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D. B. Tindall, Mark C.J. Stoddart, and Candis Callison
This article considers the relationship between news media and the sociopolitical dimensions of climate change. Media can be seen as sites where various actors contend with one another for visibility, for power, and for the opportunity to communicate, as well as where they promote their policy preferences. In the context of climate change, actors include politicians, social movement representatives, scientists, business leaders, and celebrities—to name a few.
The general public obtain much of their information about climate change and other environmental issues from the media, either directly or indirectly through sources like social media. Media have their own internal logic, and getting one’s message into the media is not straightforward. A variety of factors influence what gets into the media, including media practices, and research shows that media matter in influencing public opinion.
A variety of media practices affect reporting on climate change─one example is the journalistic norm of balance, which directs that actors on both sides of a controversy be given relatively equal attention by media outlets. In the context of global warming and climate change, in the United States, this norm has led to the distortion of the public’s understanding of these processes. Researchers have found that, in the scientific literature, there is a very strong consensus among scientists that human-caused (anthropogenic) climate change is happening. Yet media in the United States often portray the issue as a heated debate between two equal sides.
Subscription to, and readership of, print newspapers have declined among the general public; nevertheless, particular newspapers continue to be important. Despite the decline of traditional media, politicians, academics, NGO leaders, business leaders, policymakers, and other opinion leaders continue to consume the media. Furthermore, articles from particular outlets have significant readership via new media access points, such as Facebook and Twitter.
An important concept in the communication literature is the notion of framing. “Frames” are the interpretive schemas individuals use to perceive, identify, and label events in the world. Social movements have been important actors in discourse about climate change policy and in mobilizing the public to pressure governments to act. Social movements play a particularly important role in framing issues and in influencing public opinion. In the United States, the climate change denial countermovement, which has strong links to conservative think tanks, has been particularly influential. This countermovement is much more influential in the United States than in other countries. The power of the movement has been a barrier to the federal government taking significant policy action on climate change in the United States and has had consequences for international agreements and processes.
People can take extraordinary measures to protect that which they view as sacred. They may refuse financial gain, engage in bloody, inter-generational conflicts, mount hunger strikes and even sacrifice their lives. These behaviors have led researchers to propose that religious values shape our identities and give purpose to our lives in a way that secular incentives cannot. However, despite the fact that many cultural and religious frameworks already emphasize sacred aspects of our natural world, applying all of that motivating power of “the sacred” to environmental protectionism seems to be less straightforward.
Sacred elements in nature do lead people to become committed to environmental causes, particularly when religious identities emphasize conceptualization of humans as caretakers of this planet. In other cases, however, it is precisely the sacred aspect of nature which precludes environmental action and leads to the denial of climate change. This denial can take many forms, from an outright refusal of the premise of climate change to a divine confirmation of eschatological beliefs.
A resolution might require rethinking the framework that religion provides in shaping human-environment interactions. Functionalist perspectives emphasize religion’s ability to help people cope with loss—of life, property and health, which will become more frequent as storms intensify and weather patterns become more unpredictable. It is uncertain whether religious identity can facilitate the acceptance of anthropogenic climate change, but perhaps it can aid with how people adapt to its inevitable effects.
The history of the Russian Magneto-Meteorological Observatory (RMMO) in Beijing has not been extensively researched. Sources for this information are Russian (the Russian State Historical Archive, Saint Petersburg Branch of the Archive of the Academy of Sciences, Russian National Library) and Chinese (the First Historical Archive of Beijing, the Library of the Shanghai Zikavey Observatory) archives. These archival materials can be scientifically and methodologically analyzed. At the beginning of the 18th century, the Russian Orthodox Mission (ROM) was founded in the territory of Beijing. Existing until 1955, the ROM performed an important role in the development of Russian–Chinese relations. Russian scientists could only work in Beijing through the ROM due to China’s policy of fierce self-isolation. The ROM became the center of Chinese academic studies and the first training school for Russian sinologists. From its very beginning, it was considered not only a church or diplomatic mission but a research center in close cooperation with the Russian Academy of Sciences. In this context, the RMMO made important weather investigations in China and the Far East in the 19th century. The RMMO, as well as its branch stations in China and Mongolia, part of a scientific network, represented an important link between Europe and Asia and was probably the largest geographical scientific network in the world at that time.
