Climate change: Brown haze spells bad news



The haze of air pollution over the Indian Ocean may be causing as much lower atmospheric warming as the recent increase in anthropogenic greenhouse gases.
During 18 missions, Veerabhadran Ramanathan and colleagues simultaneously flew three lightweight unmanned aerial vehicles below, into and above the polluted ‘Brown Clouds’ over the Indian Ocean. Tiny instruments were deployed to measure aerosol concentrations, soot amount and solar fluxes, allowing the team to calculate atmospheric solar heating rates. Using model simulations, they conclude that atmospheric Brown Clouds enhance lower atmospheric solar heating by around 50 per cent.
Atmospheric Brown Clouds consist of a mixture of light-absorbing and light-scattering aerosols and so contribute both to atmospheric solar heating and to surface cooling. The combined effects are thought to have masked up to 50 per cent of the global warming attributed to the recent, rapid rise in greenhouse gases. This study helps to tease out the effects of atmospheric solar heating.
CONTACT
Veerabhadran Ramanathan (University of California San Diego, La Jolla, CA, USA)
Tel: +1 858 337 3114; E-mail: vram@fiji.ucsd.edu or vraman000@hotmail.com

Peter Pilewskie (University of Colorado Boulder, CO, USA) N&V author
Tel: +1 303 492 5724; E-mail: peter.pilewskie@lasp.colorado.edu