Note: Intro -- Contents -- List of Figures -- List of Tables -- Contributors -- The World Climate Research Program Strategy and Priorities: Next Decade -- 1 Introduction -- 2 Evolution of WCRP Research Mandate -- 3 Future Plans and Priorities of WCRP Major Sponsors -- 4 Overview of Following Chapters -- 5 Summary -- References -- Challenges of a Sustained Climate Observing System -- 1 Introduction -- 2 The Current Climate Observing System -- 2.1 Status of Systematic Climate Observations -- 2.2 Building a System for Climate Observations -- 2.3 Developing Operational Components -- 3 Lost in Space: Climate Observations? -- 3.1 Current and Programmed Satellite Observations -- 3.2 Adequacy of In-Situ Observations -- 3.3 The Scope of the Challenge of Satellite Observations: Adequacy and Issues -- 3.3.1 The Missing Satellite Observing System Principles -- 3.3.2 Delays and Cost Increases -- 3.4 Decadal Change Accuracy: Unbroken Chain of Uncertainty to SI Standards -- 3.4.1 Accuracy and SI Standards -- 3.4.2 Stability of Observations and Algorithms -- 3.4.3 Accuracy -- 3.5 Improving Transitions Between Observing Systems -- 3.6 How to Prioritize? -- 4 Analyses, Assessments and Reprocessing -- 4.1 Reanalyses -- 4.2 Assessments -- 5 Further Needed Improvements -- 5.1 In Situ Observations -- 5.2 Data Documentation and Adequacy of Metadata -- 5.3 Tracking Climate Observing Performance -- 5.4 Climate Observations at High Risk -- 6 Appendix A: The GCOS Organizational Framework -- References -- On the Reprocessing and Reanalysis of Observations for Climate -- 1 Reprocessing Observations -- 1.1 Data Recovery and Archiving -- 1.2 Data Set Creation and Evaluation -- 1.3 Recommendations -- 2 Reanalysis of Observations -- 2.1 Current Status -- 2.2 Integrating Earth System Analyses -- 2.3 Reanalysis Input Observations -- 2.4 Recommendations -- 3 Future Directions. , References -- Climate Processes: Clouds, Aerosols and Dynamics -- 1 Introduction -- 2 Recent Scientific Advances -- 2.1 Clouds and Convection -- 2.1.1 Boundary Layer Clouds and Dynamics -- 2.1.2 Deep Convection and Its Dynamical Coupling to Larger Scales -- 2.1.3 Microphysics -- 2.1.4 Trends, Variations and Feedbacks -- 2.2 Aerosols and Aerosol-Cloud Interactions -- 2.2.1 Sources, Ageing and Sinks of Aerosols in the Atmosphere -- 2.2.2 Direct and Indirect Radiative Effects of Aerosols on Climate -- 2.2.3 Microphysical Effects of Aerosols on Precipitation and Vice Versa -- 2.2.4 Advances in Parameterizing Aerosols -- 2.3 Dynamics from Small to Global Scales -- 2.3.1 Gravity Waves -- 2.3.2 Blocking Events -- 2.3.3 Widening of the Tropics -- 2.3.4 Impact of the Stratosphere on the Large-Scale Circulation -- 2.3.5 Impact of Warming on Rainfall Extremes, Cyclones, and Severe Storms -- 3 Current Scientific Gaps and Open Questions -- 3.1 Clouds and Convection -- 3.2 Aerosols and Aerosol-Cloud Interactions -- 3.3 Dynamics from Small to Global Scales -- 4 Strategic Opportunities and Recommendations -- 4.1 Research Foci, Strategies and Resources -- 4.1.1 Confront Two-Way Integration Across Scales -- 4.1.2 Emphasize Fundamental Science and Model Development -- 4.1.3 Explore Hierarchical Modeling Approaches -- 4.1.4 Integrate the Whole Atmosphere, Ocean and Surface -- 4.1.5 Plan for the High-Resolution Future -- 4.1.6 Bring Weather to Climate -- 4.1.7 Sustain and Improve Observations -- 4.2 Research Coordination -- 5 Summary -- References -- Aerosol Cloud-Mediated Radiative Forcing: Highly Uncertain and Opposite Effects from Shallow and Deep Clouds -- 1 Introduction -- 2 Aerosol-Induced Radiative Forcing by Boundary-Layer Warm Clouds -- 2.1 The Fundamental Physical Processes -- 2.2 Aerosol Effects on Non-precipitating and Modestly Precipitating Clouds. , 2.3 Aerosol Effects on the Transition to Precipitating Clouds -- 2.4 The Frequency of Occurrence of Aerosol-Starved Cloud Regimes -- 2.5 The Attribution of the Regime Changes to Anthropogenic Aerosols -- 2.6 The Possible Underestimation of the Radiative Forcing Via Low Clouds -- 3 Aerosol Induced Radiative Forcing by Deep Convective Clouds -- 3.1 Aerosol Invigoration of Deep Clouds in Warm and Moist Atmosphere -- 3.2 Aerosols Enhancing Detrainment of Ice and Vapor in the UTLS -- 4 Aerosol Induced Radiative Forcing by Supercooled Layer Clouds -- 5 Discussion and Implications for GCMs -- 6 What Should We Do Next? -- 7 Summary -- References -- Improving Understanding of the Global Hydrologic Cycle -- 1 Introduction: The Challenge -- 2 Current WCRP Efforts -- 3 Improve Collection of Hydrological and Water System Data -- 3.1 Ground-Based, In-Situ Observations -- 3.2 Remotely Sensed Observations -- 3.3 Managing Data -- 4 Modeling -- 5 Hydrological Sciences