Scientists’ Views about Public Engagement and Science Communication in the Context of Climate Change
John Besley and Anthony Dudo
Scientists who study issues such as climate change are often called on by both their colleagues and broader society to share what they know and why it matters. Many are willing to do so—and do it well—but others are either unwilling or may communicate without clear goals or in ways that may fail to achieve their goals. There are several central topics involved in the study of scientists as communicators. First, it is important to understand the evolving arguments behind why scientists are being called on to get involved in public engagement about contentious issues such as climate change. Second, it is also useful to consider the factors that social science suggests actually lead scientists to communicate about scientific issues. Last, it is important to consider what scientists are trying to achieve through their communication activities, and to consider to what extent we have evidence about whether scientists are achieving their desired goals.
Climate journalism is a moving target. Driven by its changing technological and economic contexts, challenged by the complex subject matter of climate change, and immersed in a polarized and politicized debate, climate journalism has shifted and diversified in recent decades. These transformations hint at the emergence of a more interpretive, sometimes advocacy-oriented journalism that explores new roles beyond that of the detached conduit of elite voices. At the same time, different patterns of doing climate journalism have evolved, because climate journalists are not a homogeneous group. Among the diversity of journalists covering the issue, a small group of expert science and environmental reporters stand out as opinion leaders and sources for other journalists covering climate change only occasionally. The former group’s expertise and specialization allow them to develop a more investigative and critical attitude toward both the deniers of anthropogenic climate change and toward climate science.
Daniel P. Aldrich, Courtney M. Page-Tan, and Christopher J. Paul
Anthropogenic climate change increasingly disrupts livelihoods, floods coastal urban cities and island nations, and exacerbates extreme weather events. There is near-universal consensus among scientists that in order to reverse or at least mitigate climate disruptions, limits must be imposed on anthropogenic sources of climate-forcing emissions and adaptation to changing global conditions will be necessary. Yet adaptation to current and future climate change at the individual, community, and national levels vary widely from merely coping, to engaging in adaptive change, to transformative shifts. Some of those affected simply cope with lower crop yields, flooded streets, and higher cooling bills. Others incrementally adapt to new environmental conditions, for example, by raising seawalls or shifting from one crop to another better suited for a hotter environment. The highest—and perhaps least likely—type of change involves transformation, radically altering practices with an eye toward the future. Transformative adaptation may involve a livelihood change or permanent migration; it might require shuttering whole industries and rethinking industrial policy at the national level. Entire island nations such as Fiji, for example, are considering relocating from vulnerable locations to areas better suited to rising sea levels.
A great deal of research has shown how social capital (the bonding, bridging, and linking connections to others) provides information on trustworthiness, facilitates collective action, and connects us to external resources during disasters and crises. We know far less about the relationship between social capital and adaptation behaviors in terms of the choices that people make to accommodate changing environmental conditions. A number of unanswered but critical questions remain: How precisely does social capital function in climate change adaptation? To what degree does strong bonding social capital substitute for successful adaptation behaviors for individuals or groups? Which combinations of social factors make coping, adapting, and transforming most likely? How can social capital help migrating populations maintain cultural identity under stress? How can local networks be integrated into higher-level policy interventions to improve adaptation? Which political and social networks contribute to transformative responses to climate change at local, regional, and international levels? This article serves as a comprehensive literature review, overview of empirical findings to date, and a research agenda for the future.
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.
Masahiro Sugiyama, Atsushi Ishii, Shinichiro Asayama, and Takanobu Kosugi
Climate engineering, a set of techniques proposed to intervene directly in the climate system to reduce risks from climate change, presents many novel governance challenges. Solar radiation management (SRM), particularly the use of stratospheric aerosol injection (SAI), is one of the most discussed proposals. It has been attracting more and more interest, and its pertinence as a potential option for responding to the threats from climate change may be set to increase because of the long-term temperature goal (well below 2°C or 1.5°C) in the 2015 Paris Agreement. Initial research has demonstrated that SAI would cool the climate system and reduce climate risks in many ways, although it is mired in unknown environmental risks and various sociopolitical ramifications. The proposed techniques are in the early stage of research and development (R&D), providing a unique opportunity for upstream public engagement, long touted as a desirable pathway to more plural and inclusive governance of emergent technologies by opening up social choices in technology. Solar geoengineering governance faces various challenges. One of the most acute of these is how to situate public engagement in international governance discourse; the two topics have been studied separately. Another challenge relates to bridging the gap between the social choices at hand and assessment of the risks and benefits of SRM. Deeper integration of knowledge across disciplines and stakeholder and public inputs is a prerequisite for enabling responsible innovation for the future of our climate.
