Confidence in Local, National, and International Scientists on Climate Change
Heather E. Hodges1
[email protected]
Sarah Oliver1
[email protected]
Aaron Sparks1
[email protected]
Eric R. A. N. Smith2
[email protected]
1
Ph.D. Student
Department of Political Science
Ellison Hall 3834
University of California
Santa Barbara, CA
93106-9420
2
Professor
Department of Political Science
Ellison Hall 3834
University of California
Santa Barbara, CA
93106-9420
805-893-6160
1
Confidence in Local, National, and International Scientists on Climate Change
When people think about scientific disputes that lie at the heart of public policy choices, they
face the problem of deciding which set of scientific experts to believe. With disagreements over
climate change, for example, most scientists agree that the earth is warming and that human
activity has caused most of the increase in temperatures. Skeptics, however, argue that that the
evidence is mixed or even fatally flawed (Begley 2007; Layzer 2002). How do people decide
which scientists and which scientific evidence to believe?
In this paper, we address this question by examining how people respond to eight examples of
news reports drawn from the New York Times, the Los Angeles Times, and Nature about climate
change research. We report the results of an experiment embedded in a 2014 public opinion
survey of Americans to test one possible explanation for people’s evaluations of the scientific
studies and decisions about whom to trust.
Studies in psychology and political science provide a number of approaches to understanding
why people accept or reject claims about climate change—motivated reasoning, denial, not being
persuaded by dire warnings, etc. Another approach to this question is to consider the messages
sent from climate change scientists and skeptics as attempts at persuasion.
Drawing on the psychological literature on persuasion to explain which experts people choose to
believe in scientific disputes may not seem obvious. Some advocates for climate change action
seem to view the situation as one in which authoritative sources of information on the climate,
namely climate scientists, are dispensing indisputable information, but the scientists face people
who irrationally deny their claims. An idealized version of this situation occurs in k-12 school
rooms when teachers instruct students. In contrast, an alternative description of the situation is
that people receive conflicting communications from different sources of information—some
warning about climate change, others dismissing it as unimportant or perhaps even a hoax.
These messages are attempts at persuasion. We therefore turn to the research on persuasion.
Persuasion
A well established finding is that a key factor influencing people's decisions about which claims
to believe are their assessments of the sources of the messages (McGuire 1985; Wilson and
Sherrell 1993). In their classic study of persuasion, Hovland and his colleagues (1953: 13)
wrote, "An important factor influencing the effectiveness of a communication is the person or
group perceived as originating the communication—and the cues provided as to the
trustworthiness, intentions, and affiliations of this source." Although there have been many
advances in our understanding of communication and persuasion over the years, communicator
credibility has continued to be recognized as an important variable. The leading contemporary
theories of persuasion, the elaboration likelihood model (Petty and Cacioppo 1983, 1986a,
1986b; Petty and Wegener 1999) and the heuristic-systematic model (Chaiken 1980; Chaiken et
al. 1989; Chen and Chaiken 1999) use communicator credibility cues as key variables.
Literature reviews of the field have concluded that previous research has discovered three groups
of source characteristics which affect message acceptance—credible vs. not credible, physically
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attractive vs. unattractive, and ideologically similar vs. dissimilar (Sternthal et al. 1978; Wilson
and Sherrell 1993). Kelman (1961) referred to the latter two categories as “identification.” The
idea is that we are more likely to be persuaded by people with whom we identify because they
are attractive or they share similar values with us.
In studies of the causes of social trust, some scholars argue that a key variable is the extent to
which people share salient values with the communicators who are trying to persuade them
(Earle and Cvetkovich 1995; Cvetkovich 1999). For example, if a liberal Democrat were to
listen to a debate between Democratic and Republican candidates about climate change, that
person would be more likely to believe the Democratic politicians than the Republican ones.
One source characteristic that has not been investigated, so far as we are aware, is the community
affiliation or proximity of a source to the recipient of the message. Would it make a difference
in persuasion if the source were local, national, or international? Although the hypothesis that a
proximate source would be found more believable than a distant source has not been tested, it is
consistent with previous studies of persuasion. A person might reasonably infer that if the source
of a persuasive message were proximate, then he or she would be more likely to share values
with the person than a distant source.
