Table of Contents

Cover

The Geological Time Scale for the Phanerozoic Aeon

Title Page

Dedication

Author Biography

Foreword

Acknowledgements

Chapter 1: Introduction

References

Chapter 2: The Great Cooling

2.1 The Founding Fathers
2.2 Charles Lyell, ‘Father of Palaeoclimatology’
2.3 Agassiz Discovers the Ice Age
2.4 Lyell Defends Icebergs
References

Chapter 3: Ice Age Cycles

3.1 The Astronomical Theory of Climate Change
3.2 James Croll Develops the Theory
3.3 Lyell Responds
3.4 Croll Defends his Position
3.5 Even More Ancient Ice Ages
3.6 Not Everyone Agrees
References

Chapter 4: Trace Gases Warm the Planet

4.1 De Saussure's Hot Box
4.2 William Herschel's Accidental Discovery
4.3 Discovering Carbon Dioxide
4.4 Fourier, the ‘Newton of Heat’, Discovers the ‘Greenhouse Effect’
4.5 Tyndall Shows How the ‘Greenhouse Effect’ Works
4.6 Arrhenius Calculates How CO₂ Affects Air Temperature
4.7 Chamberlin's Theory of Gases and Ice Ages
References

Chapter 5: Moving Continents and Dating Rocks

5.1 The Continents Drift
5.2 The Seafloor Spreads
5.3 The Dating Game
5.4 Base Maps for Palaeoclimatology
5.5 The Evolution of the Modern World
References

Chapter 6: Mapping Past Climates

6.1 Climate Indicators
6.2 Palaeoclimatologists Get to Work
6.3 Palaeomagneticians Enter the Field
6.4 Oxygen Isotopes to the Rescue
6.5 Cycles and Astronomy
6.6 Pangaean Palaeoclimates (Carboniferous, Permian, Triassic)
6.7 Post-Break-Up Palaeoclimates (Jurassic, Cretaceous)
6.8 Numerical Models Make their Appearance
6.9 From Wegener to Barron
References

Chapter 7: Into the Icehouse

7.1 Climate Clues from the Deep Ocean
7.2 Palaeoceanography
7.3 The World's Freezer
7.4 The Drill Bit Turns
7.5 Global Cooling
7.6 Arctic Glaciation
References

Chapter 8: The Greenhouse Gas Theory Matures

8.1 CO₂ in the Atmosphere and Ocean (1930–1955)
8.2 CO₂ in the Atmosphere and Ocean (1955–1979)
8.3 CO₂ in the Atmosphere and Ocean (1979–1983)
8.4 Biogeochemistry: The Merging of Physics and Biology
8.5 The Carbon Cycle
8.6 Oceanic Carbon
8.7 Measuring CO₂ in the Oceans
8.8 A Growing International Emphasis
8.9 Reflection on Developments
References

Chapter 9: Measuring and Modelling CO2 Back through Time

9.1 CO₂: The Palaeoclimate Perspective
9.2 Fossil CO₂
9.3 Measuring CO₂ Back through Time
9.4 Modelling CO₂ and Climate
9.5 The Critics Gather
References

Chapter 10: The Pulse of the Earth

10.1 Climate Cycles and Tectonic Forces
10.2 Ocean Chemistry
10.3 Black Shales
10.4 Sea Level
10.5 Biogeochemical Cycles, Gaia and Cybertectonic Earth
10.6 Meteorite Impacts
10.7 Massive Volcanic Eruptions
References

Chapter 11: Numerical Climate Models and Case Histories

11.1 CO₂ and General Circulation Models
11.2 CO₂ and Climate in the Early Cenozoic
11.3 The First Great Ice Sheet
11.4 Hyperthermal Events
11.5 Case History: The Palaeocene–Eocene Boundary
11.6 CO₂ and Climate in the Late Cenozoic
11.7 Case History: The Pliocene
References

Chapter 12: Solving the Ice Age Mystery: The Deep-Ocean Solution

12.1 Astronomical Drivers
12.2 An Ice Age Climate Signal Emerges from the Deep Ocean
12.3 The Ice Age CO₂ Signal Hidden on the Deep-Sea Floor
12.4 Flip-Flops in the Conveyor
12.5 A Surprise Millennial Signal Emerges
12.6 Ice Age Productivity
12.7 Observations on Deglaciation and Past Interglacials
12.8 Sea Level
References

Chapter 13: Solving the Ice Age Mystery: The Ice Core Tale

13.1 The Great Ice Sheets
13.2 The Greenland Story
13.3 Antarctic Ice
13.4 Seesaws
13.5 CO₂ in the Ice Age Atmosphere
13.6 The Ultimate Climate Flicker: The Younger Dryas Event
13.7 Problems in the Milankovitch Garden
13.8 The Mechanics of Change
References

Chapter 14: The Holocene Interglacial

14.1 Holocene Climate Change
14.2 The Role of Greenhouse Gases: Carbon Dioxide and Methane
14.3 Climate Variability
References

Chapter 15: Medieval Warming, the Little Ice Age and the Sun

15.1 Solar Activity and Cosmic Rays
15.2 Solar Cycles in the Geological Record
15.3 The Medieval Warm Period and the Little Ice Age
15.4 The End of the Little Ice Age
15.5 The Hockey Stick Controversy
15.6 Sea Level
References

