81-100 of 294 Results


Climate of Eastern Africa  

Pierre Camberlin

Eastern Africa, classically presented as a major dry climate anomaly region in the otherwise wet equatorial belt, is a transition zone between the monsoon domains of West Africa and the Indian Ocean. Its complex terrain, unequaled in the rest of Africa, results in a huge diversity of climatic conditions that steer a wide range of vegetation landscapes, biodiversity and human occupations. Meridional rainfall gradients dominate in the west along the Nile valley and its surroundings, where a single boreal summer peak is mostly observed. Bimodal regimes (generally peaking in April and November) prevail in the east, gradually shifting to a single austral summer peak to the south. The swift seasonal shift of the Intertropical Convergence Zone and its replacement in January–February and June–September by strong meridional, generally diverging low-level winds (e.g., the Somali Jet), account for the low rainfall. These large-scale flows interact with topography and lakes, which have their own local circulation in the form of mountain and lake breezes. This results in complex rainfall patterns, with a strong diurnal component, and a frequent asymmetry in the rainfall distribution with respect to the major relief features. Whereas highly organized rain-producing systems are uncommon, convection is partly modulated at intra-seasonal (about 30–60-day) timescales. Interannual variability shows a fair level of spatial coherence in the region, at least in July–September in the west (Ethiopia and Nile Valley) and October–December in the east along the Indian Ocean. This is associated with a strong forcing from sea-surface temperatures in the Pacific and Indian Oceans, and to a lesser extent the Atlantic Ocean. As a result, Eastern Africa shows some of the largest interannual rainfall variations in the world. Some decadal-scale variations are also found, including a drying trend of the March–May rainy season since the 1980s in the eastern part of the region. Eastern Africa overall mean temperature increased by 0.7 to 1 °C from 1973 to 2013, depending on the season. The strong, sometimes non-linear altitudinal gradients of temperature and moisture regimes, also contribute to the climate diversity of Eastern Africa.


Climate of Southern Africa  

C.J.C. Reason

Southern Africa extends from the equator to about 34°S and is essentially a narrow, peninsular land mass bordered to its south, west, and east by oceans. Its termination in the mid-ocean subtropics has important consequences for regional climate, since it allows the strongest western boundary current in the world ocean (warm Agulhas Current) to be in close proximity to an intense eastern boundary upwelling current (cold Benguela Current). Unlike other western boundary currents, the Agulhas retroflects south of the land mass and flows back into the South Indian Ocean, thereby leading to a large area of anomalously warm water south of South Africa which may influence storm development over the southern part of the land mass. Two other unique regional ocean features imprint on the climate of southern Africa—the Angola-Benguela Frontal Zone (ABFZ) and the Seychelles-Chagos thermocline ridge (SCTR). The former is important for the development of Benguela Niños and flood events over southwestern Africa, while the SCTR influences Madden-Julian Oscillation and tropical cyclone activity in the western Indian Ocean. In addition to South Atlantic and South Indian Ocean influences, there are climatic implications of the neighboring Southern Ocean. Along with Benguela Niños, the southern African climate is strongly impacted by ENSO and to lesser extent by the Southern Annular Mode (SAM) and sea-surface temperature (SST) dipole events in the Indian and South Atlantic Oceans. The regional land–sea distribution leads to a highly variable climate on a range of scales that is still not well understood due to its complexity and its sensitivity to a number of different drivers. Strong and variable gradients in surface characteristics exist not only in the neighboring oceans but also in several aspects of the land mass, and these all influence the regional climate and its interactions with climate modes of variability. Much of the interior of southern Africa consists of a plateau 1 to 1.5 km high and a narrow coastal belt that is particularly mountainous in South Africa, leading to sharp topographic gradients. The topography is able to influence the track and development of many weather systems, leading to marked gradients in rainfall and vegetation across southern Africa. The presence of the large island of Madagascar, itself a region of strong topographic and rainfall gradients, has consequences for the climate of the mainland by reducing the impact of the moist trade winds on the Mozambique coast and the likelihood of tropical cyclone landfall there. It is also likely that at least some of the relativity aridity of the Limpopo region in northern South Africa/southern Zimbabwe results from the location of Madagascar in the southwestern Indian Ocean. While leading to challenges in understanding its climate variability and change, the complex geography of southern Africa offers a very useful test bed for improving the global models used in many institutions for climate prediction. Thus, research into the relative shortcomings of the models in the southern African region may lead not only to better understanding of southern African climate but also to enhanced capability to predict climate globally.


