“THE less people know about how laws and sausages are made, the better they sleep at night.” That comment, attributed to Bismarck, could equally apply to the Intergovernmental Panel on Climate Change. The IPCC’s reports, published every six or seven years, are immense undertakings. Each depends on the unpaid work of hundreds of scientists and runs to thousands of pages. But most of the controversy is generated at the last minute, when the authors (scientists and academics) meet government officials to produce a summary of 30 or so pages. Consider the recent report, published in Berlin on April 13th, on efforts to rein in greenhouse-gas emissions.

The process was described by one participant as “exceptionally frustrating” and by another “one of the most extraordinary experiences of my academic life”. It works as follows. The authors write a draft summary. Each sentence of the draft is projected onto a big screen in a giant hall. Officials then propose changes to the text; authors decide whether the changes are justified according to the full thousand-page report. Eventually a consensus is supposed to be reached, the sentence is approved or rejected, the chairman bangs a gavel and moves on to the next sentence.

In the final day of discussions in Berlin, the delegates turned to a set of figures showing emissions by countries classified by income group (rich, middle-income, etc). A group of countries, led by Saudi Arabia, said the figures should be deleted. European countries objected. The authors suggested taking the figures out of the summary but putting in a reference instead to the underlying report where the figures remain (officials may not alter the main report). The Saudis said no. The Netherlands suggested adding a footnote saying: “The Netherlands objects to the deletion of the following figures [then a list of them].” No dice. Eventually, in the early hours of the morning, Saudi Arabia got its way.

Since the report’s publication, more unseemly wrangles have come to light. Robert Stavins, a professor at Harvard University and a lead author on the chapter in the main report dealing with international co-operation, wrote to the report’s chairman “to express my disappointment and frustration”. As he pointed out, most of the delegates to the IPCC are in the middle of negotiating a treaty, intended to be signed in Paris in 2015, limiting greenhouse-gas emissions. As Dr Stavins says, “any text that was considered inconsistent with their interests and positions in multilateral negotiations was treated as unacceptable.” It was not necessary that they should all find something objectionable. The requirement of unanimity meant one country was enough. Three-quarters of his original draft was rejected and what remains is a list of disconnected facts, not a guide to the state of knowledge.

Another professor, John Broome of Oxford University, had a little more luck with a discussion about the ethics of climate change. “Late one evening,” he writes, “the delegates formed a huddle in the corner, trying to agree text between themselves...Eventually, we [authors] were presented with a few sentences that, we were told, the developed countries would reject, and an alternative few sentences that, we were told, the developing countries would reject. We were also told that, if we simply left out the text, the developing countries would delete the whole paragraph and the previous one which would in turn cause the developed countries to delete the whole section...We counter-threatened...Eventually some brief paragraphs [survived], badly mauled and their content much diminished but not entirely empty.” He describes himself as “angry at the deletions and astonished by the process”. You can read his account here.

Not everyone is so damning. Chris Field of Stanford University, who was chairman of an IPCC report on the impact of climate change that appeared just before the one in Berlin, says the process improved his findings. Dr Stavins concedes that official approval gives the IPCC political credibility. Still, as he says, having a report reviewed by officials who are themselves interested parties “created an irreconcilable conflict of interest”. The details, arguments and numbers remain in the full report. But the summary aimed at policymakers is not necessarily a good guide to them.