The Chapter

We philosophers got on well with our colleagues in Chapter 3 of the report. This was partly achieved simply by mutual forbearance. I wrote my sections of the report without much interference from other authors, and I did not interfere with theirs. The process of writing started with bidding for space. I thought we did well in the bidding. But now that I count the pages in the report, I see we ended up with only 5 percent of our chapter, which is definitely less than our fair share. I think this must have been the result of prolix writing toward the chapter’s end. We philosophers did at least have a prominent place near the beginning, and we wrote concisely.

At one point, the leader of our chapter, Charles Kolstad, tried to abolish private fiefdoms within the chapter. He ruled that each section should be revised by someone who had not written it. My section was revised by one of my economist colleagues, who tolerantly allowed me to revise it all back again later. Nevertheless, the detrimental effect of writing by committee does show in the final result. The prose is not always good, and our chapter is longer than many books. It covers many topics, which are not welded into a coherent structure.

I look enviously on the chapter on discounting that appeared in the IPCC’s Second Assessment Report (IPCC, 1996, Chapter 4). It is only four and a half pages long, followed by a longer technical appendix. Those pages set out very neatly a classification of theories of discounting into ‘prescriptive’ and ‘descriptive’ theories. This chapter became very well known. It stimulated a renewed interest among economists in the theory of discounting. I do not agree with that chapter’s classification of theories. All theories of discounting are prescriptive: they prescribe to governments how they should discount future good. But I wish IPCC reports had remained vehicles for such clear summaries of particular subjects, rather than the monstrous compendiums they have become.

The Summary for Policymakers

Eventually we moved on to summaries. The huge main report of the IPCC attracts relatively few readers. It is the SPMs of the working groups that count. These are only a few dozen pages long, so there is strong competition for space, under the guise of cooperation. In the closing stages of writing the SPM of WG3, drafts circulated among authors by e-mail. Each of us would make changes according to our views. We used Word’s facility for ‘track changes,’ but it was undiplomatic to reverse another author’s changes. As changes piled on changes, there would come a time when some author would clear the clutter by accepting all the changes. Then the circulation would start again.

It was important, if possible, to be the last author to make changes before each deadline given us by the secretariat (known as the ‘Technical Support Unit’ or TSU). That was not easy for someone working in Britain, when there were also authors in the US. Furthermore, our deadlines never seemed final. The TSU would unexpectedly add another few days, so the exhausting process would begin again.

Once, at a meeting about the SPM in Potsdam, we were trying to think of a good opening sentence. I proposed: “Avoiding dangerous interference with the climate system is still possible but will be hard and costly.” That is an accurate statement of WG3’s conclusions. However, my suggestion was instantly shot down. The grounds were that you simply cannot have a short, sharp statement like that in an IPCC report.

There was a reason for this that I did not fully appreciate at Potsdam. More experienced IPCC authors knew what was coming. The report has to be approved by governments. The main report and its Technical Summary are approved (or not) as a whole. But the SPM is approved ‘line by line.’ This means that delegates from any of the 195 governments that make up the IPCC can edit or reject anything that the authors write in the SPM. There is therefore no point in including sentences that governments will predictably reject.

It is easier to get vague and uncontentious remarks past the governments. On the other hand, we wanted to tell the whole truth. So the writing of SPM was an exercise in compromise, which began to be fought out even before the governments saw a draft. Even at that stage the message began to be weakened. Self-censorship was in progress.

It is important to understand that this happened only to the SPM. It is sometimes claimed that the IPCC reports are subject to political influence. But the main reports and the Technical Summary are entirely the work of the authors; the government delegates have no influence on their content. Moreover, delegates cannot insert anything into the SPM that is not validated by authors. However, they can remove content from the SPM. Everything in the SPM has to be accepted by consensus, which gives the delegates the ultimate power of veto. They use it.