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Edward Hanna and Thomas E. Cropper
Many variations in the weather in the European and North Atlantic regions are linked with changes in the North Atlantic Oscillation (NAO). The NAO is measured using a south-minus-north index of atmospheric surface pressure variation across the North Atlantic and is closely connected with changes in the North Atlantic atmospheric polar jet stream and wider changes in atmospheric circulation. The physical, human, and biological impacts of NAO changes extend well beyond weather and climate, with major economic, social, and environmental effects. The NAO index based on barometric pressure records now extends as far back as 1850, based on recent work. Although there are few significant overall trends in monthly or seasonal NAO (i.e., for the whole record), there are many shorter-term multidecadal variations. A prominent increase in the NAO between the 1960s and 1990s was widely noted in previous work and was thought to be related to human-induced greenhouse gas forcing. However, since then this trend has reversed, with a significant decrease in the summer NAO since the 1990s and a striking increase in variability of the winter—especially December—NAO that has resulted in four of the six highest and two of the five lowest NAO Decembers occurring during 2004–2015 in the 116-year record, with accompanying more variable year-to-year winter weather conditions over the United Kingdom. These NAO changes are related to an increasing trend in the Greenland Blocking Index (GBI; equals high pressure over Greenland) in summer and a significantly more variable GBI in December. Such NAO and related jet stream and blocking changes are not generally present in the current generation of global climate models, although recent process studies offer insights into their possible causes. Several plausible climate forcings and feedbacks, including changes in the sun’s energy output and the Arctic amplification of global warming with accompanying reductions in sea ice, may help explain the recent NAO changes. Recent research also suggests significant skill in being able to make seasonal NAO predictions and therefore long-range weather forecasts for up to several months ahead for northwest Europe. However, global climate models remain unclear on longer-term NAO predictions for the remainder of the 21st century.
Oceanic mixing is one of the major determinants of the ocean circulation and its climatological influences. Existing distributions of mixing properties determine the rates of storage and redistribution within the climate system of fundamental scalar tracers including heat, fresh water, oxygen, carbon, and others. Observations have overturned earlier concepts that mixing rates might be approximately uniform throughout the ocean volume, with profound implications for determining the circulation and its properties. Inferences about past and potential future oceanic circulations and the resulting climate influence require determination of changed energy inputs and the expected consequent adjustment of mixing processes and their influence.
Communication campaigns play a key role in shaping what people think, feel, and do about climate change, and help shape public agendas at the local, national, and international levels. As more people around the world gain regular access to the Internet, online and social media are becoming significant contexts in which they come into contact with—or fail to come into contact with—news, debates, action, and social input related to climate change. This makes it important to understand the campaigning that takes place online. Many actors make concerted efforts to engage publics on climate change and go online to do so. These include businesses; governments and international organizations; scientists and scientific institutions; organizations, groups and individuals in civil society; public intellectuals and political, religious and entertainment leaders. Not all are ultimately concerned with climate change or engaging publics as such. Nevertheless, most campaigns involve at least one of four goals: to inform, raise awareness, and shape public understanding about the science, problems, and politics of climate change; to change consumer and citizen behavior; to network and connect concerned publics; to visibly mobilize consumers or citizens to put pressure on decision-makers. Online climate change campaigns are an emerging phenomenon and field of study. The campaigns appeared on broad front around the turn of the millennium, and have since become increasingly complex. In addition to the elements that produce variance in offline campaigns, scholars examine the role of online and social media in how campaigners render the issues and pursue their campaigns, how publics respond, and what this means for the development of the broader public discourse. Core debates concern the capacity and impact of online campaigning in the areas of informing, activating and including publics, and the ambivalences inherent in leveraging technology to engage publics on climate change.
