Climatic Changes Since 1700 (eBook)

Preface 6
Acknowledgements 10
Contents 12
List of Boxes 16
1 Introduction 17
2 The Basis: Past Climate Observations and Methods 24
2.1 Observations of Weather and Climate 24
2.2 Historical Climate Observations 27
2.2.1 Documentary and Early Instrumental Data 27
2.2.2 From National Weather Services to a Global Observing System 30
2.3 Upper-Air and Satellite Observations 32
2.4 Data Dissemination in the Course of Time 34
2.5 Uncertainties in Climatic Data 38
2.5.1 Uncertainties and Errors in Measurement Series 38
2.5.2 Inhomogeneities and Homogenisation 41
2.5.3 The Chain of Uncertainties 44
2.6 Data Products and Dynamical-Statistical Methods 45
2.6.1 Spatial Information and Geostatistical Methods 45
2.6.2 Data Assimilation and Reanalyses 49
2.7 Climate Models 53
2.7.1 Characteristics of Climate Models 53
2.7.2 Types of Climate Models and Experiments 59
2.7.3 Downscaling, Nudging, and Other Techniques 62
2.8 Palaeoclimate Information and Techniques 63
2.8.1 Climate Proxies 63
2.8.2 Problems Arising When Working with Proxies 67
2.8.3 Calibration and Modelling of Proxies 69
2.8.4 Climate Reconstructions 71
2.8.5 Data Assimilation in Palaeoclimatology 74
2.9 Datasets Used in This Book 77
2.9.1 Overview 77
2.9.2 Observations and Reanalyses 77
2.9.3 Model Simulations 79
2.9.4 Reconstructions and Offline Assimilation 80
2.9.5 Conclusions 83
3 The Machinery: Mechanisms Behind Climatic Changes 85
3.1 Basic Climate Physics: The Mean State 86
3.1.1 Energy Budget and Heat Transport 86
3.1.1.1 Global-Mean Fluxes 86
3.1.1.2 Spatial View of Heat Transport 88
3.1.2 The General Circulation of the Atmosphere 90
3.1.2.1 The Zonally Symmetric Circulation 90
3.1.2.2 The Zonally Asymmetric Circulation 93
3.1.2.3 The Weather Scale 96
3.1.2.4 Energy Transport 98
3.1.3 Stratospheric Circulation 99
3.1.3.1 Demarcation and Zonal-Mean Circulation 101
3.1.3.2 The Quasi-Biennial Oscillation (QBO) 102
3.1.3.3 Meridional Circulation and Wave–Mean Flow Interaction 103
3.1.3.4 Sudden Stratospheric Warmings and Downward Propagation 106
3.1.4 The Ocean, Air–Sea and Land-Sea Interactions 107
3.1.4.1 Ocean–Atmosphere Interaction 108
3.1.4.2 Ocean Currents 109
3.1.4.3 Land–Sea Interaction 110
3.1.4.4 Monsoon 111
3.1.4.5 Sea Ice and Snow Cover 113
3.2 Expressions and Mechanisms of Climate Variability 115
3.2.1 Statistical and Physical Perspectives of Climate Variability 115
3.2.2 Overview of Circulation Variability Modes 117
3.2.3 The North Atlantic Oscillation (NAO) 118
3.2.4 Variability Modes in the Pacific and the Southern Hemisphere 122
3.2.4.1 The Pacific-North American Pattern 122
3.2.4.2 The Pacific-South American Pattern and the Southern Annular Mode 124
3.2.5 Extratropical Circulation Variability Modes and the Stratosphere 125
3.2.6 Tropical Variability Modes: El Niño–Southern Oscillation (ENSO) 127
3.2.6.1 The ENSO Phenomenon 127
3.2.6.2 ENSO Mechanisms 127
3.2.6.3 ENSO Variability and ``Flavours'' of ENSO 130
3.2.6.4 ENSO Teleconnections 130
3.2.7 Variability Modes in the Atlantic and Indian Ocean 133
3.2.8 Decadal Climate Variability Modes 134
3.3 Forced Climatic Changes 137
3.3.1 Volcanic Effects 137
3.3.1.1 Direct (Radiative) Effects 141
3.3.1.2 Indirect Dynamical Effects 142
