Constraining the Direct Radiative Forcing of Desert Dust

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Desert dust accounts for about two thirds of the total mass of particulate matter in our atmosphere. One of the reasons that dust is so abundant is that it has increased substantially, perhaps even doubled, since the Industrial Revolution. This large increase is probably because of human actions like clearing land for agriculture. Surprisingly, the impact of the increasing desert dust on the climate system has remained mysterious. In fact, it is still an open question whether this historical increase in dust has contributed to or counteracted greenhouse gas warming of the climate system. This project will answer this question by (i) determining the change in Earth’s energy budget produced by the scattering and absorbing of solar and terrestrial radiation by dust, (ii) determining the amount by which dust has increased since the Industrial Revolution, and (iii) determining the resultant change in Earth’s energy budget from the increase in dust. These goals will be achieved by combining satellite observations, aircraft measurements, numerous records of how deposition of desert dust has changed across the world, and numerical simulations of how dust affects Earth’s radiation budget. The research will be performed by a team of scientists that include undergraduate and graduate students and a postdoctoral scholar.Determining the climate impact of the historical increase in desert dust is important because calculations of how sensitive the climate system is to greenhouse warming depend on the extent to which greenhouse warming has been counteracted by cooling produced by particulate matter like dust. This project will thus result in more accurate predictions of the climate changes produced by future increases in greenhouse gases, which is critical to an effective societal response to those changes. The project will also continue a successful outreach project to under-served high schools in the Los Angeles area.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.