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.
Christopher K. Wikle
The climate system consists of interactions between physical, biological, chemical, and human processes across a wide range of spatial and temporal scales. Characterizing the behavior of components of this system is crucial for scientists and decision makers. There is substantial uncertainty associated with observations of this system as well as our understanding of various system components and their interaction. Thus, inference and prediction in climate science should accommodate uncertainty in order to facilitate the decision-making process. Statistical science is designed to provide the tools to perform inference and prediction in the presence of uncertainty. In particular, the field of spatial statistics considers inference and prediction for uncertain processes that exhibit dependence in space and/or time. Traditionally, this is done descriptively through the characterization of the first two moments of the process, one expressing the mean structure and one accounting for dependence through covariability.
Historically, there are three primary areas of methodological development in spatial statistics: geostatistics, which considers processes that vary continuously over space; areal or lattice processes, which considers processes that are defined on a countable discrete domain (e.g., political units); and, spatial point patterns (or point processes), which consider the locations of events in space to be a random process. All of these methods have been used in the climate sciences, but the most prominent has been the geostatistical methodology. This methodology was simultaneously discovered in geology and in meteorology and provides a way to do optimal prediction (interpolation) in space and can facilitate parameter inference for spatial data. These methods rely strongly on Gaussian process theory, which is increasingly of interest in machine learning. These methods are common in the spatial statistics literature, but much development is still being done in the area to accommodate more complex processes and “big data” applications. Newer approaches are based on restricting models to neighbor-based representations or reformulating the random spatial process in terms of a basis expansion. There are many computational and flexibility advantages to these approaches, depending on the specific implementation. Complexity is also increasingly being accommodated through the use of the hierarchical modeling paradigm, which provides a probabilistically consistent way to decompose the data, process, and parameters corresponding to the spatial or spatio-temporal process.
Perhaps the biggest challenge in modern applications of spatial and spatio-temporal statistics is to develop methods that are flexible yet can account for the complex dependencies between and across processes, account for uncertainty in all aspects of the problem, and still be computationally tractable. These are daunting challenges, yet it is a very active area of research, and new solutions are constantly being developed. New methods are also being rapidly developed in the machine learning community, and these methods are increasingly more applicable to dependent processes. The interaction and cross-fertilization between the machine learning and spatial statistics community is growing, which will likely lead to a new generation of spatial statistical methods that are applicable to climate science.
Global climate models are our main tool to generate quantitative climate projections, but these models do not resolve the effects of complex topography, regional scale atmospheric processes and small-scale extreme events. To understand potential regional climatic changes, and to provide information for regional-scale impact modeling and adaptation planning, downscaling approaches have been developed. Regional climate change modeling, even though it is still a matter of basic research and questioned by many researchers, is urged to provide operational results. One major downscaling class is statistical downscaling, which exploits empirical relationships between larger-scale and local weather. The main statistical downscaling approaches are perfect prog (often referred to as empirical statistical downscaling), model output statistics (which is typically some sort of bias correction), and weather generators.
Statistical downscaling complements or adds to dynamical downscaling and is useful to generate user-tailored local-scale information, or to efficiently generate regional scale information about mean climatic changes from large global climate model ensembles. Further research is needed to assess to what extent the assumptions underlying statistical downscaling are met in typical applications, and to develop new methods for generating spatially coherent projections, and for including process-understanding in bias correction. The increasing resolution of global climate models will improve the representation of downscaling predictors and will, therefore, make downscaling an even more feasible approach that will still be required to tailor information for users.
