SLS Seminar: Damien Irving

Damien Irving, Australian Meteorological and Oceanographic Society
Friday, August 10, 2018 - 11:00am to 12:00pm

Greenhouse gases, anthropogenic aerosols and the planetary energy imbalance

Human activities have substantially altered the composition of the atmosphere, giving rise to a planetary energy imbalance. The largest contributor to this imbalance is greenhouse gases (GHGs), which are partially offset by anthropogenic aerosols (AAs). While the overall influence of GHGs and AAs is oppositional, the location (northern mid-latitudes) and trajectory (accelerated from 1950–1980 before leveling off) of AA emissions means that their opposition is not uniform in space and time. This has important implications for how the planetary energy imbalance is distributed throughout the climate system.

In this talk, I will outline the results of an extensive analysis of the CMIP5 historical (i.e. all natural and anthropogenic forcing) and single forcing (GHG-only and AA-only) experiments. We find that over the duration of the historical experiment (1861-2005), the accumulated heat flux anomaly at the top of the atmosphere (netTOA) and ocean surface (ocean heat uptake; OHU), as well as the change in ocean heat content (OHC), are all higher in the Southern Hemisphere. The single forcing experiments confirm that these interhemispheric differences in netTOA and OHU are entirely attributable to AA forcing. Interestingly, we find that this AA-induced gradient in OHU does not cause a corresponding gradient in OHC. Instead, the historical interhemispheric difference in OHC is attributable to GHG forcing, which by itself is not associated with an interhemispheric difference in OHU. On a sub-hemispheric scale, GHGs are also responsible for the highly spatially concentrated OHU and OHC change in the mid-to-high southern latitudes. During my visit to WHOI (August 9-21), I am also running a one-day Data Carpentry workshop. The associated lesson materials have been designed to not only teach the basics of Python programming in the atmosphere and ocean sciences, but also the skills required to publish reproducible computational results. I will briefly discuss the fundamental ideas underpinning the lessons and the plans for future development.

About the Series

The Atmosphere, Ocean and Climate Sack Lunch Seminar Series is an informal seminar series within PAOC that focuses on more specialized topics than the PAOC Colloquium. Seminar topics include all research concerning the science of atmosphere, ocean and climate. The seminars usually take place on Wednesdays from 12-1pm in 54-915. The presentations are either given by an invited speaker or by a member of PAOC and can focus on new research or discussion of a paper of particular interest.