BioEd Online

Climate experts at an international meeting in Bangkok, Thailand, have spent the week locked in negotiations about how to tackle the rising tide of greenhouse gases. They are scheduled to publish a summary report on Friday morning that will advise governments on how best to curb emissions and keep levels of carbon dioxide in the atmosphere in check.

But talks have been heated on the question of whether to include details of how to meet stringent targets for greenhouse-gas levels in the report's wording. Government officials from China, the world's second-largest greenhouse emitter and soon to become the first, have reportedly argued against this, saying they do not want to be left "vulnerable to demands in future climate talks", according to the news agency Reuters.

The meeting is the third in a series of high-profile summits held this year by the Intergovernmental Panel on Climate Change (IPCC), and deals with 'mitigation' — the effort to reduce greenhouse emissions and, ideally, to stabilize overall levels of the gases in the atmosphere.

The summit is the most politically fraught of the series. The first, held in Paris in February, attempted to sum up our scientific knowledge of the causes of climate change; the second, in Brussels last month, aimed to predict who will be hit hardest and how to minimize the risks. In Bangkok, the question on the agenda is: what shall we do to stop it, and how much will it cost? Observers argue that this is the most subjective and difficult question for scientists to answer so far.

Highs and lows

World greenhouse emissions are set to increase for at least the next 25 years. If levels of CO₂ in the atmosphere are to be stabilized, the first step will be to check this growth. After that, further emissions cuts will be needed.

An early draft of the report suggests that the cost of stabilizing atmospheric greenhouse concentrations at between 450 and 550 parts per million of CO₂ equivalent would cost between 1 and 5% of world economic productivity during this century. At present, greenhouse gases are at about 430 ppm CO₂ equivalent.

Stabilization below 550 ppm is regarded as the best hope for keeping global warming below an average of 2 °C, regarded as a rough benchmark for avoiding 'dangerous climate change'. Delegates from the European Union are reportedly anxious that the report should emphasize the importance of capping global warming in this way, and may be pushing for an even lower stabilization concentration.

But the target of 550 ppm will require severe belt-tightening by countries such as China, who are anxious not to dent their economic prospects, and are in the midst of a heavy expansion of their primarily coal-burning domestic power sector.

At present, the principal method for achieving emissions cuts is the Kyoto Protocol, but this expires in 2012. It is widely agreed that a successor will need to be negotiated that will deliver larger cuts on a much longer timescale. Britain recently pledged to cut its greenhouse emissions by 60% by 2050, but heavy greenhouse emitters such as China and the United States are reluctant to agree to swathing cuts.

But Hans Verolme, director of the WWF's Global Climate Change Programme, argued that China should not be demonized. "They have the renewable energy portfolio standard that the US is currently lacking, and car fuel-efficiency standards that are amongst the strictest in the world," he said at the meeting.

For an update on the report's release check back on www.nature.com/news on 4 May.