Toby Bolsen and Matthew A. Shapiro
The importance of framing as a concept is reflected by the massive amount of attention it has received from scholars across disciplines. As a communicative process, framing involves making certain considerations salient as a way to simplify or shape the way in which an audience understands a particular problem and its potential solutions. As recently as the early 2000s, social scientists began to examine how strategic frames in a communication affect both individuals’ beliefs about climate change and the actions they are willing to support to mitigate the likely effects. Research on the effects of how strategic frames influence the attitudes, beliefs, and preferences of individuals in this domain primarily builds on insights from framing theory, which explains that an individual’s attitude or preference in any given context depends on the available, accessible, and most applicable (i.e., perceived strongest) considerations. But it is much more than theory: frames related to the effects and potential solutions for climate change have been employed strategically by various actors in an effort to shape public opinion and public policy.
Perceptions of scientific consensus on climate change are thought to play an important role in determining support for policy actions. Consequently, strategic actors promote a particular agenda by accentuating the inherent uncertainty of climate science, thus casting doubt on the scientific consensus. This has contributed to partisan polarization on climate change and the rise of protective forms of information processing and reasoning in this domain. Strategic messages and frames that resonate with particular subgroups have no effect, or may even backfire, on other segments of the population. Additionally, as individuals who possess different partisan identities become more knowledgeable and numerate, they become increasingly likely to accept information and messages that bolster their existing group loyalties and to reject communications that challenge those identities. Science communicators are thus presented with a considerable barrier to building consensus among the public for action on climate change. In response, scholars have begun to identify strategies and approaches for addressing audiences with the kinds of messages that are most likely to resonate with individuals possessing a diverse range of values and political identities. Further research must identify ways to overcome partisan motivated reasoning on climate change and the persistent and deleterious effects that have resulted from the politicization of climate science.
R. Kelly Garrett
Misperceptions about climate change are widespread, and efforts to correct them must be grounded in an understanding of the factors, both individual and social, that contribute to them. These factors can be organized into four broad categories: motivated reasoning, non-motivated information processing biases, social dynamics, and the information environment. Each type of factor is associated with a host of related strategies for countering false information and beliefs. Motivated biases can be reduced with affirmations, by attempting to depoliticize the issue, and via an evidentiary “tipping point.” Other cognitive biases highlight the importance of clarity, simplicity, and repetition. When correcting errors that contain an inaccurate causal explanation, it is also important to provide an alternative account of the event in question. Message presentation techniques can also facilitate updating beliefs. Beliefs have an important social dimension. Attending to these factors shows the importance of strategies that include: ensuring that lay people consistently have the tools that help them evaluate experts; promoting confidence among those who hold accurate beliefs; facilitating diverse, unsegregated social networks; and providing corrections from unexpected sources. Finally, the prevalence of misinformation in the information environment is highly problematic. Strategies that news organizations can employ include avoiding false balance, adjudicating among contradictory claims, and encouraging accuracy on the part of political elites via fact checking. New technologies may also prove an important tool: search engines that give preferential treatment to accurate information and automated recommendations of accurate information following exposure to inaccuracies both have the potential to change how individuals learn about climate change.
Judith L. Lean
Emergent in recent decades are robust specifications and understanding of connections between the Sun’s changing radiative energy and Earth’s changing climate and atmosphere. This follows more than a century of contentious debate about the reality of such connections, fueled by ambiguous observations, dubious correlations, and lack of plausible mechanisms. It derives from a new generation of observations of the Sun and the Earth made from space, and a new generation of physical climate models that integrate the Earth’s surface and ocean with the extended overlying atmosphere. Space-based observations now cover more than three decades and enable statistical attribution of climate change related to the Sun’s 11-year activity cycle on global scales, simultaneously with other natural and anthropogenic influences. Physical models that fully resolve the stratosphere and its embedded ozone layer better replicate the complex and subtle processes that couple the Sun and Earth.
An increase of ~0.1% in the Sun’s total irradiance, as observed near peak activity during recent 11-year solar cycles, is associated with an increase of ~0.1oC in Earth’s global surface temperature, with additional complex, time-dependent regional responses. The overlying atmosphere warms more, by 0.3oC near 20 km. Because solar radiation impinges primarily at low latitudes, the increased radiant energy alters equator-to-pole thermal gradients, initiating dynamical responses that produce regions of both warming and cooling at mid to high latitudes. Because solar energy deposition depends on altitude as a result of height-dependent atmospheric absorption, changing solar radiation establishes vertical thermal gradients that further alter dynamical motions within the Earth system.
