REDUCING the amount of soot and methane released into the atmosphere could slow the world's warming by half a degree, save millions of lives, and dramatically improve global air quality, a study has found.
A group of international scientists claim 14 practical methods could reduce the pollutants, which not only contribute to global warming but also kill or debilitate millions of people each year, and increase global crop yields at the same time.
While much focus has been placed on reducing carbon dioxide emissions, methane – a powerful greenhouse gas – and black soot play a role in man-made global warming and are a significant source of air pollution.
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By screening more than 400 tried-and-tested soot and methane pollution reduction processes being used on a small scale around the world, the team, led by NASA scientist Drew Shindell, came up with a list of approaches to improve air quality and reduce global warming that could be implemented on a regional and global scale.
Changes to coal mining and natural gas extraction combined with better landfill and livestock management would reduce global methane, while improvements to diesel engines, replacing wood and dung fires with modern stoves and banning agricultural burning would lower soot emissions.
To measure the impact these pollution reduction methods could have on global warming, the team added the controls to computer models using two future emissions scenarios – one based on business as usual, where carbon emissions were not constrained, and one based on a low-carbon world.
The results show global temperature could be decreased by half a degree by 2050.
And, in a low-carbon world, the soot and methane reductions would keep the world's thermostat below the danger level of 2 degrees warming.
Lower methane levels would avoid annual crop losses of between 30 million and 137 million tonnes in 2030, while soot reductions would prevent between 700,000 and 4.7 million premature deaths a year.
"Methane emission reductions are valued at $700 to $5000 per metric tonne, which is well above the typical marginal abatement costs, [of about] $250," they said.
An atmospheric chemist at the CSIRO said that, scientifically, the research was "a very strong piece of work".
Melita Keywood, a principal research scientist at CSIRO Marine and Atmospheric Research, said: "The measures are the sort of things that can be done now, and can have a short-term consequence which will really appeal to policymakers."