Public impatience is succinctly expressed in the popular cry, ¡°Why are we waiting?¡± Nicholas Stern wants to bring the force of this impatience to the climate debate in a year in which the pivotal 21st UN Conference of the Parties meeting will take place in Paris, where binding greenhouse emissions goals for all nations are to be agreed.

Lord Stern is famous for being the Establishment figure who made the economic argument for tackling climate change. His core achievement was to shape a compelling case that it is economically rational to act, since the costs of addressing climate change are much lower than the harms that will result. Moreover, even if it costs $2 trillion to fix, that would be less than 3 per cent of total global income. That is not much more than the amount the world economy might grow in an average year. By 2051 we could be as rich as we would have been in 2050 and the climate will have been saved. Even the biggest enthusiast for economic growth can see that that¡¯s not a significant sacrifice at all.

Here, Stern puts the stress on the urgency of action, because time is critical in two senses. First, greenhouse gases stay in the atmosphere a long time. Failure to make deep cuts in emissions will mean that the ¡°stock¡± in the atmosphere will build up, and that will mean more warming for decades. Cutting now is much better than cutting later. Second, there is a societal lag. If we don¡¯t start making cuts now, we are almost certain to carry on building more coal-fired power stations and more petrol cars; then we are likely to continue to use them precisely because they are there.

His latest arguments also have a very strong global implication. If humankind is to stay on a path that gives a good chance of remaining within ¡°only¡± two degrees of warming ¨C as the United Nations and the Intergovernmental Panel on Climate Change propose ¨C then we need drastic cuts quickly.

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For Western Europe and North America this means getting close to zero emissions in less than two decades. At that point, all climate-changing emissions will essentially come from the middle-income and developing nations. The argument will no longer be about how much the US or the European Union can emit compared to the BRICS countries. It will all be about how developing economies share out the ¡°carbon space¡±.

This realisation takes us to Stern¡¯s central and best argument. He emphasises that the problem is not to work out how to address climate change in the context of the current world economy. Today¡¯s wealthy countries need to be carbon-irrelevant in a generation or so. The challenge is to envisage a way in which emerging economies can achieve the kinds of development they seek in a climate-friendly way. These societies are building their infrastructures, industries and cities now; if?things are done well, they can build them in low-carbon ways. There can be a prosperous and climate-friendly world, but the prospects for success diminish with every year of inaction.

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Stern is practised at making these arguments, and the book¡¯s central contention is highly persuasive. At times, however, the power of the text is diminished because it is repetitive and reads like a commission report rather than an energising treatise. Stern also has to admit that a number of key issues ¨C among them, how to store electrical energy and what to do about aviation ¨C are not that close to solution. Furthermore, the image of the political world he conjures up is astonishingly rational and reasonable. There is not much room for political or ideological objectives and it would be hard to understand, from this analysis, how it is that leading US Republicans end up being so denialist. Neither is there much discussion of the kind of practicalities that could get in the way of the desired future, even though the world today is littered with examples ¨C Ukraine, Syria, Libya ¨C that seem to contradict the idea that good policies will inevitably be adopted. Stern has expressed some, but not all, of the reasons we¡¯re still waiting.

Steven Yearley is professor of the sociology of scientific knowledge and co-director of the SKAPE Centre, University of Edinburgh.

Why Are We Waiting? The Logic, Urgency, and Promise of Tackling Climate Change
By Nicholas Stern
MIT Press, 376pp, ?19.95
ISBN 9780262029186
Published 3 June 2015