Sooty clouds cause climate meltdown
3 August 2007
We know the planet's hotting up, and now scientists have discovered a new climate-change culprit. Sooty clouds over Asia are causing as much local warming as nasty greenhouse gases. Antenna finds out more...
This research was published in the journal Nature on 2 August 2007.
Brown clouds over Asia as seen from space.
Image: NASA
Diesel engines and biomass fuels such as dung and wood produce dirty brown smoke full of soot. As this drifts skywards it makes the clouds sooty and brown too.
Now scientists are warning that these sooty clouds could be adding to climate change on a local scale. They've been tracking the brown clouds over Asia to try and investigate the scale of the problem.
Brown clouds like this form over large parts of Asia during the dry season in the hottest months of the year.
Image: Hung Nguyen, UCSD
Up in the clouds...
The team sent three mini unmanned planes over the Indian Ocean to measure the amount of sooty particles in the air and the levels of sunlight above, within and below the brown clouds.
The planes are small but laden with all the kit they need.
Image: UCSD
They found that as levels of sooty particles increased, the atmosphere heated up more. The particles absorbed enormous amounts of sunlight, causing solar heating in the lower atmosphere to increase by half as much again.
By combining their results with the latest climate models the scientists discovered that sooty clouds could be as much to blame as greenhouse gases for the warming of the lower atmosphere in Asia. Satellites snaps show that these brown clouds stretch all the way up to the Himalayas.
The Asian Himalayas are the highest mountain range in the world, but their snowy peaks are rapidly melting.
Image: Foundation for Ecological Security, India
Lead scientist V Ramanathan explains: 'Many climate scientists think that the large-scale melting of the Himalayan glaciers is due to global warming from greenhouse gases; our study shows there may be yet another gorilla in the form of brown clouds which are contributing as much to the warming of this area.
'While this finding is disturbing, it offers a hope for mitigating some of these problems... by reducing emissions of sooty particles,' he says.
Chief scientist V Ramanathan, University of California, San Diego.
Image: UCSD
At the moment, large areas of Asia appear affected by the brown clouds. But with worldwide populations on the up, this pollution problem could become widespread. So do other experts think we're in trouble?
'These are very interesting results,' says atmospheric scientist Peter Pilewskie. 'But because these particles aren't distributed equally throughout the globe it's difficult to say what the global implications of these findings are. This is one of the reasons that the effect of sooty particles on climate change is still highly uncertain.
'However, these findings do emphasise the need to reduce the amount of carbon soot produced in combustion processes,' he says. 'Although there are "cleaner" processes out there, these still produce carbon dioxide and other greenhouse gases which also cause climate change. At the moment there is no simple solution.'
Peter Pilewskie, Colorado University, USA
Image: Colorado University, USA
The warning is clear: we need to find cleaner, greener fuels if we are to stand any chance of mitigating climate change.
