The Intergovernmental Panel on Climate Change (IPCC), like its subject matter, can be unpredictable. In the last part of its mammoth fourth assessment report on climate change it has produced a surprisingly optimistic analysis of the possibility of mitigating climate change. Stemming the rising tide of greenhouse gases in the atmosphere need not cost the Earth, say the IPCC experts, and the range of options for geting the climate under control is growing all the time.

Chairman Rajendra Pachauri (centre) has high praise for the climate panel's latest report. Credit: S. KHAN/AFP/GETTY

The new report is likely to feed into discussions about climate plans at the G8 summit in Heiligendamm, Germany, next month, and into the United Nations climate-change conference in Bali, Indonesia, in December. Delegates at both these key meetings will try to tackle the long-discussed but little-resolved issue of how to regulate carbon emissions once the Kyoto Protocol on climate change runs out in 2012. “I hope to see the launch of negotiations on a post-2012 climate-change regime in Indonesia,” says Ivo de Boer, head of the United Nations Framework Convention on Climate Change — the organization that oversees the Kyoto Protocol.

Economical cuts

The latest report cites evidence that if carbon dioxide emissions were given a cost of US$50 per tonne, economic forces could drive global emissions in 2030 20% to 50% lower than they would otherwise have been. Policies that aim to limit human effects to the equivalent of a doubling in the carbon dioxide level compared with that at the start of the industrial revolution would cost about 3% of the world's GDP by 2030. By 2050, that amount would rise to 4% or 5%. Although these are vast amounts of money, they would lower the growth of the world's economy by no more than 0.12% a year. If the policies lead to further technological change the total costs might be even lower, although upfront costs might be higher.

These conclusions, unveiled on 4 May in Bangkok, Thailand, represent the work of the hundreds of scientists, economists, engineers and government representatives who make up the panel's Working Group III. The report of Working Group I, in February, spelled out the scope of the problem in terms of the natural science of climate change. Working Group II's report, released in April, gave a bleak prognosis of the effects that climate change would have — and in some cases is already having — on the livelihoods of people around the world, mostly in developing countries. Now, the third chapter gives governments a flexible blueprint for how to turn things around, with an emphasis on energy technologies (see '2030 vision'). With the energy sector accounting for two-thirds of emissions, and world demand set to rise by 60% by 2030, “a sound, far-reaching solution is urgently needed”, stresses de Boer.

Table 1 2030 vision
Full size table

Urgent approach

It no longer feels that countries are on different planets, politically.

Although not everyone is as rapturous about the report as IPCC chair Rajendra Pachauri, who hailed it as “stunning in its brilliance and razor-sharp in its relevance”, the document has drawn reasonably good reviews. “It's a very serious look at the kind of actions that will be required across the board,” says Robert Socolow, co-director of the Carbon Mitigation Initiative at Princeton University, New Jersey. Socolow welcomes a new urgency in the way that the panel presents its findings: “The 2001 report was much more an academic exercise, a very relaxed frame of mind. This one focuses on 2030 a lot, while that date is not even to be found in the 2001 report.” Michael Grubb, one of the report's lead authors, says that the changes in attitude during the report's preparation have been striking. “I cannot imagine that governments would have agreed this report even as little as two years ago,” Grubb says. “It no longer feels that countries are on different planets, politically.”

If everyone is on the same planet, though, the week's events showed that they are not yet all in the same place. China's delegation was reluctant to include details of more radical, and therefore expensive, schemes to stabilize greenhouse-gas concentrations. It argued that disclosing these plans would make it vulnerable to demands for severe emissions restrictions in the upcoming negotiations for a successor to the Kyoto Protocol. In the end, however, European delegates successfully pushed for the report to include details of how to restrict greenhouse-gas concentrations to significantly less than twice pre-industrial levels. That would mean that all the gases mankind is emitting would need to be kept to the equivalent of 535 parts per million of carbon dioxide (the current carbon dioxide equivalent concentration by these gases is about 430 p.p.m.). Stabilization below 535 p.p.m. is thought to provide a fair chance of limiting warming to no more than 2 °C, the commonly cited threshold for dangerous climate change.

Risky premiums

Many of those who worked on the report think that allocating 3% of GDP towards this goal represents good value. “It's a low premium to pay to reduce the risk of major climate change,” said Bill Hare, climate policy director for Greenpeace International in the Netherlands, after the Bangkok meeting. But this view is not universally accepted. “A 3% reduction in GDP would cause a global recession,” claimed James Connaughton, chairman of the White House Council on Environmental Quality.

Some governments may be happier to pursue one of the cheaper options set out by the IPCC report, in which greenhouse-gas concentrations are stabilized at higher levels. Levelling them off at 535–590 parts per million would cost between 0.2% and 2.5% of GDP by 2030, whereas allowing them to stabilize above that — at more than twice the pre-industrial level — might cost nothing at all. It might even deliver an economic benefit of up to 0.6% of GDP as a result of improved efficiency measures.

The guidance that these estimates provide for future negotiations is thus unclear. The report points out that the economic costs that it describes may depend on significant changes in policy. Those changes may be opposed by various vested interests, as well as by the desires of consumers — who are also, in many countries, voters. Some mitigation strategies would harm the economies of some countries disproportionately — notably those, such as Russia, that export fossil fuels. Although the report praises the Kyoto Protocol for creating institutions and providing a basis for future efforts, it notes that the protocol's impact will be limited (although it also says that its cost now looks to be less than previously expected).

Political trade-offs

The key message is that “Choices about the scale and timing of mitigation involve balancing the economic costs of more rapid emissions reductions now against the corresponding medium-term and long-term risks of delay”. That balancing act is essentially political, and is beyond the IPCC's remit. The latest report stresses, though, that a widening range of tools and technologies are available and have been shown to help. Grubb, who is also chief economist at the Carbon Trust, an emissions consultancy in London, UK, says that the report offers “a clearer than expected endorsement of carbon pricing” while setting out a range of credible strategies, including some with an emphasis on technology development that has in the past been seen as the opposite of mandatory carbon controls. “The nature of the problem means it is not going to be solved with one instrument — one needs a portfolio,” he says. “It's about what governments are willing to do in terms of a mixture of options.”