2 3 Modeling and Downscaling: Issues and Methodological Perspectives for the U.S. National Climate Assessment NCA Report Series, Volume 7 Climate Change Modeling and Downscaling: Issues and Methodolgical Perspectives for the U.S. National Climate Assessment NCA Report Series The National Climate Assessment (NCA) Report Series summarizes regional, sectoral, and process-related workshops and discussions being held as part of the third NCA process. This workshop focused on questions, issues, and methodological perspectives regarding the use of mathematical models for the NCA, as well as the complexities that arise when applying data and models to multiple spatial and temporal scales. The workshop was held in Arlington, VA on December 8-10, 2010. Volume 7 of the NCA Report Series summarizes the discussions and outcomes of this workshop. A list of planned and completed reports in the NCA Report Series can be found online at http://assessment.globalchange.gov. 2 3 PREFACE .................................................................................................... 6 Chapter One: Executive Summary - Modeling and Scaling Issues in the National Climate Assessment ........................................................ 7 1.1 Introduction ........................................................................................ 8 1.2 Background ....................................................................................... 8 1.3 Goals and Objectives of the NCA .................................................. 8 1.4 The Role of Modeling in the NCA ................................................... 9 1.4.1. Climate Models .......................................................................... 9 1.4.2. Impact Models ........................................................................ 10 1.4.3. Integrated Assessment Models ............................................. 10 1.5 Issues of Importance for the NCA ................................................. 10 Chapter Two: Modeling and Scaling Issues in the National Climate Assessment ............................................................................................ 14 2.1 Introduction ..................................................................................... 15 2.2 Background ..................................................................................... 15 2.3 Goals and Objectives of the NCA ................................................ 15 CONTENTS 2.4 The Role of Modeling and Associated Uncertainties in the NCA ....................................................................................... 16 2.4.1 Climate Models ........................................................................ 16 2.4.2 Impact Models ......................................................................... 17 2.4.3 Integrated Assessment Models .............................................. 18 2.5 Establishing User Needs in the NCA ............................................. 18 2.5.1 Regions ...................................................................................... 19 2.5.2 Impact Sectors ......................................................................... 19 2.6 Interaction of Adaptation and Mitigation ...................................20 2.7 Right-Scaling Model Simulations ................................................... 21 2.7.1 Right-Scaling Climate Models ................................................. 21 2. 7. 2 Right-Scaling Integrated Assessment and Other Models ... 23 2.8 Progress Over the Past 5–10 Years ................................................ 23 2.8.1 Climate Models ........................................................................ 23 2.8.2 Integrated Assessment and Impact Models ........................ 23 2.9 Currently Available Resources ...................................................... 24 2.9.1 Climate Models and Outputs .................................................. 24 2.9.2 Integrated Assessment and Sector Models .......................... 24 2.10 Characterizing Uncertainties ....................................................... 25 2.10.1 Evaluating Climate and Impact Models ............................. 25 2.10.2 Incorporating User Needs ..................................................... 27 2.11 Characterizing Uncertainty in Climate Scenarios ..................... 27 2.12 Implications for Future Research ................................................. 28 Chapter Three: Workshop Report ....................................................... 29 3.1 Introduction .....................................................................................30 3.2 Summary of Plenary Presentations and Discussions ...................30 3.2.1 Introduction to Climate Modeling and Modeling Approaches for the National Climate Assessment ..............30 3.2.2 Overview of Modeling Practices in Past U.S. National Assessments ............................................................................... 31 3.2.3 Challenges, Opportunities and Lessons Learned in Downscaling and Regional Modeling .................................. 32 3.2.4 Characterizing Uncertainty ....................................................33 3.2.5 Relevant Outcomes of the Scenarios Workshop .................34 3.2.6 Sectoral Modeling Issues .........................................................34 3.2.7 Scaling Issues ............................................................................34 3.2.8 Managing and Meeting User Expectations ..........................34 3.3 Discussion Group Reports ..............................................................35 3.3.1 Discussion Group 1. Implications of Scenario Outcomes for Climate Modeling ...............................................................35 3.3.2 Discussion Group 2. Implications of Scenarios and Outcomes for Integrated Assessment Modeling and Interactions with Adaptation or Mitigation Modeling .......... 36 3.3.3 Discussion Group 3. Implications of Scenarios and Outcomes for Regional Climate Modeling and Interactions with Sectors .......................................................... 37 3.3.4 Discussion Group 4. Tracking Uncertainties in the Assessment System in the Short Term .....................................38 CONTENTS 3.3.5 Discussion Group 5. Matching Model Outputs or Performance to Needs from User Communities and Decision Makers .......................................................................38 3.3.6 Discussion Group 6. Transitioning from the Present to Future Capabilities .................................................................... 39 3.4 Next Steps and Potential Actions .................................................. 39 3.4.1 Decision Support ...................................................................... 39 3.4.2 Science Support Context ........................................................ 39 3.4.3 Contending with Uncertainty .................................................40 3.4.4 Next Steps ..................................................................................40 REFERENCES ........................................................................................... 41 APPENDIX A: AGENDA ..........................................................................44 APPENDIX B: PARTICIPANT LIST ............................................................. 47 PREFACE In December 2010, the Office of Biological and Environmental Research of the U.S. Department of Energy in conjunction with the U.S. Global Change Research Program convened a workshop in Arlington, Virginia to address questions and issues regarding the use of mathematical models for the National Climate Assessment (NCA). The workshop also addressed the complex issues that arise when data and models are applied at multiple spatial and temporal scales, an inherent requirement of a national climate assessment. An Interagency National Climate Assessment (INCA) Task Force provided guidance regarding purpose, scope, and objectives of the workshop. The results of the workshop in turn offer guidance not only for the National Climate Assessment but also more generally for future research in the use of models for these tasks. The workshop included plenary-session presentations and panels as well as breakout group discussions. Presentations and discussions covered both global and regional climate models and linkages of these models to enable regional analyses or downscaling of variables constrained by global model results. Participants reviewed potential use of carbon cycle and other biogeochemical cycling models as well as a range of models for analyzing the impacts of climate change on various sectors and within different regions. Integrated assessment models that relate climate change to human factors were discussed, as were various options for coupling models (used to assess climate change impacts) to either data on human activities or models of various human systems. Participants offered significant insights about the use of models within the overall NCA structure of linked sectors and regions. A number of workshop findings and recommendations apply to the development of a longer-term, sustained Assessment process. Prior to the workshop, a small team (with experience in the use of models for climate change assessments and the associated issues imposed by the need to address multiple temporal and spatial scales) prepared a white paper to inform assessment planning and stimulate discussion within the assessment community. Workshop planners and participants