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Frozen Earth: The Once and Future Story of Ice Ages

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This is an absolutely fascinating account of the various ice ages that have periodically taken over the earth. From the ancient "Snowball Earth" (sometimes called "Slushball Earth," 550 to 850 million years ago) in which the entire planet was more or less frozen from pole to pole, to the "Younger Dryas," a cold spell beginning 12,800 years ago and lasting for about 1,200 years, to "Little Ice Age" in Europe (700 to 150 years ago) to the "year without a summer," in 1816, UCSD Professor of Earth Sciences Doug MacDougall chronicles the ebb and flow of glacial advance and retreat in a most interesting and informative manner.

Much of this is a historical account of how scientists discovered the past ice ages through geology and the study of cores taken from the Antarctic, the Arctic, from the sea floor, and from still standing glacial ice packs. MacDougall explains how these cores are read to reveal climate changes in the past based on evidence from isotopes, pollen, and bubbles of trapped atmospheric gases. It is really amazing how much information can come from such minute bits of evidence.

In the early chapters MacDougall recalls the first scientists who became aware of the earth's climate in previous ages--Louis Agassiz, James Croll, Milutin Milankovitch and others. MacDougall recalls their efforts to get their ideas accepted by the geological establishment. It is fascinating to see how gradually it was realized that great rocks had arrived at various places, having been carried there by ancient glaciers. A particularly interesting story is how the Channeled Scablands of the Columbia Plateau in Washington were created when the glacial Lake Missoula sudden broke through the melting ice and drove an immense wall of water clear to the Pacific Ocean.

Part of his concentration is on the glacial and interglacial periods that have characterized the environment during the rise of the genus homo and especially the last 150,000 years or so during which homo sapiens have evolved. Chapter Ten, "Ice Ages, Climate, and Evolution" is devoted to how the advance and retreat of the ice affected the evolution of hominids and other animals and plants.

For those of us who might be worried about global warning it is perhaps refreshing to be warned that we are still living in an ice age. MacDougall writes, "We are in a warm period, one of the many interglacial intervals that have occurred throughout the Pleistocene Ice Age [now three million years old]." (p. 233)

Near the end of the book MacDougall looks at today's climate and takes into account the warming due to human activities, in particular the burning of fossil fuels. But he is not alarmed. He notes that the atmosphere on the planet Venus (surface temperature 485 degrees Centigrade, more than hot enough to melt lead) is almost all CO2 while that on earth is less than four-tenths of one percent CO2. No runaway greenhouse effect seems likely here any time soon. MacDougall explains the carbon dioxide cycle on earth and assures us that most CO2 is locked up in limestone. (p. 238)

While he seems unconcerned about global warming (taking the very long view) he does remark that "It is difficult to comprehend how further additions [of CO2] to the atmosphere at current rates could fail to raise global temperatures and possibly influence the course of the [current] Pleistocene Ice Age." (p. 241) Still he ends the book with this (possibly understated) possibility: "...mankind may inadvertently bring the Pleistocene Ice Age to a premature close, ushering in another long period of ice-free existence for our planet."

Which brings me to the question, if the earth does become more or less permanently as hot and muggy as a Jurassic swamp, what will it mean for human beings? There will be less land available since the melting of the glaciers would raise sea level some 60 meters, drowning New York and London, not to mention much of Florida and a host of South Pacific islands, Bangladesh, and other low-lying lands. Will we live most of our lives indoors in air-conditioned buildings? Will the verdant plants and fantastic diversity of creatures characteristic of tropical jungles be all around us? Will dragon flies be as big as birds?

On the other hand, suppose, as MacDougall intimates, that the forces affecting the earth's climate dwarf our puny doings. In that case the present interglacial will come to a close and the immediate future will be cold as the ice once again advances from the poles. As MacDougall points out, the air will be dryer with all that water locked up in ice, and great parts of the planet will be desert and the winds will blow the sand around the globe (as happened before during such periods as evidenced by the core samplings). I am reminded of the poet Robert Frost's dilemma, "Fire or Ice?" Probably our lives will not end in such extremes, but our way of life may change dramatically, and many will endure great hardships.