We should note that the hypothesis we will test, about the sources of scientific studies, turns on
more than mere proximity. A simple version of a proximity hypothesis might be that someone
from one’s community would be more believable than someone from a distant community. The
hypothesis we will test here is whether the source of a scientific study is from one’s home state,
from a distant state, or from Europe makes a difference in how credible the study is. Even if the
simple proximity hypothesis were true, it would not necessarily follow that it would apply to the
location of the home universities of scientists. Other considerations might confound the results
and make proximity irrelevant. We are looking at universities from the respondents’ home
states, but they may actually be fairly distant from the respondents’ homes. Proximity might be
irrelevant because faculty members are typically originally from other states and universities. Or
it might be irrelevant because people do not infer similarity of values with scientists based on
proximity.
Given that we are looking at real world examples of news reports, we must take into account
people’s values and likely prior beliefs. Psychologists studying persuasion have found that prior
beliefs have a substantial influence on whether people accept persuasive messages (Albarracín
and Wyer 2001; Fishbein and Ajzen 1981; Greenwald 1968; MacCoun and Paletz 2009). In
Albarracín’s words (2002, 111), “A persuasive message does not impact a tabula rasa.” Studies
have found that people tend to believe scientific studies which are consistent with their schemas,
but reject studies which contradict them (Anderson 1983; Crocker et al. 1984; Lord et al. 1979).
Researchers have also argued that people have a "defensive motivation" to maintain beliefs that
are consistent with their "self-definitional attitudes" such as core values (Chaiken et al. 1996;
Lord et al. 1979; Pomerantz et al 1995; Pyszczynki and Greenberg 1987).
Political scientists have come to similar conclusions. Zaller's (1992) Receive-Accept-Sample
model and Lodge and Taber's (2000) motivated reasoning model differ in their reasoning, but
they both conclude that people should lean toward accepting persuasive messages that are
consistent with their ideologies and core values, and resist accepting messages that are
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inconsistent. Studies building on their work provide further support (Alvarez and Brehm 2002;
Carlisle and Smith 2001; Delli Carpini and Keeter 1996; Smith 1989, 2002). More recently,
Carlisle et al. (2010) found that both core values and specific prior beliefs influence message
acceptance.
Hypotheses
Based on our reading of the literature, we propose the following two hypotheses:
Hypothesis 1 – Respondents are more confident in news media reports of climate change
research from local universities than from distant universities.
Hypothesis 2 – Respondents are more likely to believe climate change will affect themselves,
their families, and society when the reports are based on studies from local universities than
when they are based on studies from distant universities.
The two hypotheses provide two different ways to test the central hypothesis that proximity to
the university which is the source of a scientific study should increase confidence in the research.
The first hypothesis asks respondents directly to report their confidence in the research reports.
The second hypothesis allows us indirectly to infer confidence in the reports because respondents
who are confident in the reports should be more likely to believe that the climate change will
impact themselves, their families, and society at large.
Research Design
To test our hypothesis, we used data from an internet survey conducted by Survey Sampling
International.1 The survey of 800 American adults was conducted July 28-August 1, 2014.
Internet samples, of course, are generally not representative of their target populations (Berrens
et al 2003; Malhotra and Krosnick 2007)—our sample is no exception. We can, however, say is
that it is roughly representative. Our sample over-represents whites, and under-represents blacks
and Hispanics. In addition, it over-represents college graduates and women.2
Despite the fact that our sample is only roughly representative, we believe that it provides a solid
basis for testing our central hypotheses. It is certainly better than a sample of undergraduates.
We are, after all, not making descriptive claims. We are testing how people respond to a
treatment (i.e., the home university of the researchers who did the studies). If our hypothesis is
supported by our data, it should hold up with a representative national survey as well.
The survey consisted of a short introduction followed by a series of questions asking respondents
about recent research on climate change. Respondents were asked to read a series of short,
newspaper-style articles. Each of these news report questions had three versions, which were
randomly assigned to respondents. The versions identified the scientists who conducted the
research as being from the leading public university in the respondent’s state, from Georgetown
1
http://www.surveysampling.com/
Our sample is 79% white, 9% black, and 10% Hispanic; the Census reports 81% white, 12% black, and 16%
Hispanic. In our sample, 98% graduated from high school, 40% graduated from college, and 64% are women. The
Census reports that only 86% graduated from high school and only 28% graduated from college.
