International climate adaptation assistance: Assessing public support in Switzerland

PLOS ONE | https://doi.org/10.1371/journal.pone.0317344 February 12, 2025 9 / 26 PLOS ONE Support for adaptation assistance in Switzerland Informed consent, anonymity, and confidentiality: Informed consent was sought at the beginning of the survey. Each participant had to read the informed consent statement and could decide whether to accept and agree to participate or exit the survey. In the informed consent statement, participants were informed of the purely scientific purpose of the paper and the lack of commercial and government-related purposes. Anonymity and confidential- ity guarantee related to data collection, storage, and publication were explicitly stated in the informed consent statement. The statement also included an email address at which partic- ipants could direct their concerns, which included the name of one of the authors’ institu- tions. The objective of the study was explained to participants, who have been informed at the consent stage of this process that the authors intended to study public opinion on climate change. They were also informed of the length of the survey. The informed consent statement is available in the survey instrument in Supporting information S1 File. Conjoint experimental design In the design of our experiment, we ask respondents to compare two overseas adaptation assistance packages in different countries. In each package, respondents consider two forms of assistance – aid and immigration along with different types of connections the recipient

country has with Switzerland. The ability of conjoint experiments to capture such multi- dimensionality makes them better able to mirror real-life situations. Conjoint experiment design further lessens the risk of social desirability bias because respondents can implicitly trade off one attribute against another [85]. We draw broadly on the approach implemented by Uji et al. [26] in the context of Japan. First, all respondents initially read a paragraph laying out the causes of climate change, explaining the role played by industrialized countries, including Switzerland, in the accu- mulation of greenhouse gas (GHG) emissions, and how developing countries facing extreme weather events can be supported, either by providing adaptation aid or by accepting climate migrants. The possibility that Switzerland is expected as an industrialized country to provide adaptation assistance was presented in a neutral, non-normative tone, to decrease the risk of social desirability bias. The introductory paragraph was followed by a question that served as an attention check. In the experimental phase of the survey, we randomly assigned participants to one of the three groups: a control group and two treatment groups. The objective was to assess if providing information about peers or what Switzerland has done in the past regarding aid or immigration, might frame the conjoint experiment for respondents in different ways. Data on Switzerland’s overall acceptance of migrants was obtained from the UNHCR Refugee Data

Finder, while the data on bilateral climate aid comes from the OECD Development and Coop- eration Profiles. The first treatment group (peer benchmarking) received information about annual levels of bilateral climate aid and refugee acceptance in OECD countries. The second treatment group (self-benchmarking) received similar information about Switzerland. The third group, serving as the control or reference category, received no benchmarking information. After reading the benchmarking information, respondents were provided with instructions about the task they were about to complete and were informed they were about to be shown different hypothetical policies that the Swiss government could adopt to support developing countries in adapting to climate change. Participants were asked to compare two policy packages, each with six dimensions. Then they were asked to select the one they would recommend the Swiss government to adopt. They repeated the choice task six times. This type of paired-options, forced-choice conjoint design is believed to promote higher engagement of respondents with the task at hand [86].