Provoke the beast and create a very nasty atmosphere

Over the last half century there has been an amazing change in attitudes towards the behaviour of that wisp of atmosphere round the Earth we call climate. Of course some people were always aware that climate changed, but the process was thought to be so slow that it could be scarcely be identified within a human lifetime. Indeed the distinction between climate and weather was elusive. For many God had created a world in which humans could flourish more or less in an ever present/perpetual present.

In this well written book, Spencer Weart shows why and how attitudes have changed until, as our present Prime Minister said last year, climate change has become "unquestionably the most urgent environmental challenge". In the 19th century such scientists as John Tyndall, James Croll, Svante Arrhenius and Walter Maunder identified some of the mechanisms of climate, in particular the role of positive and negative feedback, the effects of carbon dioxide and other gases in retaining the Earth's heat, and the possible influence of sunspots on climate. At the time their interpretations of the science were questioned, and their work was mostly ignored.

Attitudes began to change in the 1920s and 1930s. Here the work of Milutin Milankovitch was crucial. He correlated the successive Pleistocene ice ages with the changing relationship between the Sun and the Earth (its so called wobble, tilt and spin). Evidence accumulated from many other sources, including greatly improved meteorological observations. It became clear that human activities, in particular the emission of industrial materials into the atmosphere could be affecting global climate and adding to the greenhouse effect. Another disturbing discovery was that climate could sometimes change within decades rather than centuries.

Weart tells the story very well. It is one of scientific pioneers, sometimes in passionate disagreement with each other, and often not knowing what others were doing. Understanding climate involved astrophysicists, geochemists, geographers, biologists, meteorologists, statisticians, historians and even some times the military establishment (interested in the idea of manipulating weather to the disadvantage of an enemy). As so often in science, mistakes had fruitful results in stimulating research to correct them, and in driving new and better integrated methodologies. During the 1960s awareness of environmental problems greatly increased, and by the time of the UN Conference on the Human Environment at Stockholm in 1972, climate change was firmly on the international scientific agenda.

But it had yet to make the transition into politics and policy making. The uncertainties (was the Earth getting warmer or cooler?) made the whole subject a quagmire. By the time of the first World Climate Conference in 1979 advice had become more reliable, and more consistent. There is now a model institution of political and scientific cooperation in the form of the Intergovernmental Panel on Climate Change, and even an international treaty, the Framework Convention on Climate Change, with its implementing Kyoto Protocol.

In the meantime the volume of greenhouse gases in the atmosphere has risen to its highest for over 400,000 years, and average global surface temperature has sharply increased, particularly in the last decade, most of it due to human activities. According to the current broad scientific consensus (with a few dissidents), the prospects are that it will go still higher (somewhere between 1.5ºC and 5.8ºC between 1990 and 2100). If the increase were to go anywhere near the higher figure, life on Earth in all its aspects would undergo radical change.

There are still many unknowns. The relationship with climate and other environmental problems is equally uncertain: for example the effects of human population increase, land degradation, and destruction of biodiversity. Measures to cope with them are highly contentious, and outside the scope of this book. Some action is beginning here and there, but nowhere yet on a scale that could have much effect.

Weart has done us all a service by bringing the discovery of global warming into a short, compendious and persuasive book for general readership. He is especially strong on the early days and the scientific background. The second half of the book, mostly on the politics, is somewhat selective and US oriented, with some notably omissions, and the chronology is sometimes muddled. But the lessons come out loud and clear. As Wally Broeker once said, climate is a capricious beast, and we are poking it with a sharp stick. It is about time we stopped doing so.