2
4
University in Washington, D.C., or from the Universität of Zurich in Switzerland. For example,
the first item, drawn from the New York Times, was:
Rising temperatures and the resulting drought are causing trees in the West to die
at more than twice the pace they did a few decades ago, a new study by a research
team at [SOURCE] has found. The combination of temperature and drought has
also reduced the ability of the forests to absorb carbon dioxide, which traps heat
and thus contributes to global warming, the authors of the study said, and have
made forests sparser and more susceptible to fires and pests.
This randomly assigned source of the research report is the treatment that allows us to
distinguish proximate (home state university), distant (Georgetown University), and even more
distant (Zurich) researchers. We are aware of the fact that this is a crude measure and some
respondents may be physically close to Georgetown University as well as to their home state
university. In a future version of this study, we will use zip codes to measure the actual distances
between the respondent’s residence, his or her home state university, and Georgetown
University. The complete list of news reports and their original sources is listed in the appendix.
Following each statement, respondents were questions to measure their confidence in the report
and the likely impact of the climate change impacts being described :




How much confidence do you have that these scientists are right—a great deal of
confidence, a good deal of confidence, some confidence, not much confidence, or none at
all.
How likely do you think it is that the changes described in this study will ever affect
you—highly likely, somewhat likely, fairly likely, or not likely at all?
How likely do you think it is that the changes described in this study will ever affect
members of your family—highly likely, somewhat likely, fairly likely, or not likely at
all?
In your judgment, how likely is it that the problem described in this study will have
substantial impacts on our society—highly likely, somewhat likely, fairly likely, or not
likely at all?
Analysis and Results
To test our first hypothesis, we performed simple difference of means tests. Figure 1 graphically
presents our results. The figures display average scores for respondents for each source, with
vertical lines indicating the 95% confidence interval around that average. We see that the
relationship between confidence in the report and the source varies by article. Articles 3, 5, and
8 are the only ones to exhibit the predicted pattern with confidence decreasing as distance from
one’s home institution increases. The local source was associated with the greatest mean
confidence in the report and Zurich was associated with the lowest mean confidence in the
report. For Article, 2 respondents are most confident in the source from their local institution,
but they trust that from Zurich more than Georgetown. In Article 1, both Georgetown and Zurich
association result in greater confidence in the report. In the remaining articles (4, 6, and 7)
greater confidence in the report is associated with it being attributed to Georgetown. Over all,
5
none of the differences among sources in confidence in the report is statistically significant at p <
.05. Hypothesis 1 has to be rejected.
We repeated the analysis for each of the three questions about the impact of climate change on
the respondent, members of the respondent’s family, and society in general. Figure 2 presents
the results for whether the climate changes described would affect the respondent’s family. The
results are effectively the same. The differences among the sources are not statistically
significant at p < .05. Hypothesis 2 is not supported by the data. We obtained the same result
for impacts on the respondent and society as a whole. The data are not shown.
6
Figure 1: Mean Level of Confidence in Each Report by Source
7
Figure 2: Mean Likelihood that Information Contained in Report will Affect Your Family Based
on Source
Discussion and Conclusion
The results are clearly disappointing. Contrary to our expectations, confidence in news reports
about research on climate change was not significantly affected by the geographic source of the
reports. Our reading of the persuasion literature suggests that it should, but the evidence does
not support us. In this case, either the manipulation was not strong enough to detect a difference
or that proximity does not work as we had hypothesized.
One explanation for the null findings is that the source cue was not strong enough in the
manipulation. If respondents skimmed through the report without thinking explicitly about the
source, it would not then affect the evaluation of their confidence in the news report. Perhaps a
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more prominent reference to the source, such as a press release directly from the university,
would better cue the respondent to pay attention to the source specifically. It is also possible that
an inaccurate “local” cue was provided; perhaps a stronger manipulation would occur if the
source were a respondent’s alma mater.
Another possibility for why the manipulation did not lead to the hypothesized results is that the
source is actually unimportant to the decision of whether to accept or reject the information
provided in the report. Many may already have consolidated beliefs about the veracity of climate
change claims in general, so one, or eight, new pieces of information about climate change does
not affect overall confidence in climate change science. Then the global evaluation of climate
change science is what predicts answers to individual questions, rather than the specifics of any
given story, including the source of the information. If this explanation is accurate, then the
source, as well as a variety of other characteristics of an individual study or new finding, would
have a minimal effect on resulting attitudes. One piece of evidence in favor of this theory is the
strong correlations between responses to the various news reports. If people respond similarly
across stories, which vary in content, source, and valence, then they may have attitudes toward
climate science that are not prone to change based on these characteristics.