On the third hand, is it possible, maybe even probable, that we human beings will be able to affect the climate in such a way as to stave off the extremes? One of the cold-amplifying effects of great sheets of ice over the earth is to reflect sunlight and further cool the planet. Might not humans spread dark matter over the ice, melting it? Or in the case of too much CO2 or other greenhouse gases in the atmosphere, might humans somehow find a way to sink such gases and cool things down?

This is a distinguished work, very well written, beautifully edited, full of fascinating information about how cold the earth has been in the past (and how cold it might become again) and why.

Frozen Earth by Doug Macdougall is a fascinating book and it makes a great summer read as the heat beat downs and one tries to remember that we are in an ice age, albeit an interglacial period. The history of the discovery is told for all its glory and each chapter highlights a different personality related to the realization that the world has been through, and will continue to go through, a series of ice ages. The science is explained very neatly and the story is driven by the series of discoveries, beginning with Louis Agassiz to the very latest scientific discoveries, including alternate theories. The author also brings the story forward. All in all, a fascinating glimpse into our world, past, present, and future. Ice is a nice thing to think about on a hot summer day and this is just the book to get one truly thinking.

Doug Macdougall's "Frozen Earth" is clear, easy-to-read popular science for those interested in changes in global climate but without the scientific background to understand the often emotionally-charged discussion in the public media.

Macdougall's sub-title. "The Once and Future Story of Ice Ages", emphasizes the longer perspective he takes on how and why climate changes. He begins with the fact that we are likely living in an interglacial period of what has been a series of ice ages recurring at more or less regular intervals of several thousand years.

Macdougall gives his story a human aspect by describing how, over the last 300 years, a succession of scientists struggled to make sense of the physical evidence around them indicating that glaciers had once covered much more area than they do at present. The struggle leads to a still growing understanding of ice ages; the details of the story underline just how complex the workings of Planet Earth really are and how incomplete our understanding of these processes still is.

Macdougall loops back later in the book to relate how the ice ages interacted with human evolution; specifically, how the stress of environmental change forced both adaptation by early humans and selection of those best able to survive the changes. Macdougall's discussion of the "Little Ice Age" during the period 1600-1800 nicely links climate change to a human era we can still relate to.

Macdougall is properly cautious in weaving in the possible effects of mankind on climate change and global warming. The burning of carbon-based fuels clearly has some effect on climate, but Macdougall points out that this is only one of many factors that influence climate. At the same time, he makes clear that timing affects the impact of different factors, and lays out the possibility that the human impact may be altering the natural "schedule" of glacial and interglacial periods on earth.

This book is highly recommended to those readers interested in a longer perspective on climate change.

I was sad when I reached the end of this book! I wanted it to be at least twice as long. That's how good it is. The author has the ability to express himself very clearly and concisely but not at all in a boring way. The book covers some history and mini-biographies of key individuals who have given thought to glaciations and ice ages right up to modern methods and current thinking about this subject. There is even a discussion on how ice ages may have influenced human evolution. Written in a style that makes it nearly impossible to put down, this book is a gem that should be read by anyone with even just a passing curiosity about ice ages and glaciations.

Hey, I've been reading this kind of material for forty years....ice ages, Milankovitch cycles, loess deposits you name it. This book is a nice synopsis. The truth is in the ice cores and seafloor sediment cores....the truth is that an ice is something that nearly destroyed the human race while it changed it. The truth is that another will happen , in geological terms, VERY soon. The truth is that human caused greenhouse gases may have forestalled the onset of the next ice age already.....

This is a very good book and I recommend it for anyone with an open mind about global climate and the so called immenent dangers of global warming. However, being cynical, I'd say that people with minds open to this subject must account for less than one percent of the populace......so great is the global warming juggernaut.

Don't read the book if you want to actually KNOW something about ice ages that might shake your confidence in all the hype. Read it if you want to learn. But then, after you've learned, you'll have to keep your mouth shut on the subject since the present orthodoxy ( political correctness ) will brand you as either a fool or enemy of the planet or both if you so much as suggest that there may be more to the story than slick media propaganda teach.....

