Rajendra Pachauri has weathered a storm of criticism to hang on to his chairmanship of the Intergovernmental Panel on Climate Change. Credit: Bob Strong/Reuters/Corbis

It has been a hellish year for the Intergovernmental Panel on Climate Change (IPCC) and its beleaguered chairman, economist Rajendra Pachauri.

In late 2009, as the world pored over e-mails taken from the University of East Anglia's Climatic Research Unit in Norwich, UK, the IPCC was rocked by revelations about mistakes in its most recent climate assessment report. A storm of criticism over Pachauri's handling of the affair followed, along with allegations of conflicts of interest that put him under intense pressure to quit.

At the end of the IPCC's plenary meeting last week in Busan, South Korea, however, Pachauri was still firmly in charge. No attempt was made to force him to step down, says Ottmar Edenhofer, chief economist at the Potsdam Institute for Climate Impact Research in Germany and co-chair of the IPCC's working group on climate-change mitigation. But he is on notice, Edenhofer adds. "Governments made it very clear that they expect him to make changes," says Edenhofer — both to improve the IPCC's climate assessments and to foster greater public and political confidence in its work.

According to IPCC officials, negotiations last week were cumbersome and tainted by the looming issue of the future of the group's controversial chairman. "Delegates avoided talking about Pachauri's role," says Edenhofer. Insiders say that fear of provoking a confrontation between the IPCC's rich and poor member countries may have made the delegates reluctant to discuss the fate of Pachauri, who is from India.

Instead, delegates in Busan focused in part on how to implement recommendations for reform from the Amsterdam-based InterAcademy Council (IAC), a consortium of national science academies. In March, the United Nations — the IPCC's parent body — asked the IAC to carry out a review of the IPCC and propose organizational and procedural changes (see Nature 467, 14; 2010).

To restore some of the IPCC's lost credibility, and to make sure that its future assessments are more robust, the meeting eventually agreed on new guidelines, recommended by the IAC, on the use of non-peer-reviewed literature; on the characterization of scientific uncertainty; and on how to handle and correct errors. In future, IPCC authors will use consistent terminology to qualitatively describe uncertainties, and will cross-check more thoroughly the authenticity and robustness of data and information taken from 'grey literature' that has not been peer reviewed.

Most climate scientists say that errors in the assessment report — such as the notorious statement that all Himalayan glaciers could melt by 2035 — do not undermine the scientific case that human activity is dangerously warming the planet. But such errors must be corrected quickly and transparently to preserve the IPCC's credibility, the IAC said, and climate scientists agree. "Making the treatment of uncertainty more consistent is very important, and that task is very well on its way," says Gabriele Hegerl, a climate modeller at the University of Edinburgh, UK.

The IAC also proposed more far-reaching changes to the IPCC's management structure to streamline its decision-making. But delegates postponed any action pending the outcome of further investigation by several newly established task groups. By January 2011, these groups will propose options for improving the IPCC's management structures, review procedures, communication strategies and conflict-of-interest policies. The IPCC will decide how to implement these at its next plenary session, to be held in May 2011 in Abu Dhabi.

Several scientists lamented the slow pace of reform. "I think the IPCC needs to go further to restore its credibility with the public, policy-makers and other scientists," says Judith Curry, a climate researcher at the Georgia Institute of Technology in Atlanta. She adds that the organization needs to undergo "continued self-reflection on how to ensure the highest quality assessments and that the entire process is transparent and free from conflicts of interest".

Michael Zürn, an expert on transnational conflicts and international institutions at the Social Science Research Center Berlin (WZB), thinks that the IPCC has more fundamental problems that the reforms will not address. The IPCC is more than a loose alliance of scientists tasked by the United Nations with assessing our knowledge of climate change — its work also has a political dimension, he says.

But, Zürn adds, the 'soft' political authority that the international community has bestowed on the IPCC can all too easily clash with national interests, particularly because the IPCC's legitimacy is based on expertise rather than on a democratic mandate.

Pachauri, however, is optimistic about the future. The IPCC, he says, is well-prepared to march ahead towards producing a fifth assessment report by the end of 2014. "Despite all the noise we have not wasted a single minute to do what the world expects us to do," he told Nature. "I, for one, never lack the physical and mental energy that is required for the job."