Did covid-19 lockdowns cause a rise in global temperatures?

·2-min read
Research reveals how covid-19 lockdowns appear to have temporarily raised global temperatures.

As surprising as it may sound, the lockdowns and reduced social activity caused by the covid-19 pandemic appear to have had a slight warming impact on the planet. Scientists from the US National Center for Atmospheric Research (NCAR) found that these events temporarily raised global temperatures and explain how and why this appears to have happened.

We already know that periods of lockdown reduced emissions of certain pollutants, which can only be a good thing. Yet research suggests that this phenomenon may, in fact, have contributed to temporarily increasing global temperatures. How could that be? Scientists from NCAR explain that lockdowns during the pandemic affected emissions of certain pollutants in ways that slightly warmed the planet for several months in 2020.

By way of explanation, the scientists describe how aerosols, or airborne particles, block incoming sunlight. As a result, more of the Sun's warmth was able to reach Earth in spring last year when emissions of aerosols dropped during periods of lockdown. This was particularly the case in heavily industrialized nations, such as the USA and Russia. More precisely, the study -- published in the journal, Geophysical Research Letters -- states that temperatures over parts of Earth's land surface were about 0.1 to 0.3 degrees Celsius warmer last spring than would have been expected.

"There was a big decline in emissions from the most polluting industries, and that had immediate, short-term effects on temperatures," said NCAR scientist Andrew Gettelman, the study's lead author. "Pollution cools the planet, so it makes sense that pollution reductions would warm the planet."

Pollution is, in theory, and very often, associated with global warming. And this remains true, even if the study highlights the complex and often conflicting influences of different types of emissions. The researchers explain that, while aerosols tend to reflect heat from the Sun back into space, carbon dioxide and other greenhouse gases do the opposite, trapping heat near the Earth's surface.

However, the scientists state that the pandemic could, in fact, have the more long-term effect of slowing down climate change slightly due to reduced carbon dioxide emissions. Indeed, carbon dioxide lingers in the atmosphere for decades and has a more gradual influence on the climate, whereas aerosols have a more immediate impact which fades after a few years.

And, as the study's lead author warns, "aerosol emissions have major health ramifications. Saying we should pollute is not practical."

Christelle Pellissier