries.

By April, reports indicated that greenhouse gas emissions had reduced by about 17 per cent compared to last year.

That was as a result of reduction in emissions, which were previously fuelled by human and industrial activities. With lockdowns, people stayed at home and travelled less and this led to lower air pollution.

But, a new study has found the lockdowns and resultant lower pollution levels have very little effect on global warming.

In the study, published in the journal Nature, the researchers say by 2030, the world will only be cooler by an estimated temperature of 0.01 degrees Celsius.

Researchers Piers Forster, a professor of Physical and Climate Change at the University of Leeds and Harriet Forster, using trends from Google’s mobility data and Apple, learnt that, “mobility declined by 10 per cent or more during April 2020 in all but one of the 125 nations tracked". Using satellite data and local ground based observations, their report points out that, “the large pollution declines are expected to be temporary as pollution levels are already returning to near-normal in parts of Asia".

The study, conducted between February and June, tracked emission changes of greenhouse gases in a bid to foresee what the future would look like. “We examine the temperature response of a direct recovery to pre-Covid-19 national policies and emission levels, and also explore responses where the economic recovery to Covid-19 is driven by either a green stimulus package or an increase in fossil fuel use," says the report.


A direct effect has been reported from road travel, which causes the burning of fuels that emit gases such as nitrogen oxides and carbon dioxide. Nitrogen Oxide is said to have reduced by 30 per cent. That drop contributes to a short term cooling of about 0.01 degrees Celsius until 2025. Its effect to global warming is not as much as that of Carbon dioxide, which contributes about 99 per cent global emissions.

However, when climate change sensitisation is ignored and countries live as they used to before Covid-19, it is estimated that the warming effect by 2050 will go beyond 1.5 degrees Celsius. When the opposite of that is embraced, that the world goes the green stimulus way with climate policies enforced in countries, about 0.3 degrees Celsius of future global warming will not take place by 2050.

“These results highlight that without underlying long-term system-wide decarbonisation of economies, even massive shifts in behaviour, only lead to modest reductions in the rate of warming," say the researchers.

“This suggests that policies directed at limiting pollution from road transport could offset the short-term warming that might come from policies that reduce pollution from the power and industry sector. Therefore, we recommend that policies are enacted to cut pollution from all three sectors at the same time."