The global climate changes that led to the expansion and contraction of high latitude ice sheets during the Quaternary period were associated with equally dramatic changes in tropical environments. These included shifts in vegetation zones, changes in the hydrology and ecology of lakes and rivers, and fluctuations in the size of mountain glaciers and sandy deserts. Until recently it was thought that such changes were triggered by fluctuations in the distribution of polar ice cover. Now there is increasing recognition that the tropics themselves have acted as drivers of global climate change over a range of timescales.

The aim ofQuaternary Environmental Change in the Tropics is to provide a synthesis of the changes that occurred in tropical terrestrial and marine systems during the Pleistocene and Holocene, complementing data-derived reconstructions with output from state-of-the-art climate models. It is targeted at final-year undergraduate students and research specialists, but will provide an introduction to tropical Quaternary research for a variety of other readers.

Sarah Metcalfe is Professor of Earth and Environmental Dynamics at the University of Nottingham, UK.  She has published extensively on environmental change in Latin America, with a particular focus on Mexico.  Although primarily a palaeolimnologist, her approach is very much multi-proxy, including the use of historical and instrumental records to help to improve our understanding of recent change.

David Nash is Professor of Physical Geography at the University of Brighton, UK. He is widely known for his publications on the reconstruction of historical climate changes in southern Africa, as well as his broader research into the contemporary and Quaternary geomorphology of dryland regions including the Kalahari, Atacama and southern Europe. His research uses methods ranging from scanning electron microscopy and thin-section analysis to the interpretation of historical documents.

