On glacial-interglacial timescales, variability in Earth's climate system is largely explained by the Milankovitch-Croll hypothesis, which postulates that glacial interglacial climate changes occur in response to cyclic variations in the geometry of Earth's orbit around the sun, which control changes in solar insolation (solar output per unit time per unit area). Milankovitch-forcing occurs on time scales ranging from 20,000 to 400,000 years per cycle, although longer cycles in solar insolation that are unresolved by current paleoclimate records may be present. On longer timescales, with trends or cycles of millions to billions of years in duration, large-scale changes in solar luminosity (total solar output), tectonic shifts, and biogeochemical cycling in response to the evolution of Earth's biosphere control the long-term, "Tectonic-scale" climate state. On shorter timescales (<20,000 years per cycle), the interplay of more subtle changes in solar irriadiance (solar output per unit area), volcanic forcing, internal oscillations of the climate system and anthropogenic forcing drive climate variability. The most important of these "short-term" changes has been anthropogenic-forcing of the climate system from the Industrial Revolution to present.

I've been fortunate to receive training from John Imbrie, Warren Prell, Alan Mix, and Nick Pisias, researchers who were instrumental in the development of our understanding of Milankovitch-scale climate change as part of the CLIMAP and SPECMAP projects. I apply a quantitative, time series analysis approach to study of the interactions of various components of the Earth's climate system on glacial-interglacial timescales. As with my study of climate variability on timescales shorter than <20,000 years per cycle, I make use of sediment physical properties measurements (visible derivative spectroscopy, laser particle size analysis, and elemental analysis by x-ray florescence) to reconstruct climate variability on glacial-interglacial timescales. These methods are rapid, require little sample preparation and yield, rich, multivariate data sets that can be unmixed, or decomposed using statistical methods to partition variance related to how different processes have influenced a location through time. I also employ micropaleontological and stable isotope analysis of foraminifera as needed to answer questions about glacial-interglacial climate change. Although I am interested in global processes, I address these questions through detailed regional reconstructions and have worked in most of the World Ocean's major basins.

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