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TO THE horror of many climate researchers, one of the leading advocates of action to halt global warming is claiming that major cuts in emissions of greenhouse gases should be delayed, perhaps for several decades.

The climatologist calling for delay is Tom Wigley of the University Corporation for Atmospheric Research in Boulder, Colorado. Wigley is one of the lead authors of a report released last month by the UN鈥檚 Intergovernmental Panel on Climate Change, which called for action to halt global warming. But in this week鈥檚 issue of Nature, Wigley says that major investment to prevent warming should await the development of cheaper technologies.

The row comes at a critical time. In March, international negotiations begin on how much industrial nations should reduce their emissions of greenhouse gases after 2000. Wigley鈥檚 paper, written jointly with two leading American economists and part-funded by the US energy industry, will bolster a strong industrial lobby in the US, which is pushing its government to oppose cuts until the economic implications are clear.

Climatologists, including Wigley, who is the former director of the Climatic Research Unit at the University of East Anglia, agree that the world should set a maximum concentration in the atmosphere for carbon dioxide, the key greenhouse gas. They believe it is this concentration that will largely determine the extent of global warming.

Wigley and others back a maximum of 550 parts per million (ppm) of CO₂, roughly twice the preindustrial level and still well above the present level of 360 ppm. Such a concentration would probably cause a rise in worldwide average temperatures of between 1.5 掳C and 4 掳C. But given the long lifetime of CO₂ in the atmosphere, such a target will require big cuts in emissions from present levels.

The IPCC, as Wigley鈥檚 paper points, suggests that 鈥渁n immediate departure from business as usual is required鈥�. But in reality, Wigley says, 鈥渢his is not so鈥�. A delay of perhaps 30 years, during which annual emissions would continue to rise quickly, is not only possible, he says, but would also make the whole exercise cheaper.

As the graph shows, the IPCC envisages that 鈥渂usiness as usual鈥� should cease immediately, to be replaced by slow growth in emissions as rich nations make cuts but Third World nations are allowed increases. Emissions would peak at less than 9 billion tonnes of carbon a year around 2060.

But Wigley says the IPCC has 鈥渕ade no attempt鈥� to establish whether its scenarios for reducing emissions are realistic. He suggests an alternative path. Under this, 鈥渂usiness as usual鈥� would continue for another 30 years, and emissions would rise to more than 11 billion tonnes a year. Only then, he says, when cleaner technologies are fully developed, must cuts begin in earnest. His paper argues that 鈥渕odest reductions in the early years 鈥� followed by sharper reductions later on [are] less expensive.鈥�

The paper adds that if cuts in emissions are delayed they will allow a 鈥済reater total CO₂ production鈥�. This is because the earlier a given amount of gas is emitted, the more it will be absorbed by oceans and forests by the time the target ceiling on CO₂ concentrations is reached, in perhaps 300 years. This, he says, is another factor the IPCC has not considered.

The paper, first scheduled for publication last year, received a hostile reaction from some reviewers, resulting in counter-accusations of censorship and a substantial rewrite. But the published version remains 鈥渆xtremely loose鈥� in presenting economics issues, says Michael Grubb of the Royal Institute of International Affairs in London, who reviewed the paper鈥檚 economics. 鈥淚 fundamentally disagree with its conclusions.鈥�

A critical issue, both sides agree, is how technological innovation comes about. Does it require a kick-start, or will it happen anyway? Wigley argues that the development of alternative fuel sources that do not produce CO₂, and more energy efficient machines, is inevitable.

Grubb disagrees. 鈥淕overnment action is essential to overcome the inertia that prevents investment in R&D,鈥� he says. Without international targets to put the pressure on, the technology that Wigley expects to save the day will never be developed he believes.

In a paper published in the journal Energy Policy last April, Grubb argued that 鈥渢he sheer ease of deriving energy from fossil fuels suggests that abandoning them completely would incur real long-term resource costs鈥� 鈥� costs industry would not pay voluntarily.

Wigley鈥檚 paper specifically warns against a 鈥渨ait and see鈥� policy. He wants planning and R&D, but not a crash programme to cut emissions. But he concedes that 鈥渨hatever we say, people will misinterpret it鈥�. And that, it seems, is what is happening. According to Grubb, Wigley鈥檚 paper 鈥渋s already being used in the US, with the cooperation of some of the authors, to argue that it makes economic sense to delay action鈥�.

Wigley鈥檚 coauthors are Rich Richels of the Electric Power Research Institute, which is owned by the power industry, and Jay Edmonds of the US government鈥檚 Pacific Northwest Laboratory.

Commenting on pressure from US industrialists who prefer to ignore global warming, Wigley says: 鈥淒oing things too radically here can turn people off, make them look for reasons never to do anything, including saying there isn鈥檛 such a thing as the greenhouse effect. So we have to act in a way that is not economically disruptive.鈥�

Wigley insists he has not deviated from his view that global warming has to be tackled, but has merely added a dose of economic and political realism to the IPCC鈥檚 work. In particular, he hopes that the negotiations on new emissions targets, which begin in Geneva in early March, will agree on the need for an upper limit to CO₂ concentrations in the atmosphere, and a strategy to meet it. 鈥淚t鈥檚 a subject they keep trying to avoid, but it has to be addressed,鈥� he says.

John Houghton, chairman of the science working group of the IPCC, told 51动漫 that an economic analysis of the various ways of reducing emissions is a good thing. 鈥淏ut to suggest delaying planning is wrong.鈥� He agrees with Grubb that 鈥渢o encourage technical advance the penalties and incentives have to be in place鈥�.