Sociologists of science wish to study the Intergovernmental Panel on Climate Change (IPCC) for the same reason that they want to examine other loci at which scientific knowledge is made — whether in a laboratory, the field, a museum or at a conference. We too approached the IPCC in autumn 2010 with a request to study it from the inside; we too were told 'no' (see Nature 502, 281; 2013).

We therefore had to rely on self-reported accounts. Using document analysis and interviews with lead authors, we analysed how authors navigate the distinction between scientific description and value judgements, for example when offering information pertaining to the definition of 'dangerous climate change'.

The IPCC has become a dominant institution in climate science — in the assessment of knowledge for policy-making, and in how assessment practices alter empirical and computer-simulated climate science. Global knowledge assessments such as those undertaken by the IPCC call for carefully documented systematic studies by trained ethnographers.

Let us hope that the IPCC will recognize itself as a legitimate object for scholarly investigation this time around.