Climate of the Free Troposphere and Mountain Peaks  

Stefan Brönnimann

The free troposphere is the location of important weather and climate processes. Here, horizontal and vertical transport of energy, mass, and momentum take place, and it holds greenhouse gases, water vapor, and clouds. The free troposphere therefore plays an important role in global climate feedback processes. Mountains provide important ecosystem services for a large lowland population. Mountain ecosystems may react particularly strongly to climatic changes. This is because mountains intersect important environmental and geoecological boundaries such as the snow line and the tree line. In a changing climate, these boundaries may shift. Climate change thus affects mountain glaciers, water resources, and mountain ecosystems. Climates of mountains and of the free troposphere have attracted scientists of the enlightenment and have been studied scientifically at least since the 18th century. High-altitude observatories were installed in the late 19th century, and upper-air measurements were started soon afterwards. However, even in the early 21st century, the climate observing systems do not well cover mountain regions and specifically mountain peaks. The temperature of the free troposphere is dominated by horizontal and vertical transport of sensible and latent heat, condensation and release of latent heat, and radiation to space. Mountain peaks sometimes reach into the free troposphere, but at the same time also share characteristics of surface climate. They are strongly influenced by radiative processes of the surrounding surface, while during the day they are often within the atmospheric boundary layer. With respect to climate change, temperature trends are amplified in the tropical upper-troposphere relative to the surface due to latent heat release, while in the Arctic the surface warms faster than the free atmosphere due to strong inversions and due to feedback processes operating at the surface. Mountain peaks may see both types of amplification. Several processes have been suggested to cause an elevation dependent warming, the most important of which arguably is the snow-albedo feedback. Elevation dependent warming is also seen in model studies and in observations, although detecting this signal in observations turns out rather difficult outside the tropics due to high variability and sometimes low-data quality. The observed climatic changes are expected to continue into the future.


Climate of the Mediterranean Region  

Ricardo García-Herrera and David Barriopedro

The Mediterranean is a semi-enclosed sea surrounded by Europe to the north, Asia to the east, and Africa to the south. It covers an area of approximately 2.5 million km2, between 30–46 °N latitude and 6 °W and 36 °E longitude. The term Mediterranean climate is applied beyond the Mediterranean region itself and has been used since the early 20th century to classify other regions of the world, such as California or South Africa, usually located in the 30º–40º latitudinal band. The Mediterranean climate can be broadly characterized by warm to hot dry summers and mild wet winters. However, this broad picture hides important variations, which can be explained through the existence of two geographical gradients: North/South, with a warmer and drier south, and West/East, more influenced by Atlantic/Asian circulation. The region is located at a crossroad between the mid-latitudes and the subtropical regimes. Thus, small changes in the Atlantic storm track may lead to dramatic changes in the precipitation of the northwestern area of the basin. The variability of the descending northern branch of the Hadley cell influences the climate of the southern margin, while the eastern border climate is conditioned by the Siberian High in winter and the Indian Summer Monsoon during summer. All these large-scale factors are modulated by the complex orography of the region, the contrasting albedo, and the moisture and heat supplied by the Mediterranean Sea. The interactions occurring among all these factors lead to a complex picture with some relevant phenomena characteristic of the Mediterranean region, such as heatwaves and droughts, Saharan dust intrusions, or specific types of cyclogenesis. Climate model projections generally agree in characterizing the region as a climate change hotspot, considering that it is one of the areas of the globe likely to suffer pronounced climate changes. Anthropogenic influences are not new, since the region is densely populated and is the home of some the oldest civilizations on Earth. This has produced multiple and continuous modifications in the land cover, with measurable impacts on climate that can be traced from the rich available documentary evidence and high-resolution natural proxies.


Climate of the Sahel and West Africa  

Sharon E. Nicholson

This article provides an in-depth look at all aspects of the climate of the Sahel, including the pervasive dust in the Sahelian atmosphere. Emphasis is on two aspects: West African monsoon and the region’s rainfall regime. This includes an overview of the prevailing atmospheric circulation at the surface and aloft and the relationship between this and the rainfall regime. Aspects of the rainfall regime that are considered include its unique characteristics, its changes over time, the storm systems that produce rainfall, and factors governing its variability on interannual and decadal time scales. Variability is examined on three time scales: millennial (as seen is the paleo records of the last 20,000 years), multi-decadal (as seen over the last few centuries as seen from proxy data and, more recently, in observations), and interannual to decadal (quantified by observations from the late 19th century and onward). A unique feature of Sahel climate is that is rainfall regime is perhaps the most sensitive in the world and this sensitivity is apparent on all of these time scales.