Yah, I know the sea level is going to rise and that the floods will be terrrible. How does a 400 foot drop in sea level for oh, about 100,000 years, sound as an alternative? Hummmmmm? Just how much has the sea level actually risen BTW? It's going to be time to see some real movement in that direction soon if the hypothesis is true that man caused CO2 is raising the global temp etc. My money is on the onset of a new ice age within several thousand years......but then, I don't have to compete for tenure or research grants as a climate 'scientist'.

This is one of the best books i've read in a long time, and I read over 100 books each year. Macdougall covers a lot of territory in a rather small book, which could have been twice as long and probably been even more interesting.
Macdougall puts the long history of Earth's climate changes over billions of years into perspective. The earth had been nearly completely frozen, and nearly completely ice free several times in its history. Some of the more fascinating statistics deal with how glaciers have advanced and retreated over millions of years, how human evolution probably took a dramatic departure from our fellow apes due to glaciations, how the sea level has risen 400 feet since the last major glaciations just a few thousand years ago allowing mankind to walk the land bridges between Siberia and Alaska, and even from modern-day France to modern-day England.
This book has none of the hysterical "chicken-little" rantings of those who worry about global warming, and Macdougall shows us that there are far more plausible theories about climate change than the effect of CO2 and fossil fuel use, especially since the earth has had many more serious changes than even the un-educated Gores of the world have been predicting.
A great piece of writing by a real scientist.

"Frozen Earth" is fascinating, but also confusing. Climate is a confusing subject, but I think Macdougall could have done better. There are really two parts to "Frozen Earth": an historical account of the evolution of scientific thought about ice ages, and an attempt to make sense of the explosion of recent findings and theories, and their implications. The history makes for surprisingly good reading, and the few scientists Macdougall dwells on led really interesting lives. Macdougall has a gift for narrative, and for historical context. It is his organizational skills that leave something to be desired. Two examples. It is only in the final chapter, on "Ice Ages and the Future", that Macdougall explains how weathering of rocks has a long term effect on carbon dioxide in the air (recall that the calcium released ends up bound to carbon in the shells of small sea animals). Yet weathering is cited, without explanation, several times earlier as if the implications were obvious and even the account finally given is not as clear as it could be. In that same last chapter, Macdougall reminds the reader, once again, that the "Earth is still in an ice age". Yet in the previous chapter Macdougall says about the "Little Ice Age" of the 14th-19th centuries that the phrase "is a misnomer in technical terms, because it was far from being an ice age". Had Macdougall given a few precise definitions, and been careful how he used the terms subsequently, much confusion would have been avoided. I guess it spoils a good story that the variations in the earth's orbit do not account for ice ages, but SEEM to contribute to the LONGER range cycles in the retreat and advance of glaciers within ice ages. It sure would have been less confusing if Macdougall had more sharply made this point earlier in the book.

"Frozen Earth" describes Ice Ages from several different perspectives - their own natural history, how the existence of ice ages was uncovered, and the efforts to comprehend their cycles.
The book is very readable and would be enjoyable for anyone interested in ice ages, climate history, or geologic processes.

Frozen Earth is a very good history of the earth's ice ages. The writing is a bit academic at times, and often feels a little too detailed (which is normally a compliment, but seems to slow down the pace of this book more than it should have). This book would be an excellent resource for students of geology and climatology. If you are interested in climate change, this book would make an excellent companion piece to "The Discovery of Global Warming", because "Frozen Earth" could have been aptly titled "The Discovery of Ice Ages".

For a relatively short and comprehensive ecological history of our planet over the past billion years (with emphasis on past couple hundred million) this book could not be better. You might think the subject a bit dry (which I do not), but the author not only discusses the Earth's history but also reveals how these things were discovered and by whom. A very interesting read that is also unbiased - he does not ruin the story with a political agenda, which this subject seems to attract. I highly recommend. I have already purchased a couple of additional copies for friends.