Interaction Effects of Partisanship, Education and “Understanding” on Public Opinion about Climate

Lawrence Hamilton, University of New Hampshire, December 18, 2011


Education has opposite effects on the climate-change views of Democrats and Republicans (or of liberals and conservatives). College-educated Democrats are more likely than other Democrats to take anthropogenic climate change seriously. College-educated Republicans, on the other hand, tend to be less likely than other Republicans to do so. Consequently, the partisan divide on this issue is greatest among those with the most education. “Interaction effects” along similar lines have been noticed in data from more than twenty different surveys, using a variety of climate-change questions and analytical approaches. The first formal analysis, so far as I know, appeared in a 2008 paper (Hamilton, “Who cares about polar regions?”) in Arctic, Antarctic, and Alpine Research. The graph below, from this paper, shows probabilities that the most liberal or conservative respondents to a national survey said they would be bothered “a great deal” if sea levels rise by 20 feet, flooding coastal areas. Probabilities are calculated from a logit regression model that adjusts for other background factors and also for five measures of science education or knowledge. This graph shows conditional effects, in which other predictors are set at their mean values.


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A similar interaction occurs between partisanship and self-assessed understanding. Democrats who say they understand global warming or climate change issues well are more likely than other Democrats to be concerned about anthropogenic climate change. Republicans who say they understand well are less likely to do so. Thus, the partisan divide is greatest among those who express the most confidence in their understanding of the science. The conditional effect plot below visualizes this interaction using data from a statewide New Hampshire survey, described in a 2011 Climatic Change paper (Hamilton, “Education, politics and opinions about climate change: Evidence for interaction effects”). Respondents were asked whether they thought that global warming will pose a serious threat in their lifetime. The conditional probabilities are calculated from a logit model that controlled for age, education and other background factors.


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The Climatic Change paper and a related article by Aaron McCright cite a number of different surveys that found results along these lines. Still others have been published more recently, notably by McCright and Dunlap (2011) who analyze extensive national survey data. An April 2011 report from the Carsey Institute at the University of New Hampshire (Hamilton, “Climate change: Partisanship, understanding and public opinion”) presents data from ten surveys conducted in different U.S. regions from April 2010 through February 2011. All ten surveys found the same basic pattern involving partisanship, “understanding” and climate views. For example, respondents were asked whether they believed that climate change is happening now, caused mainly by human activities; changing now but caused mainly by natural forces; or not changing now.


A December 2011 report (Hamilton, “Do you believe the climate is changing?”) updated this work with additional New Hampshire and national surveys. The graphic below, from this report, combines seven statewide New Hampshire polls to track the percentage who believe that climate is changing now due to humans. Overall, this percentage does not change much, as shown by the central black line. Above and below that we see separate lines tracking Democrats and Republican who say they have moderate or a great deal of understanding, and their fellow partisans who say they have little or no understanding. In keeping with earlier studies, partisans most confident in their understanding stand the farthest apart. These data hint that even those who say they know “little or nothing” about the issue are increasingly lining up alongside their co-partisans. That trend will be watched closely in future polls,


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Another recent survey conducted under the Carsey Institute’s Community and Environment in Rural America (CERA) initiative shows the same basic pattern. This CERA survey interviewed 1,023 residents of Clatsop County, Oregon, and Pacific County, Washington in January and February 2011. One question asked whether respondents thought it more accurate to say that “most scientists agree that climate change is happening now, caused mainly by human activities,” or that “there is little agreement among scientists whether climate change is happening now, caused mainly by human activities.” The graph below gives percentages responding that most scientists agree, broken down by political party and education (college graduate or other). Independents fit in between Democrat and Republican, although like Democrats they are more likely to accept anthropogenic climate change if they have a college education. The widest gap separates college-graduate Democrats (83% think most scientists agree that climate is changing now, due mainly to humans) from college-graduate Republicans (only 33% think most scientists agree).


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From “Climate change: Partisanship, understanding and public opinion”:


Most people gather information about climate change not directly from scientists but indirectly, for example through news media, political activists, acquaintances, and other non-science sources. Their understanding reflects not simply scientific knowledge, but rather the adoption of views promoted by political or opinion leaders they follow. People increasingly choose news sources that match their own views. Moreover, they tend to selectively absorb information even from this biased flow, fitting it into their pre-existing beliefs. This “biased assimilation” has been demonstrated in experiments that find people reject information about the existence of a problem if they object to its possible solutions. Unlike those experimental studies, however, our surveys said nothing about possible solutions or policies related to climate change. The deeply partisan responses nevertheless suggest that many people made this association themselves, basing their beliefs about science and physical reality on what they thought would be the political implications if human-caused climate change were true.


Our question’s two elements (climate changing now, owing mainly to humans) match the central point of statements and reports from science organizations, national academies, reviews of research results, and surveys of scientists. For example, an open letter to Congress from the presidents or directors of 18 scientific organizations (including the American Association for the Advancement of Science, the American Geophysical Union, the American Meteorological Society, and the American Statistical Association) noted that “Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that the greenhouse gases emitted by human activities are the primary driver.” Many science organizations have made similar statements, expressing the same elements as our survey question. Although there remains active discussion among scientists on many details about the pace and effects of climate change, no leading science organization disagrees that human activities are now changing the Earth’s climate. The strong scientific agreement on this point contrasts with the partisan disagreement seen on all of our surveys.


If the scientists are right, evidence of climate change will become more visible and dramatic in the decades ahead. Arctic sea ice, for example, provides one closely-watched harbinger of planetary change. In its 2007 report the IPCC projected that late-summer Arctic sea ice could disappear before the end of the 21st century. Since that report was written, steeper-than-expected declines have led to suggestions that summer sea ice might be largely gone by 2030, and some think much sooner. We will find out in time — either the ice will melt, or it won’t. The Arctic Ocean, along with other aspects of the ocean-atmosphere system, presents an undeniable physical reality that could become more central to the public debate. In the meantime, however, public beliefs about physical reality remain strikingly politicized.