December 2007 Downloads & Links

In the press


Book reviews

coverThe Science and Politics of Global Climate Change—A Guide to the Debate

Andrew E. Dessler,
Edward A. Parson.
Cambridge University Press (2006). ISBN 0-521-53941-2.
ix + 190 pp.
Price: £19.99/US$ 34.99

The book tries, successfully, “ to clarify both the scientific and policy arguments now being waged over climate change” and “to help the concerned,non-expert citizen to understand what is known about climate change and how confidentially it is known in order to develop an informed opinion of what should be done about the issue”. The authors (A.E. Dessler is Associate Professor in the Dept of Atmospheric Sciences at Texas A & M University and E.A. Parson is Professor of Law and Associate Professor of Natural Resources and Environment at the University of Michigan) provide not only a resum of the scientific knowledge available on global climate change but also of the problems - and some of the solutions - with regard to policy options. The material is suitable for use in high schools and colleges.

The first Chapter examines “global climate change as a new and difficult to manage environmental problem” particularly because the changes projected for the twenty-first century are much larger than those of the twentieth century variations and their human impacts are likely to be correspondingly greater - and possibly catastrophic. The authors provide a series of published statements that give “a sense of the range of views about climate change” from, for example, Jerry Mahlmann, former Director of the US Geophysical Fluid Dynamics Laboratory and from “ the well-known scientific skeptic S. Fred Singer”. The book draws attention to the attempts made by government and learned society bodies to obtain information about misinformation, which underline the fact thatthere is more and more evidence that pseudo/phoney scientists and media professionals are willing to propound and to publish - if paid enough - messages dictated by their media masters or by multinational corporations. The authors suggest that “the risk of being discredited for advancing weak or false scientific arguments is small due to the lower standards of evidence and argument in policy than in scientific areas”.

Mike Baker





The Turbulent Ocean
S.A. Thorpe. Cambridge University Press (2005).
ISBN 0-521-83543-7.
xviii + 439 pp.
Price: £45/US$ 75.

Early studies of ocean turbulence required profound creativity. The ocean offers a vast range of potential time- and space-scales, but the technological challenge in sampling more than a tiny slice of this range was overwhelming. For example, could turbulent dispersion over sufficiently large scales be parameterized as diffusivity, as in the theory of Geoffrey Ingram Taylor (1921)? If so, what is “sufficiently large” in the ocean? In an attempt to answer this question, Lewis Fry Richardson and Henry Stommel dropped pairs of parsnips from a pier in 1948, measuring their separation rate; they determined that the effective diffusivity grows with separation distance out to the largest distances observable in the experiment, consistent with Richardson’s earlier observations of plumes from a smokestack.

By the 1980s, the study of ocean turbulence had become a specialized subset of physical oceanography. As such, the primary focus remained on relatively small scales, although the advent of satellite-tracked floating instruments allowed early pioneers to examine dispersion (driven by both turbulence and large-scale shear in the mean currents) over ever-broader distances. Theoretical calculations, most notably by Walter Munk, had already demonstrated the large-scale significance of diapycnal (density-changing) mixing in setting the structure of abyssal stratification, but these theoretical values were not testable with the existing suite of observations.

Then, in the 1990s, ocean turbulence became a central focus of physical oceanography when in situ observations of effective diapycnal diffusivity, pioneered by James Ledwell and collaborators, demonstrated an order-of-magnitude mismatch with the canonical theoretical value. A large number of studies have subsequently focused on spatial variations in mixing rates, driven, for example, by internal wave-breaking in undersea valleys, and the relative significance of processes (not only mixing) that change water’s density and set the structure of the ocean’s three-dimensional circulation. None of these developments would be possible without the recent introduction of robust, high-tech instruments capable of collecting and transmitting data in the harsh environment of corrosive saltwater, often under extreme pressure.
The Turbulent Ocean approaches this subject with a focus on the range of processes associated with turbulence, the suite of observations characterizing these processes, and the effects of turbulence (e.g. mixing) on the ocean. The author is a leading expert in the field, with a vast publication history focused primarily on internal waves, seiches and fine-scale ocean turbulence.

