The Indomitable Solomon Spirit: Unequivocal Science and Impeccable Leadership

Susan Solomon has blazed original pathways in her scientific research in the atmospheric and climate sciences, with her explorations leading to groundbreaking results, influencing the scientific thinking and forming key inputs into policy-making decisions. Susan’s research in stratospheric chemistry is legendary for the pioneering discovery of the mechanism leading to the catalytic destruction of ozone by halo-carbons in the Antarctic lower stratosphere (the Antarctic “ozone hole”). The paradigmatic shifts due to this research have extended into the interaction of chemistry with circulation and climate, including the influences of changes in atmospheric composition on stratospheric climate trends and the projection of the recovery of ozone to pre-ozone-hole levels in the 21^st Century. Her leadership as co-Chair of the International Panel on Climate Change Working Group I Fourth Assessment Report (2007) led to the careful synthesis of the scientific basis of climate change by the community, consisting of the assessment of climate observations, atmospheric composition, radiative forcing of climate, climate processes, climate model simulations, climate detection-attribution, and climate projections. These culminated in the major message, “warming of the climate system is unequivocal”, and the related conclusion about the degree of attribution to anthropogenic activity. Her scientific expertise has also clarified the importance of the different timescales in the CO₂-climate problem, and the effect of volcanoes on the climate system. Developing scientific arguments into thoughtful, clear, policy-relevant but not prescriptive, messages readily comprehended by scientists and non-scientists has been her forte throughout, made particularly evident in her roles in the WMO and IPCC assessments from the 1980s into this century. We will discuss the recent advances in climate modeling and the accompanying evolution in the understanding of global-to-regional climate change, focusing on the unresolved issues that inhibit a complete quantitative picture. We will also discuss the continuing challenges in the science-society-policy interface, taking a cue from Susan’s innate ability to go beyond the technical aspects to trustworthy information on implications. This, along with her extraordinary scientific expertise, constitutes stellar contributions to the atmospheric and climate sciences.