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As managers of agricultural and natural resources are confronted with uncertainties in global change impacts, the complexities associated with the interconnected cycling of nitrogen, carbon, and water present daunting management challenges. Existing models provide detailed information on specific sub-systems (e.g., land, air, water, and economics). An increasing awareness of the unintended consequences of management decisions resulting from interconnectedness of these sub-systems, however, necessitates coupled regional earth system models (EaSMs). Decision makers’ needs and priorities can be integrated into the model design and development processes to enhance decision-making relevance and “usability” of EaSMs. BioEarth is a research initiative currently under development with a focus on the U.S. Pacific Northwest region that explores the coupling of multiple stand-alone EaSMs to generate usable information for resource decision-making. Direct engagement between model developers and non-academic stakeholders involved in resource and environmental management decisions throughout the model development process is a critical component of this effort. BioEarth utilizes a bottom-up approach for its land surface model that preserves fine spatial-scale sensitivities and lateral hydrologic connectivity, which makes it unique among many regional EaSMs. This paper describes the BioEarth initiative and highlights opportunities and challenges associated with coupling multiple stand-alone models to generate usable information for agricultural and natural resource decision-making.

Nutrient runoff from agricultural regions of the midwestern U.S. corn belt has degraded water quality in many inland and coastal water bodies such as the Great Lakes and Gulf of Mexico. Under current climate, observational studies have shown that winter cover crops can reduce dissolved nitrogen and phosphorus losses from row-cropped agricultural watersheds, but performance of cover crops in response to climate variability and climate change has not been systematically evaluated. Using the Soil & Water Assessment Tool (SWAT) model, calibrated using multiple years of field-based data, we simulated historical and projected future nutrient loss from two representative agricultural watersheds in northern Indiana, USA. For 100% cover crop coverage, historical simulations showed a 31–33% reduction in nitrate (NO3−) loss and a 15–23% reduction in Soluble Reactive Phosphorus (SRP) loss in comparison with a no-cover-crop baseline. Under climate change scenarios, without cover crops, projected warmer and wetter conditions strongly increased nutrient loss, especially in the fallow period from Oct to Apr when changes in infiltration and runoff are largest. In the absence of cover crops, annual nutrient losses for the RCP8.5 2080s scenario were 26–38% higher for NO3−, and 9–46% higher for SRP. However, the effectiveness of cover crops also increased under climate change. For an ensemble of 60 climate change scenarios based on CMIP5 RCP4.5 and RCP8.5 scenarios, 19 out of 24 ensemble-mean simulations of future nutrient loss with 100% cover crops were less than or equal to historical simulations with 100% cover crops, despite systematic increases in nutrient loss due to climate alone. These results demonstrate that planting winter cover crops over row-cropped land areas constitutes a robust climate change adaptation strategy for reducing nutrient losses from agricultural lands, enhancing resilience to a projected warmer and wetter winter climate in the midwestern U.S. [ABSTRACT FROM AUTHOR]

Byline: Alan F. Hamlet (1,2), Se-Yeun Lee (1), Kristian E. B. Mickelson (3), Marketa M. Elsner (1,2) Abstract: Climate strongly affects energy supply and demand in the Pacific Northwest (PNW) and Washington State (WA). We evaluate potential effects of climate change on the seasonality and annual amount of PNW hydropower production, and on heating and cooling energy demand. Changes in hydropower production are estimated by linking simulated streamflow scenarios produced by a hydrology model to a simulation model of the Columbia River hydro system. Changes in energy demand are assessed using gridded estimates of heating degree days (HDD) and cooling degree days (CDD) which are then combined with population projections to create energy demand indices that respond both to climate, future population, and changes in residential air conditioning market penetration. We find that substantial changes in the amount and seasonality of energy supply and demand in the PNW are likely to occur over the next century in response to warming, precipitation changes, and population growth. By the 2040s hydropower production is projected to increase by 4.7--5.0% in winter, decrease by about 12.1--15.4% in summer, with annual reductions of 2.0--3.4%. Larger decreases of 17.1--20.8% in summer hydropower production are projected for the 2080s. Although the combined effects of population growth and warming are projected to increase heating energy demand overall (22--23% for the 2020s, 35--42% for the 2040s, and 56--74% for the 2080s), warming results in reduced per capita heating demand. Residential cooling energy demand (currently less than one percent of residential demand) increases rapidly (both overall and per capita) to 4.8--9.1% of the total demand by the 2080s due to increasing population, cooling degree days, and air conditioning penetration. Author Affiliation: (1) Department of Civil and Environmental Engineering, University of Washington, Seattle, WA, 98195, USA (2) Center for Science in the Earth System, Climate Impacts Group, University of Washington, Seattle, WA, 98195, USA (3) US Army Corps of Engineers, Seattle District, 4735 E. Marginal Way, Seattle, WA, 98134, USA Article History: Registration Date: 29/03/2010 Received Date: 04/06/2009 Accepted Date: 23/03/2010 Online Date: 05/05/2010

