The Two-Mile Time Machine: Ice Cores, Abrupt Climate Change, and Our Future [Paperback]

In part two of the text, the author lucidly describes the rationale behind the selection of ice and of Greenland as an "archival" source. He discusses the methods in and problems of obtaining and preserving the material intact and uncontaminated and the methods of analysis that produced the data. Throughout the following chapters, he lays out for the reader the thinking that went into its interpretation and how this information can be used as a paradigm with which future outcomes of climate change might be predicted. Because Alley, a professor of geoscience at Penn State, took an actual part in all of these proceedings and is an active scientist himself, he is well positioned to give an informative account of the topic. He also has a readable writing style which many such individuals do not.

Although I felt that his attempt to "get down to" the level of his non-technical audience was sometimes a little patronizing, I did think that his explanations of some of the physical systems was very clear. The description of the events leading to and during the Younger Dryas got a little confusing with the comparison to a roller coaster with a bungee jumper and a yo-yo, but by the end of the chapter one still had a fair idea of what he was trying to convey.--I think he was just trying a little too hard. His explanations of important environmental cycles with which I was already familiar--like those of the carbon, the water, the heat distribution, the oceanic and lake water overturn, and atmospheric cycles and those of the Coriolis and Milankovich effects--were very clear. In fact they were clearer than some textbook descriptions I've read. Although I had read of the effects of fresh water on the North Atlantic "conveyor belt" and its subsequent effect on global climate, I had not encountered the Dansgaard-Oeschger cycle or the Heinrich-Bond oscillations in my reading in the past. The author's presentation was therefore of interest to me.

For most readers, part five will probably be of greatest interest. Here the author puts what is known or suspected of climatic mechanics to work in predicting possible impacts of human activity on global climate and the world's population. Here too he points out the nature of the scientific method and its limitations. He is quite clear that some of what he states in his final analysis with respect to the future is personal opinion and not science.

As an earlier reviewer points out, the book is an excellent portrayal of how science works, particularly in the aspects of framing a problem and a means of approaching it experimentally, and interpreting the data that arises therefrom. I found it a very entertaining book.

The ice core data is recent and very important. I think that anyone having read this book will be up to date with the latest scientific data on climate change and its scientific justification. While some of the information is rather technical, the author has successfully attempted to make it understandable, interesting and relevant for the non-scientist.

The Greenland Ice Cap bears an astonishingly detailed record of environmental events. Far more than simply packed snow, this massive archive keeps information about distant volcanic events, how much salt is in the sea water and what kind of winds played over the Earth's surface. Even conditions in distant Asia are recorded here in the dust layered within the ice. There are records of long periods of cold and announcements about continental drifting. Alley explains all the elements that must be examined in the layered ice, how they came about and why they occurred. Earth's solar orbit, its tilting angle to the sun, and the slow precessional rotation of the poles. All these motions are further complicated by oceanic currents, wind patterns and humidity levels. Alley describes tracking some of the variations as "following a roller-coaster with a man bouncing on a bungee cord while spinning a yo-yo". It's a dizzying picture and he's quick to point out that many points remain unexplained.

Is this an issue that should concern us? Human history from the onset of agriculture has been a period of unusual stability. The future, Alley tells us, is highly uncertain. The only certainty is that climate will change - it must. Global warming is a fact, not a supposition, he asserts. One result of it will be the addition of fresh water into the "conveyor belt" of oceanic water exchange. The North Atlantic is the key site. Interruption of that exchange by extra meltwater from North America will intrude - chilling northern Europe. Human populations will be affected differently in various places. There will be winners and losers in this situation, but the losers will certainly outnumber the winners. How severe will the changes be? "I don't know". How fast will the changes come about? "I don't know". His lack of knowledge doesn't stem from lack of effort. He reminds us that the information gleaned from Greenland is still new. There's much to learn and do. He calls to us: "Send us your brightest students to help, and cheer them on!". A good piece of advice, but not one likely to be taken by a people choosing business instead of science.
[stephen a. haines - Ottawa, Canada]