Chapter 16: Putting It All Together

16.1 A Fast-Evolving Subject
16.2 Natural Envelopes of Climate Change
16.3 Evolving Knowledge
16.4 Where is Climate Headed?
16.5 Some Final Remarks
16.6 What Can Be Done?
References

Appendix A: Further Reading

Appendix B: List of Figure Sources and Attributions

Index

End User License Agreement

List of Illustrations

Chapter 2: The Great Cooling

Figure 2.1 James Hutton.
Figure 2.2 Georges Cuvier.
Figure 2.3 Alexander von Humboldt working on his botanical specimens.
Figure 2.4 Charles Lyell.
Figure 2.5 Lyell's attempt to show how changes in the positions of the continents through time might contribute to extremes of (a) heat or (b) cold.
Figure 2.6 William Buckland.
Figure 2.7 Ice transporting rocks at sea: (a) stranded iceberg carrying a load of rocks in the Fridtjof Channel, Antarctic Peninsula; (b) ice floe carrying a load of rocks in the Erebus and Terror Gulf, Antarctic Peninsula.
Figure 2.8 Louis Agassiz drawing radiates, 1872.
Figure 2.9 Archibald Geikie.
Figure 2.10 James Geikie.

Chapter 3: Ice Age Cycles

Figure 3.1 James Croll.
Figure 3.2

Chapter 4: Trace Gases Warm the Planet

Figure 4.1 Saussure's hot box: the heliothermometer, comprising several boxes encased one inside another, each of whose sides are glazed. Each case is isolated thermally from its neighbour by cork, and its bottom is painted black to minimise heat losses by reflection. Mercury thermometers, placed on the glass windows, make it possible to read the temperatures inside the various encased boxes.
Figure 4.2 Joseph Baptiste Joseph Fourier.
Figure 4.3 John Tyndall.
Figure 4.4 Tyndall's revised apparatus, 1863–64. The new apparatus was a 49.4” long tube consisting of three chambers. A heat source at one end played on a copper plate. Heat passed through the first chamber, full of dry air, then through a plate of rock salt into two more chambers filled with the gas or vapour to be measured, separated by a second plate of rock salt, then through a final plate of rock salt to a detector. The detector comprised a thermoelectric pile, in which the heating of different metal strips created a current that could be read by a galvanometer. Beyond the pile was a compensating cube to neutralise the radiation coming from the heat source, the cube being separated from the detector by an adjusting screen that helped to adjust for the compensation.
Figure 4.5 Svante August Arrhenius.
Figure 4.6 Thomas Chrowder Chamberlin.
Figure 4.7 Eduard Suess in 1869.

Chapter 5: Moving Continents and Dating Rocks

Figure 5.1 Alfred Wegener.
Figure 5.2
Figure 5.3 Köppen and Wegener's palaeogeographic map for the Carboniferous, showing regions of ice, marshes and deserts. E = signs of ice; K = coal; S = salt; G = gypsum; W = desert sands; dotted area = dry regions.
Figure 5.4 Arthur Holmes.
Figure 5.5 Harry Hammond Hess.
Figure 5.6 John Tuzo Wilson.
Figure 5.7 Henry William Menard.
Figure 5.8 Alan Smith's palaeoreconstruction maps, showing current outlines, palaeoshorelines, land area (stippled) and highland (shaded). (a) Early Triassic, 245 Ma ago. (b) Mid Cretaceous (Albian), 105 Ma ago.
Figure 5.9 Sea level curves through time. From Vail (Exxon) and Hallam (University of Birmingham), prepared by Robert A. Rohde and made available through Global Warming Art at http://commons.wikimedia.org/wiki/File:Phanerozoic_Sea_Level.png (last accessed 29 January 2015).

Chapter 6: Mapping Past Climates

Figure 6.1 Floral distribution in the Carboniferous and Permian. From Figure 8 in Köppen, W. and Wegener, A. (1924) Die Klimate der geologischen Vorzeit. Borntraeger, Berlin, pp. 1–255.
Figure 6.2 Wladimir Köppen in 1875.
Figure 6.3 Köppen's climate classification system. The heavy serrated line denotes a large and a small southern continent. See Box 6.1 for explanation of symbols. f = constantly humid; s = dry summers; w = dry winters.
Figure 6.4 Palaeolatitudinal zonation of climate-sensitive deposits. Frequency in number of deposits against palaeolatitude.
Figure 6.5 Milutin Milankovitch.
Figure 6.6
Figure 6.7 Robinson's conceptual climate model. Distribution of climatic regions on a hypothetical continent of low and uniform relief, after Köppen (compare Figure 6.3).
Figure 6.8 Past distribution of atmospheric pressure for the earliest Triassic, with northern winter above and northern summer below. Heavy solid lines are isobars; arrows represent wind directions. H = high-pressure centre; L = low-pressure centre.
Figure 6.9 Upwelling predictions from qualitative circulation models: Cenomanian (99.6–93.6 Ma ago). The map shows highland in dark shading, lowland in medium shading and flooded continental edges in light shading. Lines represent isobars, with H = high pressure and L = low pressure. Upwelling indicated by cross-hatching along continental margins. Dots = locations of samples of organic rich rocks.
Figure 6.10 Jane Francis.
Figure 6.11
Figure 6.12 Deep-ocean drilling vessel dv JOIDES Resolution (1989–).

