UC Riverside

Planetary climates are controlled by the delicate radiative balance between incoming and outgoing energy. Any perturbation to either side of the equation disrupts the surface temperature with implications for the physical environment and (bio)geochemical processes that in their turn impose additional alterations to the radiative energy balance. In this dissertation, I use numerical approaches to investigate the role of changing greenhouse gas concentrations and astronomical forcing (quasi-periodic variations in solar radiation via gradual changes in Earth's orbit and tilt) on the surface climate, carbon cycling, and the environmental consequences of associated feedback processes, on Earth and beyond.

First, I address the impact of carbon dioxide release to the atmosphere on geological timescales. Past carbon release events and episodes of global warming that are preserved in paleoclimate records are compared to an ensemble of Earth system model simulations to estimate the carbon input and output fluxes during past events and determine how the Earth responded to such perturbations. Next, I provide the reader with a thorough analysis of the impact of astronomical forcing and its imprint on the marine environment as simulated in an Earth system model. The transient modeling approach allows direct comparison between time-varying model output and multi-million-year-long paleoclimate records and thereby provides an opportunity to determine from model-data (mis)matches what feedback processes are the main drivers for variations in the climate-carbon system on astronomical timescales across tens of thousand to millions of years. Lastly, I examine with the use of orbital and obliquity simulations how the frequency and amplitude of astronomical cycles change as a function of planetary architecture and assess their impact on surface conditions and planetary habitability across million-year timescales. This research contributes to identifying exoplanets in other systems that may have been able to maintain habitable conditions over prolonged periods of time required for the development and evolution of life elsewhere in the universe.