Byline: Julie A. Vano (1), Michael J. Scott (2), Nathalie Voisin (1), Claudio O. Stockle (3), Alan F. Hamlet (1,4), Kristian E. B. Mickelson (1,5), Marketa McGuire Elsner (4), Dennis P. Lettenmaier (1,4) Abstract: The Yakima River Reservoir system supplies water to ~180,000 irrigated hectares through the operation of five reservoirs with cumulative storage of ~30% mean annual river flow. Runoff is derived mostly from winter precipitation in the Cascade Mountains, much of which is stored as snowpack. Climate change is expected to result in earlier snowmelt runoff and reduced summer flows. Effects of these changes on irrigated agriculture were simulated using a reservoir system model coupled to a hydrological model driven by downscaled scenarios from 20 climate models archived by the 2007 Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. We find earlier snowmelt results in increased water delivery curtailments. Historically, the basin experienced substantial water shortages in 14% of years. Without adaptations, for IPCC A1B global emission scenarios, water shortages increase to 27% (13% to 49% range) in the 2020s, to 33% in the 2040s, and 68% in the 2080s. For IPCC B1 emissions scenarios, shortages occur in 24% (7% to 54%) of years in the 2020s, 31% in the 2040s and 43% in the 2080s. Historically unprecedented conditions where senior water rights holders suffer shortfalls occur with increasing frequency in both A1B and B1 scenarios. Economic losses include expected annual production declines of 5%--16%, with greater probabilities of operating losses for junior water rights holders. Author Affiliation: (1) Department of Civil and Environmental Engineering, University of Washington, Box 352700, Seattle, WA, 98195-2700, USA (2) Pacific Northwest National Laboratory, P.O. Box 999, MSIN K6-05, Richland, WA, 99352, USA (3) Department of Biological Systems Engineering, Washington State University, PO Box 646120, Pullman, WA, 99164-6120, USA (4) JISAO/CSES Climate Impacts Group, University of Washington, Box 355672, Seattle, WA, 98195-5672, USA (5) Water Management, US Army Corps of Engineers - Seattle District, 4735 East Marginal Way South, Seattle, WA, 98134, USA Article History: Registration Date: 29/03/2010 Received Date: 04/06/2009 Accepted Date: 23/03/2010 Online Date: 07/05/2010

Byline: Marketa M. Elsner (1), Lan Cuo (2), Nathalie Voisin (3), Jeffrey S. Deems (4), Alan F. Hamlet (1,3), Julie A. Vano (3), Kristian E. B. Mickelson (5), Se-Yeun Lee (3), Dennis P. Lettenmaier (1,3) Abstract: Pacific Northwest (PNW) hydrology is particularly sensitive to changes in climate because snowmelt dominates seasonal runoff, and temperature changes impact the rain/snow balance. Based on results from the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4), we updated previous studies of implications of climate change on PNW hydrology. PNW 21st century hydrology was simulated using 20 Global Climate Models (GCMs) and 2 greenhouse gas emissions scenarios over Washington and the greater Columbia River watershed, with additional focus on the Yakima River watershed and the Puget Sound which are particularly sensitive to climate change. We evaluated projected changes in snow water equivalent (SWE), soil moisture, runoff, and streamflow for A1B and B1 emissions scenarios for the 2020s, 2040s, and 2080s. April 1 SWE is projected to decrease by approximately 38--46% by the 2040s (compared with the mean over water years 1917--2006), based on composite scenarios of B1 and A1B, respectively, which represent average effects of all climate models. In three relatively warm transient watersheds west of the Cascade crest, April 1 SWE is projected to almost completely disappear by the 2080s. By the 2080s, seasonal streamflow timing will shift significantly in both snowmelt dominant and rain--snow mixed watersheds. Annual runoff across the State is projected to increase by 2--3% by the 2040s these changes are mainly driven by projected increases in winter precipitation. Author Affiliation: (1) Center for Science in the Earth System, Climate Impacts Group, University of Washington, Box 355672, Seattle, WA, 98195-5672, USA (2) Australia Commonwealth Scientific and Industrial Research Organization (CSIRO), 37 Graham Road, Highett, VIC, 3190, Australia (3) Department of Civil and Environmental Engineering, University of Washington, Box 352700, Seattle, WA, 98195-2700, USA (4) National Snow and Ice Data Center, 449 UCB University of Colorado, Boulder, CO, 80309-0449, USA (5) US Army Corps of Engineers, Seattle District, P.O. Box 3755, Seattle, WA, 98124-3755, USA Article History: Registration Date: 29/03/2010 Received Date: 04/06/2009 Accepted Date: 23/03/2010 Online Date: 04/05/2010

