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[Henk Vreekamp]

New light-reflecting particles could cool Earth and fix the ozone layer  
====================== 
Honouring the commitments made at last year's historic Paris climate 
deal will take a huge international effort to lower carbon emissions - 
but scientists say there's another way we can help reduce rising global 
temperatures at the same time.  
  
In a process called solar geoengineering, light-reflecting particles 
could be introduced into Earth's stratosphere to bounce the Sun's rays 
back into space and keep the planet cooler. While this controversial 
concept has been discussed for decades, the risks of geoengineering have 
kept the research largely sidelined - but now researchers say they might 
have a way of making it safe.  
  
Solar geoengineering usually refers to dispersing sulphate aerosols into 
the stratosphere. This naturally occurs during volcanic explosions, 
where the particles reflect sunlight and have a cooling effect on the 
planet. But the problem with sulphate aerosols is that they produce 
sulphuric acid in the stratosphere, which damages the ozone layer. 
  
But now, looking for particles capable of neutralising sulphuric, 
nitric, and hydrochloric acid on their surface, researchers from Harvard 
University discovered that calcite was what they needed, as it can 
convert the acids into stable salts. Mimicking stratospheric conditions 
in lab experiments, the team says that calcite can indeed reflect light 
while countering ozone loss - and its abundance on Earth would also make 
it a practical resource for geoengineering.  
  
But despite the promising new lead, the team says a huge amount of 
additional research needs to be done. The potential dangers of a botched 
geoengineering endeavour aren't to be understated - it even ranked as a 
high-risk environmental threat on a list of global catastrophic risks 
published earlier this year. 

Science Alert - December 14, 2016 
 http://www.merit.unu.edu/itweekly/ref.php?nid=5791 

  
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