Climate change and health: on the latest IPCC report.

www.thelancet.com Vol 383 April 5, 2014 1185 The Intergovernmental Panel on Climate Change (IPCC) released its latest report on March 31, 2014. This report was the second instalment of the Fifth Assessment Report, prepared by Working Group 2, on impacts, vulnerability, and adaptation to climate change. In this Comment, we, as contributors to the chapter on human health, explain how the IPCC report was prepared and highlight important fi ndings. The IPCC reviews and assesses the scientifi c published work on climate change. As an intergovernmental body composed of members of the UN, the IPCC does not undertake research itself; instead it appoints Working Groups who assess the work. This assessment means more than simply to summarise the state of knowledge: Working Groups are asked to weigh what has been written (in both peer-reviewed publications and grey literature), to make judgments about likelihood and uncertainty, and to fl ag important emerging issues. The focus for Working Group 2 was mainly, but not exclusively, on what had been written since the previous assessment in 2007; papers were eligible for inclusion if they were published, or accepted for publication, before Aug 31, 2013. The Working Groups were required to highlight what might be relevant to policy, but did not recommend policies. The Fifth Assessment Report Working Group 1 reported on the physical science of climate change in September, 2013 (appendix). Working Group 3, concerned with mitigation (ie, reduction of greenhouse gas emissions), will release its report in April, 2014. The scale of the enterprise is remarkable—indeed, reports by the IPCC together probably represent the largest scientifi c assessment exercise in history. There are 310 authors and review editors in Working Group 2, and an even greater number of contributing authors who have added to the report from their areas of special expertise. In addition to health, Working Group 2 examined natural and managed resources (eg, fresh water, coastal systems, and food production), human settlements, and other aspects of wellbeing such as security and livelihoods. The report (30 chapters) will be published in two volumes, and includes integrated assessments of impacts and adaptation in nine geographic regions and an overarching summary for policy makers. Work on the Fifth Assessment Report began 5 years ago (appendix) and aspects of the IPCC process distinguish its assessments from other reviews and scientifi c publications. One diff erence is the substantial role of member states in determination of, in the initial stages, the scope of the reports and the membership of writing groups. At the beginning of each round of assessment, meetings organised by the IPCC decide on the structure of the reports, including the number of chapters and the topics to be covered, and then member states nominate potential authors. The fi nal decision about authors is made by a subgroup from the IPCC, the Bureau, on the basis of scientifi c merit and the necessary institutional and disciplinary perspectives for each chapter, seeking, at the same time, to achieve a balance of representation by gender and region. Once appointed, the IPCC authors work independently; government input occurs as part of the peer review process. However, the member states must approve and sign off on the fi nal report. Thus, the IPCC assessments are the outputs of many iterative interactions between scientists and policy makers. Another feature of the IPCC process is the intensity of peer review. There were four rounds of review for the Fifth Assessment Report, two of which involved hundreds of self-nominated experts and scientists appointed by member-state governments. Each round generated an enormous number of comments, questions, and requests for change. For instance, the IPCC received 1009 reviewer comments just on the second-order draft of chapter 11 (human health). Two dedicated review editors per chapter are charged with ensuring that the authors consider each comment seriously and, if they reject it, that they do so with good reasons. Both the comments and the chapter authors’ responses will be published on the IPCC website. The IPCC does not prescribe how chapter groups should gather and interpret the scientifi c work, partly because conventions and practice diff er among disciplines. Contributors to the health chapter used many strategies to identify relevant published work. Due to the breadth of the topic, including the range of health outcomes and exposure pathways, the chapter team decided that one systematic review would not be possible. Climate change and health: on the latest IPCC report