I am normally a great fan of book reviews, but one which covered a book on a climate caught my attention. I was troubled with the review that appeared in the Philadelphia Inquirer because of the way it treated climate science in general and modeling in particular.
The book review, Digging deeper on climate change by Frank Wilson [Philadelphia Inquirer, October 13, 2013], concerned the book The Whole Story of Climate: What Science Reveals About the Nature of Endless Change by E. Kirsten Peters. Wilson wrote:
“Climate science, with its computer models, is a Johnny-come-lately to the narrative. Not so geology. ‘For almost 200 years,’ Peters writes, ‘geologists have studied the basic evidence of how climate has changed on our planet.’ They work, not with computer models, but with ‘direct physical evidence left in the muck and rocks.’ “
This seems to denigrate the role of models. It is certainly important to look to the past to better understand our climate –– its trends and the mechanisms that caused those trends. However, it is also important to understand the trends on a time scale that is much smaller than the geological — that is, since the beginning of the industrial revolution — and the role of increasing CO2 in atmosphere. Modeling the physics of the atmosphere and performing simulations using high performance computing play a crucial role in understanding the possible state of the climate in the next 100 years and beyond.
Contrast the observation in Wilson’s book review to a recent textbook on climate science by Hans Kaper and Hans Engler, Mathematics and Climate [SIAM, 2013]. This book, intended for master’s level students or advanced undergraduates, introduces students to “mathematically interesting topics from climate science.” It addresses a broad range of topics, beginning with the variability of climate over geologic history as gleaned from “proxy data” taken from deep-sea sediment cores. Certainly this variability informs our understanding of past climate history, including warming and cooling trends.
The book moves from data of past climate history on to models of the ocean and atmosphere, coupled with data, covering an interesting bit of mathematics along the way. For example, students are exposed to the role of salinity in ocean circulation models, and learn something about dynamical systems that are used in these models. To give another example to show the breadth of mathematical topics covered, various statistics and analytical tools are introduced and are used to analyze the Mauna Loa CO2 data.
Wilson, in his book review, states that “Using direct evidence rather than computer models, a geologist says a cold spell could be near.” That could be comforting news to some who want to ignore predictions of a warming planet, but it would be cold comfort. Mathematics, when used in the geosciences, tends to take a more balanced and calculating approach.
As Kaper and Engler point out in the preface to their book, “Understanding the Earth’s climate system and predicting its behavior under a range of ‘what if’ scenarios are among the greatest challenges for science today.” Physical modeling, mathematics, numerical simulation, and statistical analysis will continue to play a major role in addressing that challenge.