It remains uncertain whether there are long-term changes in solar irradiance on multidecadal time scales other than due to the varying amplitude of the 11-year cycle. If so the magnitude of the additional change is expected to be comparable to that observed during the solar activity cycle. Were the Sun’s activity to become anomalously low, declining during the next century to levels of the Maunder Minimum (from 1645 to 1715), the expected global surface temperature cooling is less than a few tenths oC. In contrast, a scenario of moderate greenhouse gas increase with climate forcing of 2.6 W m−2 over the next century is expected to warm the globe 1.5 to 1.9oC, an order of magnitude more than the hypothesized solar-induced cooling over the same period.
Future challenges include the following: securing sufficiently robust observations of the Sun and Earth to elucidate changes on climatological time scales; advancing physical climate models to simulate realistic responses to changing solar radiation on decadal time scales, synergistically at the Earth’s surface and in the ocean and atmosphere; disentangling the Sun’s influence from that of other natural and anthropogenic influences as the climate and atmosphere evolve; projecting past and future changes in the Sun and Earth’s climate and atmosphere; and communicating new understanding across scientific disciplines, and to political and societal stakeholders.
Bridie McGreavy and David Hart
Direct experience, scientific reports, and international media coverage make clear that the breadth, severity, and multiple consequences from climate change are far-reaching and increasing. Like many places globally, the northeastern United States is already experiencing climate change, including one of the world’s highest rates of ocean warming, reduced durations of winter ice cover on lakes, a marked increase in the frequency of extreme precipitation events, and climate-mediated ecological disruptions of invasive species. Given current and projected changes in ecosystems, communities, and economies, it is essential to find ways to anticipate and reduce vulnerabilities to change and, at the same time, promote sustainable economic development and human well-being.
The emerging field of sustainability science offers a promising conceptual and analytic framework for accelerating progress towards sustainable development. Sustainability science aims to be use-inspired and to connect basic and applied knowledge with solutions for societal benefit. This approach draws from diverse disciplines, theories, and methods organized around the broad goal of maintaining and improving life support systems, ecosystem health, and human well-being. Partners in New England have been using sustainability science as a framework for stakeholder-engaged, interdisciplinary research that has generated use-inspired knowledge and multiple solutions for more than a decade. Sustainability science has helped produce a landscape-scale approach to wetland conservation; emergency response plans for invasive species that threaten livelihoods and cultures; decision support tools for improved water quality management and public health for beach use and shellfish consumption; and the development of robust partnership networks across disciplines and institutions. Understanding and reducing vulnerability to climate change is a central motivating factor in this portfolio of projects because linking knowledge about social-ecological systems with effective policy action requires a holistic view that addresses complex intersecting stressors.
One common theme in these varied efforts is the way that communication fundamentally shapes collaborative research and social, technical, and policy outcomes from sustainability science. Communication as a discipline has, for more than two thousand years, sought to understand how environments and symbols shape human life, forms of social organization, and collective decision making. The result is a body of scholarship and practical techniques that are diverse and well adapted to meet the complexity of contemporary sustainability challenges. The complexity of the issues that sustainability science aspires to solve requires diversity and flexibility to be able to adapt approaches to the specific needs of a situation. Long-term, cross-scale, and multi-institutional sustainability science collaborations show that communication research and practice can help build communities and networks, and advance technical and policy solutions to confront the challenges of climate change and promote sustainability now and in future.
