Global Warming Contributions to Twenty-First Century Drought Trends.

Droughts are extreme climate events defined as moisture deficits that propagate through the hydrologic cycle, with reductions in precipitation (meteorological droughts) often translating into dry soils (agricultural droughts) and reduced streamflow and reservoir levels (hydrological droughts). Because of the importance of water availability, droughts can therefore have significant impacts on natural and human systems (e.g., agriculture, power generation, ecosystem functioning), making it a priority to understand to what extent drought activity will shift with climate change. I will present a broad overview of how anthropogenic climate change will contribute to drought variability and trends in the coming decades and centuries, discussing how reductions in supply (precipitation) and increases in demand (evaporation) will act in concert to intensify droughts in many regions of the world (e.g., Western North America, the Mediterranean, the Amazon, etc). For North America, I will demonstrate that these future aridity trends will likely eclipse even the extreme "megadrought" periods of the 12th and 13th centuries, when droughts in the Southwest and Central Plains persisted for multiple decades at a time. Finally, I will discuss to what extent the anthropogenic contribution to recent drought events (e.g., California, the Southwest United States, Syria) can be detected.