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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.
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.
Edward Maibach, Bernadette Woods Placky, Joe Witte, Keith Seitter, Ned Gardiner, Teresa Myers, Sean Sublette, and Heidi Cullen
Global climate change is influencing the weather in every region of the United States, often in harmful ways. Yet, like people in many countries, most Americans view climate change as a threat that is distant in space (i.e., not here), time (i.e., not now), and species (i.e., not us). To manage risk and avoid harm, it is imperative that the public, professionals, and policy-makers make decisions with an informed understanding of our changing climate. In the United States, broadcast meteorologists are ideally positioned to educate Americans about the current and projected impacts of climate change in their community. They have tremendous reach, are trusted sources of climate information, and are highly skilled science communicators. When our project began in 2009, we learned that many U.S.-based TV weathercasters were potentially interested in reporting on climate change, but few actually were, citing significant barriers including a lack of time to prepare and air stories, and lack of access to high-quality content that can be rapidly used in their broadcasts, social media, and community presentations. To test the premise that TV weathercasters can be effective climate educators—if supported with high-quality localized climate communication content—in 2010 George Mason University, Climate Central, and WLTX-TV (Columbia, SC) developed and pilot-tested Climate Matters, a series of short on-air (and online) segments about the local impacts of climate change, delivered by the station’s chief meteorologist. During the first year, more than a dozen stories aired. To formally evaluate Climate Matters, we conducted pre- and post-test surveys of local TV news viewers in Columbia. After one year, WLTX viewers had developed a more science-based understanding of climate change than viewers of other local news stations, confirming our premise that when TV weathercasters report on the local implications of climate change, their viewers learn. Through a series of expansions, including the addition of important new partners—the American Meteorological Society, National Aeronautical and Space Administration (NASA), National Oceanic and Atmospheric Administration (NOAA), and Yale University—Climate Matters has become a comprehensive nationwide climate communication resource program for American broadcast meteorologists. As of March 2016, 313 local weathercasters nationwide (at 202 stations in 111 media markets) are participating in the program, receiving new content on a weekly basis. Some leaders in the World Meteorological Organization are now promoting the concept of “TV weather presenters as climate change communicators,” and collaborative discussions are underway with Climate Central. In this article, we review the theoretical basis of the program, detail its development and national scale-up, and conclude with insights for how to develop climate communication initiatives for other professional communities of practice in the U.S. and other countries.
International climate negotiations seek to limit warming to an average of two degrees Celsius (2°C). This objective is justified by the claim that scientists have identified two degrees of warming as the point at which climate change becomes dangerous. Climate scientists themselves maintain that while science can provide projections of possible impacts at different levels of warming, determining what constitutes an acceptable level of risk is not a matter to be decided by science alone, but is a value choice to be deliberated upon by societies as a whole. Hence, while climate science can inform debates about how much warming is too much, it cannot provide a definitive answer to that question. In order to fully understand how climate change came to be defined as a phenomenon with a single global dangerous limit of 2°C, it is necessary to incorporate insights from the social sciences.
Political economy, culture, economics, sociology, geography, and social psychology have all played a role in defining what constitutes an acceptable level of climate risk. These perspectives can be applied through the framework of institutional analysis to examine reports from the Intergovernmental Panel on Climate Change and other international organizations. This interdisciplinary approach offers the potential to provide a comprehensive history of how climate science has been interpreted in policy making. An interdisciplinary analysis is also essential in order to move beyond historical description to provide a narrative of considerable explanatory power. Such insights offer a valuable framework for considering current debates about whether or not it will be possible to limit warming to 2°C.
Benjamin Mark Sanderson
Long-term planning for many sectors of society—including infrastructure, human health, agriculture, food security, water supply, insurance, conflict, and migration—requires an assessment of the range of possible futures which the planet might experience. Unlike short-term forecasts for which validation data exists for comparing forecast to observation, long-term forecasts have almost no validation data. As a result, researchers must rely on supporting evidence to make their projections. A review of methods for quantifying the uncertainty of climate predictions is given. The primary tool for quantifying these uncertainties are climate models, which attempt to model all the relevant processes that are important in climate change. However, neither the construction nor calibration of climate models is perfect, and therefore the uncertainties due to model errors must also be taken into account in the uncertainty quantification.
Typically, prediction uncertainty is quantified by generating ensembles of solutions from climate models to span possible futures. For instance, initial condition uncertainty is quantified by generating an ensemble of initial states that are consistent with available observations and then integrating the climate model starting from each initial condition. A climate model is itself subject to uncertain choices in modeling certain physical processes. Some of these choices can be sampled using so-called perturbed physics ensembles, whereby uncertain parameters or structural switches are perturbed within a single climate model framework. For a variety of reasons, there is a strong reliance on so-called ensembles of opportunity, which are multi-model ensembles (MMEs) formed by collecting predictions from different climate modeling centers, each using a potentially different framework to represent relevant processes for climate change. The most extensive collection of these MMEs is associated with the Coupled Model Intercomparison Project (CMIP). However, the component models have biases, simplifications, and interdependencies that must be taken into account when making formal risk assessments. Techniques and concepts for integrating model projections in MMEs are reviewed, including differing paradigms of ensembles and how they relate to observations and reality. Aspects of these conceptual issues then inform the more practical matters of how to combine and weight model projections to best represent the uncertainties associated with projected climate change.
