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Andrew E. Dessler, Cambridge University Press, 2011, xiii+238 pp., graphs and illustrations, ISBN 978-0-521-17315-5, paperback: $50
Many scientists and educators with broad backgrounds in physics and chemistry find themselves at a loss when friends and students ask them to comment on the latest news regarding global warming. How many of us hasn’t wished for a primer that covers the basics, and which we would feel comfortable recommending to others? Andrew Dessler’s book is just the ticket. An accomplished climate scientist at Texas A&M University, Dessler has prepared his Introduction to Modern Climate Change as a text for one-semester, algebra-level general education science class. Its 14 chapters are about equally divided between coverage of the underlying science (the first seven chapters) and associated economic and policy issues (the last seven). The writing is clear, has a nice balance of formal and informal prose, and includes occasional elements of dry humor to lighten discussions of otherwise very serious issues.
Chapter 1 opens with preliminaries such as definitions of weather, climate, and climate change, along with the caution that an expert on weather is not necessarily also an expert on climate. This chapter also presents something unusual for a college-level text: a section titled “Why you should believe this textbook”. Dessler argues that his readers should trust in the consensus opinion of professional climate scientists, particularly as reflected in the massive IPCC reports. In contrast, many climate-change skeptics are not experts in the field; rather, they often operate by casting largely unsubstantiated doubt on the science or positing that there exists a widespread conspiracy on the part of climate scientists, a notion Dessler demolishes as ridiculous.
Chapter 2 presents evidence for historical and current episodes of climate change, mostly as reflected through temperature-anomaly records. Over its history, Earth has certainly been warmer and cooler than it is at present, but it is the rate of recent warming that seems unprecedented: about 0.74oC over the 20th century. Chapter 3 covers electromagnetic and blackbody radiation, the Stefan-Boltzmann and Wien laws, and conservation of energy; this part will be a quick read for physicists and serves as a lead-in to Chapter 4, where readers encounter the idea of a climate model. The solar constant and Earth’s energy budget and average albedo are introduced, concepts which set the stage for consideration of a one-layer “greenhouse atmosphere” model, which is refined to a two-layer and finally an n-layer model.
In Chapter 5, chemistry comes to the fore. Dessler describes the composition of Earth’s atmosphere, the properties of greenhouse gases, and statistics on the carbon content of the atmosphere and the rate at which it is changing due to fossil-fuel burning. Prior to the Industrial Revolution, the atmospheric abundance of CO2 had been largely within the range of about 260-280 parts per million (ppm), but has since risen to 390 ppm and is increasing at about 2 ppm per year. Chapter 6 examines climate forcing, feedback mechanisms, and climate sensitivity. Factors here include greenhouse gases, aerosols (anthropogenic and volcanic), soot, albedo changes due to ice melts and land use patterns, and permafrost melting. The IPCC’s best estimate is for about 3oC of warming above pre-industrial levels if the CO2 abundance should rise to 560 ppm. Chapter 7 gets to the issue of why the climate has been changing over the past few decades: is it due to external or natural variations, human activities, or a combination of both? After examining factors such as continental drift, the solar cycle, variations in Earth’s orbit, the El Nino Southern Oscillation, and carbon-cycle timescales, Dessler comes firmly to the conclusion that anthropogenic greenhouse-gas emissions are responsible for most of the rapid late-20th-century warming.
Chapter 8 shifts the discussion to economic and policy issues. Trends in factors that control emissions are examined (population, affluence, energy and carbon intensities), as are various IPCC model projections of how these factors might evolve over the balance of this century; Dessler emphasizes that these are not intended to be predictions. Warming scenarios for the 21st century run from 1.8 to 3.6oC on top of the 0.7oC that has occurred during the 20th century; we are already committed to an additional warming of at least about 0.4oC over the next several decades, even if emissions were stabilized to year-2000 levels. Chapter 9 examines anticipated impacts of this warming. These will vary by latitude and location (especially within continents and along coastlines), but could involve permafrost melts, increased wet and dry spells, flooding and erosion, ocean acidification and rise, less-efficient photosynthesis, loss of alpine systems, extinction of temperature-sensitive species, and decreased fresh-water supplies. Dessler’s tone is not alarmist or frantic, just sober and to the point.
Chapter 10 gets to the cost-benefit economics of dealing with climate change, with an emphasis on how the present value of a future cost can be computed given an interest rate. Do we spend money today to mitigate effects predicted for decades hence, or leave those costs and effects to our descendants? Much depends on the choice of an assumed interest rate, a matter of hot debate among economists. Chapter 11 turns to the fundamentals of climate policy. Dessler divides policy considerations into three categories: adaptation, mitigation, and geoengineering. Adaptation will have to be part of our response to warming, but depending on adaptation as the only approach has a moral dimension: it abandons the poorest of the world to face the impacts of a situation that they did not create. Given time lags in the climate system, mitigation (reducing emissions) will become effective only during the latter half of the 21st century; Dessler reviews strategies for reducing emissions via various carbon-safe energy sources. Geoengineering is appealing, but potentially risky. Chapter 12 moves to mitigation policies, and examines carbon taxes and cap-and-trade scenarios. The United States has yet to develop a comprehensive mitigation policy.
Chapter 13 offers a history of climate change and policies, from Joseph Fourier on up to the Kyoto Accord and the limbo of the December 2009 Copenhagen meeting. Dessler traces the “strategy of doubt” employed by skeptics from its origins in the tobacco industry through the issues of ozone depletion, acid rain, and CFCs. The increasing certainty of the anthropogenicity of warming as indicated in a succession of IPCC reports, however, should convince any sensible reader that no reasonable doubts can be maintained.
The book closes with Chapter 14, which addresses the prospects for long-term policies. We face making decisions knowing that there are uncertainties in how much warming could occur, how much of it could be avoided, and what the cost could be. Dessler advocates for action now: If climate change turns out to be not as serious as anticipated, mitigation efforts could be scaled back in the future; also, switching to clean energy sources will lead to reductions in energy imports and air pollution. But if we do nothing to reduce emissions and worst-case scenarios come to pass, we doom our planet to irreversible, possibly catastrophic damage. Dessler offers a suite of strategies he feels necessary to achieve a middle-of-the road target of holding warming to 2oC above pre-industrial levels: put a price on emissions, reduce coal burning, implement improved efficiency standards, fund research and development of new technologies, prepare to adapt, and be ready to amend policies as necessary.
I learned a lot from this book and will be keeping it at hand. Each chapter contains a list of references as well as qualitative and quantitative questions, although no answers are provided for the latter. I was surprised that the infamous IPCC “hockey stick” was not mentioned, although one of Dessler’s graphs derives from it; anybody trolling the web is bound to come across this controversy. In the end, Dessler is optimistic that human creativity can solve the coupled problems of energy and climate. Left unstated, however, is the question of whether or not we have the will, foresight, and leadership to do so.