CONTENTS

       Timeline—Earth’s History

       Prologue: The Dance of the White Caps

       1.Melting

       2.Between Fire and Ice

       3.The First Snow

       A Closer Look: The Greenhouse Effect

       A Closer Look: Albedo—the Effect of Whiteness

       4.In the Realm of the Snow Queen

       5.Life beneath the Snow

       6.More Than a Hundred Words for Snow

       7.Traces of Ice: The Discovery of Our Frozen Past

       8.Paradise

       9.The Backbone of the Continent

       10.The Alps: When the Cryosphere Becomes Dangerous

       11.The River Goddess and Her Sisters

       12.Toward Niflheim

       13.The White Continent

       A Closer Look: The Cryosphere Today

       14.Laboratory Earth: Life’s Frozen History

       15.Children of the Ice

       16.Out of Eden

       17.When the Ice Returned

       18.Thin Ice: What’s Happening to the Cryosphere?

       19.The Roof of the World Is Melting

       20.Invisible Glaciers and Cryoactivists

       21.Frozen Earth

       22.Climate Bombs in the Tundra

       23.Climate Help from the Animal Kingdom

       24.Last Dance? (Is There a Future for the Cryosphere?)

       Notes

       Index

TIMELINE

       Earth’s History

      4,500 MILLION YEARS AGO (MYA): The Earth is formed

      4,280 MYA: Water begins to condense in the atmosphere

      3,600 MYA: The first supercontinent (Vaalbara) is formed

      3,500 MYA: The first single-celled organisms, prokaryotes, appear; also, the first oxygen-producing bacteria

      2,900 MYA: First glaciation (Pongola) occurs; possibly first snowball Earth event

      2,400 MYA: The “oxygen catastrophe”; oxygen forms in earnest

      2,400 TO 2,100 MYA: The Huronian ice age (with at least two snowball Earth events)

      CA. 2,000 MYA: The first eukaryotes appear (first complex organisms with cell nuclei)

      850 TO 635 MYA: Ice age (Sturtian-Varangian), with two more snowball Earth events

      600 MYA: The first multicellular organisms appear

      542 MYA: The “Cambrian explosion”; many new species appear

      443 MYA: The supercontinent Gondwana becomes covered in ice; mass extinction of marine animals

      420 MYA: First land plants appear, along with first fish with jaws (sharks), insects on land

      252 MYA: Volcanic period; carbon dioxide in the atmosphere increases to 2,000 ppm; oxygen falls from 30 percent to 12 percent

      251 MYA: Mass extinction; 90 percent of marine animals and 70 percent of land animals die out

      199.6 MYA: The Jurassic (age of dinosaurs) begins

      55.5 MYA: Episode of warming (PETM, Paleocene–Eocene Thermal Maximum); North Pole at 73 degrees Fahrenheit

      50 MYA: India collides with Asia; the Himalayas are formed

      35.6 MYA: Temperature falls 18 degrees Fahrenheit in the Eocene epoch

      34 MYA: Ice forms on Antarctica

      30 MYA: Australia and South America separate from Antarctica

      3.9 MYA: Australopithecus appears

      3.0 MYA: Ice cap in the Arctic forms

      2.58 MYA: The Pleistocene, the most recent ice age epoch, begins

      2.4 MYA: Homo habilis appears

      CA. 200,000 YEARS AGO: Homo sapiens appears

      125,000 YEARS AGO: Interglacial period

      116,000 YEARS AGO: The last ice age begins

      CA. 21,000 YEARS AGO: The last ice age peaks

      11,600 YEARS AGO: The ice age (and Younger Dryas) ends; the Holocene begins

      CA. 1350 TO 1850: Little Ice Age

      CA. 1950: The Holocene ends, and the Anthropocene begins

Prologue

       THE DANCE OF THE WHITE CAPS

      WE HAVE ALL seen the famous photo taken from Apollo 17 in 1972. This picture of our planet, alone out there in endless space, taught us to think of Earth as our home, our only home, as something precarious and fragile that we needed to take care of. For the environmental movement, the photograph became almost iconic. The picture also gave us our perception of Earth as the “blue planet,” because so much of the surface is covered in blue oceans.

      But there is something this picture does not tell us, something we could have seen if the image of the Earth had been filmed from out there rather than just photographed. Not for just a few minutes, either, but continuously, throughout the entire year and—if it were possible—over millions of years. If that film were then played back at high speed, we would see a different image: we would see a planet in constant flux, the white caps at either pole expanding—over land and sea—and then shrinking again, in time with the seasons. When it was winter in the north, most of the landmasses would be covered in snow, which would vanish again when summer came. And likewise