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Causes of Variability and Trends in Earth’s Radiation Budget over the 21st Century

December 6, 2019 @ 12:00 pm - 1:00 pm

Shiv Priyam Raghuraman

What to Expect

The latest satellite observations show significant interannual and interdecadal anomalies in the global radiation budget during 2000-2018. Changes in the reflection of solar radiation and emission of thermal radiation perturb Earth’s energy balance and play a crucial role in the climate system, yet these changes’ key controls are poorly comprehended. In this presentation, we will breakdown the causes for variability and trends in two important elements of Earth’s energy budget: the clear sky greenhouse effect (G) and Earth’s energy imbalance (EEI). We quantify the contributions to G — the trapping of infrared radiation by the atmosphere in the absence of clouds — due to changes in surface temperature, atmospheric temperature, and water vapor individually. Furthermore, we analyze the occurrence of the “super greenhouse effect”, a phenomenon in which the outgoing longwave radiation and surface temperature are anti-correlated, and explain how it is generated. Finally, we use a general circulation model (GFDL AM4) to simulate a large initial condition ensemble of realizations of Earth to study 1) the range of anomalies possible for EEI given the same sea surface temperature (SST) spatial pattern and 2) the impact of variability in SST vs. anthropogenic forcing on EEI. We demonstrate that while interannual anomalies in EEI can be explained by SST variability, anthropogenic forcing is required to explain the observed increasing trend in EEI.

Speaker Bio

Raghuraman is a graduate student at Princeton advised by V. Ramaswamy. His thesis research uses satellite observations and climate models to understand the mechanisms responsible for short-term and long-term changes in Earth’s reflection of solar radiation and emission of thermal radiation. He received my B.S. in Mathematics and minor in Physics from the University of Minnesota, Twin Cities in 2016.

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B74-324 Conference Room