Reanalysis of Historical Climate Data for Key Atmospheric Features
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1 U.S. Climate Change Science Program 2 3 4 Synthesis and Assessment Product 1.3 5 6 Reanalysis of Historical Climate 7 Data for Key Atmospheric Features: 8 Implications for Attribution of 9 Causes of Observed Change 10 11 12 13 Lead Agency: 14 National Oceanic and Atmospheric Administration 15 16 Contributing Agencies: 17 Department of Energy 18 National Aeronautics and Space Administration 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Note to Reviewers: This report has not yet undergone rigorous copy-editing 34 and will do so prior to layout for publication CCSP 1.3 August 29, 2008 35 Table of Contents 36 Abstract.............................................................................................................................. v 37 P.1 OVERVIEW OF REPORT ................................................................................. vii 38 P.2 PRIMARY FOCUS OF REPORT........................................................................ x 39 P.2.1 Reanalysis of Historical Climate Data for Key Atmospheric Features..... xi 40 P.2.2 Attribution of the Causes of Climate Variations and Trends over North 41 America...................................................................................................................xiii 42 P.3 TREATMENT OF UNCERTAINTY................................................................ xiv 43 P.4 SCOPE AND LIMITATIONS OF THIS REPORT.......................................... xv 44 Executive Summary.......................................................................................................... 1 45 ES.1 PRIMARY RESULTS AND FINDINGS........................................................... 2 46 ES.1.1 Strengths and Limitations of Current Reanalysis Datasets for 47 Representing Key Atmospheric Features ............................................................... 2 48 KEY FINDINGS (from Chapter 2)............................................................................. 2 49 ES.1.2 Attribution of the Causes of Climate Variations and Trends over North 50 America during the Modern Reanalysis Period..................................................... 4 51 KEY FINDINGS (from Chapter 3)............................................................................. 4 52 ES.2 RECOMMENDATIONS..................................................................................... 8 53 Chapter 1. Introduction.................................................................................................. 11 54 FUNDAMENTAL CONCEPTS ................................................................................ 11 55 1.1 REANALYSIS....................................................................................................... 11 56 1.2 ATTRIBUTION .................................................................................................... 16 57 1.3 CONNECTIONS BETWEEN REANALYSIS AND ATTRIBUTION............ 18 58 1.3.1 Steps in climate science.................................................................................. 19 59 1.3.2 Further comments.......................................................................................... 20 60 1.4 REANALYSIS APPLICATIONS AND USES................................................... 23 61 CHAPTER 1 REFERENCES .................................................................................... 25 62 Chapter 2. Reanalysis of Historical Climate Data for Key Atmospheric Features .. 27 63 KEY FINDINGS ......................................................................................................... 27 64 2.1. CLIMATE REANALYSIS AND ITS ROLE WITHIN A COMPREHENSIVE 65 CLIMATE OBSERVING SYSTEM......................................................................... 29 66 2.1.1 Introduction.................................................................................................... 29 67 2.1.2 What is a Climate Analysis? ......................................................................... 30 68 2.1.3 What is a Climate Reanalysis?...................................................................... 39 69 2.1.4. What Role Does Reanalysis Play within a Climate Observing System?.. 40 70 2.2. ROLE OF REANALYSIS IN UNDERSTANDING CLIMATE PROCESSES 71 AND EVALUATING CLIMATE MODELS ........................................................... 46 72 2.2.1 Introduction........................................................................................................ 46 73 2.2.2 Assessing Systematic Errors ......................................................................... 48 74 2.2.3 Inferences about Climate Forcing ................................................................ 51 75 2.2.4 Outlook............................................................................................................ 53 76 2.3. USING CURRENT REANALYSES TO IDENTIFY AND UNDERSTAND 77 MAJOR SEASONAL-TO-DECADAL CLIMATE VARIATIONS ...................... 54 78 2.3.1. Climate Variability ....................................................................................... 55 Do Not Cite or Quote ii NOAA Review Draft CCSP 1.3 August 29, 2008 79 2.3.2 Reanalysis and Climate Variability.............................................................. 61 80 2.4 CLIMATE TRENDS IN SURFACE TEMPERATURE AND 81 PRECIPITATION DERIVED FROM REANALYSES VERSUS FROM 82 INDEPENDENT DATA ............................................................................................. 77 83 2.4.1. Trend Comparisons: Reanalyses Versus Independent Measurements.... 78 84 2.4.2. Factors Complicating the Calculation of Trend ........................................ 83 85 2.4.3. Outlook........................................................................................................... 88 86 2.5 STEPS NEEDED TO IMPROVE CLIMATE REANALYIS........................... 90 87 2.5.1 Instrument and Sampling Issues .................................................................. 91 88 2.5.2 Modeling and Data Assimilation Issues ..................................................... 100 89 Chapter 3. Attribution of the Causes of Climate Variations and Trends over North 90 America during the Modern Reanalysis Period......................................................... 131 91 KEY FINDINGS ....................................................................................................... 131 92 INTRODUCTION..................................................................................................... 134 93 3.1 CLIMATE ATTRIBUTION AND SCIENTIFIC METHODS USED FOR 94 ESTABLISHING ATTRIBUTION......................................................................... 141 95 3.1.1 What is Attribution?.................................................................................... 141 96 3.1.2 How is Attribution Performed?.................................................................. 142 97 3.2 PRESENT UNDERSTANDING OF NORTH AMERICAN ANNUAL 98 TEMPERATURE AND PRECIPITATION CLIMATE TRENDS FROM 1951 99 TO 2006...................................................................................................................... 160 100 3.2.1 Summary of IPCC Fourth Assessment Report......................................... 160 101 3.2.2 North American Annual Mean Temperature ........................................... 163 102 3.3 PRESENT UNDERSTANDING OF UNITED STATES SEASONAL AND 103 REGIONAL DIFFERENCES IN TEMPERATURE AND PRECIPITATION 104 TRENDS FROM 1951 TO 2006 .............................................................................. 180 105 3.3.1 Introduction.................................................................................................. 180 106 3.3.2 Temperature Trends.................................................................................... 182 107 3.3.3 Precipitation Trends .................................................................................... 197 108 3.4 NATURE AND CAUSE OF APPARENT RAPID CLIMATE SHIFTS FROM 109 1951 TO 2006............................................................................................................. 207 110 3.4.1 Introduction.................................................................................................. 207 111 3.4.2 Defining Rapid Climate Shifts .................................................................... 208 112 3.4.3 Mechanisms for Rapid Climate Shifts ....................................................... 209 113 3.4.4 Rapid Climate Shifts since 1950 ................................................................. 210 114 3.5 UNDERSTANDING OF THE CAUSES FOR NORTH AMERICAN HIGH- 115 IMPACT DROUGHT EVENTS FOR 1951 TO 2006 ........................................... 217 116 3.5.1. Introduction................................................................................................. 217 117 3.5.2 Definition of Drought................................................................................... 218 118 3.5.3 Drought Causes ............................................................................................ 219 119 CHAPTER 3 REFERENCES .................................................................................. 240 120 4.1 NEED FOR A SYSTEMATIC APPROACH TO CLIMATE ANALYSIS AND 121 REANALYSIS........................................................................................................... 257 122 4.2 RECOMMENDATIONS FOR IMPROVING FUTURE CLIMATE 123 ANALYSES AND REANALYSES.......................................................................... 258 124 4.3 NEED FOR IMPROVED CLIMATE ATTRIBUTION