How did interviewees rate the terms?
Table 1 shows the presented terms in order of participants’ mean ratings on a scale from 1 (not easy at all) to 5 (very easy). It also indicates whether mean ratings were significantly different from the scale midpoint of 3, as indicated by one-sample t-tests. The lowest mean ratings were given to mitigation, carbon neutral, and unprecedented transition. Five terms received mean ratings that were significantly above the scale midpoint of 3, suggesting that they were perceived as easy to understand: sustainable development, carbon dioxide removal, tipping point, adaptation, and abrupt change. Table 1 also shows participants’ mean ratings after seeing the sentences, and results of paired t-tests that examined whether mean ratings changed significantly after (vs. before) seeing the sentence. For mitigation, the most difficult term, reading the sentence improved participants’ mean ratings. For four terms, reading the sentence reduced mean ratings, while for three of the terms, it made no difference. Nevertheless, participants’ interpretations revealed some potential confusion about each term (see below).
While a sample size of 20 is large enough to identify medium-to-large effect sizes of ≥.67 in paired-sample t-tests (power = .8, alpha = .05), it can only identify extremely large effect sizes of ≥1.40 in between-group t-tests (power = .80, alpha = .05). Hence, it should be no surprise that we did not find any significant differences between participants’ ratings of the terms, by whether they had indicated that climate change was mostly human-caused vs. selected other responses. Even the mean rating across the eight terms, which had good internal consistency (Cronbach’s alpha = 0.76), did not show a significant difference between participants who had indicated that climate change was mostly human-caused vs. selected other responses (M = 3.55, SD = 0.67 vs. M = 3.84, SD = 0.81), t(18) = 0.86, p = 0.40.
Climate-concerned vs. climate-ambivalent participants
Despite having limited statistical power for between-subjects t-tests, we did find that participants who viewed climate change as human-caused judged it much more likely that climate change was happening now, as compared to participants who thought of climate change as having other causes (M = 5.00, SD = 0.00 vs. M = 3.73, SD = 1.10), t(18) = −3.44, p < .01. To illustrate how these groups of participants discussed the presented terms, we indicate for each quote below whether it was shared by a participant from the former group (henceforth: climate-concerned) or the latter group (henceforth: climate-ambivalent).
How did interviewees interpret the terms?
We identified potential confusion that arose in participants’ interpretations of each presented term, when presented alone and in a sentence (Table 2). We also identified simplified wording that participants suggested if it agreed with IPCC’s intended meaning (Table 3). Below, we indicate the next steps for how participants’ suggestions may be used to describe terms when preparing public communications about climate change. For brevity, our discussion of participants’ responses to the sentences is limited to what was said about the focal terms. Below, we also report how many participants used each interpretation of a presented term and indicate whether example quotes were taken from climate-concerned or climate-ambivalent participants Section 3.1.. However, we repeat the caution that qualitative interviews are designed to identify which and not how often interpretations arose in this sample or its subgroups (Bruine de Bruin and Bostrom 2013).
As many as seven participants (35%) indicated not knowing how to describe mitigation in their own words. Participants who attempted to describe the term mitigation tended to interpret it based on their mental models of other contexts, where the meaning differed from the climate context. Eleven participants (55%) referred to legal or insurance contexts, where mitigation had negative connotations. For example, one climate-concerned participant said, “Mitigation, oh God I hate this word. […] To me personally it means mitigating costs, keeping costs low […] to prevent the expenditure of filing a lawsuit” (interview 16). A climate-ambivalent participant said, “this is the way people in companies get out of being in trouble. Mitigation is a workaround. It means I can continue doing something bad over here, if I help something over there. I mean, that’s basically legally what it means” (interview 13). Furthermore, seven participants (35%) seemed to confuse mitigation with mediation, referring to intervening if there is a conflict, or finding common ground. For example, one climate-concerned participant said, “I feel like I’ve heard it here and there but I have no idea what it means. I would assume like discussion, like discussing with peers. […] I don’t think this is a word very commonly used outside of academia.” (interview 3). One climate-ambivalent participant stated, “say you were having an argument with someone, and you have someone come in, a third party, to mitigate or go between” (interview 5).
Combining participants’ suggestions to use straightforward wording and to emphasize links to climate change, mitigation might be described as “policies that reduce emissions to stop climate change (from getting worse).” References to specific climate change actions or climate change policies should reduce confusion with other contexts, in which mitigation may have a different meaning.
