PAOC Colloquium - Angeline Pendergrass (Cornell)

Angeline Pendergrass (Cornell)
Monday, March 29, 2021 - 12:00pm to 1:00pm

Precipitation and its changes with climate: A CMIP6 perspective

Climate change alters the flow of energy through the climate system. Precipitation is one part of this energy flow, some aspects of which are impactful. How does precipitation respond to climate change? 

In this talk, we will confront aspects of the precipitation response identified with previous climate model simulations with a new generation of simulations, CMIP phase 6. First, we will revisit two emergent constraints that relate projected changes in global-mean precipitation to observable quantities – one based on the sensitivity of clear-sky shortwave absorption to water vapor concentrations, and another based on the surface longwave radiative cloud effect. Then, we will revisit the potential relationship between equilibrium climate sensitivity and global-mean precipitation change, which has been hypothesized on the basis of a process-level relationship between surface longwave and top-of-atmosphere shortwave cloud radiative effects. This new set of simulations serves as an out‐of‐sample test for observational constraints on HS proposed based on CMIP phase 5.

We will see that the constraint based on clear‐sky shortwave absorption sensitivity to water vapor has weakened, and that a proposed constraint based on surface low cloud longwave radiative effects does not apply to global-mean precipitation change. Finally, while a previously proposed mechanism connecting global-mean precipitation change and climate sensitivity via low clouds is present in the CMIP6 ensemble, it is not an important factor for variations in global-mean precipitation change. This explains why global-mean precipitation change is uncorrelated with climate sensitivity across the CMIP5 and CMIP6 ensembles.

About This Series

The PAOC Colloquium is a weekly interdisciplinary seminar series that brings together the whole PAOC community. Seminar topics include all research concerning the physics, chemistry, and biology of the atmospheres, oceans and climate, but also talks about e.g. societal impacts of climatic processes. The seminars take place on Monday from 12-1pm.