Contents



    Preface                                                                         ix
    Acknowledgments                                                                xiii
    List of                                  flgures                                xv
    List of tables                                                                 xix
    List of abbreviations and acronyms                                             xxi


    1    Life   and climate in an ice age                                            1
         1.1     Continental climates during the Ice Age                             1
         1.2     The glacial world—according to Wally                                8
         1.3     Ice Age forests                                                    10



   2    Variability of the Earth's climate                                          13
        2.1 Factors that influence global climate                                   13
        2.2 Stable extremes of the Earth's climate                                  16
        2.3 Continental drift and Continental geometry as a factor in paleo-
             climate change                                                         19
             2.3.1 Effects of continental geometry                                  19
             2.3.2 Evolution of glaciation near the south pole ~34 million
                       years ago                                                   23
             2.3.3 The effect of the Isthmus of Panama on NH glaciation in
                       the past 2,700,000 years                                    25
        2.4 Ice ages in the recent geological past                                 29
        2.5 Geological evidence of ice ages                                        30




vi Contents

3   Ice core methodology                                                 37
    3.1 History of ice core research                                     37
    3.2 Dating ice core data                                             42
          3.2.1 Introduction                                             42
          3.2.2 Age markers                                              43
          3.2.3 Counting layers visually                                 45
          3.2.4 Layers determined by measurement                         49
          3.2.5 Ice flow modeling                                        50
          3.2.6 Other dating methods                                     53
          3.2.7 Synchronization of dating of ice cores from Greenland
                 and Antarctica                                          54
          3.2.8 GISP2 experience                                         54
          3.2.9 Tuning                                                   55
          3.2.10 Flimsy logic                                            56
    3.3 Processing ice core data                                         58
          3.3.1 Temperature estimates from ice cores                     58
          3.3.2 Climate variations                                       65
          3.3.3 Trapped gases                                            65

4   Ice core data                                                        67
    4.1 Greenland ice core historical temperatures                       67
    4.2 Antarctica ice core historical temperatures                      71
          4.2.1 Vostok and EPICA data                                    71
          4.2.2 Homogeneity of Antarctic ice cores                       73
    4.3 North-south synchrony                                            76
    4.4 Data from high-elevation ice cores                               79
    4.5 Carbon dioxide                                                   80
    4.6 Sudden climate changes                                           83

5   Ocean sediment data                                                   87
    5.1 Introduction                                                      87
    5.2 Chronology                                                        92
    5.3 Universality of ocean sediment data                               97
    5.4 Summary of ocean sediment ice volume data                         98
    5.5 Comparison of ocean sediment data with polar ice core data . .    99
    5.6 Historical sea surface temperatures                              102
    5.7 Ice-rafted debris                                                103

6   Other data sources                                                   105
    6.1 Devil's Hole                                                     105
         6.1.1   Devil's Hole data                                       105
         6.1.2 Comparison of Devil's Hole data with ocean sediment
                 data                                                    106
         6.1.3 Devil's Hole: global or regional data?                    108
         6.1.4 Comparison of Devil's Hole data with Vostok data . . .    109
                                                                       Contents vii

    6.2   Speleothems in caves                                                  110
    6.3   Magnetism in rocks and loess                                          113
          6.3.1 Magnetism in loess                                              113
          6.3.2   Rock magnetism in lake Sediments                              113
    6.4   Pollen records                                                        114
    6.5   Physical indicators                                                   116
          6.5.1 Ice sheet moraines                                              116
          6.5.2 Coral terraces                                                  116
          6.5.3 Mountain glaciers                                               118
    6.6   Red Sea Sediments                                                     118

7   Summary of climate variations                                               121
    7.1 Origin of glaciation—past 34 million years                              121
    7.2 The past 3 million years                                                121
    7.3 The past 800,000 years                                                  122
    7.4 The most recent ice age and its aftermath                               122
    7.5 The last termination                                                    123
    7.6 North-south synchrony                                                   125
    7.7 Carbon dioxide and methane                                              125

8   Overview of the various modeis for ice ages in the recent past (3 million
    years ago to the present)                                                   127
    8.1 Introduction                                                            128
    8.2 Variability of the Sun                                                  129
    8.3 Astronomical theory                                                     130
    8.4 Volcanism                                                               131
    8.5 Greenhouse gases                                                        134
    8.6 Role of the oceans                                                      134
          8.6.1   Glacial-interglacial cycles: the consensus view               134
          8.6.2   Sudden climate change: the consensus view                     138
          8.6.3 Wunsch's objections                                             141
    8.7 Models based on clouds                                                  147
          8.7.1   Extraterrestrial dust accretion                               148
          8.7.2 Clouds induced by cosmic rays                                   149
          8.7.3 Ocean-atmosphere model                                          152
    8.8 Models based on the southern hemisphere                                 153

9   Variability of the Earth's orbit: Astronomical theory                       155
    9.1 Introduction                                                            155
    9.2 Variability of the Earth's orbit                                        157
         9.2.1 Variability within the orbital plane                             157
         9.2.2 Variability of the orbital plane                                 159
    9.3 Calculation of solar intensities                                        160
    9.4 Importance of each orbital parameter                                    162
    9.5 Historical solar irradiance at higher latitudes                         165
viii Contents

    9.6   Connection between solar variability and glaciation/deglaciation
          cycles according to astronomical theory                             169
          9.6.1 Models for ice volume                                         170
          9.6.2   Review of the Imbries' model                                178
          9.6.3 Memory model                                                  181
    9.7   A model based on eccentricity                                       181
    9.8   North or south?                                                     183

10 Comparison of astronomical theory with data                                185
   10.1 Introduction                                                          185
   10.2 Comparison of data with astronomical theory                           186
        10.2.1 Direct comparison of the variability of solar intensity with
                ice core data                                                 188
        10.2.2 Comparison of Imbries' ice volume model with ocean
                sediment data                                                 194
   10.3 Spectral analysis                                                     196
         10.3.1 Introduction                                                  196
         10.3.2 Spectral analysis of solar and paleoclimate data              201
   10.4 Status of our understanding                                           206

11 Future prospects                                                           211
   11.1 The next ice age (or lack thereof)                                    211
         11.1.1 Introduction                                                  211
         11.1.2 Orthodoxy in climatology                                      212
         11.1.3 Effect of CO 2 growth on global temperature                   216
         11.1.4 Other evidence                                                228
         11.1.5 Will global warming prevent or initiate the next ice age?     233
   11.2 Approaches for improving our understanding                            237
         11.2.1 The need to depoliticize climate change                       237
         11.2.2 Technical progress                                            240

References                                                                    2 45
Index                                                                         259