Participation by citizens and stakeholder groups is an important aspect of climate governance at the regional, national, international, and global levels. Increasing awareness of anthropogenic causes of climate change has fueled calls for democratic action and renewal that promise to enrich both existing and emerging forms of political engagement. Participation is not a panacea, however, and has many limitations. Three substantial critiques of participatory and deliberative approaches to climate change hinge on questions of power, authority, and opportunities for dissent. The climate system itself poses unique challenges to democratic governance. Accelerating rates of environmental change associated with climate change make past experience less applicable to current situations and complicate predicting the future even further. As such, participatory and deliberative approaches may need to be reconfigured to respond adequately to the challenges of climate change. Systems approaches broaden the scope of participation and deliberation, and innovative participatory methods are increasingly moving beyond narrow framings of climate change. As deliberative and participatory initiatives become more common, it is no longer a question of supporting or rejecting participatory forms of climate governance. Rather, questions need to address what kinds of consequences will occur and in whose interests certain participatory processes operate. Which social views and values are supported and which are marginalized, and what are the consequences of collective responses to this pressing environmental and social issue?
Deborah Lynn Guber
Despite an accumulation of scientific evidence on both the causes and consequences of climate change, U.S. public opinion on the subject has splintered sharply along party lines. While a vast majority of Democrats now believe that global warming is real, that its effects will happen within their lifetime, and that human activity is the dominant cause, Republicans have grown increasingly skeptical, creating a yawning gap that complicates efforts to communicate the urgency of the problem and the need for aggressive action.
When attitudes harden and diverge, it is often driven by the behavior of political elites, who shape the frames and mental models that people use to interpret events. Scholars have long observed that people resort instinctively to heuristics to ease the burden of making decisions, especially on issues like climate, where there is an obvious disconnect between scientific understanding and mass competence. Those cues, however, are often unreliable and prone to cognitive bias. When voters act upon signals provided by their preferred political party and by selective exposure to preferred media outlets, they may do so mechanically, with little regard for the accuracy of the evidence that they receive, or they may ignore and distort information in a way that reinforces preexisting assumptions.
In the end, beliefs about climate change are as complex as the issue itself, which suggests that awareness of the problem and an understanding of its effects will not translate automatically—or even easily—into increased concern, issue salience, or policy preferences. The “pictures in our heads,” to borrow Walter Lippmann’s famous phrase, are shaped less by factual knowledge than by a variety of other factors more difficult to control—by personal experience and assorted real-world cues (such as the weather), but also by opinion leaders, media narratives, and political rhetoric, each of which provides a competing frame of reference with the power to filter and mislead. Because climate change has become so heavily laden with values and so absorbed into partisan identity, it will be nearly impossible to build social consensus through conventional means. Once a “hard” issue for all, which seemed to demand sophisticated calculation or technical expertise, it has now become an “easy” one for many, where the reactions that it prompts are familiar, stable, and symbolic, increasingly polarized, immune to rational argument, and vulnerable to manipulation by elites.
Rachel I. McDonald
There is mounting scientific evidence linking extreme weather events such as wildfires in the western United States and Hurricane Sandy with anthropogenic climate change. However, those in developed nations that contribute the most to carbon emissions associated with anthropogenic climate change are the least likely to suffer severe consequences. This asymmetry presents a challenge for climate change communication, given that those who most need to act on climate change (the largest emitters) are those likely to be the most removed from the impacts of carbon emissions, and may thus be less convinced of the critical need to act.
The psychological distance that people perceive from the impacts of climate change may also have implications for their belief in, concern about, and willingness to act on climate change. Psychological distance is the extent to which an object is perceived as distant from the self in time, space, certainty, or social similarity. Though climate change may be perceived by those in developed nations as distant on any or all of these dimensions, temporal and geographic distance are likely to be particularly important in the context of climate change, given the global nature of the problem and the long time horizons associated with predicted impacts.
