Adventures in Climate Fingerprinting with Jerry Meehl

In the mid-1990s, Jerry Meehl and Warren Washington led a pioneering project that used the DOE/NCAR Parallel Climate Model (PCM) to perform a large suite of simulations with individual and combined changes in different forcing mechanisms. This innovative set of numerical experiments helped researchers to understand and quantify the climate change contributions arising from forcing by well-mixed greenhouse gases, anthropogenic aerosols, stratospheric ozone, solar irradiance, and volcanic activity. The PCM simulations included multiple initial condition realizations of each numerical experiment. This systematic exploration of external forcings and internal variability proved to be a valuable scientific resource for the entire climate science community. It was particularly useful for climate change detection and attribution (“D&A”) research. The PCM simulations were a key component of successful efforts to identify human fingerprints in atmospheric temperature, tropopause height, water vapor, and many other observables. In addition to discussing the D&A work enabled by the PCM ensemble, my talk will also cover Jerry’s long-standing efforts to advance scientific understanding of decadal modes of natural internal variability – the background “noise” against which anthropogenic fingerprints must be identified.