Chapter 7: Into the Icehouse

Figure 7.1 Jim Kennett.
Figure 7.2 Cesar Emiliani. Taken during the early 1950s, when he was doing his pioneering research at the University of Chicago.
Figure 7.3 Nicholas J. Shackleton.
Figure 7.4 Antarctica. Showing main features and locations of main ice core sites.
Figure 7.5 Peter Barrett.
Figure 7.6 Global compilation of oxygen isotope records for the Cenozoic. Solid bars span intervals of ice-sheet activity in the Antarctic and Northern Hemisphere.
Figure 7.7 Variations in bottom-water temperature and sea level for the past 108 Ma. Data smoothed to show only variations on >5 Ma timescales. Vertical bars indicate the approximate cumulative range of sea level variations due to ice sheets. EAIS = East Antarctic Ice Sheet, WAIS = West Antarctic Ice Sheet, GIS = Greenland Ice Sheet, NHIS = Northern Hemisphere ice sheets, NJSL = New Jersey sea level. Shading indicates confidence levels; cross-hatching indicates uncertainties in either temperature (top) or seawater ∂¹⁸O (bottom) estimates. The latter do not necessarily reflect realistic uncertainty in ice-volume calculations.

Chapter 8: The Greenhouse Gas Theory Matures

Figure 8.1 Gilbert Norman Plass.
Figure 8.2 Roger Revelle in August 1952.
Figure 8.3 Hans Suess in 1972.
Figure 8.4 Hubert Horace Lamb.
Figure 8.5 Mikhail Ivanovich Budyko.
Figure 8.6 Budyko's measurements show the effects of growing aerosol concentration. A = actual measurement; B = adjustment for cloudless sky. 5 year running means of the anomalies of direct radiation expressed in per cent of its normal amount, calculated from the data observed at a number of stations. Attenuation is equal to about 6%.
Figure 8.7 Wallace Smith Broecker.
Figure 8.8 The elements of the long-term carbon cycle. Readers interested in the equations for the various chemical reactions involved should consult Bob Berner's 1999 paper in GSA Today⁸⁷. In effect, his work expands on that of Ebelmen in France in the 1840s⁸⁸.

Chapter 9: Measuring and Modelling CO2 Back through Time

Figure 9.1 Hans Oeschger.
Figure 9.2 Concentrations of CO₂ in the atmosphere from bubbles in ice cores over the past 1000 years (symbols) and from atmospheric measurements at Mauna Loa between 1957 and 2013 (solid line). Ice core data sourced from Law Dome^{25, 26}, Siple Dome²⁷, EPICA Dronning Maud Land²⁸ and the South Pole²⁸.
Figure 9.3 Relation of cold and cool intervals to CO₂ through time. (a) Comparison of model predictions from GEOCARB III with proxy reconstructions of CO₂, at 10 Ma time-steps. (b) Intervals of glacial (dark) and cool (light) climates. (c) Latitudinal distribution of direct glacial evidence (tillites, striated bedrock, etc.) throughout the Phanerozoic.
Figure 9.4 Variation in atmospheric CO₂ through the past 65 Ma. Deep-sea temperatures (upper panel) generally track the estimates of atmospheric CO₂ (lower panel), reconstructed from terrestrial and marine proxies and showing error bars. Symbols with arrows indicate either upper or lower limits. Vertical grey bar at right indicates glacial–interglacial CO₂ range from ice cores. The top dark bar represents development of Antarctic ice sheet. Horizontal dashed line indicates present-day atmospheric CO₂ concentration in 2011 (390 ppm).
Figure 9.5 Robert Arbuckle Berner.
Figure 9.6 Bill Ruddiman.
Figure 9.7 Cenozoic CO₂ and temperature records, as of 2012. The temperature record is from Hansen, based on the benthic ∂¹⁸O record of Zachos, and is a rough minimum estimate of global surface temperature change relative to preindustrial conditions. The CO₂ record is updated from Beerling and Royer; the dashed line is the preindustrial value (280 ppm).

Chapter 10: The Pulse of the Earth

Figure 10.1 Alfred George Fischer.
Figure 10.2 Vaughan's view of alternating cool and warm periods through time. (a) Late Neoproterozoic and Phanerozoic climate modes of Frakes and colleagues¹⁵. (b) Dark grey = glacial or cool conditions; white = warm conditions, through late Neoproterozoic and Palaeozoic to recent time. Cool intervals are labelled (e.g. c1–c19), as are warm intervals (e.g. w1–w5). Modified from Royer et al.¹⁸, and including the palaeotemperature curve from that source (dashed line). Brackets above (b) show durations of high and low CO₂ modes for Phanerozoic climate.
Figure 10.3 Change in sea level and related climate variables over the past 20 Ma. Analysis of (a) the smoothed ∂¹⁸O record of Zachos leads to (b) Northern Hemisphere temperature change with respect to preindustrial conditions and (c) sea level (related to ice volume). (d) The reconstructed CO₂ record comes from inverting the relation between Northern Hemishpere temperatures and CO₂ data. Thick lines represent 400 Ka running mean. Grey error bars indicate standard deviation of model input and output.
Figure 10.4 Links between Large Igneous Provinces and biological extinctions.

