The Long Thaw

By David Archer (Princeton University Press, Princeton, NJ, 2009), 178 pp., $22.95 cloth, $16.95 paper, ISBN 978-1-4008-2876-0.

Reviewed by Manish Gupta

David Archer’s The Long Thaw is a refreshing new addition to the plethora of books about global climate change. Unlike most texts on the subject, which tend to focus on the emission of anthropogenic CO2 and the resulting environment impact over the next 100 years, Professor Archer’s book deals with the long-term consequences of CO2 emissions. The manuscript is neatly divided into 3 sections: the present (1900–2100), the past (<1900), and the future (>2100). The “present” section summarizes the science (e.g. radiative forcing) and evidence (e.g. the short-term temperature record) of global warming. It also includes the IPCC forecast for the next 100 years under a “business as usual” scenario. This section closely resembles the treatment found in many books on climate change, including Dr. Archer’s excellent treatise Global Warming: Understanding the Forecast. Archer is a Professor of Geophysical Sciences at the University of Chicago and has published extensively on the global carbon cycle and its relation to global climate.

The “past” section focuses on temperature proxies (e.g. carbonates, pollen, ice core gases, tree rings, etc…) and what they tell us about historic, naturally-driven climate change. Professor Archer provides simple, intuitive explanations of complex phenomenon including Dansgaard-Oeschger events, the 8.2 kiloyear event, and the Paleocene–Eocene Thermal Maximum (PETM). Though well-written, these explanations can be difficult to follow; the text would have benefited from a more graphical presentation. The presentation of the PETM as a proxy for a large anthropogenic CO2 release addresses Dr. Archer’s central question of long-term CO2 equilibrium by natural means. Prior to discussing any future projections, the book includes a very helpful review chapter that summarizes the past and present. It is important to note that Professor Archer is not an alarmist and repeatedly notes that current anthropogenic warming is similar to that observed in the recent past due to natural forcing.

The unique aspect of this book is its “future” section. This section details the expected fate of a large CO2 release (e.g. the anthropogenic burning of the entire coal reserve in 200 years) over several timescales. First, CO2 will dissolve in the ocean over an approximately 300 year time period that corresponds to the turnover time of deep ocean water. As the oceans acidify, they will absorb less CO2 and approximately 20–40% of the release will remain in the atmosphere. Over about 5000 years, weathering reaction will bring carbonates into the ocean, helping to neutralize the acidity, and allow for more CO2 dissolution. However, about 10 % of the release will still be in the atmosphere. This portion will very slowly (during about 400,000 years) diminish due to reactions with igneous rocks. Thus, mankind has the possibility to effect Earth’s atmosphere over a very long timescale.

The final chapters in the book are dedicated to discussing the potential for catastrophic environmental changes, including thermal tipping points and dramatic sea level increases. Finally, Professor Archer suggests that a relatively small investment today can help mitigate an extremely large, long-term hazard, making the economics of climate change mitigation viable. Overall, this book provides novel insights into the fate of CO2 in the environment and this reviewer highly recommends it for anyone interested in the science of climate change.

Manish Gupta
VP Research & Development, Los Gatos Research

These contributions have not been peer-refereed. They represent solely the view(s) of the author(s) and not necessarily the view of APS.