Climate of Western and Central Equatorial Africa  

Amin Dezfuli

Western and Central Equatorial Africa (WCEA), home to the Congo rainforests, is the green heart of the otherwise dry continent of Africa. Despite its crucial role in the Earth system, WCEA’s climate variability has received little attention compared to the rest of Africa. Climate variability in the region is a result of complex interactions among various features acting on local and global scales. The mesoscale convective systems (MCSs) that have a preferentially westward propagation and present a distinct diurnal cycle are the main source of rainfall in the region. As a result of strong MCS activity, WCEA stands out as a convective anomaly within the tropics and experiences the world’s most intense thunderstorms as well as the highest lightning flash rates. The moisture of the region is supplied primarily from the Atlantic Ocean, with additional contributions from local recycling and East Africa. WCEA, in turn, serves as a moisture source for other parts of the continent. One striking characteristic of WCEA is its intrinsic heterogeneity with respect to interannual variability of rainfall, resulting in delineation of the region primarily in the zonal direction. This is in contrast to the meridionally oriented spatial variability of the annual cycle and underlines the fact that driving factors of the two can be quite different. The annual cycle is mainly determined by the seasonal excursion of the sun. However, the interannual and intraseasonal variability of the region are modulated by remote forcings from all three oceans, reflected via zonal atmospheric cells and equatorial wave dynamics. The local atmospheric jets and regional Walker-like circulations also contribute to WCEA’s climate variability by modulating the moisture transport and vertical motion. The region has experienced an increasing rate of deforestation in recent decades and has made a significant contribution to the global biomass burning emissions that can alter regional and global circulation, along with energy and water cycles. The mean annual temperature of the region has increased by about 1°C in the past 70 years. The annual rainfall over the same period presents a negative trend, though that is quite negligible in the eastern sector of the region.


Climate Policy and Governance across Africa  

Opha Pauline Dube

This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Climate Science. Please check back later for the full article. Africa, a continent with the largest number of countries falling under the category of Least Developed Countries (LDCs), remains highly dependent on rain-fed agriculture that suffers from low intake of water, exacerbating the vulnerability to climate variability and anthropogenic climate change. The increasing frequency and severity of climate extremes impose major strains on the economies of these countries. The loss of livelihoods due to interaction of climate change with existing stressors is elevating internal and cross-border migration. The continent is experiencing rapid urbanization, and its cities represent the most vulnerable locations to climate change due in part to incapacitated local governance. Overall, the institutional capacity to coordinate, regulate, and facilitate development in Africa is weak. The general public is less empowered to hold government accountable. The rule of law, media, and other watchdog organizations, and systems of checks and balances are constrained in different ways, contributing to poor governance and resulting in low capacity to respond to climate risks. As a result, climate policy and governance are inseparable in Africa, and capacitating the government is as essential as establishing climate policy. With the highest level of vulnerability to climate change compared with the rest of the world, governance in Africa is pivotal in crafting and implementing viable climate policies. It is indisputable that African climate policy should focus first and foremost on adaptation to climate change. It is pertinent, therefore, to assess Africa’s governance ability to identify and address the continent’s needs for adaptation. One key aspect of effective climate policy is access to up-to-date and contextually relevant information that encompasses indigenous knowledge. African countries have endeavored to meet international requirements for reports such as the National Communications on Climate Change Impacts and Vulnerabilities and the National Adaptation Programmes of Action (NAPAs). However, the capacity to deliver on-time quality reports is lacking; also the implementation, in particular integration of adaptation plans into the overall development agenda, remains a challenge. There are a few successes, but overall adaptation operates mainly at project level. Furthermore, the capacity to access and effectively utilize availed international resources, such as extra funding or technology transfer, is limited in Africa. While the continent is an insignificant source of emissions on a global scale, a more forward looking climate policy would require integrating adaptation with mitigation to put in place a foundation for transformation of the development agenda, towards a low carbon driven economy. Such a futuristic approach calls for a comprehensive and robust climate policy governance that goes beyond climate to embrace the Sustainable Development Goals Agenda 2030. Both governance and climate policy in Africa will need to be viewed broadly, encompassing the process of globalization, which has paved the way to a new geological epoch, the Anthropocene. The question is, what should be the focus of climate policy and governance across Africa under the Anthropocene era?


Syukuro Manabe: Recipient of Nobel Prize in Physics 2021  

Antonio Navarra

Syukuro Manabe was awarded the Nobel Prize in Physics in 2021 for his work on climate modeling. The Prize recognizes an exceptional career that pioneered a new area of the scientific enterprise revealing the power of numerical simulations and methods for advancing scientific discovery and producing new knowledge. Manabe contributed decisively to the creation of the modern scientific discipline of climate science through numerical modeling, stressing clarity of ideas and simplicity of approach. He described in no uncertain terms the role of greenhouse gases in the atmosphere and the impact of changes in the radiation balance of the atmosphere caused by the anthropogenic increase of such gases, and he revealed the role of water vapor in the greenhouse effect. He also understood the importance of including all the components of the climate system (the oceans, sea ice, and land surface) to reach a comprehensive treatment of the mechanisms of climate in a general circulation model, paving the way to the modern earth system models and the establishment of climate modeling as a leading scientific discipline.