The first chapter of the book is an overview of the terminology and fundamentals of turbulence and demonstrates a concerted effort throughout to minimize the mathematics so that it is accessible to a physics undergraduate student. It proceeds to highlight the historical development and fundamental significance of ocean turbulence in modern physical oceanography, from Richardson and Stommel’s parsnip experiment to the latest estimates of globally-averaged energy transfer into breaking internal waves.

Chapter 2 presents an overview of internal waves, including their characteristics, wave-wave interaction and generation. Chapters 3-5 describe various turbulent processes, with numerous clear illustrations and laboratory tank photographs of developing instabilities, convective overturning and other types of turbulent processes to guide the reader in understanding generation, development and structure.
Chapter 6 reviews the instruments used in past and present studies to measure turbulence and mixing and focuses upon how, and how well, various key coefficients and parameters are measured. Chapters 7-9 present observations of turbulence, and related properties, such as dispersion, in the interior, bottom and surface boundary layers of the ocean. Chapters 10-12 focus on particular subdomains: shallow seas, surf zones, and bathymetric features such as submarine canyons and fjords. From these relatively small scales, Chapter 13 jumps to the mesoscale and gyre-scale features of ocean turbulence, including its impacts on ocean dispersion and mixing.

The Tubulent Ocean cannot replace basic textbooks, nor is it intended to do so. Thorpe aims instead to provide an accessible look at the basic processes that lead to ocean turbulence and their effects on ocean dispersion, characteristics and circulation. The Turbulent Ocean succeeds impressively in this endeavour. It certainly provides a comprehensive overview of the field, from the earliest experiments in turbulence to recent multi-institution oceanographic projects such as the Brazil Basin and Hawaiian Ocean Mixing experiments. Numerous footnotes provide examples, citations, and colourful asides.

The most impressive aspect of The Turbulent Ocean is the obvious effort to provide clear illustrations whenever possible, ranging from data time series to sketches and diagrams to photographs. For example, a discussion of turbulence in unstratified shear flow, focusing on the billows, braids and knots that characterize the flow, is accompanied by a colour photograph of the ocean surface, a series of schematic diagrams and several photographs from laboratory tank experiments. Similar examples can be found throughout the book, and serve to guide the reader toward a more intuitive feel for the processes being described.

Thorpe takes the reader on an impressive and inspiring tour of ocean turbulence. His passion for the subject is obvious and infectious. The Turbulent Ocean is ideal for exposing higher-level undergraduate and graduate students to our current state of knowledge in this field and how we obtained it. It is also an excellent field guide for researchers seeking both a comprehensive review of ocean turbulence literature and a deeply insightful and experienced view of what is unknown. The reader will undoubtedly recall passages of the book when watching a tide course through a restricted channel or convergent streaks forming across the surface of a bay … or even when passing the parsnips at the local grocery store.
Rick Lumpkin


New book received


Climate and Land Degradation

Mannava V.K. Sivakumar, Ndegwa’ui (Eds). Springer (2007).
IBSN 978-3-540-72437-7.
xxv + 623 pp.
Price: US$ 229

In many parts of the world, climatic variations are recognized as one of the major factors contributing to land degradation and impacting agricultural systems performance and management. To accurately assess sustainable land management practices, the climate resources and the risk of climate-related or induced natural disasters in a region must be known. Only when climate resources are paired with management or development practices can land degradation potential be assessed and appropriate mitigation technologies developed.
This book is based on an International Workshop held in Arusha, United Republic of Tanzania.




Short printable version English
MeteoWorld archive
50 years ago...
High-impact weather
Related sites
Art gallery
International Polar Year
Contact for content: pwmu[at] - WMO - OMM ©2007 Geneva, Switzerland