The term carbon neutral was rated as the second-most difficult (Table 1). Five participants (25%) indicated that they did not know the definition. For example, a climate-concerned participant said, “I know carbon is used in front of a lot of words, carbon dioxide, carbon monoxide. […] Carbon neutral means – I don’t know.” (interview 7). A climate-ambivalent participant said, “it’s definitely not in my everyday language” (interview 1).
Additionally, three participants confused the term neutral with zero emissions. For example, a climate-ambivalent participant said, “Neutral [means] you have to make it zero. No plus, no minus. No positive, no negative. […] I don’t think that’s possible, but that would be no carbon released into the atmosphere.” (interview 11). In line with this thinking, three participants (15%) thought that carbon neutral referred to balancing good and bad effects of carbon emissions. For example, one climate-concerned participant stated, “I guess carbon neutral [means that] the atmosphere wouldn’t be affected by whether there’s too much carbon in the air or too little carbon.” (interview 19). Upon reading carbon neutral in the sentence (Table 1), a climate-ambivalent participant recognized that “It’s a process that doesn’t [necessarily] wind up with zero emissions. Well, it’s actually, if you want to really get technical, it’s net carbon neutral.” (interview 13). Yet, the sentence did not help everyone, as seen in this statement by a climate-concerned participant: “I thought I understood it but the more that I read it I kind of do not understand this one.” (interview 18).
Furthermore, the process of achieving a carbon neutral state was unclear. For example, one climate-concerned participant said, “I don’t remember how [it works] specifically. I know through, like, maybe – maybe you adjust how, if, you know, you’re a company and you have a fleet of trucks, maybe you switch to more fuel-efficient vehicles in your fleet. Or you know, adjust your production so it’s not as polluting. Or, I don’t know if they still do this, but carbon credits that you purchase.” (interviewee 2). One climate-ambivalent participant said, “if one group adds some and somebody else somehow somewhere else in a system somewhere, somebody else has to leave less, so that it’s neutral.” (interview 4).
Eleven participants (55%) used definitions of carbon neutral that referred to compensation upon first seeing the term. A climate-concerned participant said, “even though you are not ceasing carbon emissions you are compensating for carbon emissions by reducing or eliminating emissions in other ways” (interview 6).Footnote 2 Nine participants (45%) knew that carbon neutral meant not increasing the overall carbon dioxide released into the atmosphere. Specifically, one climate-concerned participant stated: “It’s something that doesn’t increase or decrease the amount of carbon dioxide that is released into the air” (interview 16). When asked for improvements, a climate-ambivalent participant suggested that the term carbon neutral was too technical (interview 10) and a climate-concerned participant suggested providing a definition whenever it is used (interview 18). For example, a climate-concerned participant suggested “to balance out the emissions we put in the air to an even level” (interview 20), and a climate-ambivalent participant suggested “net amount of carbon added to the environment is zero” (interview 4). Six participants used “carbon dioxide” instead of “carbon,” but none used “CO2.”
Overall, our findings suggest the need for everyday wording. Spelling out “carbon dioxide” may avoid confusion about the type of carbon involved. Referring to “no net increases in carbon dioxide in the air” or to “balance out the carbon dioxide we put into the air” may help to avoid confusion with “zero carbon.” To clarify the process, these descriptions may need to include examples of carbon dioxide removal (see below).
When presented with the term unprecedented transition, which was rated as the third-most difficult, five participants (25%) indicated not knowing how to describe it. One climate-ambivalent participant noted, “I feel like unprecedented is kind of a big word. [But] transition, I think that seems like an easy word.” (interview 4). Thirteen participants (65%) recognized that transition meant “change,” with two (10%) referring to it as “movement.”
Eight participants (40%) mistook unprecedented to mean “unexpected” or “unknown.” Eleven participants (55%) mentioned that unprecedented had recently become more familiar. One climate-concerned participant clarified this sentiment by saying, “unprecedented is actually not that common of a word, until now of course with the pandemic” (interview 18).
Only three participants (15%) referred to unprecedented transition in the context of extreme weather or climate change. For example, one climate-concerned participant explained, “it’s in the 80s today and then tomorrow during the day it drops down to like 50 or 60. […] I haven’t been aware of that happening here, or if I did I’ve forgotten about it, but that’s how I would see it, an unprecedented transition” (interview 19). A climate-ambivalent participant stated, “it has never been seen, these types of temperatures” (interview 5). Although the presented sentence referred to unprecedented transitions as actions society should take to address climate change (Table 1), participants’ initial definitions tended to treat the term as referring to climatic or environmental changes.