Considering the potential distancing of climate change from the self, this review examines how perceptions of temporal and geographic distance impact public opinion about climate change, in terms of belief in anthropogenic climate change, concern, and support for action. Many researchers have suggested that the distal nature of climate change is a key reason for failures to engage in widespread mitigation action. However, studies of temporal and geographic distance reveal mixed effects on belief in climate change and support for action. For example, support for climate change action varies as a function of impacts being described as affecting near versus distant victims, and these effects vary as a function of political ideology, with Democrats more likely to support action when exposed to distal victims, and Republicans more supportive when victims are closer to them. Similarly, another study indicated that perceptions of global risk are associated with policy support, whereas perceptions of risk in one’s local area is linked to individual intentions to take action. These findings reveal that it may not always be ideal to perceive climate change as psychologically close in order to promote support for climate action, and a number of studies examined here explore when psychological distance and closeness may help or hinder climate change action.
Christopher P. Borick and Barry G. Rabe
The factors that determine individual perceptions of climate change have been a focus of social science research for many years. An array of studies have found that individual-level characteristics, such as partisan affiliation, ideological beliefs, educational attainment, and race, affect one’s views on the existence of global warming, as well as the levels of concern regarding this matter. But in addition to the individual-level attributes that have been shown to affect perceptions of climate change, a growing body of literature has found that individual experiences with weather can shape a variety of views and beliefs that individuals maintain regarding climate change. These studies indicate that direct experiences with extreme weather events and abnormal seasonal temperature and precipitation levels can affect the likelihood that an individual will perceive global warming to be occurring, and in some cases their policy preferences for addressing the problem. The emerging literature on this relationship indicates that individuals are more likely to express skepticism regarding the existence of global warming when experiencing below average temperatures or above average snowfall in the period preceding an interview on their views. Conversely, higher temperatures and various extreme weather events can elevate acceptance of global warming’s existence.
A number of studies also find that individuals are more likely to report weather conditions such as drought and extreme heat affected their acceptance of global warming when such conditions were occurring in their region. For example, the severe drought that has encompassed much of the western United States between 2005 and 2016 has increasingly been cited by residents of the region as the primary reason for their belief that climate change is occurring. What remains unclear at this point is whether the weather conditions are actually changing opinions regarding climate change or if the preexisting opinions are causing individuals to see the weather events in a manner consistent with those opinions.
Notably, the relationship between weather experiences and beliefs regarding climate change appear to be multidirectional in nature. Numerous studies have found that not only do weather experiences shape the views of individuals regarding global warming, but also individuals’ views on the existence of global warming can affect their perceptions of the weather that they have experienced. In particular, recent research has shown that individuals who are skeptical about the existence of global warming are less likely to report the weather recorded in their area accurately than individuals who believe global warming is happening.
The reconstruction of climate in Poland in the past millennium, as measured by several kinds of proxy data, is more complete than that of many other regions in Europe and the world. In fact, the methods of climate reconstruction used here are commonly utilized for other regions. Proxy data available for Poland (whether by documentary, biological, or geothermal evidence) mainly allow for reconstructions of three meteorological variables: air temperature, ground-surface temperature, and precipitation. It must be underlined however, that air temperature reconstructions are possible only for certain times of the year. This is particularly characteristic of biological proxies (e.g., tree rings measure January–April temperature, chironomids provide data for August temperature, chrysophyte cysts identify cold seasons, etc.). Potentially, such limitation has no corresponding documentary evidence. In Poland these data are available only for climate reconstructions covering mainly the last 500 years because the number of historical sources pre-1500 is usually too small. Geothermal data allow for reconstruction of mean annual ground surface temperature generally for the last 500 years. Reconstructions of air temperature that cover the entire, or almost the entire, millennium and have high time resolution are only available from biological proxies (tree rings, chironomids, diatoms, etc.).