Byline: Lara C. Whitely Binder (1), Jennifer Krencicki Barcelos (2), Derek B. Booth (3), Meriel Darzen (2), Marketa McGuire Elsner (1), Richard Fenske (4), Thomas F. Graham (2), Alan F. Hamlet (5), John Hodges-Howell (2), J. Elizabeth Jackson (6), Catherine Karr (7), Patrick W. Keys (5), Jeremy S. Littell (1), Nathan Mantua (1), Jennifer Marlow (2), Don McKenzie (8), Michael Robinson-Dorn (2), Eric A. Rosenberg (5), Claudio O. Stockle (9), Julie A. Vano (5) Abstract: Climate change is expected to bring potentially significant changes to Washington State's natural, institutional, cultural, and economic landscape. Addressing climate change impacts will require a sustained commitment to integrating climate information into the day-to-day governance and management of infrastructure, programs, and services that may be affected by climate change. This paper discusses fundamental concepts for planning for climate change and identifies options for adapting to the climate impacts evaluated in the Washington Climate Change Impacts Assessment. Additionally, the paper highlights potential avenues for increasing flexibility in the policies and regulations used to govern human and natural systems in Washington. Author Affiliation: (1) JISAO/CSES Climate Impacts Group, University of Washington, Seattle, WA, 98195-5672, USA (2) Kathy and Steve Berman Environmental Law Clinic, University of Washington, Seattle, WA, 98195-3020, USA (3) Stillwater Consultants, Berkeley, CA, 94705, USA (4) Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA, 98195-7234, USA (5) Department of Civil and Environmental Engineering, University of Washington, Seattle, WA, 98195-2700, USA (6) School of Public Health and Community Medicine, University of Washington, Seattle, WA, 98195-7230, USA (7) Department of Pediatrics, University of Washington, Seattle, WA, 98195-6320, USA (8) College of Forest Resources, University of Washington, Seattle, WA, 98195-2100, USA (9) Department of Biological Systems Engineering, Washington State University, Pullman, WA, 99164-6120, USA Article History: Registration Date: 24/03/2010 Received Date: 04/06/2009 Accepted Date: 23/03/2010 Online Date: 27/04/2010

