David Archer's "The Long Thaw": A Summary Review

David Archer’s The Long Thaw may just have the best symbolic cover graphic of any recent book on climate change: a human fingerprint, 90% submerged in true iceberg fashion, beneath a cloudy sky. One scarcely needs the subtitle—How Humans Are Changing The Next 100,000 Years Of Earth’s Climate.

Archer, an oceanographer and professor of geophysical sciences at the University of Chicago, is a master of the “Plain Style”—informal, and given as much to the simple declarative sentence as to the factual. (To take one example, it’s hard to get much pithier than the unadorned statement that “Satellites are expensive.”) He is also very much the verbal architect, carefully structuring his argument, and his book is the stronger for it.

The Long Thaw is laid out in three large sections--Present, Past, and Future--working in each case from the relatively immediate to the more distant. Chapters 1 through 3 examine the present, beginning with the scientific basis for the greenhouse effect, examining human climate impacts so far, and laying out the forecast for the next century.

Professor Archer does a good job of addressing common questions about climate and the problems of understanding and forecasting it. For example, in Chapter 1 he addresses the question of how climate can be forecast when accurate weather forecasts are only possible over spans of a few days:

Perhaps this is as good a definition for the word “climate” as any: those aspects of the weather that can be predicted far in the future, in spite of the fact that weather is chaotic.

Another question involves possible alternate explanations for the warming we have experienced over the past three decades. Could some factor other than human activity explain it? Could it be natural?

It is true, says Dr. Archer, that natural factors (“forcings” in the jargon) affect climate now and in the past. However,

The bottom line is that there are no competing theories or models for climate that can explain the climate record but do not predict serious global warming. The range of uncertainty that we have about the real world does not encompass the possibility that there will not be global warming from continued CO2 release.

What does this mean for us? After all, 3-5 degrees C doesn’t seem like a large change. But it would mean that:

The climate in my home city of Chicago is expected to come to resemble that of present-day Texas or Arkansas. . .

The past is discussed in Chapters 4 through 7. This portion of the book offers a great deal of information on "paleoclimatology" (the study of ancient climate states.) We learn about the Little Ice Age and Medieval Optimum (often called the “Medieval Warm Period”) of the relatively recent past, go deeper into the more distant past of the Ice Ages, and then, in Chapter 6, learn about geologic climate cycles.

The author tells us that on timescales of 35 million years and more the Earth actually “breathes,” exhaling carbon dioxide from volcanos and hot springs (many of the latter undersea), and inhaling it from the atmosphere into the oceans and forests--and eventually into the rocky crust, or even the fiery mantle beneath.

Chapter 7 examines the past record from the perspective of its lessons for the present—and gives us some of the most unsettling pages of the work:

. . .the global warming event is not unprecedented in Earth history. Climate changes through the glacial cycles were probably as severe as global warming has the potential to be. The Earth and the biosphere will survive.

Viewed in the same time perspective, however, human civilization is also totally unprecedented in Earth history. Culture. . . arose about 40 thousand years ago, in the depths of the glacial climate. . . Civilized humanity has never seen a climate change as severe as global warming.

Part Three turns to a detailed consideration of future possibilities. Chapter 8 discusses the intricate dance of carbon among air, land, sea, and living creatures, and how this dance might change in a warmer, more CO2-rich future. The fertilization of trees and plankton by CO2 and other chemicals plays a role, and so does the slow interaction of carbon dioxide and calcium carbonate. There are many uncertainties, Professor Archer tells us, but it is clear that the CO2 we release into the atmosphere will affect the climate for millennia.

Chapter 9 explains the issue of ocean acidification. Carbon dioxide reacts with water to form carbonic acid, H2CO3; this substance then reacts with calcium carbonate, which is the building block used by many marine organisms to build their shells or exoskeletons. (This includes corals, which are doubly at risk since they are stressed by warming waters as well as the more acidic water.)  Past hot episodes may also have involved ocean acidification, and this acidification may be a partial explanation of extinctions that occurred.

But ominously:

Our CO2 acidity storm could be harsher [than] those in the past, because atmospheric CO2 concentration is increasing more quickly.

Chapter 10 considers the possibilities for future carbon cycle feedbacks. Currently, the carbon cycle is damping human-induced climate changes, but there are ways in which this could change. In past climate changes, warming temperatures produced increased CO2 concentrations in the atmosphere, unlike today, when humans release CO2 which is partially absorbed by plants and by seawater.