Chapter 11: Numerical Climate Models and Case Histories

Figure 11.1 Mid Cretaceous modelled temperatures for 4× CO₂. (a) December, January and February. (b) June, July and August. Warming is evident everywhere, especially at high latitudes. DJF Arctic warming locally exceeds 40 °C. High-latitude continental interiors remain below freezing in winter. Tropical ocean surface temperatures increase by 1.5–2.0 °C. Tropical continental regions experience greater warming. The polar warming approaches palaeoclimate observations, but Arctic temperatures remain too cold. Mid-latitude temperatures are close to realistic. Tropical temperatures are close to exceeding the range of observed values.
Figure 11.2 Weathering of continental basalts through time. (a) Estimates of land area within equatorial humid belt (5° S–5° N) as a function of time since 120 Ma ago. (b) Estimates of most weatherable land areas of volcanic-arc provinces (Java, Sumatra, Andes), large basaltic provinces (Deccan Traps, Ethiopian Traps) and mixed igneous–metamorphic provinces (South Indochina, Borneo, New Guinea) in the equatorial humid belt (5° S–5° N) as a function of time from 120 Ma ago to present.
Figure 11.3 Extraction of CO₂ through time by chemical weathering. Total CO₂ consumption rates from silicate weathering since 120 Ma ago of land areas in the equatorial humid belt (5° S–5° N), obtained by multiplying a nominal CO₂ consumption rate of 100 tonnes CO₂/yr/km² for basaltic provinces, 50 tonnes CO₂/yr/km² for mixed basaltic–metamorphic provinces and 5 tonnes CO₂/yr/km² for the remaining continental land areas, by the corresponding cumulative distribution curves in Figure 11.2. These total consumption rates should be divided by two for net CO₂ consumption, because half of the CO₂ consumed by silicate weathering is returned to the atmosphere–ocean during carbonate precipitation.
Figure 11.4 Hysteresis in simulated development of the Antarctic ice sheet. (a) Solid curve shows ice volume from a 10 million-year simulation representing the Eocene–Oligocene transition, with imposed orbital forcing and a long-term linear decline in atmospheric CO₂ from four to two times present levels over the duration of the run. Note the relatively sudden nonlinear transition from very small ice amounts to a near continental expanse as CO₂ drops slightly below three times present levels. This stepped profile resembles the observed Eocene–Oligocene transition in ∂¹⁸O records. The dashed (upper) curve in (a) shows a reversed run, starting with a full continental ice sheet under a warming climate, with time running from right to left, and CO₂ increasing from two to four present values. As expected, the change displays hysteresis, with the main transition delayed compared to the forward simulation, because the pre-existing ice sheet topography is much higher and steeper than the baseline bedrock topography, so that the snowline has to be raised substantially before the overall ice sheet budget becomes negative. (b) The same pair of forward and reversed runs, but with no orbital cycles. The slow CO₂ trend is the only external forcing. Without orbital variability, the main transition and the substeps are delayed considerably, and the hysteresis between forward and reversed runs increases several-fold. Evidently, orbital cycles provide essential extra forcing on the gradual CO₂trend, so that particular thresholds are reached earlier than in the absence of orbital forcing.
Figure 11.5 The Palaeocene–Eocene Thermal Maximum (PETM), as recorded in benthic foraminiferal isotopic records. A rapid decrease in carbon isotope ratios (top panel) indicates a large increase in atmospheric greenhouse gases (CO₂ and CH₄), coincident with 5 °C global warming (centre panel). Much of the added CO₂ would have been absorbed by the ocean, thereby lowering seawater pH and causing widespread dissolution of seafloor carbonates (lower panel), manifest as a transient reduction in the carbonate (CaCO₃) content of sediments. The ocean's carbonate saturation horizon rapidly shoaled more than 2 km, then gradually recovered as buffering processes slowly restored the chemical balance of the ocean.
Figure 11.6 Closing of the Central American Seaway linked to episodes of ice-rafting in the North Atlantic. The closing of the seaway is estimated from the difference in salinity between Caribbean ODP site 999 and East Pacific ODP site 1241, deduced from variations in ∂¹⁸O and Mg/Ca-based sea surface temperatures in Globigerinoides sacculifer, a species growing at 50–100 m water depth. A ∂¹⁸O gradient of 0.6–0.7 equates to a sea surface salinity gradient of 1.2–1.8 salinity units, which corresponds to full closure of the seaway. Salinity increases in the Caribbean and decreases in the East Pacific with closure. IRD = ice-rafted debris abundance at site 907, north of Iceland. IW = Intermediate Water connection. Arrows indicate closures centred on (i) 3.2 Ma, (ii) 2.9 Ma and (iii) 2.65 Ma, after which connection was essentially closed. Sea surface temperatures in the Irminger Current and North Atlantic Current increased with closures, by 2–3 °C, while deep-water temperatures decreased by 1.5–2.0 °C. Warming mainly affected temperature at temperate sites (609 and 610, west of Ireland) and subpolar sites (984, south of Iceland). At the same time, flow increased from the Pacific to the Arctic and thermally isolated Greenland, leading to the onset of major Northern Hemisphere glaciation near 2.8 Ma ago.

