Customer Reviews

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

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I have lived in a good many places in the world, and I think I have never lived in a place where people didn't voice the witticism, "If you don't like the weather here, stick around twenty minutes and it'll change." We are quite used to rapid changes in weather, and all of us seem fascinated by the way one day is different from another, or at the mistakes the weather forecasters make. Only over the past few decades, however, have scientists been able to get a grip on something else fascinating: climate. Ice in Greenland has been piling up year by year for 100,000 years. This ice carries inside it a record of the climate that produced each yearly layer. In _The Two-Mile Time Machine: Ice Cores, Abrupt Climate Change, and Our Future_ (Princeton University Press), Richard B. Alley, who has done research in Greenland and Antarctica, gives us a view of his narrow and deep studies, and tells us why they are important. It is the first book for the layman to show how climate historians are doing their jobs, drilling five inch cores two miles down, and analyzing the ice in many clever ways.

For most of the 100,000 year record, the climate has had wild jumps, centuries of cold followed by abrupt heating. Humans have lived in an anomalous period of stability. There have been climate changes that influenced human life, like the warm spell that lured the Vikings to Greenland and the cold that drove them out, but these represent one degree shifts shown in the recent ice records. Teensy temperature changes have made what we would consider big climate differences, but when it comes to the wild changes, we ain't seen nothing yet.

Yet. Alley devotes the main part of his book, after showing how scientists draw facts out of buried ice, to discussing what drives global climate change over decades and over eons. He is able to paint a vivid, if brief, picture for those who are not acquainted with his field. His comparisons are felicitous, explaining that the ocean loses carbon dioxide when heated just as a carbonated soft drink would, or showing how a glacier pushes Greenland down into the deep, hot, soft rock below like a person sitting on a waterbed full of syrup. He is in no way a scaremonger, and takes the correct tentative tone because we don't have all the information yet. However, he concentrates on a switching mechanism involving the flow of the Atlantic Gulf Stream; it seems that minor changes in temperature or salinity may jam the "conveyor belt" of the oceans as they transfer heat from the equator to northern latitudes. If it does jam, the results for Europe would be disastrous, and it would affect the rest of the world as well. We know about this switch, and there must be others that we do not know about, and all of them may be vulnerable in our current period of stability to being switched off and making the climate careen again. His moderate advice is that climate change is inevitable, that it will trouble more people than it benefits, and that there are reasons to think that what we are doing to the atmosphere may kick it into instability. If we continue, we may well suffer a crash of a climate change that uses up more of our resources than we have; prudence suggests that we all (especially in developed nations) should be trying to reduce our impact per person. We have used the current centuries of stability for all they are worth; if you don't like the weather now, stick around for twenty years or two hundred, because it is going to be quite different.

One of the most critical aspects of science appears on page 174 of The Two-Mile Time Machine by Richard B. Alley:

ALL scientific ideas are subject to revision; we should never be absolutely sure that the truth has been reached. Old ideas should be tested continually, in an effort to tear them down and replace them with better ones. Ideas that survive this constant attack will be especially robust. Experience shows that if we behave as if these surviving ideas are true, we will succeed.... But, on the other hand, the ideas may be true, they may be reasonable approximations of the truth, or we may just be lucky.

In science, no idea, be it speculation, hypothesis, theory, law, model, or FACT, is ever considered to be the final answer. That's the way science works. We ALWAYS act on uncertain answers; we never know if something is the truth with a capital T.

The Two-Mile Time Machine is not only an excellent exposition of the use of ice core [and other] data to figure out the recent and future climate situation on Earth, but it is an excellent exposition of how science in general works. Richard B. Alley, a participating scientist in the GISP2 ice core project in Greenland, has written an easy-to-read, but pull-no-punches book on a complicated scientific topic. The book starts out with the basics of coring, dating, and analyzing ice, and takes the reader through to the political, social, and ethical implications of future climate changes, and concludes with Alley's take on what our responses should be. He always states how much uncertainty is attached to any of the ideas he writes about. If a person of a non-scientific background is going to have a complaint about the book, it will probably be that the book goes into too much detail about the evidence supporting the ideas.

This book is highly recommended to anybody interested in Earth history, climate, Arctic research, the methods of science, and anybody who wants an excellent science read. The book is especially recommended to anybody interested in or involved in the debate over the future of the Earth's climate. All people involved in this issue need to UNDERSTAND the scientific details. The issue of the Earth's climate future has become way too politicized. Our actions are always based on ideas that have some level of uncertainty, but we must act, because the future of humanity will depend on what we do.

Alley joins the growing number of field scientists relating their experiences and the they research perform. In his case the field is the top of the Greenland Ice Cap. The research is the study of ice patterns stretching back over 100 000 years. What do these patterns tell us? Need we care? He explains detail with clarity and detail how the research is done, and describes what has been revealed by it. What those finds tells us of the past, present and might mean in the future become the remainder of the book. One thing stands out vividly - climate not only varies more than we believe, it changes far more rapidly than we expected.

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]

Although I never completed the degree, I have most of a baccalaureate in geology. Since paleontology and earth history were my main interests, the title Two-Mile Time Machine: Ice Cores, Abrupt Climate Change, and Our Future by Richard B. Alley naturally caught my eye. The book is an excellent exposition on the recent data collection from ice cores obtained from the more stable portions of the Greenland ice sheet. I had come across this data source before while on a geologic field trip on Santorini helping with research on the volcanic activity that occured there during the Minoan period. It had been information from this source that had helped to date the volcanic event, so I was particularly interested in learning more about how it was obtained and about its reliability.

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.

I have been researching Greenland for a project I am working on and heard about ice coring in Greenland a couple of months ago. As I soon discovered, Greenland also plays quite an important role in the climate change discussion. I wanted to learn more.
This book served my purpose.