The understanding of past changes in climate and ocean circulation is to a large extent based on information from marine sediments. Marine deposits contain a variety of microfossils, which archive (paleo)-environmental information, both in their floral and faunal assemblages and in their stable isotope and trace element compositions. Sampling campaigns in the late 19th and early 20th centuries were dedicated to the inventory of sediment types and microfossil taxa. With the initiation of various national and international drilling programs in the second half of the 20th century, sediment cores were systematically recovered from all ocean basins and since then have shaped our knowledge of the oceans and climate history. The stable oxygen isotope composition of foraminiferal tests from the sediment cores delivered a continuous record of late Cretaceous–Cenozoic glaciation history. This record impressively proved the effects of periodic changes in the orbital configuration of the Earth on climate on timescales of tens to hundreds of thousands of years, described as Milankovitch cycles. Based on the origination and extinction patterns of marine microfossil groups, biostratigraphic schemes have been established, which are readily used for the dating of sediment successions. The species composition of assemblages of planktic microfossils, such as planktic foraminifera, radiolarians, dinoflagellates, coccolithophorids, and diatoms, is mainly related to sea-surface temperature and salinity but also to the distribution of nutrients and sea ice. Benthic microfossil groups, in particular benthic foraminifera but also ostracods, respond to changes in water depth, oxygen, and food availability at the sea floor, and provide information on sea-level changes and benthic-pelagic coupling in the ocean. The establishment and application of transfer functions delivers quantitative environmental data, which can be used in the validation of results from ocean and climate modeling experiments. Progress in analytical facilities and procedures allows for the development of new proxies based on the stable isotope and trace element composition of calcareous, siliceous, and organic microfossils. The combination of faunal and geochemical data delivers information on both environmental and biotic changes from the same sample set. Knowledge of the response of marine microorganisms to past climate changes at various amplitudes and pacing serves as a basis for the assessment of future resilience of marine ecosystems to the anticipated impacts of global warming.
An orbitally induced increase in summer insolation during the last glacial-interglacial transition enhanced the thermal contrast between land and sea, with land masses heating up compared to the adjacent ocean surface. In North Africa, warmer land surfaces created a low-pressure zone, driving the northward penetration of monsoonal rains originating from the Atlantic Ocean. As a consequence, regions today among the driest of the world were covered by permanent and deep freshwater lakes, some of them being exceptionally large, such as the “Mega” Lake Chad, which covered some 400 000 square kilometers. A dense network of rivers developed.
What were the consequences of this climate change on plant distribution and biodiversity? Pollen grains that accumulated over time in lake sediments are useful tools to reconstruct past vegetation assemblages since they are extremely resistant to decay and are produced in great quantities. In addition, their morphological character allows the determination of most plant families and genera.
In response to the postglacial humidity increase, tropical taxa that survived as strongly reduced populations during the last glacial period spread widely, shifting latitudes or elevations, expanding population size, or both. In the Saharan desert, pollen of tropical trees (e.g., Celtis) were found in sites located at up to 25°N in southern Libya. In the Equatorial mountains, trees (e.g., Olea and Podocarpus) migrated to higher elevations to form the present-day Afro-montane forests. Patterns of migration were individualistic, with the entire range of some taxa displaced to higher latitudes or shifted from one elevation belt to another. New combinations of climate/environmental conditions allowed the cooccurrences of taxa growing today in separate regions. Such migrational processes and species-overlapping ranges led to a tremendous increase in biodiversity, particularly in the Saharan desert, where more humid-adapted taxa expanded along water courses, lakes, and wetlands, whereas xerophytic populations persisted in drier areas.
At the end of the Holocene era, some 2,500 to 4,500 years ago, the majority of sites in tropical Africa recorded a shift to drier conditions, with many lakes and wetlands drying out. The vegetation response to this shift was the overall disruption of the forests and the wide expansion of open landscapes (wooded grasslands, grasslands, and steppes). This environmental crisis created favorable conditions for further plant exploitation and cereal cultivation in the Congo Basin.
Vienna was a metropolis in the middle of the Danube monarchy of Austria-Hungary and under the rule (1848–1916) of Emperor Franz Joseph I (1830–1916) the city experienced rapid growth and an unprecedented flowering of culture, the arts, architecture and science. The capital of the monarchy, an intellectual melting pot, was a city of distinguished personalities who formed the Second Viennese School of music, the Austrian School of economic thought and many more doctrines, including the ideas of Sigmund Freud, the founder of psychoanalysis. Vienna clearly reflected the zeitgeist of the fin de siècle in its economic, scientific, and cultural heyday.