3.3.1.3 Aerosol Size 146
3.3.1.4 Quantification of Past Volcanic Forcing 149
3.3.2 Solar Influences 150
3.3.2.1 Changes in Solar Activity 151
3.3.2.2 Observed Solar Effects 152
3.3.2.3 Possible Mechanisms 153
3.3.2.4 Beyond the Sunspot Cycle 155
3.3.2.5 Time Series of Solar Forcing 157
3.3.3 Well-Mixed Greenhouse Gases 159
3.3.3.1 Mechanism 159
3.3.3.2 Impacts on Future Climate 161
3.3.3.3 Effects of Greenhouse Gases on Past Climate 162
3.3.3.4 Changes in Greenhouse Gas Concentrations Since 1600 164
3.3.4 Tropospheric Aerosols and Reactive Trace Gases 164
3.3.4.1 Properties of Aerosols 165
3.3.4.2 Sources and Spatial Distribution of Aerosols 166
3.3.4.3 Impacts on Climate 167
3.3.4.4 Tropospheric Trace Gases 170
3.3.5 Land Surface 171
3.3.5.1 Mechanisms 171
3.3.5.2 Climate Impacts and Development of Land Cover Since 1600 173
3.4 Coupling Between Systems and Feedback Mechanisms 175
3.4.1 Interaction Within the Machinery 175
3.4.2 Feedbacks Involving Water Vapour and Clouds 177
3.4.3 Feedbacks Involving Freezing Water: Arctic Amplification and the Cryosphere 178
3.4.4 Water as a Reactant: The Role of the Hydroxyl Radical 178
3.4.5 Feedbacks Involving Evaporating Water: Land Surface Feedbacks 179
4 Climatic Changes Since 1700 181
4.1 Climatic Changes of the Past Centuries: An Overview 182
4.1.1 The Last Millennium 182
4.1.2 An Overview of Climatic Changes Since 1700: Brükner's View 185
4.1.3 Climatic Changes Since 1700 in Climate Reconstructions 188
4.1.3.1 Global and Northern Hemisphere Temperature Changes 188
4.1.3.2 Continental Temperature Reconstructions 190
4.1.3.3 Precipitation and Drought Reconstructions 193
4.1.3.4 Sea-Surface Temperature Reconstructions 195
4.1.3.5 Regional Climate: Central Europe and the European Alps 197
4.1.4 Climatic Changes in CCC400 and EKF400 199
4.1.4.1 Global, Hemisphere and Continental Scales 199
4.1.4.2 Changes in the Zonal-Mean Circulation 200
4.1.4.3 Changes in Regional Circulation Indices 202
4.1.4.4 Changes in Extremes 205
4.1.5 Drivers of Global Climate Since 1600 207
4.2 The Period from 1700 to 1890: The Little Ice Age 211
4.2.1 Climate of the 18th and 19th Centuries 212
4.2.1.1 Mean Climate of the 1700–1890 Period 212
4.2.1.2 Triggers of the Little Ice Age 213
4.2.2 The Maunder Minimum: A Compelling Case for Solar Forcing? 215
4.2.2.1 The Late Maunder Minimum: Rock Bottom of the Little Ice Age Climate 216
4.2.2.2 The Late Maunder Minimum in EKF400 218
4.2.3 The 1790s: Temporary Warmth and Strong Tropical Circulation 219
4.2.3.1 The Summers of 1800–1804 in Switzerland 220
4.2.3.2 Warming in Europe 221
4.2.3.3 Regional or Global? 222
4.2.3.4 Causes of the 1790s Warmth 222
4.2.4 Tambora Eruption, Dalton Minimum, and the Year Without a Summer of 1816 224
4.2.4.1 Anatomy of the Year Without a Summer 225
4.2.4.2 Causes 226
4.2.4.3 The Year Without a Summer of 1816 in EKF400 and Early Instrumental Data 226
4.2.4.4 The Mistery Continues 228
4.2.5 The Maximum State of Alpine Glaciers in the 1850s 230
4.2.5.1 A 19th Century View of Glacier Changes 230
4.2.5.2 Causes of the 1850s Glacier Advance 232
4.2.5.3 Climate and Glacier Growth Assessed from HISTALP Data 233
4.2.5.4 Retreat 233
4.2.6 Global Droughts During 1876–1878 and El Niño 235
4.2.6.1 The 1877/1878 Drought in EKF400, CCC400, and 20CR 236