Chapter 12: Solving the Ice Age Mystery: The Deep-Ocean Solution

Figure 12.1 The Berger Astronomical Model of Orbital Variability Present and Future. These curves have been produced in numerous formats in several publications by André Berger and Marie-France Loutre. Obliquity is expressed in degrees of tilt of the Earth's axis. Insolation at the summer solstice at 65° N is expressed in W/m².
Figure 12.2 John Imbrie.
Figure 12.3 Benthic oxygen isotope stack, constructed by the graphic correlation of 57 globally distributed benthic ∂¹⁸O records covering 5.3 Ma. Note that the scale of the vertical axis changes from panel to panel. From this stack, a number of new MISs were identified in the early Pliocene. MISs are identified by number back to 2.6 Ma ago; before that, the lettering refers to the name of the magnetic chron in which the isotope peaks appear (e.g. Si = Sidufjall, Co = Cochiti etc).
Figure 12.4 Ocean thermohaline conveyor belt, showing the directions and depths of cold, salty, oxygen-rich deep currents, warm surface currents and vertical connections from deep to shallow and vice versa.

Chapter 13: Solving the Ice Age Mystery: The Ice Core Tale

Figure 13.1 The large ice sheets of the Northern Hemisphere at the Last Glacial Maximum. Cordilleran (CIS), Laurentide (LIS), British Isles (BIIS), Scandinavian (SIS) and Barent-Kara (BKIS) ice sheets are labelled, as are the Lake Michigan (LML), Lake Huron (LHL) and Des Moines (DML) ice lobes and the New England margin (NE). Small dots = dated points. Large dots = specific ocean cores. Black arrows = directions taken by meltwater flow from BKIS via East Greenland Current (EGC) and from LIS to the Gulf of Mexico (GOM).
Figure 13.2 Willi Dansgaard.
Figure 13.3 Links between Dansgaard–Oeschger and Heinrich events and CO₂ (65–30 Ka ago). (a) δ¹⁸O_ice from GRIP 2 as a proxy for surface temperature. Bold numbers = Dansgaard–Oeschger warm events. (b) δ¹⁸O_ice from Byrd station and Antarctic warm events A1–A4. (c) Atmospheric CO₂. Small solid circles back to 47 Ka are existing data from Byrd; open circles prior to 47 Ka are new data from Byrd; large solid dots are data from Taylor Dome; triangles are control points for the synchronisation of gas ages between Byrd and Taylor Dome records. (d) CH₄ from Byrd ice core. Ages are adjusted to synchronise abrupt increases of CH₄ and Greenland temperature. Vertical shaded bars represent cold Heinrich events. Note that atmospheric CO₂ rose several thousand years before abrupt warming in Greenland associated with Dansgaard–Oeschger events 8, 12, 14 and 17, the four large warm events that followed Heinrich events. The CO₂ rise predated Heinrich events associated with these Dansgaard–Oeschger events and terminated at the onset of Greenland warming for each of them. Atmospheric CO₂ is strongly correlated with the Antarctic isotopic temperature proxy, with an average time lag of 720 ± 370 years (mean ±1σ) during the time interval studied.
Figure 13.4 Claude Lorius.
Figure 13.5
Figure 13.6 EPICA Dome C: the climate of the past 800 000 years. The Dome C temperature anomaly record with respect to the mean temperature of the last millennium (based on deuterium isotope data). Data for CO₂ are from Taylor Dome (75–25 Ka ago), Vostok (425–25 Ka ago) and Dome C. Horizontal lines are the mean values of temperature and CO₂ for the time periods 799–650, 650–450, 450–270 and 270–50 Ka ago. T_I: glacial termination. MISs are numbered.
Figure 13.7 Synchronous proxy temperature (T_proxy) and atmospheric CO₂ signals in the last deglaciation at Byrd and Siple coring sites, displaying the bipolar seesaw. Significant warming and cooling trends in T_proxy are represented by shaded vertical bands. Climate in the North Atlantic region is represented by the NorthGRIP ice core ∂¹⁸O record at top. Changes in the slope of Antarctic T_proxy are synchronous with climate transitions in the North Atlantic (vertical dashed lines), within relative dating uncertainties (horizontal error bars). The deglacial increase in CO₂ occurs in two steps, starting at 19 and 13 Ka and corresponding to significant warming trends in T_proxy. A pause in the CO₂ rise is aligned with a break in the Antarctic warming trend during the Antarctic Cold Reversal (ACR). Within the core of the Antarctic Cold Reversal, significant cooling in T_proxy (dark shaded band) coincides with an apparent decrease in CO₂. Note that the North Atlantic cools while the Antarctic warms from 19.0 to 14.8 Ka ago, then the North Atlantic warms into the Bølling–Allerød warm stage as Antarctic Cold Reversal begins. The Antarctic then warms as Younger Dryas cooling takes place. The Younger Dryas ends as Antarctic warming stops, at 11.8 Ka ago. Fast-acting interhemispheric coupling mechanisms linking Antarctica, Greenland and the Southern Ocean are required to satisfy these timing constraints.