But CO2 release in response to warming could easily happen again, if any of the things acting today as carbon sinks--the oceans, for instance, or the great boreal forests--begin instead to emit CO2 as they warm. For instance, the ocean waters grow less able to hold CO2 as temperatures warm. Permafrost can melt, releasing CO2 or methane, and the massive amounts of methane held as hydrates buried in oceanic sediments could melt and bubble up through the water column to enter the atmosphere.

It is not possible to predict which, if any, of these things will happen, or when. But if they do, it is possible that the warming effect of CO2 could quickly double.

Chapter 11 examines the much discussed issue of sea level rise. Dr. Archer is quite clear that the long-term potential rise is enormous: at least tens of meters. But not so certain is how quickly the ice of Greenland and West Antarctica--which would contribute the greatest share to such a rise--can melt.

The "conventional wisdom" sea level rise prediction is currently for about 1-1.5 meters by 2100. But the “Heinrich events” 30 to 70 thousand years ago saw the Laurentide Ice Sheet (which then covered North America) collapse into “armadas” of icebergs. These melted quickly, raising sea levels “several meters within a few centuries.” We are unable to say whether such events could happen to today’s great ice sheets.  But if similar events were to occur in the near, the conservative predictions of the IPCC would be utterly eclipsed--and millions would be in the way of the rising waters.  Dr. Archer asks:

Is this possibility a fair trade for cheap and convenient energy in the short term?

Chapter 12 considers the possibility that we could prevent—or may already have prevented—the next ice age. We are, after all, living in an interglacial period, a respite from the cold of the Great Ice Age that still continues its slow rhythms. It seems from a variety of calculations that this is possible, and that:

. . .humankind has the capacity to overpower the climate impact of Earth’s orbit, taking the reins of the climate system that has operated on Earth for millions of years.

If so, there may be a silver lining to all the clouds we have brewed—though if our descendants don’t survive the chaos of climate change, it may be that other organisms will be the only ones to enjoy the warmth we will have provided for them.

The Long Thaw concludes with an extended epilog which considers “carbon ethics and economics.” Archer lays out the scale of the challenge we face, technologically and economically, in constructing a sustainable future economy. We will need to develop massive sources of clean energy, and deploy many techniques to avoid excessive emission of CO2. These strategies are usually referred to as “stabilization wedges,” because each takes a wedge-shaped piece out of the projected graph of future emissions.

But Archer doesn’t give technology and technique the last word:

Ultimately the question may come down to ethics, rather than economics. . . it didn’t matter whether [slavery] was economically beneficial or costly to give up. It was simply wrong.

The costs and benefits of fossil fuel use are not shared fairly. . . the benefits. . . accrue mostly to the industrialized nations in the temperate latitudes [while] the costs. . . will be paid most dearly in the tropics. . . The benefits to using fossil fuels accrue now and into the coming century until the fuel runs out, while the costs will last for millennia.

Ethics and fairness are a lot to ask of the political process, especially when most of the people affected by the decision. . do not have a voice in the decision. . .

No book can be all things to all people, of course. For some, The Long Thaw may be a little too sober, a little too judicious, a little too plain. As noted above, the language is straightforward, and though the graphs and charts are both apt and informative, they do not attempt to excite. But Archer is, after all, being a scientist. For him, the physical data speaks loudly enough; he does not seem to think that its interpretation is helped by authorial "shouting."

For this reader, his approach works. Perhaps at times the tone seemed a little too directly out of the lecture hall--as in the quip, "I will go out on a limb here and predict that the impacts of this sea level rise will be most noticeable in the low-lying coastal regions." At others, Archer's faith in this reader's ability to read not just the text, but "the facts" themselves, was just a bit too great, leaving this reader wishing for just one more sentence to help clarify the meaning.

Yet any loss on these accounts is more than balanced by the authenticity of "voice." Dr. Archer convinces, not only because he presents solid data; not only because he considers both sides of the question; and not only because he has organized his presentation so clearly. In the end, he convinces by speaking as himself--reasonable, careful, conservative--and concerned.

We believe him when, speaking of the ice core data, he exclaims, "What I as an oceanographer would give for comparable ancient seawater samples!" We believe his carefully listed reasons to believe that humanity has indeed acquired the ability to affect our planet on a grand scale, and not merely developed delusions of grandeur.

And we believe him not least when, at the end of his sober consideration of carbon ethics, he leaves us with an almost gentle wish:

May we use our newfound powers wisely.