Researchers using an array of satellite observations discovered that the effect of air pollution on climate has dropped by up to 30% from 2000 levels, Science reported.
Although this is positive for public health, it's bad for global warming or climate change, Science observed.
The cleaner air has effectively boosted the total warming from carbon dioxide emitted over the same time from 15% to 50%, according to Johannes Quaas, a climate scientist at Leipzig University, who conducted the research.
Quaas' new research emerged from last year’s U.N. climate assessment, Science reported. It shows aerosol declines in North America and Europe but no clear global trends. Quaas and his co-authors thought two NASA satellites, Terra and Aqua, operating since 1999 and 2002, could help, Science reported.
But one instrument on Aqua and Terra has also shown a decline in reflected light. Models suggested a decrease in aerosols is partly responsible.
From 2000 to 2019, haze over North America, Europe, and East Asia declined, although it continued to thicken over India, which is coal-dependent. Quaas and researchers found a clear decrease in cloud droplet concentrations in the same regions where aerosols declined.
It will grow as air quality continues to improve around the world, Science observed. The answer isn’t to keep polluting, said Jan Cermak, a remote-sensing scientist at the Karlsruhe Institute of Technology.
“Air pollution kills people," Cermak said. "We need clean air."
Instead, efforts to reduce greenhouse gases need to be redoubled, he says, as the Earth warms each year.
"I believe their conclusions are correct," said James Hansen, a retired NASA climate scientist, Science reported.
Hansen said it’s impressive scientific detective work because no satellite could directly measure global aerosols over this whole period.
"It's like deducing the properties of unobserved dark matter by looking at its gravitational effects," he said.
Hansen expects there will be follow-up work as researchers seek to quantify the boost to warming.