Coronavirus lockdowns led to a 20% reduction in global nitrogen dioxide concentrations.

That’s according to new research by NASA, which suggests the drop in nitrogen dioxide concentrations was largest in cities and ranged from between 20% and 60% reductions in 50 of the 61 urban centres which were analysed.

Nitrogen dioxide is a polluting gas composed of nitrogen and oxygen – it forms when fossil fuels, such as coal, oil, gas, or diesel are burnt at high temperatures.

Researchers used computer models to generate a Covid-free year for comparison with data from 5,756 observation sites on the ground in 2020.

Wuhan, in China, which was at the epicentre of the pandemic, was the first to show 60% lower nitrogen dioxide emissions than simulated values.

The report also showed a 60% decrease in Milan and a 45% decrease in New York as their local restrictions went into effect.

Lead Author Christoph Keller of the study said: “In some ways, I was surprised by how much it dropped.

“Many countries have already done a very good job in lowering their nitrogen dioxide concentrations over the last decades due to clean air regulations, but what our results clearly show is that there is still a significant human behaviour-driven contribution.”