Assessment of Hydroclimate Responses to Anthropogenic Forcing and Implications for Human Systems

Changes in the mean and extreme climate characteristics are undeniably evident in observational records. Over the United States, the mean temperature has approximately increased by 1oC since the late 19th century and an additional warming of up to 2.2oC is projected by the mid 21st century. Similarly, changes in the temperature and precipitation extremes are also visible through a decreasing trend in the number of rain days and an increasing trend in the frequency of droughts, heat waves and heavy downpours. Discernable evidence suggests that such changes in hydroclimate characteristic are impacting human systems such as energy, agriculture and critical infrastructure. Within this context, this research investigates the responses of regional hydroclimate over the United States to projected increases in radiative forcing in the near term future and its implications for the human systems. This investigation is divided in four parts. The first part quantifies potential changes in county-level residential space heating and cooling requirements as a result of projected changes in heating and cooling degree days. The second part investigates the characteristics of dry versus humid heatwaves and the associated thermodynamic changes in the present and warmer future climate. The third part studies changes in the spatial and temporal characteristics of precipitation events, including extent, intensity and frequency in response to increase in radiative forcing. The fourth part evaluates potential changes in the magnitude of probable maximum precipitation, which is used as a design criteria for critical infrastructure, in the warmer and moister future climate over a hydrological basin in the southeastern United States. Overall, this research should enable development of rigorous analytical frameworks for better planning to cope with the challenges posed by climate change.