Chapter 14: The Holocene Interglacial

Figure 14.1 Main forcings during the Holocene. (a) Solar insolation due to orbital changes from two specific sites in the Northern and Southern Hemispheres during the corresponding summer. (b) Volcanic forcing during the past 6 Ka, depicted by the sulphate concentration of two ice cores form Greenland (above the line) and Antarctica (below the line). (c) Solar activity fluctuations based on ¹⁰Be measurements in polar ice. (d) Forcing due to rising CO₂ concentrations. The six vertical bars show the timing but not the duration of six cold periods.
Figure 14.2 Greenland temperatures adjusted for changing elevation. Temperature change in Greenland derived from Agassiz and Renland ¹⁸O records and average rate of elevation change of ice sheets at the DYE-3 and Camp Century drill sites. Elevation changes distort the temperature records for these drill sites.
Figure 14.3 Holocene temperature history of the Antarctic Peninsula. Top panel: Sea surface temperature (SST) reconstruction from off the shore of the western Antarctic Peninsula. Middle panel: James Ross Island ice-core temperature reconstruction relative to the 1961–1990 mean, in 100-year averages, with grey shading indicating the standard error of the calibration. Lower panel: Temperature reconstructions from the Dome C (uppermost) and Dronning Maud Land (lowermost) ice cores from East Antarctica. Horizontal bars show intervals when open water was present in the area of the Prince Gustav Channel.
Figure 14.4 Sea ice area around Antarctica. Relative abundances of (a) the Fragilariopsis curta group (ragged grey line) and (b) the Fragilariopsis kerguelensis group (ragged grey line) versus calendar ages in core MD03-2601 close to the coast of Adelie Land, Antarctica. F. curta is a sea ice diatom, whose abundance represents denser and longer-lasting coverage of the ocean by sea ice. F. kerguelensis, in contrast, is most abundant along the polar front, where there is less sea ice and temperatures are warmer. Polynomial regressions indicate the first-order evolution for the F. curta group (solid smooth line in (a)) and the F. kerguelensis group (solid smooth line in (b)), compared to simulated time series of the March sea ice area (black zigzag line in (a)) and the October–April temperature for East Antarctica over the last 9000 years (black zigzag line in (b)), plotted as deviation from the preindustrial mean. The data show warming from a cool early Holocene into a warm mid Holocene hypsithermal with low sea ice, then into a cool late Holocene neoglacial with abundant sea ice.

