The monthly peak amount of carbon dioxide in the Earth's atmosphere in 2019 jumped by a near-record amount to reach 414.8 parts per million (ppm) in May, which is the highest level in human history and likely the highest level in the past 3 million years.
We find that minor and seemingly arbitrary differences in the way public opinion researchers ask questions about climate change can have major effects on their findings.
For example, some surveys ask respondents to choose whether they think climate change is caused by human activity or natural causes (we call this a “discrete choice” question). Others ask respondents how much they agree or disagree with the idea that climate change is human caused, using Likert scales ranging from Strongly Agree to Strongly Disagree.
Because surveys take time to administer and ask questions about topics that some might find uninteresting, some people simply agree with questions they are asked — a phenomenon known as acquiescence bias. Likert-style questions can therefore inflate the number of people who say they “agree,” no matter what the question is about.
Surveys about climate opinion vary in other ways as well. For example, some explicitly tell respondents that they can say they “don’t know” their stance on an issue, while others do not.
And because many Americans do not consider climate change to be a high priority, some surveys explain what climate change is (“introductory text”) before asking respondents questions about it. On politically contentious issues, like climate change, the use of introductory text like this has been shown to increase partisan disagreement.