Hari is an earth system scientist. He studies the interactions between different components of the world around us, from plate tectonics to the climate, biosphere and human systems. His interest in the earth sciences initially stemmed from a fascination with the beauty, balance and magnitude of earth processes, particularly in mountain landscapes. Unsurprisingly, the questions that have motivated his research operate on large scales—from the regional to continental scale spatially, and over geological timescales spanning millions of years.
His recent research has centered on the evolution of climate in western North America over the past 65 million years. Using the isotopes of oxygen and hydrogen in sediments, he produces and interprets geochemical records and models of climate to answer such questions as: 1) How and when did the mountains of western North America rise, and how did their uplift affect atmospheric circulation? 2) How did the evolution of grassland ecosystems affect climate and water vapor recycling to the atmosphere? And 3) How hot and how wet was western North America during high-CO2 times in the past? Some of his current and upcoming projects include studies of the topographic and climatic histories of the Sierra Nevada and the Alaska Range, measuring the temperature of Earth's earliest oceans, and comparing multiple paleothermometry techniques in the western US. He is developing a modern water isotope facility at Santa Clara, which can be used in a wide variety of climate science, hydrology and environmental applications.