Chapter 15: Medieval Warming, the Little Ice Age and the Sun

Figure 15.1 Variations in solar energy with time. (a) Geomagnetic dipole field strength relative to today, with variance. (b) Cosmic radiation based on the first principal component of several radionuclide records, 22-year averages, over the last 8000 years. Time is given as year before present (BP). Grey band represents the standard deviation of the individual radionuclide records. Black dashed line represents the average cosmic ray intensity for 1944–1988 AD. (c) Same as (b), but just for the past millennium. Capital letters mark grand solar minima: O, Oort; W, Wolf; S, Spörer; M, Maunder; D, Dalton; G, Gleissberg. (d) Same as (c), but just for the past 350 years. Time is given as year AD. Circles and zigzag curve for post-1940 are 22-year averages and yearly averages of cosmic ray intensity calculated using the solar modulation potential, obtained from neutron monitor and ionisation chamber data. At bottom are the annual sunspot numbers.
Figure 15.2 Solar variation and European lake levels. Comparison between the Polar Circulation Index (PCI) at GISP2, the atmospheric residual ¹⁴C variations, the Greenland ¹⁰Be record, the mid-European phases of higher lake level and the ice-rafting debris (IRD) events in the North Atlantic Ocean.
Figure 15.3 Lamb's graphs of temperature in central England, showing 50-year averages: (a) annual, (b) summer (July and August), (c) winter (December, January and February). The ranges indicated by vertical bars are three times the standard error of the estimates. Heavy solid line (from 1680) indicates observed values. Fine dotted line indicates unadjusted values based on purely meteorological evidence. Heavy dashed line indicates preferred values, including temperatures adjusted to fit botanical indications. Heavy dotted line (pre 1150 AD) connects points corresponding to 100–200-year means indicated by sparse data. Thin solid line (back from 1400 AD) is Lamb's preferred option.
Figure 15.4 The Figure the IPCC got wrong – Lamb's graph of English temperature taken as global. Captioned ‘Schematic Diagrams of Global Temperature Variations Since the Last Thousand Years. The Dashed Line Nominally Represents Conditions Near the Beginning of the Twentieth Century’.
Figure 15.5 Mean time series of centennial proxy anomalies separated by (a) data type, (b) continents, (c) latitude and (d) seasonality of signal. The curves in (b–d) show the mean confidence intervals (±2σ). The numbers in parentheses indicates the number of proxies in each category.
Figure 15.6 Phase diagram for Northern Hemisphere temperature versus an ice core proxy for Northern Hemisphere westerlies (calcium ions in the GISP ice core). Cluster over box at lower right centre = 800–1400 AD; cluster over box at upper left centre = 1401–1930 AD; cluster over box at far right and along the line of dots stretching from mid top centre to lower right = 1931–85 AD. Shaded boxes represent the mean ± 1σ for each period. Black line = 1980–85, the last 5 years of the data record. Clearly, climatic conditions since 1930 diverge from those of both the Medieval Warm Period and the Little Ice Age.
Figure 15.7 Temperature history of the Antarctic Peninsula over 2000 years. Lower panel: the James Ross Island (JRI) ice core temperature reconstruction with 100-year averaging (heavy line) and 10-year averaging (grey ranges) relative to the 1961–1990 mean (dashed line). Warming by 1.56 °C over the past 100 years is highly unusual in the context of natural variability. Middle panel: sea surface temperature (SST) record from Ocean Drilling Program site 1098 in Bellingshausen Sea west of the Antarctic Peninsula. Upper panel: reconstructed Northern Hemisphere temperature anomaly relative to the 1961–1990 mean, with envelope showing 95% confidence interval.
Figure 15.8 Divergence of temperature and solar data, showing annual averages of solar activity indices and global surface temperature since the year 1950. S(t) is total solar irradiance measured by satellites (only since 1978). Climax CRF is the cosmic ray flux measured at Climax in Colorado. The aa index is a geomagnetic index prepared by the International Service of Geomagnetic Indices. Tglobe UEA is global surface temperature anomalies from HadCRUT3, with total uncertainty at the 95% level. NRF is the net radiative forcing of the Sun (i.e. S(t) divided by 4 and multiplied by 0.7). Only the Tglobe curve has an upward trend (0.11 °C per decade, r = 0.87, since 1950). All other curves oscillate about a trend that is basically flat or, in the case of S(t), slightly declining. Large dips of the Tglobe curve occurred just after major volcanic eruptions (e.g. 1963, 1982 and 1991).
Figure 15.9 Northern Hemisphere temperature reconstruction based on maximum density (MXD) tree ring data from northern Scandinavia. Summer (June, July, August; JJA) temperature reconstruction and fit with regional instrumental data. (a) Reconstruction extending back to 138 BC, highlighting cool and warm periods on decadal to centennial scales (black curve, 100-year spline filter) amid variation between extremely cool and warm summers (jagged dark data) and a long-term cooling trend of −0.31 °C per 1000 years from 138 BC to 1900 AD (dashed line), within an overall uncertainty area (grey) representing 2σ. (b) MXD trend (darker line) compared with measured JJA temperatures (light line) from 1876 to 2006 AD. Correlation between MXD and instrumental data is 0.77. Lighter jagged values in (a) post-1876 indicate measured air temperatures from (b).
Figure 15.10 Mann's Hockey Stick graph, 2001. Millennial Northern Hemisphere temperature reconstruction for 1000 to 1999 AD (jagged dark profile), with smoothed version (heavy dark line) and trend line to 1850 (dashed line), within 2σ error limits (grey envelope). From 1902, lighter jagged line represents addition of instrumental data.
Figure 15.11 IPCC temperature reconstruction 2007 for Northern Hemisphere temperature variation over the last 1.3 Ka. (a) Annual mean instrumental temperature records. (b) Reconstructions using multiple climate proxy records and the HadCRUT2v instrumental temperature record (heavy black line from c.1850 onward). (c) Overlap of the published multidecadal time scale uncertainty ranges of all temperature records, with temperatures within ±1 standard error (SE) of a reconstruction ‘scoring’ 10% and regions within the 5–95% range ‘scoring’ 5% (the maximum 100% is obtained only for temperatures that fall within ±1 SE of all 10 reconstructions). The HadCRUT2v instrumental temperature record is shown in black. All series have been smoothed to remove fluctuations on time scales less than 30 years. All temperatures represent anomalies (°C) from the 1961–90 mean.
Figure 15.12 Global temperature for the last 2000 years, represented by 30-year means. The zero on the temperature scale represents the average from 1950 to 2000, which is also the last data point.
Figure 15.13 Sea level reconstruction since 1700. Shading represents the error window of the reconstruction. Fitted curve is a second-order polynomial.

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1. Atmospheric carbon dioxide. 2. Climatic changes--Research. 3. Geological carbon sequestration. 4. Paleoclimatology.

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Cover image: The Glacier de Frébouze at the southern edge of the Mont Blanc Massif, taken from the south side of the Italian Val Ferret, near the Col de Ferret, looking north and showing bare rock exposed by glacial retreat, plus abundant scattered erratic blocks left by the shrinking glacier. © Colin Summerhayes, 2007

Foreword

Climate change is becoming increasingly obvious, through melting glaciers, extreme weather events and rising insurance premiums. Research on the topic is reported and reviewed more thoroughly than any other aspect of the world we live in, and yet we allow the principal cause, greenhouse gas emissions, to continue to rise.

In the last few years, many eminent climate scientists have shifted their focus from seeking new knowledge to reviewing what we already know of our warming world and what our followers will have to cope with in the future. All conclude with a call for action. What makes this book different is its multi-million-year perspective, looking at the climate of the past. Surprisingly, it turns out not only to be relevant for appreciating what we will be facing in coming decades and centuries, but also to add to the urgency of the need for action.