The East African Rift System (EARS) transecting the high-elevation East African plateau is one of the most outstanding rift systems on earth. Rifting was caused by a huge uprising mantle plume under East Africa. Two distinct rift branches are distinguished: an older, volcanically very active Eastern Branch and a younger, much less volcanic Western Branch. The Eastern Branch is generally characterized by high elevation, whereas the Western Branch comprises a number of deep rift lakes (e.g., Lake Tanganyika, Lake Malaŵi). These differences reflect different plate strengths, the latter of which are largely governed by differences in how the mantle plume interacted with the East African lithosphere. Much of the topography forming the East African plateau has been caused by the uprising mantle plume. The onset of topographic uplift in the EARS is poorly dated but preceded graben development, the latter of which commenced at ~24 Ma in the Ethiopian Rift, at ~12 Ma in Kenya, and at ~10 Ma in the Western Branch. Increased uplift of the East African plateau since ~15–10 Ma might be connected to climate change in East Africa and human evolution. East Africa experienced cooling starting at 15.5–12.5 Ma that heralded profound faunal changes at 8–5 Ma, when the hominin lineage split from the chimpanzee lineage. The Pliocene is characterized by warm and wet climate between 5.3 and 3.3 Ma transitioning into a period of cooler and more arid conditions after ~3 Ma. The climate in the EARS is controlled by westerly monsoonal flow over equatorial West Africa and easterly monsoonal flow over the Indian Ocean. The uplifting East African plateau intercepted those winds and contributed to the increased aridification of East Africa.
Deborah R. Coen
The advent of climate science can be defined as the historical emergence of a research program to study climate according to a modern definition of climate. Climate in this sense: (1) refers not simply to the average state of the atmosphere but also to its variability; (2) is multiscalar, concerned with phenomena ranging from the very small and fast to the very large and slow; and (3) is understood to be influenced by the oceans, lithosphere, cryosphere, and biosphere. Most accounts of the history of climate science to date have focused on the development of computerized general circulation models since World War Two. However, following this definition, the advent of climate science occurred well before the computer age. This entry therefore seeks to dispel the image of climate science as a recent invention and as the preserve of an exclusive, North American elite. The historical roots of today’s knowledge of climate change stretch surprisingly far back into the past and clear across the world, though the geographic focus here is on Europe and North America. The modern science of climate emerged out of interactions between learned and vernacular knowledge traditions, and has simultaneously appropriated and undermined traditional and indigenous forms of climate knowledge. Important precedents emerged in the 17th and 18th centuries, and it was in the late 19th century that a modern science of climate coalesced into a coordinated research program in part through the unification of divergent knowledge traditions around standardized techniques of measurement and analysis.
Wilfried Haeberli, Johannes Oerlemans, and Michael Zemp
Like many comparable mountain ranges at lower latitudes, the European Alps are increasingly losing their glaciers. Following roughly 10,000 years of limited climate and glacier variability, with a slight trend of increasing glacier sizes to Holocene maximum extents of the Little Ice Age, glaciers in the Alps started to generally retreat after 1850. Long-term observations with a monitoring network of unique density document this development. Strong acceleration of mass losses started to take place after 1980 as related to accelerating atmospheric temperature rise. Model calculations, using simple to high-complexity approaches and relating to individual glaciers as well as to large samples of glaciers, provide robust results concerning scenarios for the future: under the influence of greenhouse-gas forced global warming, glaciers in the Alps will largely disappear within the 21st century. Anticipating and modeling new landscapes and land-forming processes in de-glaciating areas is an emerging research field based on modeled glacier-bed topographies that are likely to become future surface topographies. Such analyses provide a knowledge basis to early planning of sustainable adaptation strategies, for example, concerning opportunities and risks related to the formation of glacial lakes in over-deepened parts of presently still ice-covered glacier beds.
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.
Neil T. Gavin
Television and cable are two routes by which broadcasters reach the public. Citizens are known to rely on a variety of media sources; however, television is seen by people in a very wide range of geographical locales, as a main or major source of reliable and trusted information. The coverage of climate change by broadcasters is, however, modest relative to press coverage of the topic and reports on topics other than global warming. Journalists in the televisual media can struggle to justify the inclusion of climate change in programming because it can lack the “newsworthiness” that draws editors and reporters to other issues. A range of incentives and pressures have tended to ensure that commentary and claims that stand outside the scientific consensus are represented in “balanced” reporting. The literature on broadcast programming output on climate change is highly diverse and often country specific. Nevertheless, certain features do stand out across locales, notably a focus on alarming (and possibly alarmist) commentary, limited reporting on the causes and consequences of climate change, and widespread reproduction of climate sceptic claims. These common forms of coverage seem unlikely to prompt full understanding of, serious engagement with, or concern about the issue.