Martin Claussen, Anne Dallmeyer, and Jürgen Bader
There is ample evidence from palaeobotanic and palaeoclimatic reconstructions that during early and mid-Holocene between some 11,700 years (in some regions, a few thousand years earlier) and some 4200 years ago, subtropical North Africa was much more humid and greener than today. This African Humid Period (AHP) was triggered by changes in the orbital forcing, with the climatic precession as the dominant pacemaker. Climate system modeling in the 1990s revealed that orbital forcing alone cannot explain the large changes in the North African summer monsoon and subsequent ecosystem changes in the Sahara. Feedbacks between atmosphere, land surface, and ocean were shown to strongly amplify monsoon and vegetation changes. Forcing and feedbacks have caused changes far larger in amplitude and extent than experienced today in the Sahara and Sahel. Most, if not all, climate system models, however, tend to underestimate the amplitude of past African monsoon changes and the extent of the land-surface changes in the Sahara. Hence, it seems plausible that some feedback processes are not properly described, or are even missing, in the climate system models.
Perhaps even more challenging than explaining the existence of the AHP and the Green Sahara is the interpretation of data that reveal an abrupt termination of the last AHP. Based on climate system modeling and theoretical considerations in the late 1990s, it was proposed that the AHP could have ended, and the Sahara could have expanded, within just a few centuries—that is, much faster than orbital forcing. In 2000, paleo records of terrestrial dust deposition off Mauritania seemingly corroborated the prediction of an abrupt termination. However, with the uncovering of more paleo data, considerable controversy has arisen over the geological evidence of abrupt climate and ecosystem changes. Some records clearly show abrupt changes in some climate and terrestrial parameters, while others do not. Also, climate system modeling provides an ambiguous picture.
The prediction of abrupt climate and ecosystem changes at the end of the AHP is hampered by limitations implicit in the climate system. Because of the ubiquitous climate variability, it is extremely unlikely that individual paleo records and model simulations completely match. They could do so in a statistical sense, that is, if the statistics of a large ensemble of paleo data and of model simulations converge. Likewise, the interpretation regarding the strength of terrestrial feedback from individual records is elusive. Plant diversity, rarely captured in climate system models, can obliterate any abrupt shift between green and desert state. Hence, the strength of climate—vegetation feedback is probably not a universal property of a certain region but depends on the vegetation composition, which can change with time. Because of spatial heterogeneity of the African landscape and the African monsoon circulation, abrupt changes can occur in several, but not all, regions at different times during the transition from the humid mid-Holocene climate to the present-day more arid climate. Abrupt changes in one region can be induced by abrupt changes in other regions, a process sometimes referred to as “induced tipping.” The African monsoon system seems to be prone to fast and potentially abrupt changes, which to understand and to predict remains one of the grand challenges in African climate science.
Across many parts of the globe the relationship between journalists and news sources has been transformed by digital technologies, increased reliance on public relations practitioners, and the rise of citizen journalism. With fewer gatekeepers, and the growing influence of digital and social media, identifying whose voices are authoritative in making sense of complex climate science proves an increasing challenge. An increasing array of news sources are vying for their particular perspective to be established including scientists, government, industry, environmental NGOs, individual citizens and, more recently, celebrities. The boundaries between audience, consumer and producer are less defined and the distinction between ‘factual’ and ‘opinion-based’ reporting has become more blurred.
All these developments suggest the need for a more complex account of the myriad influences on journalistic decisions. More research needs to examine behind-the-scenes relations between sources and journalists, and the efforts of news sources to frame the issues or seek to silence news media attention. Also although we now know a great deal more about marginalized sources and their communication strategies we know relatively little about those of powerful multinational corporate organizations, governments and lobby groups. The shifting media environment and the networked nature of information demand a major rethinking of early media-centric approaches to examining journalist/source relations as applied to climate change. The metaphors of ‘network’ and field’ capture the diverse linkages across different spheres better than the Hierarchy of Influences model.
Climate change is often said to herald the anthropocene, where humans become active participants in the remaking of global geology. The corollary of the wide acceptance of a geological anthropocene is the emergence of a new form of self-aware climate agency. With awareness comes blame, invoking responsibility for action. What kind of social action arises from climate agency has become the critical question of our era. In the context of climate deterioration, the prevalence of inaction is itself an exercise of agency, creating in its path new fields of social struggle. The opening sphere of climate agency has the effect of subsuming other fields, reconfiguring established categories of human justice and ethical well-being. In this respect we can think of climate agency as having a distinctive, even revolutionary logic, which remains emergent, enveloping multiple aspects of social action.
From this perspective the question of climate change and social movement participation is centrally important. To what extent is something that we can characterize as “climate agency” emerging through social movement participation? What potential has this phenomenon to develop beyond ideological confinement and delimitation to make wider and transformative claims on society? A genuine social movement, we are taught from history, is indeed a transformative force capable of remaking social and political relations. It remains unclear, but what are the emergent dynamics of climate movement participation that depart from established systemic parameters, to offer such a challenge? How are such developments reconfiguring “climate change communication,” forcing an insurgent element into the polity?
Though scholarship addressing these questions on social movement participation and climate change exists, the field undoubtedly remains relatively underdeveloped. This reflects the extent to which inquiry into climate change has been dominated by scientific and economic discourses. It also reflects the difficulty that social science, and specifically political sociology, the “home” of social movement studies, has had in apprehending the scope of the challenge. Climate change can disrupt deeply sedimented assumptions about the relationship between social movements and capitalist modernity, and force a reconsideration of the role of social movements across developmentalist hierarchies. Such rethinking can be theoretically challenging, and force new approaches into view. These possibilities reflect the broader challenges to political culture posed by climate change.
