Environ. Res. Lett. 12 (2017) 084019 Table 2. Definitions of the Endorsement, Impact, and Solvable Points used to code levels of acknowledgment of AGW as real and human-caused, serious, and solvable, respectively. See section S1, supplementary information, for details on the content analysis and coding scheme. AGW as Real and Human-Caused Endorsement points (EPs) Description ‘Acknowledge’ (EP1) Explicit endorsement with quantification ‘No position’ ‘Doubt’ Explicitly supports position that humans are the primary cause of global warming (with quantification) (EP2) Explicit endorsement without quantification Explicitly supports position that humans are the primary cause of global warming (without quantification) or refers to anthropogenic global warming as a known fact (EP3a) Implicit endorsement Implicitly supports position that humans are the primary cause of global warming. e.g. research assumes greenhouse gas emissions cause warming without explicitly stating humans are the cause (EP3b) Implicit endorsement of consensus Implicitly supports position that humans are the primary cause of global warming by referring to a consensus of the scientific community (EP4a) No position Does not address the cause of global warming (EP4b- 1) Uncertain of reality of AGW Expresses position that the reality of recent global warming is uncertain/undefined, namely ‘it’s not happening’ 2) Uncertain of human contribution to AGW Expresses position that the human contribution to recent global warming is uncertain/undefined, namely ‘it’s not us’ AGW as Serious Impact points (IPs) Description ‘Acknowledge’ (IP1) Acknowledgment ‘No position’ (IP2) No position ‘Doubt’ (IP3) Uncertain Acknowledges and/or articulates known or predicted negative impacts of global warming e.g. geophysical, economic, sociopolitical Does not address the negative impacts of global warming (beyond generic references to climate change as a ‘risk’) Expresses position that the reality of negative impacts of global warming is uncertain/undefined/exaggerated, namely ‘it’s not bad’ AGW as Solvable Solvable points (SPs) ‘Doubt’ Description (SP1) Uncertain Expresses position that the difficulties of mitigating global warming are potentially insurmountable and/or exceed the benefits, namely ‘it’s too hard’ Level (EL) (intercoder reliability of Endorsement Levels: 89%; Kripp. a ¼ 0:85): ‘No Position’ (all text and figures are EP4a only); ‘Acknowledge’ (EP1–3 only); ‘Acknowledge and Doubt’ (EP1–3 and EP4b); ‘Reasonable Doubt’ (EP4b only, deemed reasonable as defined above); or ‘Doubt’ (EP4b only, deemed unreasonable). ‘Acknowledge and Doubt’ reflects the fact that some communications acknowledge aspects of AGW yet emphasize other areas of doubt or uncertainty. Our filtering of reasonable doubt (see also section S1.4.2, supplementary information) helps address the challenge of characterizing the positions of documents published during a period of rapidly evolving scientific opinion. Otherwise, however, our coding scheme is agnostic to each document’s publication year. 2.1.2. ‘Serious’ We assign ‘Impact Points’ (IP1 to IP3, defined in table 2) throughout each document based on its 4 positions on AGW as having known or predicted negative impacts (for example, geophysical, economic, or sociopolitical) (intercoder reliability of Impact Points: 94%; Kripp. a ¼ 0:86). Each document is then assigned one of four overall Impact Levels (ILs): ‘No Position’ (all text and figures are IP2 only); ‘Acknowledge’ (IP1 only); ‘Acknowledge and Doubt’ (IP1 and IP3); or ‘Doubt’ (IP3 only) (intercoder reliability of Impact Levels: 89%; Kripp. a ¼ 0:77). 2.1.3. ‘Solvable’ We identify documents that express ‘Doubt’ (SP1, defined in table 2) as to whether AGW can be mitigated or whether the costs of doing so exceed the benefits (intercoder reliability: 97%; Kripp. a ¼ 0:84). While the question of AGW’s solvability is not resolvable on purely technical grounds, the relative extent to which documents promote doubt on the matter remains relevant to the character of climate communications, insofar as assertions that AGW