Byline: Nathan Mantua (1,2), Ingrid Tohver (1), Alan Hamlet (1,3) Abstract: This study evaluates the sensitivity of Washington State's freshwater habitat of Pacific Salmon (Oncorhynchus spp.) to climate change. Our analysis focuses on summertime stream temperatures, seasonal low flows, and changes in peak and base flows because these physical factors are likely to be key pressure points for many of Washington's salmon populations. Weekly summertime water temperatures and extreme daily high and low streamflows are evaluated under multimodel composites for A1B and B1 greenhouse gas emissions scenarios. Simulations predict rising water temperatures will thermally stress salmon throughout Washington's watersheds, becoming increasingly severe later in the twenty-first century. Streamflow simulations predict that basins strongly influenced by transient runoff (a mix of direct runoff from cool-season rainfall and springtime snowmelt) are most sensitive to climate change. By the 2080s, hydrologic simulations predict a complete loss of Washington's snowmelt dominant basins, and only about ten transient basins remaining in the north Cascades. Historically transient runoff watersheds will shift towards rainfall dominant behavior, undergoing more severe summer low flow periods and more frequent days with intense winter flooding. While cool-season stream temperature changes and impacts on salmon are not assessed in this study, it is possible that climate-induced warming in winter and spring will benefit parts of the freshwater life-cycle of some salmon populations enough to increase their reproductive success (or overall fitness). However, the combined effects of warming summertime stream temperatures and altered streamflows will likely reduce the reproductive success for many Washington salmon populations, with impacts varying for different life history-types and watershed-types. Diminishing streamflows and higher stream temperatures in summer will be stressful for stream-type salmon populations that have freshwater rearing periods in summer. Increased winter flooding in transient runoff watersheds will likely reduce the egg-to-fry survival rates for ocean-type and stream-type salmon. Author Affiliation: (1) JISAO/CSES Climate Impacts Group, University of Washington, Box 355672, Seattle, WA, 98195-5672, USA (2) School of Aquatic and Fishery Sciences, University of Washington, Box 354235, Seattle, WA, 98195-4235, USA (3) Department of Civil and Environmental Engineering, University of Washington, Box 352700, Seattle, WA, 98195-2700, USA Article History: Registration Date: 24/03/2010 Received Date: 04/06/2009 Accepted Date: 23/03/2010 Online Date: 27/04/2010

Byline: Julie A. Vano (1), Nathalie Voisin (1), Lan Cuo (1,4), Alan F. Hamlet (1,2), Marketa McGuire Elsner (2), Richard N. Palmer (3), Austin Polebitski (1), Dennis P. Lettenmaier (1,2) Abstract: Climate change is projected to result, on average, in earlier snowmelt and reduced summer flows in the Pacific Northwest, patterns not well represented in historical observations used in water planning. We evaluate the sensitivities of water supply systems in the Puget Sound basin cities of Everett, Seattle, and Tacoma to historical and projected future streamflow variability and water demands. We simulate streamflow for the 2020s, 2040s, and 2080s using the distributed hydrology--soil--vegetation model (DHSVM), driven by downscaled ensembles of climate simulations archived from the 2007 IPCC Fourth Assessment Report. We use these streamflow predictions as inputs to reservoir system models for the three water supply systems. Over the next century, under average conditions all systems are projected to experience declines and eventual disappearance of the springtime snowmelt peak. How these shifts affect management depends on physical characteristics, operating objectives, and the adaptive capacity of each system. Without adaptations, average seasonal drawdown of reservoir storage is projected to increase in all three systems throughout the 21st century. Reliability of all systems in the absence of demand increases is robust through the 2020s however, and remains above 98% for Seattle and Everett in the 2040s and 2080s. With demand increases, however, reliability of the systems in their current configurations and with current operating policies progressively declines through the century. Author Affiliation: (1) Department of Civil and Environmental Engineering, University of Washington, Box 352700, Seattle, WA, 98195-2700, USA (2) JISAO/CSES Climate Impacts Group, University of Washington, Box 355672, Seattle, WA, 98195-5672, USA (3) Department of Civil and Environmental Engineering, University of Massachusetts Amherst, 224 Marston Hall, 130 Natural Resources Road, Amherst, MA, 01003-9293, USA (4) Australia Commonwealth Scientific and Industrial Research Organization (CSIRO), 37 Graham Road, Highett, VIC, 3190, Australia Article History: Registration Date: 24/03/2010 Received Date: 04/06/2009 Accepted Date: 23/03/2010 Online Date: 27/04/2010

