An important measure of attitude strength is knowledge. A significant portion of Americans – over half in the last decade – believed they knew at least a moderate amount on the issue of global warming. In 1997, 42% said they knew a moderate amount or a lot about the topic, compared to an all-time high of 75% in 2020, as shown in the graphic below.

Question wording can be found here.


For just about every policy issue, a small group of people consider it to be of great personal importance. This group of people is called the “issue public” on the issue, (1) and its size is estimated by the percentage of the American public who say the issue is extremely important to them personally. These are the people who are passionate about it, follow it closely, and actively seek out information on the issue. More importantly, the issue public is especially likely to cast votes based on the issue (a more detailed discussion can be found on the Voter Behavior page).

Personal importance appears to be the root of policy issue engagement for citizens (2) – personal importance has been shown to have much more impact than national importance on candidate choices, policy preference expression, and financial contributions to political lobbying organizations. In other words, citizens for whom an issue is highly personally important are the ones most likely to write letters to the media and to representatives expressing their views on the issue, to volunteer with organizations advocating to influence policy on the issue, and to vote in line with their views on that issue.

Over the years, the size of the global warming issue public has hovered at about 15% of the American adult population. In 2020, an all-time high of 25% of the public were members of the global warming issue public (see the figure below).

Question wording can be found here

Another way to assess a person’s level of engagement with an issue is to measure their strength of opinion on it.

As the graph below indicates, the percentage of Americans with very or extremely strong opinions on global warming from 2010 to 2015 has hovered at about 40-45%. In 2010, 41% of respondents reported having very or extremely strong opinions on global warming. However, 54% of respondents in 2018 and 55% in 2020, an all-time high, reported this intensity of opinion in 2018.

Question wording can be found here



(1) Krosnick, Jon A. “Government policy and citizen passion: A study of issue publics in contemporary America.” Political Behavior 12.1 (1990): 59-92.

(2) Miller, J. M., Krosnick, J. A., & Fabrigar, L. R. (2016). The origins of policy issue salience: Personal and national importance impact on behavioral, cognitive, and emotional issue engagement. In Political Psychology: New Explorations (pp. 125-171).