Needs for the Twenty-First Century in the Earth System Context -- 5.1 Climate, Water, and Social Adaptation -- 5.2 Water, Energy, Agricultural Nexus -- 5.3 Water Quality and Ecosystems -- 6 A Grand Challenge in Hydrologic and Water-Resources Modeling -- 7 Conclusions -- References -- Land Use and Land Cover Changes and Their Impacts on Hydroclimate, Ecosystems and Society -- 1 Introduction -- 2 Land Use Change and Hydroclimate -- 3 Land Use Change and Ecosystems -- 4 Societal Needs for Research on Water Over Land -- 5 Current Gaps, and Future Challenges -- 6 Concluding Remarks -- References -- Prediction from Weeks to Decades -- 1 Introduction -- 2 Sub-seasonal Prediction -- 2.1 Madden Julian Oscillation -- 2.2 Other Sources of Sub-seasonal Predictability -- 3 Seasonal-to-Interannual Prediction -- 3.1 El Nino Southern Oscillation (ENSO) -- 3.2 Tropical Atlantic Variability. , 3.3 Tropical Indian Ocean Variability -- 3.4 Other Sources of Seasonal to Interannual Predictability -- 3.4.1 Upper Ocean Heat Content -- 3.4.2 Snow Cover -- 3.4.3 Stratosphere -- 3.4.4 Vegetation and Land Use -- 3.4.5 Polar Sea Ice -- 4 Decadal Prediction -- 4.1 Potential Sources of Decadal Predictability -- 4.1.1 External Forcing -- 4.1.2 Atlantic Multi-decadal Variability -- 4.1.3 Pacific Decadal Variability -- 4.1.4 Other Sources of Decadal Predictability -- 4.2 Achievements So Far -- 5 Summary -- 5.1 Improving the Fidelity of the Climate Models at the Heart of Forecast Systems -- 5.2 Developing More Sophisticated Measures of Defining and Verifying Forecast Reliability and Skill for the Different Lead Times -- 5.3 Design of Ensemble Prediction Systems -- 5.4 Utility of Monthly to Decadal Predictions -- References -- Assessing the Reliability of Climate Models, CMIP5 -- 1 Introduction -- 2 The Implications (and Usefulness) of Model Spread -- 3 New Observations and Diagnostics -- 4 Examples of Process Evaluations Currently in Progress -- 5 Summary and Recommendations for WCRP -- References -- Changes in Variability Associated with Climate Change -- 1 Introduction -- 2 How Do Changes in Greenhouse Gases and Solar and Orbital Parameters Impact the Tropics? -- 2.1 ENSO -- 2.2 Width of the Tropics -- 3 How Does Climate Change Impact Middle and High Latitudes? -- 3.1 The Northern Annular Mode and Related Latitudinal Shifts of the Eddy-Driven Jet -- 3.2 The Southern Annular Mode -- 3.3 Sea Ice and Associated Atmospheric and Oceanic Circulations -- 4 How Do Greenhouse Gas Induced Climate Changes Interact with Ozone Depletion? -- 5 Summary -- References -- Understanding and Predicting Climate Variability and Change at Monsoon Regions -- 1 Introduction -- 2 Regional Perspectives -- 2.1 Asian-Australian Monsoons. , 2.1.1 Regional Variability and Predictability -- 2.1.2 Long-Term Trends and Projections -- 2.2 American Monsoon Systems -- 2.2.1 Regional Variability and Predictability -- 2.2.2 Long-Term Trends and Projections -- 2.3 Sub-Saharan Africa -- 2.3.1 Regional Variability and Predictability -- 2.3.2 Long-Term Trends and Projections -- 3 Regional Climate Simulation -- 3.1 Regionalization Needs -- 3.2 Coordinated Downscaling Exercises -- 4 Challenges in Monsoon Simulation and Prediction -- 4.1 Large to Regional Scale Processes Influencing Monsoon Variability and Predictability -- 4.2 Key Local to Regional Processes Influencing Monsoon Variability and Predictability -- 4.2.1 Surface Heterogeneity -- 4.2.2 Diurnal Cycle -- 4.2.3 Low Level Jets -- 4.2.4 Regional Ocean-Atmosphere Coupling -- 5 Challenges in Generating Actionable Regional Climate Information -- 6 Concluding Remarks -- References -- Attribution of Weather and Climate-Related Events -- 1 Introduction -- 2 Relevance of Attribution Assessments of Weather and Climate-Related Events -- 2.1 Improved Climate Science -- 2.2 General Public -- 2.3 Litigation -- 2.4 Adaptation -- 2.5 Geoengineering -- 2.6 Insurance -- 3 Development of Event Attribution -- 4 Examples of Event Attribution for Specific Cases -- 4.1 2003 Central European Summer Temperatures -- 4.2 2000 UK Floods -- 4.3 2008 Cool US -- 4.4 2010 Russian Heatwave -- 5 Attribution of Climate-Related Events Group -- 6 Development of Near-Real Time Weather and Climate Event Attribution -- 6.1 Coupled Model Approaches -- 6.2 Very Large Ensembles Using Distributed Computing Experiments -- 6.3 Analogue Methods for Diagnosing the Influence of Circulation Characteristics -- 6.4 A Near-Real Time Attribution Capability Linked to Seasonal Forecasting -- 7 Discussion: Lessons Learned and Future Research Needs -- References. , Climate Extremes: Challenges in Estimating and Understanding Recent Changes in the Frequency and Intensity of Extreme Climate and Weather Events.