Clouds and Aerosols as the Crux of Global Change

The largest uncertainty in the fast response of the climate system to changes in surface temperature is due to the response of clouds: cloud feedbacks. In addition, the largest uncertainty in anthropogenic radiative forcing is the response of clouds to aerosol perturbations, often termed Aerosol-Cloud Interactions (ACI). Some have even proposed to use these same processes to roll back climate change by intentionally engineering clouds and aerosols to cool the planet. Clouds and aerosols are thus at the center of understanding the future trajectory of the earth system. While we see clouds (and aerosols) all the time, quantitative observations useful for understanding and prediction are difficult and sparse. Simulating clouds and aerosol effects on clouds at climate relevant scales is extremely challenging and extremely important. This presentation will discuss what we know and what we need to know about clouds and aerosols to better understand and predict climate change, using modeling, observations and examples, which traces the arc of the last few decades (and perhaps the next decade) of my scientific journey.