Catch 22: How cutting pollution heats up the planet
STORY: Air pollution kills millions of people globally each year...
but experts say efforts to clean the air - may actually speed up climate change.
It's an unintuitive finding that scientists found...
...after poring over the results of China's decade-long 'war on pollution'.
Six leading climate experts, say its highlighted what amounts to a catch-22.
The drive to banish sulphur dioxide from the atmosphere has saved thousands of lives...
but it has also removed an effective shield against the sun's heat... albeit a toxic one...
“We're actually heating the planet by improving the air quality..."
Yangyang Xu is a climate scientists at Texas A&M University:
“Sulfur (dioxide) pollution works like particles in the atmosphere. They reflect sunlight, just like typical sunscreen.”
President Xi Jinping pledged to tackle air pollution when he took power in 2012..
following decades of coal burning that had made China the so-called "factory of the world.''
Under new rules, power plants and steel mines were forced to switch to lower-sulphur coal.
Hundreds of inefficient factories were shuttered, and vehicle standards toughened up.
The measures worked.. China's emissions plummeted 87% between 2013 and 2021 to 2.7 million metric tons.
But the drop in pollution was accompanied by a leap in warming.
Since 2014, China's average temperatures have gone up by 0.7 degrees Celsius, according to a Reuters review of meteorological data and scientists interviewed.
In fact, scientists say the removal of air pollution may have had a greater effect on temperatures in some industrial Chinese cities over the last decade than the warming from greenhouse gases themselves.
Venkatachalam Ramaswamy is the director of the Geophysical Fluid Dynamics Laboratory at the U.S. National Oceanic and Atmospheric Administration:
"You know, the floods observed in region X, is that due to the sulfate reduction? Heat waves observed in region Y, is that due to sulfate (reduction)? It probably is. It probably is a causal factor. But exactly how they are related, how the mechanisms play out, this is still something that the scientists are still trying to tease out."
China's environment ministry didn't immediately respond to a request for the comment.
The problem is not unique to China, though.
Other highly polluted parts in the world, like India and the Middle East, could see similar jumps in warming if they clean up their skies.
So what's the answer?
One proposal, known as 'solar radiation management', envisions deliberately injecting sulphur aerosols into the atmosphere to cool temperatures,
but many scientists worry that could unleash unintended consequences.
A more mainstream plan is to curb methane emissions.
This is seen as the quickest way to tame global temperatures because the effects of the gas in the atmosphere last only a decade or so.
While more than 100 countries have pledged to reduce methane emissions by 30% by the end of the decade,
few have gone further than drawing up "action plans" and "pathways" to cuts.
China - the world's biggest emitter - has yet to publish its plan.
