Through the study of social history, we are able to learn valuable lessons and, hopefully learn from the mistakes to improve the path of the future. The same must also be true for natural history, particularly earth history.
Recently there have been a spate of books on the impacts of global and regional climate/weather on history and civilization (see for example, Brian M. Fagan's books, The Little Ice Age and Floods, Famines, and Emperors) which have show us how abrupt changes in climate patterns have influenced major changes in civilizations across the planet. Having seen that such changes can rock the foundation of society, it is important that we learn how to cope with major potential climate fluctuations in the future, and if possible, foresee at least the direction of those changes years ahead.
To give us the knowledge of what climate conditions may be in store for us in this century and the next (far off though it seems), we need to know the history and causes of climate change in the past. Unfortunately, the historical record of climate is only a few millennia old, and we must look to indirect records of climate variability written in its impact on the full Earth system. Such data are called proxy data, and from them we can, with a little detective work, produce a fairly accurate picture of the climate record for tens of thousands of years.
The Two-Mile Time Machine: Ice Cores, Abrupt Climate Change and Our Future by Richard B. Alley provides a fascinating story of the detective work undertaken by scientists who are piecing together Earth's climate history over the past 110,000 years. Alley, one of the world's leading climate researchers, presents us with "a progress report on abrupt climate change" telling us "what has been learned, how this knowledge was gained, and what it might mean to us." His style is very readable, highly understandable and utterly fascinating. I found that he explains the various methods used to tease the record of past climates from the ice in a way that most readers will understand immediately.
In the process of telling the story of the acquisition and interpretation of information from deep ice cores collected in Greenland, Alley shows us how these cores, supplemented by other data, are providing a picture of abrupt and wild climate swings over the past 100 millennia. Indeed, they show that the past ten thousand years, in which humanity has developed to its current high level of civilization, may have been a period of rather mild changes.
After telling us how the Greenland ice archives records of past climate and what knowledge we are able to glean those records, Alley paints us a picture of the factors which may produce the observed large climate swings. He shows us how the huge oceanic "conveyor belt" forming in the North Atlantic Ocean may be one of the major switches within the global picture that controls climate variations. Finally, he spends a few pages looking at how we can use this climate information with a view to the future.
The Greenland ice cores disclose a history of sudden climate changes during the period generally much colder than the current interval during which humanity developed. Moreover, change can be triggered by variations in Earth's orbit and tilt or by minor changes in the atmospheric balance of greenhouse gases.
Alley takes a path just left of centre in the debate on climate change, acknowledging that the science shows us we may be headed for major climate changes soon enough that we should be considering how humanity will cope with such changes. In the final chapter, "An Ice-Core View of the Future," Alley allows himself some opinion on our future, including such seemingly obvious statements that: "The climate will change" and "Climate change will give winners and losers." In expanding on these two statements in his remaining five crystal ball looks at the future, Alley suggests some avenues that we should consider in order to learn from the past as recorded in "the two-mile time machine."
The Two-Mile Time Machine is one book on climate change that I give my highest ratings. The book is forceful in its scope without resorting to the exaggeration and fear-mongering that I fell results in fatalistic indifference rather than positive planning and action.
In ending the tale as we now interpret it, Alley informs us: "We have come to a rest stop on the long road from central Greenland to our future." I look forward to a sequel in which we continue the journey with Alley as he and other researchers unlink more secrets from the frozen past.
Keith C. Heidorn, PhD, ACM
THE WEATHER DOCTOR
June 20, 2001