Degrees of understanding

Most people have heard of global warming and have some idea of the consequences of the increasing human burning of fossil fuels or the rapid destruction of tropical forests. Few, however, understand the science underlying the controlling factors that determine the earth's climate or the science behind events like El Ni$o with its devastating connections with floods in some places and prolonged droughts in others.

One of the problems hindering understanding is the large natural variability of climate. Increased "greenhouse gases" will not lead to a uniform rise in temperature everywhere. In fact, the impact of climate change due to human activities will vary a great deal. Some places will benefit: for instance, the growing season in northern Canada or Siberia is likely to lengthen. But because most communities have adjusted to the present climate, the substantial changes in temperature, rainfall patterns or in the rise of sea level likely to arise from global warming will in many places tend to be disadvantageous to both humans and ecosystems. So that wise decisions are taken about the mitigation of anthropogenic climate change, the acquisition of greater scientific understanding by all concerned is of vital importance.

George Philander's book is in three parts. Two short chapters at the beginning pose the question of whether the climate system is robust or fragile; is it easily knocked off course? The main message here is that relatively small changes, if persistent, can accumulate over time to produce large effects. The ice ages were triggered by changes in the distribution of solar radiation resulting from small changes in the earth's orbit. The ozone hole has been caused by adding to the atmosphere what seem tiny amounts of very reactive chemicals - the CFCs. This provides further arguments why the effects of human pollution on climate need to be carefully studied.

Part two contains the meat of the book, where Philander tries to help the lay person (in the way he does in his introductory lectures to students with little knowledge of mathematics) in some of that careful study that is required. He is keen to give his readers some feeling for the science of weather and climate with the wide range of aspects it involves, especially explaining how certain or uncertain parts of that science might be. He takes us through the way the sun's energy acts as the main driver for the atmosphere's structure and circulation, the importance of water vapour and the influence of clouds, the main weather and climate systems and how they can be modelled on computers. Then the atmosphere is not on its own but strongly connected to the ocean and its circulation. Nowhere is that connection more clearly experienced than in the El Ni$o phenomenon (to which a very useful chapter is devoted), in which what happens in the Pacific ocean produces often quite devastating impacts across the world.

The final part of the book first explains some of the changes of climate in the past and finishes with two chapters, one on the ozone hole and the other on global warming in which is given a brief account of the increase of carbon dioxide and of some of the main points of contention about its effects.

It is this last chapter, of a mere 14 pages, that addresses the title of the book, Is the Temperature Rising? In it a brief summary is provided of the global warming issue, including the areas of uncertainty, but because there is little reference back to part two, readers are unable to excercise the scientific knowledge they have gained. Further, some important issues are not mentioned, such as the debate about possible inconsistency between satellite and surface temperature measurements, and the rise of sea level that is closely tied to the increase in global average temperature. A more thorough chapter that was better integrated with part two would have provided a more adequate answer to the question in the book's title.

Buy the book not because you are intrigued by its title but because you want Philander's informative introductory lecture series for lay people on the science of weather and climate.

Sir John Houghton is chairman, Royal Commission on Environmental Pollution, and co-chairman, Scientific Assessment Working Group, Intergovernmental Panel on Climate Change.