It took no time for countries under quarantine to see energy use plummet, and with it, pollution levels.
However, even as citizens of Los Angeles and Jalandhar exuberantly posted photos of the Hollywood sign and the Himalayas visible without smog for the first time in decades, climate scientists warned the dramatic drop in emissions would do little if anything to slow the pace of global warming.
New measurements of atmospheric carbon dioxide released on Thursday (June 4) from the Scripps Institution of Oceanography at the University of California, San Diego confirm that prediction.
As expected, CO2 levels reached a new record in May: 417.2 parts per million gas molecules in the atmosphere, continuing a trend that's gone unbroken for six decades.
That's 2.4 ppm above the reading for May 2019, which matches the average annual increase for 2010-2019.
The US National Oceanic and Atmospheric Administration registered a similar 417.1 ppm.
The concentration of carbon dioxide in the atmosphere isn't a direct measure of industrial emissions.
What's left in the air is slightly less than half of total emissions, with the rest drawn down by plants on land and the ocean itself.
Before the industrial age, atmospheric CO2 stood at 280 ppm.
Geological evidence suggests concentrations haven't been as high as they are today in at least three million years.
Nothing has vaporised carbon at this rate-or even a tenth of this rate-since a meteor ended the dinosaurs' reign 66 million years ago.
The vast amounts of CO2 are turning the oceans acidic more quickly than at any point going back an estimated 300 million years.
The Global Carbon Project, an international research collaboration, estimated the previous month that CO2 emissions may fall 4 per cent in 2020 if Covid-19 restrictions are lifted this summer, or as much as 7 per cent if they persist through year-end.
"Although the fall in emissions is massive, on its own it does nothing to slow climate change," said professor of climate science Corinne Le Quéré of the University of East Anglia, about the Project's 2020 estimate the previous month.
"However, government actions now could make a huge difference."
To move the global energy system onto a footing consistent with the Paris Agreement's most aggressive limit of a 1.5 degrees Celsius temperature rise, the UN Environment Programme reported last fall, the world needs to slash emissions 7.6 per cent per year through 2030.