List of contributors, xi

Preface, xiii

Acknowledgements, xiv

I Global contexts, 1

1 Introduction, 3
Sarah E. Metcalfe and David J. Nash

1.1 Why the tropics matter, 3

1.1.1 Defining the tropics, 3

1.1.2 Importance of the tropics, 4

1.2 Development of ideas, 8

1.2.1 Early ideas about tropical environmental change, 8

1.2.2 The twentieth century revolution, 9

1.2.3 Advances in modelling, 12

1.3 Establishment of the tropical climate system, 13

1.4 Drivers of tropical environmental change, 17

1.5 The tropics as drivers of change, 20

1.5.1 The tropics and greenhouse gas concentrations, 20

1.5.2 Impacts of low latitude volcanic eruptions, 22

1.5.3 Dust emissions from the tropics and subtropics, 23

1.6 Extra-tropical forcing, 24

1.7 Organisation of the volume, 24

Acknowledgements, 25

References, 25

2 Contemporary climate and circulation of the tropics, 34
Stefan Hastenrath

2.1 Introduction, 34

2.2 Diurnal and local processes, 34

2.3 Planetary context, 35

2.4 Regional circulation systems, 36

2.4.1 Jet streams, 36

2.4.2 Subtropical highs and trade winds, 37

2.4.3 Equatorial trough zone, 37

2.4.4 Monsoons, 38

2.4.5 Equatorial zonal circulations, 38

2.5 Climatic variability, 39

2.5.1 Southern Oscillation and El Niño, 39

2.5.2 Indian Monsoon, 40

2.5.3 Northeast Brazil, 41

2.5.4 Sahel, 41

2.5.5 Timescales of variability, 42

2.6 Concluding remarks, 42

References, 42

II Regional environmental change, 45

3 Tropical oceans, 47
Jan-Berend W. Stuut, Matthias Prange, Ute Merkel and Silke Steph

3.1 Tropical oceans in the global climate system, 47

3.1.1 Modern climatology, 47

3.1.2 El NiñoSouthern Oscillation and its relatives, 50

3.1.3 Solar and volcanic radiative forcing of tropical oceans, 51

3.1.4 Tropical oceans and monsoons, 53

3.1.5 The tropical oceans as part of the global conveyor belt, 53

3.2 Reconstructing past ocean conditions, 55

3.2.1 Proxies for SST and SSS, 55

3.2.2 Reconstructing continental climate using marine archives, 57

3.3 Tropical oceans throughout the Quaternary, 57

3.3.1 Glacialinterglacial cycles, 57

3.3.2 Early Quaternary (the 41-kyr world), 57

3.3.3 Mid-Pleistocene Transition, 58

3.3.4 Late Quaternary (the 100-kyr world), 60

3.4 The past 20 000 years, 60

3.4.1 The Last Glacial Maximum, 60

3.4.2 Glacial termination: an active role for the tropics?, 61

3.4.3 History of the equatorial Pacific and the state of ENSO, 65

3.4.4 The Holocene, 66

3.5 Outlook, 68

References, 69

4 Africa, 79
David J. Nash and Michael E. Meadows

4.1 Introduction, 79

4.2 Potential climate forcing factors, 85

4.3 Mediterranean North Africa, 88

4.3.1 Contemporary climate and sources of palaeoenvironmental information, 88

4.3.2 Longer records, 88

4.3.3 The Last Glacial Maximum, 89

4.3.4 The last glacialinterglacial transition, 92

4.3.5 The Holocene, 93

4.4 The Sahara and the Sahel, 94

4.4.1 Contemporary climate and sources of palaeoenvironmental information, 94

4.4.2 Longer records, 95

4.4.3 The Last Glacial Maximum, 96

4.4.4 The last glacialinterglacial transition, 97

4.4.5 The Holocene, 99

4.5 Equatorial Africa, 103

4.5.1 Contemporary climate and sources of palaeoenvironmental information, 103

4.5.2 Longer records, 104

4.5.3 The Last Glacial Maximum, 107

4.5.4 The last glacialinterglacial transition, 109

4.5.5 The Holocene, 110

4.6 Southern Africa, 113

4.6.1 Contemporary climate and sources of palaeoenvironmental information, 113

4.6.2 Longer records, 113

4.6.3 The Last Glacial Maximum, 118

4.6.4 The last glacialinterglacial transition, 121

4.6.5 The Holocene, 122

4.7 Synthesis, 127

4.8 Directions for future research, 129

References, 129

5 India, Arabia and adjacent regions, 151
Ashok K. Singhvi, Nilesh Bhatt, Ken W. Glennie and Pradeep Srivastava

5.1 Introduction, 151

5.2 Quaternary of India and Tibet, 153

5.2.1 Arid and semi-arid regions, 154

5.2.2 Aeolian sands, 154

5.2.3 Aeolian dust (loess deposits), 159

5.2.4 Volcanic ash, 159

5.2.5 Lacustrine records, 161

5.2.6 Peat deposits, 166

5.2.7 Calcretes, 167

5.2.8 Coastal records, 167

5.2.9 Fluvial records, 171

5.2.10 Cave deposits, 176

5.3 Quaternary of the Arabian Sea and Bay of Bengal, 176

5.4 Quaternary of Arabia and the Middle East, 177

5.4.1 Fluvial (wadi) systems, 179

5.4.2 Lacustrine (and sabkha) records, 180

5.4.3 Cave deposits, 182

5.4.4 Aeolian sands, 183

5.4.5 Gypsum in dunes, 187

5.4.6 Late Quaternary Persian (Arabian) Gulf, 188

5.4.7 Dating aeolian sediment supply, 189

5.4.8 Climatic optimum and modern Arabian civilisation, 191

5.4.9 Summary of environmental changes in Arabia and the Middle East, 191

5.5 Conclusions, 192

Acknowledgements, 196

References, 196

6 China and Southeast Asia, 207
Dan Penny

6.1 The South and Southeast Asian region as a component of the Earth system, 207