Colin has had a remarkable career, beginning in the 1960s as a scientist in the early days of the plate tectonics revolution, making discoveries in ocean circulation in the 1970s, and then in the 1980s moving into petroleum exploration to reconstruct geography and environments in the distant past to help find more oil. Since then, he has worked with UNESCO's Intergovernmental Oceanographic Commission and the World Meteorological Organization on the contribution of the oceans to modern climate change, going on to the Scientific Committee on Antarctic Research to oversee the development of Antarctic multidisciplinary studies of climate change and its effects on all time scales from the distant past to the future. His stories remind us that scientists are also human.

The real stimulus for this book came recently, through his realisation that many colleagues were still climate change ‘sceptics’, actively persuading the public that changes in climate in recent decades were either not significant or not related to greenhouse gas emissions, or both. First, he led a group within the Geological Society of London to develop a position paper for the Society on the issue. This paved the way for taking the case to the public through this book.

The story is a fascinating one, for a number of reasons. It reveals how much of our current understanding of Earth's climate history and the role of atmospheric CO₂ has been known for well over a century. In the 1830s, Charles Lyell, Father of Geology, described the great cooling of the last 50 million years, leading to the Ice Age of the last 2 million years. By 1896, Svente Arrhenius, at the behest of a geological colleague, had estimated the climatic consequences of increasing CO₂ levels in the atmosphere. Since then, this basic understanding has been improved upon and verified in remarkable detail through advances in imaging strata beneath the Earth's surface, and in determining environmental conditions (including temperature and atmospheric CO₂ levels) at various times and places in the past from ice and sediment cores going back tens of millions of years.

Colin also includes in his story the most recent scientific tool of all, numerical simulation of Earth's climate through computer modelling of various interactions involving atmosphere, water on land and in the oceans, snow and ice and the living world. These models are of course the only means we have for making projections of future climate, providing a rational basis for assessing possible consequences for both the physical and biological worlds. After 40 years of development, and astonishing advances in computer power, we now find broad agreement between model estimates of past climate and geological knowledge of the same periods, but also some mismatches, as well as significant differences between results from different modelling groups. As you'll see from Colin's overview of the field, the crucial issues are now in finding ways of increasing the robustness of the models for projecting regional consequences of climate change. However, critical issues, such as how fast these changes will be, have yet to be resolved, with ice loss and sea level rise a key concern.

Three aspects of the book are especially significant. The first is the extensive knowledge of the details of Earth's climate and its interaction with the ocean. These are not only captured from observations over the last 150 years and modelling in the last 30, but now include similar studies covering the period since the Last Glacial Maximum 20 000 years ago, and into the stable warm climate of the last 10 000 years, which led to the development of agriculture and our present society. We also get confirmation of the temperature–CO₂ link from much warmer times millions of years ago, reflecting Earth's future climate, to which all species (not just us) will have to adapt by 2100 if present emission rates continue. While our understanding of the Earth system is not complete, it is nevertheless huge, and fully justifies our confidence in acting on this new knowledge. The second aspect is the abundant evidence that Earth is now warming beyond the ‘natural envelope’ of the Ice Age glacial–interglacial climate cycles of the last 2.6 million years, a development that is becoming increasing significant for all life on Earth. The third is our growing appreciation that there is a lag between increasing greenhouse gas levels in the atmosphere and the response of warming of the atmosphere (more or less instantaneous), of the oceans (in decades to centuries) and of the ice sheets (decades to millennia). On the bright side, this gives us some time to act, but our geological knowledge shows us the ultimate consequences of not changing our present course. We might be able to cope with warmer temperatures in most places, but sea level rise of 10–20 metres in several hundred years will be more difficult. That prospect now seems inevitable, though we can still delay the worst if we reduce our emissions in coming decades. Earth has been there before, but change came slowly. Do we want to get there in a geological instant?

Beyond the message from climate science itself, Colin also provides intriguing glimpses of how scientists in the past were regarded by their contemporaries, and the context in which they worked. Some were very effective networkers long before the Internet age! I hope readers will also enjoy discovering from these pages how science makes progress, despite the human limitations to which we are all subject – occasionally pausing, but in the end always self-correcting.

P.J. Barrett

Fellow of the Royal Society of New Zealand

Holder of the NZ Antarctic Medal

Honorary Fellow, Geological Society of London

Emeritus Professor of Geology, Victoria University of Wellington

Wellington, New Zealand

Era	Period	Epoch	Base Age (Ma)
Cenozoic^a	Quaternary	Holocene	0.0117
		Pleistocene	2.6
	Neogene	Pliocene	5.3
		Miocene	23
	Palaeogene	Oligocene	33.9
		Eocene	55.8
		Palaeocene	65.5
Mesozoic	Cretaceous	Upper	99.6
		Lower	145.5
	Jurassic	Upper	161.2
		Middle	175.6
		Lower	199.6
	Triassic	Upper	228.7
		Middle	245.9
		Lower	251
Palaeozoic	Permian	Upper	260.4
		Middle	270.6
		Lower	299
	Carboniferous	Upper	318.1
		Lower	359.2
	Devonian	Upper	385.3
		Middle	397.5
		Lower	416
	Silurian		443.7
	Ordovician		488.3
	Cambrian		542