When prompted for improvements, participants suggested using everyday language. After seeing an unprecedented transition in its sentence (Table 1), a climate-concerned participant said it was “too wordy” and a climate-ambivalent participant said, “It sounds like you’re talking over people (...) when I see this stuff on TV, and you see these talking heads on Nova and whatnot, they’re talking way over people’s heads” (interview 13). When describing unprecedented transition, eight participants (40%) suggested simplified wording. For example, a climate-concerned participant suggested “a change that never occurred before” (interview 17), and a climate-ambivalent participant suggested “a change not seen before” (interview 12). The sentence clarified for some that unprecedented transition would require action in the context of climate change.Footnote 3 For example, a climate-concerned participant said, “it’s going to be a big job to do it” (interview 6), and a climate-ambivalent participant said, “[it] would require massive changes in every aspect of what we do in our daily life” (interview 10). Participants also suggested giving examples of what unprecedented transition entails, with one climate-ambivalent participant stating: “you’ve got to let people know what you’re talking about.” (interview 5).
Combining the suggestion to use simple wording and clarify the context of climate action, descriptions of unprecedented transition could include “making big changes together to stop climate change.” Examples should specify which big changes are required.
Tipping point was, on average, rated as the fourth-most difficult term (Table 1), with only three participants (15%) indicating that they did not know it. Twelve participants (60%) defined it as the tipping of a balance, and eight (40%) as difficulties in reverting back to a previous state. Although three participants (15%) mentioned climate change in their initial definition of tipping point, none described tipping point as a change with cascading effects, whether in the climate system or in any other context. Yet, for the climate system, tipping point refers to a critical threshold at which the global or regional climate changes from one stable state to another stable state (Table 3).
As an example, a climate-concerned participant defined tipping point by relying on a mental model of another context: “like [in] an argument [when] people are trying to persuade the other person and then you get to a fact or something that happened or whatever, a reality, and it – that could be the tipping point that could persuade the other person to change their mind” (interview 19). Similarly, a climate-ambivalent participant said: “To me the tipping point is when you’re pushing somebody [and] before they break there’s a tipping point – a breaking point, tipping point. If you’re trying to level something out like a seesaw you get [to] the tipping point where it goes on over or it’ll tip over. You can push something, like say a life float. You can tip it so far and then there’s a certain point, it’d be a tipping point and then it just goes.” (interview 11).
When asked for definitions and improvements, participants again suggested simplified language. Five participants (25%) suggested the simple phrase “point of no return,” and two (10%) used the more complex term “inflection point.” When seeing the sentence (Table 1), a climate-concerned participant also suggested that tipping point could mean “danger zone” (interview 7) and two climate-ambivalent participants mentioned consequences such as “once we reach that point there is no turning back” (interview 9) and it would be “too late to fix anything” (interview 11).
The three participants (15%) who did refer to climate change in their initial definitions of tipping point provided the following insights. Two climate-concerned participants said: “the point when there is no longer a way for us to reverse the course of action that has led to climate change.” (interview 17) and “It’s the end of the ability to reverse the damage that’s been done.” (interview 16). A climate-ambivalent participant said, “as soon as we hit this particular point of heat or carbon emissions or something that there’s a big change in the environment” (interview 4).
Our findings suggest a need for descriptions of tipping point that highlights the connection with climate change, the seriousness of the issue at hand, and the role of cascading effects in the climate system. For example, this may include a phrase such as “point at which we can no longer undo climate change (and its effects on ...)” or “when it is too late to stop climate change (and its effects on ...),” with specific examples.
Only two participants (10%) expressed not knowing how to describe sustainable development, which was on average ranked among the four most easy terms to understand (Table 1). A climate-concerned participant noted issues with sustainability: “It’s a pretty popular term to try to be sustainable but it is a little bit opaque as to what sustainability means in each different context” (interview 6). A climate-ambivalent participant stated: “I don’t know what sustainable means. I know what development is. If you’re putting these two words together, it’s saying that something is growing. But, it’s growing in a stable manner” (interview 15). While technically not wrong (Table 3), four participants (20%) associated sustainable development with “a renewable resource” and four (20%) mentioned, “it’s self-sufficient.”
Furthermore, the term development led to the potential confusion, with thirteen participants (65%) defining it as buildings and infrastructure. For example, one climate-concerned participant said, “Development being like buildings or infrastructure that has a lessor impact on the environment” (interview 2) and one climate-ambivalent participant said, “environmentally friendly construction.” (interview 13). This interpretation did not necessarily change after seeing sustainable development presented within the sentence, which was a climate-concerned participant referred to as “absolutely too wordy” (interview 7).