At present, the best source of information about climate in Poland in the last millennium is still documentary evidence. This evidence defines a Medieval Warm Period (MWP), which was present in the 11th century and probably ended in the 14th or early 15th century. Air temperature in the MWP was probably about 0.5–1.0°C warmer than contemporary conditions on average, and the climate was characterized by the greatest degree of oceanity throughout the entire millennium. A Little Ice Age (LIA) can be also distinguished in Poland’s climate history. Data show that it clearly began around the mid-16th century and probably ended in the second half of the 19th century. In this LIA, winters were 1.5–3.0°C colder than present conditions, while summers tended to be warmer by about 0.5°C. As a result, the continentality of the climate in the LIA was the greatest for the entire millennium. Mean annual air temperature was probably lower than the modern temperature by about 0.9–1.5°C. The average rise of air temperature since the mid-19th century, which is often called the Contemporary Warming Period (CWP), is equal to about 1°C and is in line with the results of reconstructions using geothermal and dendrochronological methods. The reconstruction of precipitation in Poland is much more uncertain than the reconstruction of air temperature. There was probably considerably higher average precipitation in the 12th century (and particularly in the second half of this century), in the first half of the 16th century, and also in the first half of the 18th century. The second half of the 13th century and the first half of the 19th century were drier than average. In other periods, precipitation conditions were close to average, including for the entire CWP period.
Emily K. Vraga
Political participation on the issue of climate change can encompass many different forms of individual and collective actions designed to affect governmental policies. At the most basic level, issue-specific political participation occurs when individuals directly attempt to influence governmental actors or policies on climate change—most notably by voting, but also through donating money and communicating with public officials. These types of participation tend to be relatively rare, limited to a small subset of deeply committed individuals. In contrast, personal action on climate change is more widely dispersed, especially if one includes impact-oriented actions (e.g., actions that influence the environment but are primarily undertaken for other reasons, like convenience or saving money) rather than purely intention-based actions, which occur when individuals adopt behaviors with the goal of addressing climate change. Additionally, opportunities to engage in expressive participation, largely online, create new spaces for individuals to build networks to engage in political action, as well as potentially to reach unengaged groups that are less likely to seek out information on the issue.
A number of forces can contribute to whether an individual chooses to participate on the issue of climate change. Individual characteristics, like perceptions of impersonal and personal risks associated with climate change, knowledge of the issues, and environmental values all tend to produce people more likely to participate—especially when these attitudes become part of an individual’s identity as an opinion leader or activist. As a global issue, social norms play a particularly powerful role; when individuals believe others support and are likely to take action themselves, it tends to foster a sense of efficacy that such behaviors will be effective in producing change. Individual choices about media sources also intersect with media coverage and framing of the issue to influence perceptions of the issue and likelihood of taking action. Such media framing can exacerbate or mitigate the heightened political polarization on the issue of climate change that has erected barriers to effective political action in many democratic societies in recent years, most notably in the United States. New forms of political participation may create opportunities to encourage more participation on the issue of climate change, but they also raise ethical questions about inequality and participatory divides that privilege some groups over others.
Climate change specifically and the environment more generally are becoming increasingly central features in much of contemporary persuasive messages. From World Wildlife Fund public service announcements showing the Earth as a melting scoop of ice cream to advertisements for environmentally friendly hybrid cars set against backdrops of lush, green fields, climate change and the environment are closely linked to strategic communication and consumer behavior. This growing focus on the connection between climate change and consumption represents a wide and varied field of study, underscoring the ways in which the two can at once be symbiotic and yet also antagonistic.
Meaningful academic attention to environmental cues in advertising can be thought of as occurring in two waves. In the first wave, peaking in the 1990s, research was concerned primarily with content analyses of advertising containing environmental appeals. Questions about deceptive environmental claims, often referred to as greenwashing, were a primary concern during this phase. Climate change specifically was not a central element, and instead, issues of environmental preservation and conservation dominated. In the second wave, which emerged in the late 2000s and continues unabated, researchers have broadened their focus to examine not only how the environment was depicted in advertising messages but also how audiences understood them. Attention was paid to message factors, like framing, source cues, and visual depictions, as well as individual-level factors, such as environmental concern, political ideology and regulatory focus.
While concerns about greenwashing and deceptive advertising continue to plague green advertising, a collection of new critiques has emerged, including questions about the implications of emphasizing consumer behavior as a source of climate change mitigation, of relying on nature as a commodity to be sold and used, and of engaging individuals as consumers rather than as citizens in attempts to effect environmental change.