Syukuro Manabe arrived in Washington, DC, in the fall of 1958. He had just finished a PhD at the University of Tokyo and had been invited to work on climate models at the US Weather Bureau. He worked there until 1963, when he moved to Princeton’s newly founded Geophysical Fluid Dynamics Laboratory (GFDL), where he spent the rest of his career. He and his colleagues built the first climate model in the US, and Manabe is now regarded as the leading figure in climate model development in this country. Anthony Broccoli worked with Manabe in the 1980s. Together they applied the climate model to various paleoclimate epochs, such as the Last Glacial Maximum. Broccoli then moved to Rutgers University, where he is a professor of environmental sciences. Their new book, Beyond Global Warming: How Numerical Models Revealed the Secrets of Climate Change, is a summary of the many major developments that Manabe pioneered, and it stands as a tribute to his career.
Syukuro Manabe in his office at the Geophysical Fluid Dynamics Laboratory in the late 1970s.
Syukuro Manabe in his office at the Geophysical Fluid Dynamics Laboratory in the late 1970s.
Beyond Global Warming begins with the history and basic science behind Manabe’s work. The first chapters introduce us to the greenhouse effect and global warming, along with early studies of warming such as the pioneering work of Sweden’s Svante Arrhenius in the late 19th century. Arrhenius was the first person to estimate the surface-temperature change resulting from a change in atmospheric carbon dioxide concentration. From there, the book moves on to focus on Manabe’s career. It describes his work on one-dimensional models of radiative–convective equilibrium and the early development of global atmosphere general circulation models.
In chapter 5, Manabe and Broccoli describe Manabe’s work using early GFDL atmosphere models, including the first computational experiment in which the atmospheric concentration of carbon dioxide was doubled; that experiment is still a standard for all today’s climate models. Manabe was one of the first people to use a realistic distribution of land masses and a mixed-layer model of the very upper ocean in his modeling; those firsts strongly influence the spatial pattern of the surface temperature response to carbon dioxide changes.
The middle chapters focus on climate sensitivity, which climate scientists define as the equilibrium increase in globally averaged surface temperature due to a doubling of carbon dioxide. Chapter 6 is a general discussion of the various factors that affect climate sensitivity. Manabe was one of the first scientists to show that how clouds were parameterized had a large effect on a model’s climate sensitivity. That remains true in all current state-of-the-art climate models. Chapter 7 covers Manabe and Broccoli’s work in the mid 1980s, when they determined that the GFDL model had a climate sensitivity of 3.2 °C. In Beyond Global Warming, the authors speculate that that number is close to the actual sensitivity of Earth’s climate.
The final three chapters highlight the role of the ocean in climate change. Chapter 8 discusses Manabe’s work with coupled models using the ocean general circulation model Kirk Bryan developed at GFDL during the 1970s. Manabe and his colleagues suggested early on that the strength of the robust meridional overturning circulation in the North Atlantic Ocean would weaken as the carbon dioxide level increased. That conclusion remains a feature of all future projections made by climate models. Chapter 9 speculates about changes to deep water formation in the ocean when the climate is cold, as at the Last Glacial Maximum. Finally, chapter 10 discusses how the water cycle between the atmosphere and ocean accelerates with global warming as evaporation increases due to higher ocean surface temperatures. As more evaporation leads to increased rainfall, Manabe and Broccoli suggest that wet regions will get wetter and dry regions will get drier.
I have only one point of disagreement with the book, which centers on the discussion of flux adjustments in chapter 8. Flux adjustments are arbitrary changes to the fluxes of heat and fresh water between the atmospheric and oceanic components of a climate model. In early models the adjustments were necessary for a model to maintain a modern climate state as it was integrated forward in time. However, improved climate models, including several developed at GFDL, have been able to run without them for over 20 years now. The need for them indicates inadequacies in the model, which include low spatial resolution, poor parameterizations of important processes, and missing processes. In my opinion, it is preferable to run climate models without using arbitrary flux adjustments, but Manabe and Broccoli endorse their continued use.
This book was a pleasure to read. It is also unlike any other book on climate that I have read because Manabe is unique among climate model developers, and because no other climate book documents a single career. Beyond Global Warming will be essential reading for graduate students and postdocs wanting to learn about climate modeling. It will also be an interesting read for any physicist interested in the climate and how future projections are made. It is a fitting tribute to Manabe’s career, and I recommend it very highly.
Peter R. Gent is a senior scientist at the National Center for Atmospheric Research in Boulder, Colorado. He was the chief scientist of the Community Climate System Model project from 2005 to 2009.