Great reliance is placed on past and present climate models, crop models and pronouncements of the Intergovernmental Panel on Climate Change (IPCC).  The models and the IPCC all have predicted significant CO2-induced global warming, with projected temperature increases far beyond any that have occurred thus far in the real world.  The impression is given, beginning with the first paragraph of the Prologue and ending with the first paragraph of the Epilogue, that it is an established fact that the global warming of the past century is due to the atmospheric CO2 increase experienced over the same time period.  However, this cause-and-effect relationship is still a matter of controversy among the scientific community.

The book's basic premise is that significant further warming is inevitable, and that it will have deleterious consequences for crops, particularly those grown in the Northern Hemisphere and equatorial countries, where most of the world's population resides and the great bulk of the planet's agriculture occurs.  What is not appropriately emphasized is that if the earth does warm further, millions of hectares of land in North America, Northern Europe, Russia and China that are currently too dry or too cold for cost-effective agriculture will be brought into profitable production.  Instead, the perceived harmful consequences of a warmer climate are emphasized in a series of chapters on Weeds, Insects and Diseases, Agricultural Emissions of Greenhouse Gases, Water Resources, Sea-Level Rises and Regions At Risk.  The conclusions reached in these chapters are that rising temperatures will almost invariably have negative impacts on crops, and that the reductions in productivity are not likely to be overcome by the beneficial effects of the rising levels of atmospheric CO2.  These extrapolations, however, are drawn from models, not facts.  In another inconsistency, more space is devoted to the chapter on Agricultural Emissions of Greenhouse Gases than to the chapter on Carbon Dioxide, Climate Change and Crop Yields, although the focus of the book is supposed to be the Global Harvest.

For those who truly know the intricacies of global agriculture, inter-annual variabilities of weather parameters related to temperature and precipitation have far more impact on crop yields than do most long term trends.  Seasonal periods of drought, flooding, heat waves, and freezing temperatures are the features of climate that make or break crop yields; but the book makes little mention of these short term weather events that directly determine crop productivity on a regional basis.

Global crop productivity, the well-being of people and livestock, the growth of forests, and the productivity of rangelands are all currently far more limited by cold than by warmth in both the Northern and Southern Hemispheres.  Modest warming, therefore, would be an asset, not a hindrance, to the global economy.  Indeed, there is virtually no place on earth too hot or too humid to grow sweet potatoes, cassava, or plantains; while corn, soybeans, rice and many other crops are successfully grown from the equator to 45 degrees latitude north and south.

One of the major premises of this volume is that any warming will increase the probability, frequency, and severity of extreme weather.  However, there are no data to substantiate this claim.  Rather, the opposite may well occur, since the climate models have traditionally projected a reduction in the equator-to-pole temperature gradient.

The book also suffers from serious omissions.  Although it was published in 1998, there are few references since 1995.  This is especially true for Chapter 3, the only chapter specifically related to agricultural productivity.  In fact, in this chapter, the authors cite not a single journal article that reports a single positive effect of elevated levels of atmospheric CO2 on a single food crop after the year 1995.  The most recently cited references are limited to those of the authors and reports emanating from the IPCC.  No reference is made to my own comprehensive volume, Climate, Food and Carbon Dioxide (1995), or to Abrol et al.'s Climate Variability and Agriculture (1996).  There is likewise no reference, except for a single brief mention of lettuce, to the historically significant and economically important utilization of elevated levels of CO2 in greenhouse crop production that began in Europe nearly 50 years ago.  CO2-enhanced crop production is currently an annual five billion dollar industry in the Netherlands alone, where crops are grown year-round and through their entire life cycles at a CO2 level of approximately 1000 ppm, or nearly triple the globe's current concentration.  Yields are typically increased by 20 to 40 percent under these conditions, and the crops usually experience improvements in quality.  In much the same vein, only brief paragraphs of the Regions at Risk chapter are devoted to crop production in China and India, two of the world's most important producers of food and fiber. China, for example, is the world's largest producer of rice, wheat, cotton and sweet potatoes, and second only to the U.S. in corn production.  There is also little reference to Russia and the former USSR, where there are still millions of hectares of land too cold and/or dry for crop production.

The authors do state (p.71) that "if atmospheric accumulation of CO2 were occurring without concomitant changes in temperature and water regimes, it might indeed be a blessing to agriculture."  What they fail to mention, however, is that there is a wealth of data that demonstrates that atmospheric CO2 enrichment actually helps plants to compensate for changes in temperature and water availability.  For the future, therefore, a modest increase in both temperature and atmospheric CO2 would most likely be a welcomed global subsidy for agriculture, freely enhancing the bounty of the global harvest.