Author Template for Journal Articles s3

Supplemental Material — Question Wording

1 Knowledge

Correct answers for each question are shown in parentheses. 1. The “greenhouse effect” refers to… (The way certain gases in the Earth’s atmosphere trap heat.) 2. Check ALL of the following that are greenhouse gasses. (Carbon dioxide, Methane) 3. By studying ice cores, scientists have shown that when carbon dioxide levels in the atmosphere are higher… (The Earth’s average temperature is higher.) 4. Check ALL of the following that are fossil fuels. (Coal, Oil, Natural gas) 5. What is the main gas produced by burning fossil fuels? (Carbon dioxide) 6. How does the US compare to the rest of the world in its use of natural resources? (More) 7. Check the ONE impact NOT from global warming. (More earthquakes) 8. Which of the following naturally takes carbon dioxide out of the atmosphere? (Trees) 9. Which of the following is a source of methane? (Cow burps) 10. The amount of carbon dioxide in the atmosphere TODAY is: (Higher)

2 Positive engagement

Response options for each question are shown in parentheses.

2.1 Global Warming’s Six Americas

1. Do you think global warming is happening? (1 = Extremely sure GW is NOT happening to 9 = Extremely sure GW IS happening.) 2. Assuming global warming is happening, do you think it is. (1 = Caused mostly by human activities to 4 = None of the above because global warming isn’t happening) 3. How much do you think global warming will harm: you personally? (0 = Don’t know to 4 = A great deal) 4. How much do you think global warming will harm: future generations? (0 = Don’t know to 4 = A great deal) 5. When do you think global warming will start to harm people in the United States? (1 = Never to 6 = They are being harmed now.) 6. Which of the following statements comes closest to your view? (1 = GW isn’t happening to 5 Humans can reduce global warming, and we are going to do so successfully) 7. How worried are you about global warming? (1 = Not at all to 4 = Very) 8. How much had you thought about global warming before today? (1 = Not at all to 4 = A lot) 9. How important is the issue of global warming to you personally? (1 = Not at all to 5 = Extremely important) 10. How much do you agree or disagree with the following statement: “I could easily change my mind about global warming.” (1 = Strongly agree to 4 = Strongly disagree) 11. How many of your friends share your views on global warming? (1 = None to 5 = All) 12. Over the past 12 months, how often have you punished companies that are opposing steps to reduce global warming by NOT buying their products? (0 = Don’t know to 5 = Many times [6+]) 13. Do you think global warming should be a low, medium, high, or very high priority for the next president and Congress? (1 = Low to 4 = Very High) 14. Do you think citizens themselves should be doing more or less to address global warming? (1 = Much less to 5 = Much More) 15. The United States should reduce its greenhouse gas emissions. (0 = Don’t know to 4 = Regardless of what other countries do)

2.2 Recognition of scientific agreement

Recognition of scientific agreement was a single question. Response options are shown in parentheses. 1. Which statement comes closest to your own view? (1 = Most scientists think global warming is happening; 0 = Most scientists think global warming is not happening; 0 = There is disagreement among scientists; 0 = Don’t know) 2.3 Self-efficacy

Both questions used the same response scale — 1 = Not at all confident to 10 = Very confident. 1. How confident are you that you could help start a project to reduce your school’s carbon footprint? 2. How confident are you that you could explain global warming to others?

2.4 Behavioral intentions

All three questions used the same response scale — 1 = Not at all likely to 10 = Very likely. 1. In the next three months, how likely are you to take actions such as the ones listed above to reduce your carbon footprint? 2. In the next three months, how likely are you to ask your friends to take actions that reduce their carbon footprints? 3. In the next three months, how likely are you to ask your parents to take actions that reduce their carbon footprints?

3 Behavior

All behavior questions used the same response scale — 1 = Yes; 0 = No, I don’t remember, or No answer.

3.1 Communication behavior

1. Yesterday, did you talk with your parents about climate change? 2. Yesterday, did you talk with your friends about climate change?

3.2 Conservation behavior

1. Yesterday, did you carry a reusable water bottle to school? 2. Yesterday, did you unplug gadgets and electronics when not using them? 3. Yesterday, did you take a shower less than 5 minutes long? 4. Yesterday, did you turn off lights when leaving a room for more than 10 minutes? 5. Yesterday, did you recycle paper, glass, cans, and/or plastics?