Looking to future research. One possible avenue would be to study proximity using research on
climate change that directly affects an area locally. For instance, one of the articles in this study
specifically referenced sea level rise in the Gulf Coast. Those who live in the Gulf Coast region
may be more sensitive to proximity of the source of the research if the focus of the study is also
local. This would require research of a smaller geographical sample and more targeted reports.
This change in design could also accompany more attention to the source in order to make the
manipulation more obvious.
Appendix: List of News Reports and Sources
1. Rising temperatures and the resulting drought are causing trees in the West to die at more
than twice the pace they did a few decades ago, a new study by a research team at
[SOURCE] has found. The combination of temperature and drought has also reduced the
ability of the forests to absorb carbon dioxide, which traps heat and thus contributes to global
warming, the authors of the study said, and have made forests sparser and more susceptible
to fires and pests.3
2. Power plants across the country are at increased risk of temporary shutdowns and reduced
generation as temperatures and sea levels and rise and water becomes less available, a new
report from [SOURCE] warns. By 2030, there will be nearly $1 trillion in energy assets in
the Gulf Coast region alone at risk from increasingly costly extreme hurricanes and sea levels
rises.4
3. The nation’s entire energy system is vulnerable to increasingly severe and costly weather
events driven by climate change, according to a new report from [SOURCE]. The blackouts
and other energy disruptions of Hurricane Sandy were just a foretaste, the report says. Every
3
4
Mireya Navarro, “Heat and Drought Blamed in Tree Deaths in the West.” New York Times 23 January 2009, a13.
Marina Villeneuve, “Extreme Weather Threatens Power Plants, Study Says.” Los Angeles Times 15 July 2013.
9
corner of the country’s energy infrastructure—oil wells, hydroelectric dams, nuclear power
plants—will be stressed in coming years by more intense storms, rising seas, higher
temperatures and more frequent droughts.5
4. Warming air from climate isn’t the only thing that will speed melting near the poles—so will
the warming water beneath the ice, a new study from [SOURCE] says. In a new report,
researchers say warming oceans could mean polar ice is melting faster than had been
expected. One coauthor said, “This paper adds to the evidence that we could have sea level
rise by the end of this century of around 1 meter.”6
5. New research from [SOURCE] suggests that global warming is causing the cycle of
evaporation and rainfall over the oceans to intensify more than scientists had expected, an
ominous finding that may indicate a higher potential for extreme weather in coming decades.
By measuring changes in salinity on the ocean’s surface, the researchers inferred that the
water cycle had accelerated by about 4 percent over the last half century. If the estimate
holds up, it implies that the water cycle could quicken by as much as 20 percent later in this
century as the planet warms, potentially leading to more droughts and floods.7
6. Climate change could result in decreasing yields of staple food crops in most parts of the
world from the 2030s onwards. A research team from [SOURCE] compared the results of
more than 1,700 simulations of climate change impacts on annual wheat, race, and maize
(corn) yields. The data suggest that, without adaptation, average food-crop supplies will
decline by about 5% per degree of Celsius warming.8
7. Finally, some good news about the effects of climate change, according to a stuy from
[SOURCE]. It may have triggered a growth spurt in two of California’s iconic tree species:
coast redwoods and giant sequoias. Since the 1970s, some coast redwoods have grown at the
fastest rate ever, according to scientists who studied corings from trees more than 1,000 years
old.9
8. Reduced sea-ice extent and thickness would increase the seasonal duration of polar
navigation on rivers and in coastal areas that are presently affected by seasonal ice cover,
according to a study by [SOURCE]. Improved opportunities for water transport, tourism, and
trade at high latitudes are expected as a result. These activities will have important
implications for the people, economies, and navies of nations along the Arctic rim. Reduced
sea ice will provide safer approaches for tourist ships and new opportunities for sightseeing
around Antarctica and the Arctic.10
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5
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6
“Faster Melt Predicted for Polar Ice.” Los Angeles Times 4 July 2011.
7
Justin Gillis, “Study Indicates a Greater Threat of Extreme Weather.” New York Times 27 April 2012.
8
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9
Bettina Boxall, “Growth Spurt: Climate Change May Be Proving Beneficial for California’s Redwoods.” Los Angeles
Times 14 August, 2013, aa1.
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IPCC reports http://www.ipcc.ch/ipccreports/sres/regional/index.php?idp=54
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