Nine participants (45%) provided useful definitions of sustainable development that referred to its positive or neutral impact on the environment. For example, one climate-concerned participant defined it as “that we can continue to do it and that we can continue to support the population as a whole without overtaxing the environment.” (interview 16), and a climate-ambivalent participant described it as “something that can be ongoing, that it’s not suicidal” (interview 10). Five (25%) participants referred to the development as plans or policies. After being asked for improvements, a climate-concerned participant suggested “controlled growth” (interview 19) and two climate-ambivalent participants suggested “environmentally friendly” (interviews 4, 13).
Participants also needed more information. A climate-concerned participant asked for “just a little bit more information about what sustainable development means as a goal and as a target” (interview 6). A climate-ambivalent participant recommended saying, “sustainable development of, and then like put what topic or like area you’re thinking like sustainable development of, you know, manufacturing facilities or whatever it might be” (interview 8).
Combining participants’ suggestions to use everyday wording and provide detail, definitions could include “environmentally friendly policies to…” or “environmentally friendly growth in….” However, the definition of sustainable development is more complex than what is captured by these simplified wordings and refers to meeting the needs of people living today without compromising the needs of people living in the future (Table 3).
Carbon dioxide removal
Only two participants (10%) indicated not knowing this term, which was rated as third easiest to understand. Thirteen participants (65%) recognized that it meant removing carbon dioxide from somewhere. Thirteen (65%) mentioned removal from the atmosphere or the air, and seven (35%) mentioned removal from manufacturing or emissions. Seven participants (35%) expressed confusion about the process of carbon dioxide removal. For example, a climate-concerned participant said, “I know they want to remove carbon dioxide, obviously, but … I didn’t know how the process is done” (interview 20). A climate-ambivalent participant wondered, “It doesn’t say from what, you know? It just says carbon dioxide removal. Does that mean from, you know, my basement? Does it mean from my car? I don’t know.” (interview 8). Four participants (20%) mentioned natural processes of carbon dioxide removal, without expressing awareness of technological processes. For example, one climate-concerned participant stated, “when I think of carbon dioxide removal, I think of photosynthesis and plants,” but when prompted, admitted, “it could refer to any kind of process in which carbon dioxide is removed from the air or a vacuum or wherever.” (interview 16). A climate-ambivalent participant said, “Trees live off carbon dioxide. Carbon dioxide goes into trees and comes out as oxygen, whereas we take oxygen in as humans and breathe out carbon dioxide. I mean, I think it’s easy to understand that you’re just trying to remove carbon dioxide” (interview 5).
The sentence did not necessarily help to clarify the process of carbon dioxide removal. One climate-concerned participant said, “I’m still not clear on what carbon dioxide removal is.” However, a climate-ambivalent participant did become aware of technological processes for carbon dioxide removal: “The sentence is saying that we know that there’s gonna be emissions of some sort that will have carbon dioxide emitted, and for those scenarios, there’s ways that we can remove that emitted carbon dioxide. I would not have guessed technological by itself. I would’ve assumed the simple natural way of a tree, at first.” (interview 9).
To clarify the process of carbon dioxide removal, it might be possible to borrow from other participants’ explanations. One climate-concerned participant provided a description of the natural process of carbon dioxide removal: “In terms of like biology and ecology that’s kind of the process of we, as humans, we expel carbon dioxide and there has to be a process for removing that carbon dioxide and converting back into breathable oxygen, which is why we have trees, basically,” while also suggesting to use CO2 instead of carbon dioxide (interview 6). A climate-ambivalent participant described a technological process: “I think [to] remove carbon dioxide they need to filter it somehow to get rid of the carbon dioxide. They need to filter out the emissions” (interview 11).
Descriptions of carbon dioxide removal could incorporate participants’ suggestions to specify what carbon dioxide is removed from, how it is removed, and where emissions come from. Simplified descriptions could include: “taking carbon dioxide out of the air” and “removing carbon dioxide from the air.” Natural carbon dioxide removal processes, like “planting trees,” and more advanced technologies could be mentioned separately.
All participants indicated knowing the term adaptation, which was rated as the second easiest term to understand (Table 1). One climate-concerned participant noted: “Adaptation is very commonly used and so I feel like it’s a very well-known word” (interview 2). Yet, there was a call for improvement, with one climate-ambivalent participant noting: “Just say you’ll need to adjust. I hate to say adapt” (interview 11). Five participants (25%) referred to adaptation with its synonym “adaption.” One climate-concerned and one climate-ambivalent participant referred to adaptation as “books that are made into movies” (interviews 16 and 13), thus drawing from a mental model or context where the term had a different meaning than for climate change (Table 3).