Ashley A. Anderson
Early research on the relationship between social media use and its relationship to climate change opinion, knowledge, and behavior suggests several positive impacts. Social media encourages greater knowledge of climate change, mobilization of climate change activists, space for discussing the issue with others, and online discussions that frame climate change as a negative for society. Social media, however, does provide space for framing climate change skeptically and activating those with a skeptical perspective of climate change. Further examination of the relationship between social media use and climate change perceptions is warranted.
Research Methods for Assessing Online Climate Change Communication, Social Media Discussion, and Behavior
Leona Yi-Fan Su, Heather Akin, and Dominique Brossard
In recent years, increased Internet access and new communication technologies have led to the development of online methods for gathering public opinion and behavioral data related to controversial issues like climate change. To help climate-change researchers better adapt to the new era of online-based research, a review of, and methodological applications for, prevailing Internet-based research methods are provided here. Online surveys have become more common in the last decade for several reasons, including their relatively low administration cost, the pervasiveness of Internet communication, and declining response rates associated with traditional survey methods. Experiments embedded within online surveys have also become a useful tool for examining the extent to which online communications influence publics’ attitudes and behaviors. Other research methods that have gained growing attention from scholars are content analyses of online communication using big data approaches. By mining the seemingly infinite amount of user-generated content extracted from different social media sites, researchers are able to analyze issue awareness, responses to instant news, and emerging sentiments. This article provides a detailed overview of these Internet-based research methods, including their potential advantages and pitfalls, their applications in the science-communication and climate-change research fields, as well as suggestions for future research.
Regional models were originally developed to serve weather forecasting and regional process studies. Typical simulations encompass time periods in the order of days or weeks. Thereafter regional models were also used more and more as regional climate models for longer integrations and climate change downscaling. Regional climate modeling or regional dynamic downscaling, which are used interchangeably, developed as its own branch in climate research since the end of the 1990s out of the need to bridge the obvious inconsistencies at the interface of global climate research and climate impact research. The primary aim of regional downscaling is to provide consistent regional climate change scenarios with relevant spatial resolution to serve detailed climate impact assessments.
Similar to global climate modeling, the early attempts at regional climate modeling were based on uncoupled atmospheric models or stand-alone ocean models, an approach that is still maintained as the most common on the regional scale. However, this approach has some fundamental limitations, since regional air-sea interaction remains unresolved and regional feedbacks are neglected. This is crucial when assessing climate change impacts in the coastal zone or the regional marine environment. To overcome these limitations, regional climate modeling is currently in a transition from uncoupled regional models into coupled atmosphere-ocean models, leading to fully integrated earth system models. Coupled ice-ocean-atmosphere models have been developed during the last decade and are currently robust and well established on the regional scale. Their added value has been demonstrated for regional climate modeling in marine regions, and the importance of regional air-sea interaction became obvious. Coupled atmosphere-ice-ocean models, but also coupled physical-biogeochemical modeling approaches are increasingly used for the marine realm. First attempts to couple these two approaches together with land surface models are underway. Physical coupled atmosphere-ocean modeling is also developing further and first model configurations resolving wave effects at the atmosphere-ocean interface are now available. These new developments now open up for improved regional assessment under broad consideration of local feedbacks and interactions between the regional atmosphere, cryosphere, hydrosphere, and biosphere.
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.
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.
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?
The Tibetan Plateau (TP) is subjected to strong interactions among the atmosphere, hydrosphere, cryosphere, and biosphere. The Plateau exerts huge thermal forcing on the mid-troposphere over the mid-latitude of the Northern Hemisphere during spring and summer. This region also contains the headwaters of major rivers in Asia and provides a large portion of the water resources used for economic activities in adjacent regions. Since the beginning of the 1980s, the TP has undergone evident climate changes, with overall surface air warming and moistening, solar dimming, and decrease in wind speed. Surface warming, which depends on elevation and its horizontal pattern (warming in most of the TP but cooling in the westernmost TP), was consistent with glacial changes. Accompanying the warming was air moistening, with a sudden increase in precipitable water in 1998. Both triggered more deep clouds, which resulted in solar dimming. Surface wind speed declined from the 1970s and started to recover in 2002, as a result of atmospheric circulation adjustment caused by the differential surface warming between Asian high latitudes and low latitudes.
The climate changes over the TP have changed energy and water cycles and has thus reshaped the local environment. Thermal forcing over the TP has weakened. The warming and decrease in wind speed lowered the Bowen ratio and has led to less surface sensible heating. Atmospheric radiative cooling has been enhanced, mainly through outgoing longwave emission from the warming planetary system and slightly enhanced solar radiation reflection. The trend in both energy terms has contributed to the weakening of thermal forcing over the Plateau. The water cycle has been significantly altered by the climate changes. The monsoon-impacted region (i.e., the southern and eastern regions of the TP) has received less precipitation, more evaporation, less soil moisture and less runoff, which has resulted in the general shrinkage of lakes and pools in this region, although glacier melt has increased. The region dominated by westerlies (i.e., central, northern and western regions of the TP) received more precipitation, more evaporation, more soil moisture and more runoff, which together with more glacier melt resulted in the general expansion of lakes in this region. The overall wetting in the TP is due to both the warmer and moister conditions at the surface, which increased convective available potential energy and may eventually depend on decadal variability of atmospheric circulations such as Atlantic Multi-decadal Oscillation and an intensified Siberian High. The drying process in the southern region is perhaps related to the expansion of Hadley circulation. All these processes have not been well understood.