PNNL

Abstract

Geoengineering, defined as the deliberate modification of the climate to combat global warming, continues to receive increased attention. With advances in climate modeling studies of geoengineering, as well as new proposals for field experiments, there is even greater need for understanding the potential impacts of geoengineering on the human-Earth system. In addition, the field is rapidly expanding, and there is great need for new ideas and fresh talent to provide momentum in geoengineering research. In this spirit, we hosted an Early Career Summer School on geoengineering at the National Center for Atmospheric Research on 20–24 July 2015. The 31 participants, from throughout the world attended lectures and engaged in group discussions with the purpose of gaining greater exposure to this topic. On 22–23 July, they were joined by an additional 16 experts in geoengineering for the Fifth Geoengineering Model Intercomparison Project (GeoMIP) meeting. Feedback from the early career participants showed that this interaction allowed them to make contacts with leading scientists, learn the latest discoveries in the field, and experience how research in this field is done. Many participants said they left the meeting motivated to pursue ideas conceived at the workshop with their newly met collaborators. The workshop revealed multiple important directions in geoengineering research, some continuing from the inception of GeoMIP five years ago, and some that have recently emerged. Attendees expressed the need to compare the base state of climate models with observations so that there is improved confidence in their ability to represent the effects of geoengineering. Model representations of stratospheric aerosol microphysics and aerosol-cloud interactions have critical uncertainties. Attendees also voiced the desire to explore cloud resolving model simulations to inform GeoMIP studies of marine cloud brightening or cirrus thinning. One commonly expressed need is to move from assessments of climate effects (such as temperature or precipitation) to climate impacts (such as agricultural production or water scarcity). GeoMIP is an officially endorsed participant in the Coupled Model Intercomparison Project Phase 6 (CMIP6). Until that project is well underway, activities will focus on the GeoMIP Testbed, a new feature in which individual groups can propose experiments, vet them with a small number of models, and then make a case for them being adopted formally into GeoMIP. Currently, analyses of the sea spray geoengineering experiments are underway, and the archive of output from the initial four experiments is still being mined for innovative analyses. Many of these new results will be discussed at the Sixth GeoMIP meeting, to be held at the University of Oslo in the summer of 2016.