Although nineteen participants (95%) referred to adaptation as a process of adjustment or getting used to something, they did not necessarily draw the link to climate change. Four participants (20%) referred to evolution. One climate-concerned participant noted, “In [an] evolutionary context it means to change over time to suit your environment” (interview 6). A climate-ambivalent participant said, “a new way or a new process where plants [are] becoming adapted to their new environment, changing how they live in a particular environment to adapt to where it’s at” (interview 4). Others described adaptation as a part of life. A climate-concerned participant stated, “everybody has to adapt at some time in your life, whether it’s weather, a job, you know, children, a new relationship? Everyone has to adapt, whether you even know what you’re doing is adapting, you know?” (interview 19). A climate-ambivalent participant said, “You need to adapt to your living situation. If you’re very wealthy [and] you lose everything and you have to live in an old trailer somewhere in the hills you have to learn to adapt” (interview 11).
Seeing adaptation in the presented sentence (Table 1) tended to highlight the climate context, though participants still guessed at the adaptation strategies the sentence referred to. One climate-concerned participant said: “I believe it’s saying that island nations need to change, I’m not sure what, though, need to change certain things in order to prevent flood risks… Maybe potentially moving to higher ground?” (interview 3) and a climate-ambivalent participant said “building levees or dams, or building up on the island to make it higher” (interview 11). As in previous research (Harcourt et al. 2019; Van Kasteren 2014), there was some conflation of adaptation with mitigation: For example, a climate-concerned participant said: “[Adaptation means] that we would make our investments in green energy technology, solar, wind farming I believe is another big thing that people need to get used to” (interview 17).
When providing their own descriptions of the term adaptation, a climate-concerned participant suggested “survival” (interview 7) and climate-ambivalent participants suggested “getting used to or accustomed to something” (interview 4), as well as to “adjust to your surroundings” (interview 11).
Some descriptions pointed explicitly to more active decisions, with climate-concerned participants suggesting to “make it work” (interview 18) and “compensation” (interview 7), and climate-ambivalent participant suggesting “making necessary changes to deal with your environment” (interview 9), as well as to “overcome things” (interview 12). A climate-concerned participant suggested to “give some sort of indication of what the adaptation is” (interview 6), in line with a climate-ambivalent participants’ question “adaption of what? adapting what?” (interview 4).
Using participants’ suggestions to use everyday wording and to make the context of climate action more clear without introducing conflation with mitigation, potential explanations of adaptation could include “make changes to survive climate change,” “adjusting to climate change,” or “to protect against climate change” with specific examples of what those actions would entail.
All participants said they understood the term abrupt change, which was rated as the easiest term to understand (Table 1). Although participants had not necessarily heard the words “abrupt” and “change” used together, eighteen participants (90%) were able to define it as a quick or sudden change. Only one participant, who was climate-concerned, described an abrupt change in the context of climate and weather: “[In Hawaii] it would go from being a nice, calm day to all of the sudden, you know, storms and thunder and lightning, you know, thunder and rain, you know? It would just be crazy. […] And then abrupt change, if you do something to – you can make an abrupt change to change what nature is already doing” (interview 19).
The sentence helped participants to put abrupt change in a climate context, though three climate-ambivalent participants (15%) complained that abrupt did not fit the time scale mentioned in the sentence (Table 1). For example, one said: “the word ‘abrupt’ – I was thinking, ‘fast,’ and following words in the sentence say “centuries,” and so centuries is not something I think of as fast.” (interview 9). Another climate-ambivalent participant asked, “And how is it different than abrupt changes that nature sometimes brings us anyway?” (interview 4).
When providing definitions and improvements for abrupt change, climate-concerned and climate-ambivalent participants made helpful suggestions such as “sudden change” (interview 3, 10, 20), “a change that happens [...] all of a sudden without a warning” (interview 8), “sudden difference” (interview 11), or “a very serious change in a very short time” (interview 14). Climate-concerned and climate-ambivalent participants suggested to “change abrupt to quick or fast” (interview 5) or to “quickly and unexpectedly” (interview 15) or “out of the blue” or “dramatic” (interview 18).
While the term “abrupt change” was perceived as well-understood, participants suggested alternatives for the term “abrupt,” such as “sudden” and “quick” to indicate the speed of the change, or “serious” and “dramatic” for the size of the change. It may be useful to make the climate context explicit, with references to the size, speed, timing, or something altogether unexpected.