6.2 Setting the stage for the Quaternary: environmental context and controls, 211

6.3 Regional syntheses, 214

6.3.1 China, 214

6.3.2 Indochina, 221

6.3.3 Sundaland and Wallacea, 225

6.4 The Asian tropics during the Quaternary: driver of planetary change?, 229

References, 230

7 Australia and the southwest Pacific, 236
Peter Kershaw and Sander van der Kaars

7.1 Introduction, 236

7.2 Northeastern Australia, 240

7.2.1 Orbital timescale, 240

7.2.2 Suborbital timescale, 244

7.2.3 Termination 1 and the Holocene, 244

7.3 Northern Australia, 245

7.3.1 Orbital timescale, 245

7.3.2 Termination 1 and the Holocene, 246

7.4 Northwestern Australia, 247

7.4.1 Orbital timescale, 247

7.4.2 Termination 1 and the Holocene, 249

7.5 Western Australia, 249

7.5.1 Orbital timescale, 249

7.5.2 Termination 1 and the Holocene, 251

7.6 Central Australia, 251

7.6.1 Orbital timescale, 251

7.6.2 Termination 1 and the Holocene, 253

7.7 Southwest Pacific Islands, 253

7.8 General discussion and conclusions, 254

7.8.1 Early Quaternary, 254

7.8.2 Late Quaternary cyclicity and abrupt events, 255

7.8.3 Late Quaternary climate alterations, 256

Acknowledgements, 258

References, 258

8 Latin America and the Caribbean, 263
Mark B. Bush and Sarah E. Metcalfe

8.1 Introduction, 263

8.2 Precursor to the Quaternary, 264

8.2.1 Climatic consequences of closure of the Isthmus of Panama, 267

8.2.2 Biotic consequences of closure of the Isthmus of Panama, 267

8.3 Climate mechanisms, 267

8.3.1 Modern climatology, 267

8.3.2 The forcing of Neotropical climates, 270

8.4 Long term climate forcings and cycles, 271

8.4.1 Eccentricity, 271

8.4.2 Precessional cycles and precipitation patterns, 272

8.4.3 Precession as a mixed signal, 273

8.5 Records of climate change, 274

8.5.1 Glacial advance and the LGM, 274

8.5.2 Glacial cooling, 276

8.5.3 Glacial-age precipitation, 278

8.5.4 The status of the refugial hypothesis of tropical diversity, 284

8.5.5 The last deglaciation, 286

8.5.6 The early-mid Holocene, 287

8.5.7 Late Holocene oscillations, 289

8.6 Other climate forcings, 289

8.6.1 Millennial-scale oscillations, 289

8.6.2 Solar cycles, 291

8.6.3 El NiñoSouthern Oscillation, 292

8.7 El Niño records, 292

8.7.1 Archaeology, 292

8.7.2 Historical records, 293

8.7.3 Tree ring records, 293

8.7.4 Corals, 294

8.7.5 Sedimentary records, 295

8.8 Climate and societies, 296

8.8.1 Early agriculture, 296

8.8.2 Cultural collapse, 297

8.9 Conclusions, 298

Acknowledgements, 301

References, 301

III Global syntheses, 313

9 Modelling of tropical environments during the Quaternary, 315
Zhengyu Liu and Pascale Braconnot

9.1 Introduction, 315

9.2 Tropical climate in the Holocene: response to orbital forcing, 316

9.2.1 Orbital forcing, 316

9.2.2 Monsoon response, 317

9.2.3 SST response and oceanic feedback, 319

9.2.4 Precession forcing and obliquity forcing, 324

9.2.5 Ecosystem response and feedback, 330

9.3 Tropical climate at the LGM: the roles of GHGs and ice sheet forcing, 333

9.3.1 Greenhouse gases and ice sheet forcing, 333

9.3.2 Temperature response and climate sensitivity, 333

9.3.3 Monsoon and hydrological response, 338

9.3.4 Ecosystem response and feedbacks, 339

9.4 Tropical climate variability, 339

9.4.1 ENSO and oceanatmosphere interaction, 340

9.4.2 Abrupt change of monsoon climate, 343

9.4.3 Tropical variability and its interaction with high-latitude variability, 344

9.5 Summary and further discussion, 349

9.5.1 Summary, 349

9.5.2 Other issues in Quaternary tropical climate modelling, 350

9.5.3 Climate models of intermediate complexity, 350

9.5.4 Perspective of Earth system modelling of past climate, 351

References, 352

10 Historical environmental change in the tropics, 360
Georgina H. Endfi eld and Robert B. Marks

10.1 Introduction, 360

10.2 Climate change and society in the tropics in the last 1000 years, 361

10.2.1 Climate variability and harvest history in China, 365

10.2.2 Climate and crisis in colonial Mexico, 370

10.3 Exploring anthropogenic impacts in the tropics, 375

10.3.1 Deforesting China, 378

10.3.2 Exploring pre- and post-conquest land use changes in central Mexico, 380

10.4 Recent and future environmental changes in the vulnerable tropics, 382

References, 384

11 Past environmental changes, future environmental challenges, 392
David J. Nash and Sarah E. Metcalfe

11.1 Patterns of tropical environmental change, 392

11.1.1 Last Interglacial, 392

11.1.2 Last Glacial Maximum, 394

11.1.3 The last deglaciation or last glacialinterglacial transition, 396

11.1.4 The Holocene, 398

11.2 Forcings, 401

11.3 Future change in the tropics, 402

11.3.1 Climate responses, 402

11.3.2 Water resources, 404

11.3.3 Biodiversity, 406

11.4 The tropics as drivers of change, 406

11.5 Conclusions, 408

References, 409

Index, 412

Colour plate pages fall between pp. 210 and 211