Improved air quality

By 27 May 2020June 3rd, 2020No Comments

We highlight some early indications of the effects of the pandemic on air pollution.

Analysis of world-wide data by the UK-based website Carbon Brief has suggested that the coronavirus pandemic could result this year in cuts in emissions of carbon dioxide (CO2) in the region of 2,000 million tonnes, equivalent to around 5.5% of the current global total. This would trigger the largest annual fall in CO2 emissions ever recorded – though still not enough to make much of an impact in bringing the 1.5C global temperature limit within reach.

It’s not just CO2 emissions which have plummeted. Other data sources reveal marked reductions in the principal pollutants of air, nitrogen dioxide (NO2) and particulate matter (PM), as well as bringing significant improvements in visibility.

Two of the world’s most populous and polluted nations – China and India – have experienced some of the sharpest falls in air pollution. But it is perhaps inevitable that those areas with existing high levels of pollution, in these countries and elsewhere, seem to be the worst hit by high rates of virus infection.

In Europe, measures to reduce the rate of infection have led to a 40% reduction in the average level of NO2 and a 10% reduction in PM pollution during the month of April compared with March. These measures will have avoided more than 10,000 deaths from air pollution, most notably in Germany, the UK, Italy, France and Spain: a substantial number, but unfortunately insignificant in the context of the European death toll from the virus. This effect comes as power generation from coal and oil combustion – still the main sources of NO2 and PM pollution across much of Europe – has fallen by 30% or more. The marked decrease in NO2 hot spots (shown dark on these satellite images) is already apparent at the end of March 2020.

A similar effect has been seen in London, despite a delay in introducing lockdown.

Statistics compiled by Defra indicate that other UK cities, such as Brighton and Portsmouth, have seen NO2 levels fall by more than 60%.
As it takes several weeks to gather data and generate reliable results from manually operated NO2 diffusion tubes and particulate monitors, the only sources of data available for the current period in the Borough of Merton are the two automated stations monitored by Kings College, University of London. In order to allow for variable seasonal weather effects, data in 2020 has been compared with the same period in 2019 (see charts below).

Although the 2020 data has yet to be fully verified, a noticeable reduction in NO2 levels is apparent since mid-March, probably because this pollutant is produced primarily by vehicle exhausts, and traffic across the borough has decreased considerably in recent weeks. The picture for PM is less clear over such a limited timescale, but no doubt it will be clarified as more data is gathered in the coming months.

The Covid-19 crisis will doubtless be pivotal in influencing future environmental and sustainability pathways around the world. Our value systems will of necessity change, hopefully for the better. However, we will need to ensure that these new pathways are truly sustainable and do indeed lead to the desired outcomes of improved society, environment and economy.

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