White clouds over ocean can stop global warming: Study

The Indian Express , Wednesday, July 21, 2010
Correspondent : Agencies
Whiter clouds over oceans could stop global warming and bring more rains to the land, according to a recent study.

“Clouds reflect sunlight and cool the planet. Clouds with bigger droplets tend to be darker and clouds with tiny droplets for the same amount of water are whiter. If the droplet number in the clouds is increased, the reflectivity increases and it will increase rainfall on land and also slow down global warming,” Prof Govindasamy Bala, the lead author of the study from Indian Institute of Science (IISC),Bangalore told PTI today.

“Reducing the droplet size and thus increasing the reflectivity is the basic mechanism behind the proposal for whitening the marine clouds to counteract global warming,” Bala said.

The new climate modelling study by the IISC, in collaboration with the Carnegie Institution, Stanford University, and NASA-AMES, California suggested that altered atmospheric circulation under the scheme could create a monsoonal circulation and cause the continents to become wetter, not drier, on average.

The study is reported in the latest issue of the journal ‘Climate Dynamics’ titled ‘Albedo enhancement of marine clouds to counteract global warming: impacts on the hydrological cycle.’ When asked how can the number of marine cloud droplets be increased, Bala, from Divecha Center for Climate Change and Center for Atmospheric and Oceanic Sciences at the IISC said, “This can be done by spraying tiny droplets of sea water into the marine atmosphere. The salt particles in sea water serves as seeds for many tiny cloud droplets,” Bala said.

“For uniform reductions in sunlight over land and oceans, our earlier modelling work showed that the planet could become drier.” “However, when you selectively reduce the sunlight over only the ocean surface by whitening only the marine clouds (which we have done in the current model), a monsoonal circulation is triggered which increases the rainfall over land. We find an increase of 7.5 per cent in the overall water budget over land,” Bala said.

To test the climate consequences of doing this, Bala and his co-authors used a computer simulation of the global climate system in which atmospheric carbon dioxide concentrations were set at approximately twice that of present-day.

Cloud droplets over the oceans in the model were reduced to make the clouds more reflective. Clouds over land were unaltered.

“As expected, the whitened clouds reflected more solar radiation and offset the warming effect of the high carbon dioxide levels,” Bala said.

 
SOURCE : http://www.indianexpress.com/news/white-clouds-over-ocean-can-stop-global-warming-study/649358/2
 


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