This is a good question primarily because some people do not believe in climate change and if they do believe there is such, they would not do anything about it.
As a former instructor of research writing, I would say that the best data gathering method would be utilize the combination of quantitative and qualitative tools: a structured survey questionnaire and an open-ended questionnaire will help. The structured survey questionnaire should deal with quantifiable data, while the open-ended questionnaire should be about the respondents' opinion. It will really depend on what information you need to have.