I found this book easy to read. It kept me engaged from the start when I started to read it. The author clearly and simply describes many of the methods used to analyze ice cores. All while relating them to the bigger picture and also comparing the analysis of ice cores with other methods of analyzing past climate such as tree rings or layers of sediments in bodies of water - past or present.

I appreciated the simple analogies (and charts) throughout the book. While some readers may think they are too simplistic, I think they are perfect. I don't think the book is aimed at people already familiar with the subject but at the layman / general reader. That's what one of the quotes says on the back too. The author's sense of humor also shows in his writing. This is good.

While reading, there were some passages where I started to get confused. Thankfully, the author realized that it might come across that way and quickly moved to summarize the recently presented information.

While the illustrations are good, improvements to the book might be more maps showing the locations he talks about. I only recall a map of Greenland. It wasn't a problem for me since I have studied Greenland intensively recently and I also have traveled widely and have a good knowledge of geography, but I suspect some might get confused.

The discussion on the conveyor belt shutting off could have been more succintly written and concluded better. While the author explains how a section of the world will cool if the conveyor is shut off (Europe), he doesn't talk much about how other parts will warm. It seems to be only in general terms. "The South Atlantic will be warmer." "The monsoon will be affected in Asia."

On the positive side - the author does note that we might/should be entering an ice age cycle, he does point out that our actions in warming the planet will easily be greater than the natural decline in temperature that would otherwise take place. Though I also wonder how a significant drop in global temperature 10-15F over a few years (Something which the ice core shows has happened in the past) would contrast with our actions in warming the planet. More hypothesis would be appreciated.

A good overall explanation of climate change including the conveyor belt is on the Union of Concerned Scientists website.

I would have also appreciated a little more discussion on the ice coring efforts in Antarctica as the author has been there several times also. It is discussed and compared, but I feel more could have been written about it although Antarctica isn't the main focus of the book.

In summary, this is an excellent and accesible read on the science of ice coring and what it tells us about the past and why the Greenland ice cores are so important. The book stumbles a bit on discussing scenarios in the future based on the findings. Though I feel the author may have deliberately left this out.

The whole issue of global warming has seemed confusing to the ordinary punter. On the one hand we hear dire warnings, on the other we also hear that "the jury is still out". This book was written by a scientist who was involved in analysing the information provided by ice cores during "three trips to Antarctica, five trips to Greenland, and countless hours in frozen laboratories". He knows what he is talking about. In this book he explains for the lay reader why the two-mile ice cores obtained from Greenland are so important, what they tell us about the Earth's climate in the past (and how this information is supported by other climate records), and what they suggest about the Earth's climate in the future.

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 remarkable discovery of abrupt climate change is presented at what I considered just the right level. The annotated bibliography refers the reader to the original research papers. The acknowledgements are a graceful and detailed tribute to the author's colleagues. No superfluous material. The author's scientific personality shines through. This is the most enjoyable science book I've read in the past few years.

The author, a scientist, actually did of OK job of keeping me interested in the book. The thing is... the discussion wasn't technical enough to warrant considering on that level. And perhaps it's just me, but it the author didn't provide any strong opinions or speculation of what may have happened and what may happen... just "layman" (weak) facts about how the tests were performed and what it probably means.

I think it would have been much better if the author would have included an extra couple chapters in the end with just some interesting ideas in a story form of "what happened and what's going to happen."

As it is, if it wanted to be a technical book, it's not technical enough. For entertainment, it's not entertainment enough. In the middle without any strong points in either direction is a bad place to be.

No one can dispute Alley's credentials in climatology. He is one of the most experienced in glaciology which is where most of what we know about the history of climate comes from. Here in plain language he describes how climate works and how drilling into ice tells us about climate's past. That past reveals larger and faster changes than civilized man has ever seen. The causes are many and complex. But we are far from knowing all of those causes and how they react with each other. We can be certain, however that significant climate change is not the result of a simplistic phenomenon.

Alley writes as a scientist, not as a politician or advocate. He welcomes dissent and like all good scientists realizes that it is the road to progress. Try this. "What are the odds that natural or human activities will trigger an abrupt climate change big enough, fast enough, and soon enough to matter in economic discussions? The simple answer again is that we do not know." .... "Much knowledge is needed before we can begin to predict the known light switch, and it remains possible, though unproven, that "chaos" in the system will render such predictions difficult or impossible". "Nature certainly can start the climate jumping again. But can humans? The answer is 'maybe".

I have read dozens of books on climate change and have studied it for nineteen years. If you want the best general book on this subject, one that tries to make a complex science understandable, that even uses real humor, then read this. It is a book that is clear on its science. That is so because it is not dirtied up with politics, social advocacy or secular religion. After reading it, think for yourself. Then you will realize that scientific forecasts for the future of climate are merely the opinions of some scientists and those opinions are all over the place.

Opinions are not science. Clear, falsifiable conclusions based on real evidence are. Such does not exist for the future of our climate. One should not confuse the elevation of some scientific opinion to authority with science itself. Science arose in opposition to authority. If you are truly interested in the real nature and status of the science of climate, read this.

The Two-Mile Time Machine is a fascinating look into one of the most important scientific endeavors in recent history, the extraction of a two-mile ice core in Greenland that gives us clues to the past earth climate, with some startling revelations on how climate has changed abruptly in the past, and could do so in the near future. Very well-written first-hand account that's easy to read, steering clear of dense technical jargon that has hampered similar books.

If you are interested in learning more about global warming and climate change, this book is valuable background information on some of the science behind why scientists have made the recent global warming predictions that give concern about abrupt climate change, tipping points, and positive feedback cycles. This book, however, steers clear of making any bold predictions. It's a very even, balanced look at the results of the Greenland ice core analysis.