How relevant is climate change research for climate change policy? An empirical analysis based on Overton data

[1], one of the discoverers of the greenhouse effect, even welcomed a hotter climate for North- ern Europe. According to Weart [2], the World Climate Conference in Geneva in 1979 and the reports of the US National Academy of Sciences (NAS) and the US Environmental Protec- tion Agency (EPA) in 1983 are important milestones at the beginning of the climate debate, particularly beyond the scientific community. In the 1960s many experts assumed that swings of the global mean temperature take tens of thousands of years; in the 1970s, they assumed thousands of years. Meanwhile, ice core data from the last Glacial Period show that abrupt global warming is possible and can happen within a few decades or even within a few years as a climate shock [see 3, climate change beyond 2100, irreversibility and abrupt changes]. In the 1980s, climate change was no longer a theoretical problem. It was widely agreed among experts that global warming could be a con- crete threat. A growing number of well-respected climate researchers (like Roger Revelle, Ste- phen Schneider, James Hansen, Bert Bolin) were deeply concerned and pointed out that the earth was getting noticeably warmer. A series of meetings of meteorologists held in Villach, Austria, led to a growing conviction that global warming may not be a problem of the far future but might become serious within the scientists’ own lifetimes. Subsequently, scientists took an active stance and prompted governments to act soon, because the rate and degree of future warming could be influenced by governmental policy [see 2, breaking into policy].

The year 1988 marked an important turning point for climate science and policy. Sup- ported by governments around the globe, the Intergovernmental Panel on Climate Change (IPCC) was founded under the roof of the World Meteorological Organization (WMO) and the United Nations Environment Program (UNEP) as a unique science-policy interface. The panel, i.e., participating governments, tasked a set of elected scientists to assess the state of cli- mate science in dedicated reports, i.e., to review and synthesize scientific information relevant to understanding the scientific basis of climate change and of its risk, its environmental, politi- cal, and economic impacts and possible response options (see https://www.ipcc.ch/reports/). The latest report is from 2021 [4]. These assessments follow strict principles and procedures (see https://www.ipcc.ch/site/ assets/uploads/2018/09/ipcc-principles.pdf and https://www.ipcc.ch/site/assets/uploads/2018/ 09/ipcc-principles-appendix-a-final.pdf) to ensure policy relevance without being policy pre- scriptive. Hundreds of scientists and other experts contribute to the assessment in diverse author teams from a wide range of disciplines including climate physics, engineering, econom- ics, geography, political science, psychology, sociology or urban science and from different world regions to ensure balanced findings. Review is another critical element of IPCC reports. Authors have to respond to tens of thousands of submitted comments by experts and govern-

ments in two rounds of review. Important for the dignity of IPCC assessments in the political sphere is the formal acceptance of the reports by the 195 member countries and the line-by- line approval of the summary for policymakers [5–8]. IPCC has been designed and used as the prime scientific input to international climate diplomacy under the United Nations Framework Convention on Climate Change–and as such contributed to international climate agreements–most importantly, the Kyoto Protocol and the Paris Agreement. Meanwhile, climate policy has become an integral part of most national policy programs. These programs include political actions that governments take to achieve the goal of limiting climate change and its consequences [see 9]. In its summary for policymakers, the Climate change 2014 synthesis report [3] states that “human influence on the climate system is clear, and recent anthropogenic emissions of green- house gases are the highest in history. Recent climate changes have had widespread impacts on human and natural systems” (p. 2). A recent study found that detectable and attributable cli- mate impacts are documented in tens of thousands of scientific studies affecting 80% of the PLOS ONE How relevant is climate change research for climate change policy? PLOS ONE | https://doi.org/10.1371/journal.pone.0274693 September 22, 2022 2 / 24