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The Amazon has undergone rapid deforestation and degradation in recent decades, fundamentally altering its role in regulating global energy and water cycles. While we know forest loss releases carbon, the full biophysical impact, particularly how it is mediated by clouds, has remained elusive.
In this seminar, I will discuss the complex relationship between the Amazon rainforest and the Earth's climate, focusing specifically on the role of clouds. I'll start by isolating the biophysical signals of forest loss to present an "all-sky" perspective that integrates both surface and atmospheric effects. I will show that deforestation-induced clouds preferentially forming over deforested areas lead to a top-of-atmosphere (TOA) cooling that scales with the fraction of forest loss, reaching 6.8 ± 0.6 W/m2 in high-loss areas. Remarkably, the cloud response effectively doubles the cooling effect compared to surface brightening alone, acting as a significant but often overlooked component, with MODIS imagery often revealing clouds strikingly echoing the underlying deforestation pattern. I will then relate this radiative effect to the changing climate of the Amazon, showing that this cloud response is tightly coupled to the background atmospheric state, emerging in two distinct regimes: a moisture-limited regime and a moister "deepening" regime that provides stronger TOA cooling and precipitation. These findings suggest that as the Amazon trends toward a warmer and drier climate, a shift in these cloud regimes could diminish the TOA cooling currently offsetting some of the impacts of deforestation, with critical implications for the region's hydrological and radiative future.
Tom Dror is a CIRES Postdoctoral Visiting Fellow at the University of Colorado Boulder, working in the Clouds, Aerosol & Climate group at the NOAA Chemical Sciences Laboratory (CSL). Tom's research focuses on the coupling between the land and atmosphere and its effect on clouds, particularly in the tropics and the Amazon forest. Prior to joining CIRES and NOAA CSL, Tom received her Ph.D. in Atmosphere and Cloud Physics from the Weizmann Institute of Science (2023), and her B.Sc. in Climate, Atmospheric Sciences, and Oceanography from the Hebrew University of Jerusalem (2012).
ALL Seminar attendees agree not to cite, quote, copy, or distribute material presented without the explicit written consent of the seminar presenter. Any opinions expressed in this seminar are those of the speaker alone and do not necessarily reflect the opinions of NOAA or CSL.