At the end of the 19th century, meteorology and climatology became recognized scientific disciplines, and dynamical meteorology developed during the first quarter of the 20th century. The fact that imperial Austria took a leading position in these developments mostly owes to the work of renowned scientists of the Central Institute for Meteorology and Geodynamics (Zentralanstalt für Meteorologie und Geodynamik, ZAMG) in Vienna.
The institute was founded in 1851, and the astronomer Karl Kreil (1798–1862) became the first director. One of Kreil’s goals was to ensure that both the central meteorological station and the growing number of new meteorological stations across the entire territory of the Austrian Empire were equipped with all the appropriate instruments. Another important goal was the processing of the existing observations to publish in the institute’s yearbooks. In truth, that was the starting signal for all further scientific developments, including that of the Viennese School of Climatology.
During the first decade of the 1900s, Julius Hann (1839–1921), the third director of the ZAMG, was already being acknowledged as a renowned meteorologist and climatologist. He was a pioneer in gathering and synthesizing global climatological and meteorological data, and his Handbook of Climatology (Handbuch der Klimatologie; Hann, 1883 [Hann, J. (1883). Handbuch der Klimatologie. Stuttgart, Germany: J. Engelhorn]) and Textbook of Meteorology (Hann, 1901 [Hann, J. (1901). Lehrbuch der Meteorologie. Leipzig, Germany: C. H. Tauchnitz]) were standard setters (Davies, 2001 [Davies, H. C. (2001). Vienna and the founding of dynamical meteorology. In C. Hammerl, W. Lenhardt, R. Steinacker, & P. Steinhauser (Eds.), Die Zentralanstalt für Meteorologie und Geodynamik 1851–2001: 150 Jahre Meteorologie und Geophysik in Österreich (pp. 301–312). Graz, Austria: Leykam Buchverlagsgesellschaft]). In Hann’s era, one began to speak of a “Viennese or Austrian school.” Heinrich Ficker, who later became director of the institute, defined its distinguishing characteristic as a school that did not simply adhere to one direction but promoted each direction, every peculiar talent, and the ideas that a meteorologist with necessary characteristics was always present at key turning points in meteorological research.
Robyn S. Wilson, Sarah M. McCaffrey, and Eric Toman
Throughout the late 19th century and most of the 20th century, risks associated with wildfire were addressed by suppressing fires as quickly as possible. However, by the 1960s, it became clear that fire exclusion policies were having adverse effects on ecological health, as well as contributing to larger and more damaging wildfires over time. Although federal fire policy has changed to allow fire to be used as a management tool on the landscape, this change has been slow to take place, while the number of people living in high-risk wildland–urban interface communities continues to increase. Under a variety of climate scenarios, in particular for states in the western United States, it is expected that the frequency and severity of fires will continue to increase, posing even greater risks to local communities and regional economies.
Resource managers and public safety officials are increasingly aware of the need for strategic communication to both encourage appropriate risk mitigation behavior at the household level, as well as build continued public support for the use of fire as a management tool aimed at reducing future wildfire risk. Household decision making encompasses both proactively engaging in risk mitigation activities on private property, as well as taking appropriate action during a wildfire event to protect personal safety. Very little research has directly explored the connection between climate-related beliefs, wildfire risk perception, and action; however, the limited existing research suggests that climate-related beliefs have little direct effect on wildfire-related action. Instead, action appears to depend on understanding the benefits of different mitigation actions and in engaging the public in interactive, participatory communication programs that build trust between the public and natural resource managers. A relatively new line of research focuses on resource managers as critical decision makers in the risk management process, pointing to the need to thoughtfully engage audiences other than the lay public to improve risk management.
Ultimately, improving the decision making of both the public and managers charged with mitigating the risks associated with wildfire can be achieved by carefully addressing several common themes from the literature. These themes are to (1) promote increased efficacy through interactive learning, (2) build trust and capacity through social interaction, (3) account for behavioral constraints and barriers to action, and (4) facilitate thoughtful consideration of risk-benefit tradeoffs. Careful attention to these challenges will improve the likelihood of successfully managing the increasing risks that wildfire poses to the public and ecosystems alike in a changing climate.
Maria Ojala and Yuliya Lakew
One important group to include in efforts to combat climate change is young people. This group comprises the future leaders of society, besides being citizens of today, and they will be the ones handling the future negative consequences of this global problem. This article provides an overview of some research about climate change communication and young people. The aim is to gain a better understanding of how this group relates to and communicates about climate change in different contexts, and how to best promote knowledge, a sense of efficacy, and engagement concerning this problem. The focus is on young people who are between late childhood and young adulthood. Questions in focus are: How do media messages about climate change influence young people, and how do they themselves use media, for instance social networks, to engage with this issue? Can art-based and entertainment approaches to communication overcome the distant and complex character of climate change and make young people feel more empowered and engaged? Is it possible to communicate about climate change and raise awareness by promoting contact with nature and animals? How do young people cope with the negative emotions that are often evoked by information about this problem? In what way do young people communicate in everyday life with parents, peers, and teachers about climate change? Are participatory approaches to climate change communication a good way to prepare young people for future extreme climate events?