613 Seminar: Jasper Kok

Department of Atmospheric and Oceanic Sciences, University of California - Los Angeles


Desert dust aerosols affect Earth's global energy balance through interactions with both shortwave and longwave radiation. But the magnitudes of these effects are so uncertain that it remains unclear whether the dust direct effect net warms or cools the climate. Consequently, it is still uncertain whether large changes in atmospheric dust loading over the past century have slowed or accelerated anthropogenic climate change, or what the climate feedback from future changes in dust loading will be. Here we analyze remote sensing, in situ, and model data of dust aerosol sizes and abundance to constrain the dust direct radiative effect, and find that atmospheric dust is substantially coarser than represented in current global models. Because coarse dust warms the climate, the dust direct radiative effect (DRE) is likely less cooling than the ~0.4 W/m2 estimated by models in a current global aerosol model ensemble. Instead, we constrain the dust DRE to -0.48 to +0.20 W/m2, which includes the possibility that dust causes a net warming of the planet. We use this constraint on the dust DRE to estimate the feedback arising from projected future dust loading changes, finding that the direct dust–climate feedback is likely in the range of −0.04 to +0.02 Wm−2K−1. On a regional scale, this dust feedback is enhanced by approximately an order of magnitude close to major source regions, and could play an important role in shaping the future climates of Northern Africa, the Sahel, the Mediterranean region, the Middle East, and Central Asia.

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