Effect on global warming of wind-dependent aerosol generation at the ocean surface

Abstract

CONSIDERABLE effort is being devoted^1,2 to elucidating the influence of clouds on climate, and in particular to assessing the influence on global warming of modifications to cloud cover or microphysical characteristics. Such assessments are hindered by the present poor understanding of the many feedback processes involved. Here we demonstrate the existence of a negative feedback process in which an increase in wind speed (a possible result of atmospheric warming) produces, over oceanic regions, increased emissions of sea-salt aerosol particles, which subsequently act as cloud condensation nuclei. Activation of these nuclei could then significantly increase the number concentration of cloud droplets in marine stratus, thereby enhancing the albedo of these clouds for incoming short-wave radiation and so producing a cooling effect. Our calculations indicate that an increase in wind speeds of about 5–10 m s⁻¹ would produce an increase in cloud albedo² sufficient to compensate for predicted levels of global warming.