Using an ensemble of 10 statistically downscaled global climate model (GCM) simulations, we project future climate change impacts on the state of Indiana (IN) for two scenarios of greenhouse gas concentrations (a medium scenario—RCP4.5 and a high scenario—RCP 8.5) for three future time periods (2020s, 2050s, 2080s). Relative to a 1971–2000 baseline, the projections show substantial changes in temperature (T) for IN, with a change in the annual ensemble mean T for the 2080s RCP8.5 scenario of about 5.6 °C (10.1 °F). Such changes also indicate major changes in T extremes. For southern IN, the number of days with daily maximum T above 35 °C (95 °F) is projected to be about 100 days per year for the 2080s RCP8.5 scenario, as opposed to an average of 5 days for the historical baseline climate. Locations in northern IN could experience 50 days per year above 35 °C (95 °F) for the same conditions. Energy demand for cooling, as measured by cooling degree days (CDD), is projected to increase nearly fourfold in response to this extreme warming, but heating demand as measured by heating degree days (HDD) is projected to decline by 30%, which would result in a net reduction in annual heating/cooling energy demand for consumers. The length of the growing season is projected to increase by about 30 to 50 days by the 2080s for the RCP8.5 scenario, and USDA hardiness zones are projected to shift by about one full zone throughout IN. By the 2080s, all GCM simulations for the RCP8.5 scenario show higher annual precipitation (P) over the Midwest and IN. Projected seasonal changes in P include a 25–30% increase in winter and spring by the 2080s for the RCP8.5 scenarios and a 1–7% decline in summer and fall P (although there is a low model agreement in the latter two seasons). Rising T is projected to cause systematic decreases in the snow-to-rain ratio from Nov-Mar. Snow is projected to become uncommon in southern IN by the 2080s for the RCP8.5 scenario, and snowfall is substantially reduced in other areas of the state. The combined effects of these changes in T, P, and snowfall will likely result in increased surface runoff and flooding during winter and spring. [ABSTRACT FROM AUTHOR]

The potential effects of climate change on the hydrology and water resources of the Columbia River Basin (CRB) were evaluated using simulations from the U.S. Department of Energy and National Center for Atmospheric Research Parallel Climate Model (DOE/NCAR PCM). This study focuses on three climate projections for the 21st century based on a `business as usual'' (BAU) global emissions scenario, evaluated with respect to a control climate scenario based on static 1995 emissions. Time-varying monthly PCM temperature and precipitation changes were statistically downscaled and temporally disaggregated to produce daily forcings that drove a macro-scale hydrologic simulation model of the Columbia River basin at ¼-degree spatial resolution. For comparison with the direct statistical downscaling approach, a dynamical downscaling approach using a regional climate model (RCM) was also used to derive hydrologic model forcings for 20-year subsets from the PCM control climate (1995–2015) scenario and from the three BAU climate (2040–2060) projections. The statistically downscaled PCM scenario results were assessed for three analysis periods (denoted Periods 1–3: 2010–2039, 2040–2069, 2070–2098) in which changes in annual average temperature were +0.5, +1.3 and +2.1 °C, respectively, while critical winter season precipitation changes were –3, +5 and +1 percent. For RCM, the predicted temperature change for the 2040–2060 period was +1.2 °C and the average winter precipitation change was –3 percent, relative to the RCM control climate. Due to the modest changes in winter precipitation, temperature changes dominated the simulated hydrologic effects by reducing winter snow accumulation, thus shifting summer streamflow to the winter. The hydrologic changes caused increased competition for reservoir storage between firm hydropower and instream flow targets developed pursuant to the Endangered Species Act listing of Columbia River salmonids. We examined several alternative reservoir operating policies designed to mitigate reservoir system performance losses. In general, the combination of earlier reservoir refill with greater storage allocations for instream flow targets mitigated some of the negative impacts to flow, but only with significant losses in firm hydropower production (ranging from –9 percent in Period 1 to –35 percent for RCM). Simulated hydropower revenue changes were less than 5 percent for all scenarios, however, primarily due to small changes in annual runoff. [ABSTRACT FROM AUTHOR]

The impacts of year-to-year and decade-to-decade climatic variations on some of the Pacific Northwest's key natural resources can be quantified to estimate sensitivity to regional climatic changes expected as part of anthropogenic global climatic change. Warmer, drier years, often associated with El Niño events and/or the warm phase of the Pacific Decadal Oscillation, tend to be associated with below-average snowpack, streamflow, and flood risk, below-average salmon survival, below-average forest growth, and above-average risk of forest fire. During the 20th century, the region experienced a warming of 0.8 °C. Using output from eight climate models, we project a further warming of 0.5–2.5 °C (central estimate 1.5 °C) by the 2020s, 1.5–3.2 °C (2.3 °C) by the 2040s, and an increase in precipitation except in summer. The foremost impact of a warming climate will be the reduction of regional snowpack, which presently supplies water for ecosystems and human uses during the dry summers. Our understanding of past climate also illustrates the responses of human management systems to climatic stresses, and suggests that a warming of the rate projected would pose significant challenges to the management of natural resources. Resource managers and planners currently have few plans for adapting to or mitigating the ecological and economic effects of climatic change. [ABSTRACT FROM AUTHOR]