4.2.7 Frequent Flooding in the Central European Alps: 1830–1880s 240
4.2.7.1 The 1868 Flood in 20CR and Instrumental Data 241
4.2.8 The Broad Lines: The Little Ice Age 243
4.3 The Period from 1890 to 1945: Out of the Cold 244
4.3.1 Global Drivers and Global Changes 245
4.3.1.1 Changes in Circulation Indices 246
4.3.2 The Warming of the European Arctic from the 1910s to the 1940s 251
4.3.2.1 Mechanisms of the Early 20th Century Arctic Warming 252
4.3.2.2 The Early 20th Century Arctic Warming in CCC400, 20CR, and REC1 253
4.3.3 The ``Dust Bowl'' Droughts of the 1930s 257
4.3.3.1 Development and Causes of the Dust Bowl 258
4.3.3.2 The Dust Bowl in CCC400, 20CR, Reconstruction and Upper-Level Data 261
4.3.3.3 Puzzle Solved? 263
4.3.4 Global Climate Anomalies During the 1939–1942 El Niño 264
4.3.4.1 The 1940–1942 Climate Anomaly in REC1, CCC400, and HISTOZ 265
4.3.4.2 Wider Effects of El Niño 268
4.3.5 The Broad Lines: Out of the Cold 268
4.4 The Period from 1945 to 1985: Delusive Stability 273
4.4.1 Global Drivers and Global Changes 274
4.4.2 Changes in Atmospheric Constituents 276
4.4.2.1 Tropospheric Aerosols 277
4.4.2.2 Ozone, Methane and Earth's Changing Oxidation Capacity 278
4.4.2.3 A Thickening Ozone Layer? 281
4.4.3 European Summers of 1945–1949 281
4.4.3.1 Causes and Mechanisms 282
4.4.3.2 The Droughts in CCC400, 20CR, and REC2 283
4.4.3.3 The 1947 Heatwaves 286
4.4.4 Sahel Pluvial and Drought 287
4.4.4.1 Causes and Mechanisms of the Drought 287
4.4.4.2 The Sahel Pluvial and Droughts in CCC400, REC2, and ECHAM-HAM Nudged Simulations 289
4.4.5 The Climate Shift of 1976/1977 290
4.4.6 The Broad Lines: Delusive Stability 293
4.5 The Period Since 1985: Accelerated and Slowed Warming 297
4.5.1 Global Drivers and Global Changes 298
4.5.1.1 Global Warming and More 298
4.5.1.2 Greenhouse Gases and Global Brightening 302
4.5.2 The Ozone Hole 303
4.5.2.1 Ozone Depletion and the Ozone Hole in the CASTRO Simulations 304
4.5.2.2 Effect of the Ozone Hole on Climate 307
4.5.2.3 The Southern Annular Mode 308
4.5.3 Eruption of Pinatubo 310
4.5.3.1 Stratospheric Ozone and Temperatures 310
4.5.3.2 Effects on the Energy Budget and the Water Cycle 311
4.5.3.3 Effects on the Biosphere 312
4.5.3.4 Small Eruptions 313
4.5.4 Warm European Winters, Increased Storminess and Positive NAO in the 1990s 314
4.5.4.1 Winter Storms 315
4.5.4.2 Forced NAO? 318
4.5.5 The El Niño of 1997/1998, Forest Fires and the Atmospheric Brown Cloud 319
4.5.5.1 Forest Fires 320
4.5.5.2 The Atmospheric Brown Cloud 320
4.5.6 Droughts in Australia and the Northern Subtropics 322
4.5.6.1 Subtropical Drought 1998–2004 322
4.5.6.2 The Millenium Drought in Australia 323
4.5.7 Megaheatwaves 324
4.5.7.1 Record-Breaking Heatwaves in the NCEP/NCAR Reanalysis 324
4.5.7.2 Changes in Heatwaves 325
4.5.8 Recent Arctic Warming 326
4.5.8.1 Record Sea Ice Loss 327
4.5.8.2 Vertical Structure of Temperature and Moisture Changes 328
4.5.8.3 Links with the Extratropics and Atmospheric Circulation 329
4.5.9 The Global Warming Hiatus 330
4.5.9.1 Trends 331
4.5.9.2 Data and Models 332
4.5.9.3 Statistical Perspective 332
4.5.9.4 Process-Based Perspective: Internal Variability 333
4.5.9.5 Changes in the Forcing 334
5 Conclusions 336
References 340