County-level climate change information to support decision-making on working lands

Abstract

Farmers, ranchers, and forest landowners across the USA make weather- and climate-related management decisions at varying temporal and spatial scales, often with input from local experts like crop consultants and cooperative extension (CE) personnel. In order to provide additional guidance to such longer-term planning efforts, we developed a tool that shows statistically downscaled climate projections of temperature and precipitation consolidated to the county level for the contiguous US. Using the county as a fundamental mapping unit encourages the use of this information within existing institutional structures like CE and other U.S. Department of Agriculture (USDA) programs. A "quick-look" metric based on the spatial variability of climate within each county aids in the interpretation of county-level information. For instance, relatively higher spatial variability within a county indicates that more localized information should be used to support stakeholder planning. Changes in annual precipitation show a latitudinal dipole where increases are projected for much of the northern US while declines are projected for counties across the southern US. Seasonal shifts in county-level precipitation are projected nationwide with declines most evident in summer months in most regions. Changes in the spatial variability of annual precipitation for most counties were less than 10 mm, indicating fairly spatially homogenous midcentury precipitation changes at the county level. Annual and seasonal midcentury temperatures are projected to increase across the USA, with relatively low change in the spatial variability (< 0.3 A degrees C) of temperature across most counties. The utility of these data is shown for forage and almond applications, both indicating a potential decline in production in some future years, to illustrate use of county-level seasonal projections in adaptation planning and decision-making.