CLIMATE CHANGE

CLIMATE CHANGE Guy Jacques and Herv� Le Treut, 2005, 175 pp., $17.50, paperbound, UNESCO Publishing, ISBN 92-3-103938-5

Guy Jacques and Herv� Le Treut address the growing need for public understanding of science and policy issues relating to anthropogenic climate change. Their book overviews key scientific aspects and gives historical information along with a general appreciation of impacts of climate conditions on human activity. The book also summarizes the complexity of isolating and predicting anthropogenic effects, and gives insights on policy debates. Unlike another recent book (Hardy 2003), Climate Change avoids detail on the many impacts of climate change, and focuses on the basics of climate change itself.

The presentation in Climate Change is nicely done. It covers many key physical processes associated with the understanding of "climate change" issues. It boldly presents some scientific details. In a few places, such details may be confusing, especially to nonscientists. Overall, the book should help the general public to understand the policy debate issues better. A number of popularized books with varying goals are available. It is fortunate that Climate Change retains an open and objective perspective. One has confidence that it has a valid scientific basis and fosters a partnership between the scientific community and the general public. An interesting exception to this is the statement on page 42 in a section discussing current-day warning signs of global warming, where it is stated "you scientists are lost in your dreams about a distant future."

Chapter 1, on civilizations and climate, is a very special opening to the book. Its examples of human perceptions of weather and climate in a number of civilizations provide a unique attraction for all readers.

Chapter 2, on changes in climate, notes the large range of time scales for such variations. It highlights the current concentration of carbon dioxide in the atmosphere, which has not been seen in the past 400,000 years and which has an unprecedented current rate of increase. These are important facts to make known early in the book. There are a few statements that could be improved. For example, it is stated that "the increase in greenhouse effect reached a peak during the last few decades," which implies that the rate of increase has since gone down. It is suggested that the negative mean surface temperature trend in the Northern Hemisphere between 1940 and 1960 did not occur in the Southern Hemisphere, where the warming has been "relatively continuous." Figure 2.7 on page 114 in the Intergovernmental Panel on Climate Change (IPCC; 2001) report shows that a comparable cooling did occur. In another place it is noted that the "atmospheric window" is "the frequency band in which the atmosphere absorbs very little of the incoming solar radiation," when often this term refers to frequency bands where the atmosphere absorbs little infrared radiation.

Chapter 3, on the greenhouse effect, is a key chapter for understanding the science of climate change. This chapter is generally done well, with extensive discussion of the natural greenhouse effect. However, some of the scientific descriptions could be clarified. In the Earth-surface albedo discussion, the overall solar radiation energy returned to space from the Earth's surface (given as 4%) is smaller than the albedo for any of the Earth-surface components listed (none less than 5%). The discussion about the horizontal transfers in the ocean and atmosphere needs more connection with the other transports described. The special box on "synthesis of the radiation balance" refers to an Earth-surface balance that is actually a radiation imbalance, where overall energy balance is achieved by including sensible and latent heat transfers.

Chapter 4 provides a good general descriptive introduction to the climate system. My comments are on minor points. Figures 4.1 and 4.2 are rather abstract and do not clearly depict the different circulations and circulation cells described (although the text associated with these figures is clearer). It is stated erroneously that an altitude of more than 10 kilometers in the atmosphere is too cold for water to exist as vapor. The statement that the climate at polar latitudes will always be variable due to "huge whirlwinds" confuses climate with weather. It is stated that the rapid increases in global mean temperature after 1960 correspond to greenhouse gases that "started" to increase 10 years before, whereas in reality an increase started well before then. In the discussion of ocean currents, a "few tens of centimeters per second" is equated to "less than 1 kilometre a day"-a distance that is off by a factor of nearly ten.

Chapter 5, on the carbon sinks, is an excellent discussion uncluttered by excessive details. A number of ideas for biosphere carbon sinks are presented. The special box discussion on "carbon isotopes and vegetation" is also excellent. In one place, the "I" in IPCC was translated to "International" instead of "Intergovernmental."

Chapter 6, on the Sahara climate history extending back millions of years, is extremely interesting and was one of the most eye-opening parts of the book for me. It includes discussion of changes in climate when Africa drifted from the South Pole region to where it is now.

Chapter 7 presents important material for the modeling of climate change. It includes historical aspects and describes some of the challenges of numerical forecasting. It describes an interesting example of time scales for carbon dioxide changes. It is stated that a numerical model simulation will reach an equilibrium roughly 20 years after a new level of (atmospheric) carbon dioxide is established and held fixed. This is in contrast to a later discussion that states that 1,000 years are needed for the physical system to come to an equilibrium after additional carbon dioxide has been added to the atmosphere. The reader needs to understand that the carbon dioxide concentration in the air is not held constant in the second case. It would have been useful to note that the predictions of local temperature changes-such as shown in Figure 7.2-are fluctuating far more from model to model than those for global mean predictions, as seen in Figure 7.1.

Chapter 8, on the arguments and pressure groups concerning climate change, introduces the subject well. The authors, both French, present examples of comments by French skeptics and opponents to the concept of climate change. They then point out that such misleading statements have parallels in many other countries. In this chapter, the authors reemphasize the shortness of the time scale for human-produced climate change compared to many modes of natural variability. The brief mention of other explanations for climate change serves to remind us about the overall complexity of the entire issue.

Chapter 9, on the Kyoto Protocol, brings forth an excellent overview of the issues involved in the discussion of reducing overall greenhouse gas emissions in the world. The complexity of the issue and ideas for solutions are summarized well. Examples of the applications of the Kyoto Protocol are given for Germany, the Russian Federation, India, and China.

The book ends with a brief concluding section that gives good closure to the book. There is also a listing of publications for further reading as well as a glossary with 169 entries, which is intended for those with extra scientific curiosity about the technical discussion. A few glossary definitions could be improved. For instance, "climate system" is defined only as "a set of average climate conditions." The definition of convergence and divergence given for the ocean could be expanded to apply to the atmosphere.

In summary, this book is recommended for someone who wants an overview of the key points of the climate change issue and some broad perspectives on climate. The reader should be aware that some scientific aptitude would be helpful to understand some of the scientific details.

-DAVID D. HOUGHTON

[Reference]

REFERENCES

Hardy, John T., 2003: Climate Change: Causes, Effects, and Solutions. John Wiley & Sons, 260 pp.

Houghton, J. T., Y. Ding, D. J. Griggs, M. Noguer, P. J. van der Linden, and D. Xiaosu, Eds., 2001: Climate Change 2001: The Scientific Basis: Contributions of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, 881 pp.

[Author Affiliation]

David D. Houghton is professor emeritus of atmospheric and oceanic sciences at the University of Wisconsin-Madison in Madison, Wisconsin.