Climatic Changes and Cultural Responses During the African Humid Period Recorded in Multi-Proxy Data  

David McGee and Peter B. deMenocal

The expansion and intensification of summer monsoon precipitation in North and East Africa during the African Humid Period (AHP; c. 15,000–5,000 years before present) is recorded by a wide range of natural archives, including lake and marine sediments, animal and plant remains, and human archaeological remnants. Collectively this diverse proxy evidence provides a detailed portrait of environmental changes during the AHP, illuminating the mechanisms, temporal and spatial evolution, and cultural impacts of this remarkable period of monsoon expansion across the vast expanse of North and East Africa. The AHP corresponds to a period of high local summer insolation due to orbital precession that peaked at ~11–10 ka, and it is the most recent of many such precessionally paced pluvial periods over the last several million years. Low-latitude sites in the North African tropics and Sahel record an intensification of summer monsoon precipitation at ~15 ka, associated with both rising summer insolation and an abrupt warming of the high northern latitudes at this time. Following a weakening of monsoon strength during the Younger Dryas cold period (12.9–11.7 ka), proxy data point to peak intensification of the West African monsoon between 10–8 ka. These data document lake and wetland expansions throughout almost all of North Africa, expansion of grasslands, shrubs and even some tropical trees throughout much of the Sahara, increases in Nile and Niger River runoff, and proliferation of human settlements across the modern Sahara. The AHP was also marked by a pronounced reduction in windblown mineral dust emissions from the Sahara. Proxy data suggest a time-transgressive end of the AHP, as sites in the northern and eastern Sahara become arid after 8–7 ka, while sites closer to the equator became arid later, between 5–3 ka. Locally abrupt drops in precipitation or monsoon strength appear to have been superimposed on this gradual, insolation-paced decline, with several sites to the north and east of the modern arid/semi-arid boundary showing evidence of century-scale shifts to drier conditions around 5 ka. This abrupt drying appears synchronous with rapid depopulation of the North African interior and an increase in settlement along the Nile River, suggesting a relationship between the end of the AHP and the establishment of proto-pharaonic culture. Proxy data from the AHP provide an important testing ground for model simulations of mid-Holocene climate. Comparisons with proxy-based precipitation estimates have long indicated that mid-Holocene simulations by general circulation models substantially underestimate the documented expansion of the West African monsoon during the AHP. Proxy data point to potential feedbacks that may have played key roles in amplifying monsoon expansion during the AHP, including changes in vegetation cover, lake surface area, and mineral dust loading. This article also highlights key areas for future research. Among these are the role of land surface and mineral aerosol changes in amplifying West African monsoon variability; the nature and drivers of monsoon variability during the AHP; the response of human populations to the end of the AHP; and understanding locally abrupt drying at the end of the AHP.


Climatic Determinism and the Conceptualization of the Tropics in British India  

Rituparna Ray Chowdhury

The geographic concept of tropicality emerged as an operative tool in the colonizing efforts of the European powers in the 18th and 19th centuries. Since the colonizing encounters proved fatal for many Europeans in South Asia, particularly during the initial phase of settlement when their mortality rate was far higher than that of the natives, attempts were made to understand the impact of the tropical climate upon the Western constitution. Based on the ancient Hippocratic doctrines of humoral pathology and the narrative of Enlightenment thinkers, colonial medical professionals endeavored to determine a correlation between health and environment. According to Western classical understanding, health was dependent upon various climatic and environmental factors. With the prevailing perception that the oppressive climatic conditions of India and its hazardous disease-infused environs were inimical to the survival of the Anglo-Indians in South Asia, the ancient concept of climatic determinism was revitalized during the colonial period. This theory, which argued that people tended to resemble the dominant characteristics of the climate in which they lived, proved convenient at a time of aggressive expansion, when moral grounds were required for justifying the Western designs of conquest and exploitation. Explanations like environmental determinism encouraged conjectures that the tropical climate of India bred only “lazy” and “degenerative” people, in contrast to the “manly” and “strong” individuals of the temperate zone. This notion, with its insidious veneer of rationality, facilitated a justification of the ideology of imperial colonization, while also discouraging permanent settlement of the European colonizers upon Indian soil.


Clustering Techniques in Climate Analysis  

David M. Straus

This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Climate Science. Please check back later for the full article. Clustering techniques are used in the analysis of weather and climate to identify distinct, discrete groups of atmospheric and oceanic structures and evolutions from observations, reanalyses, and numerical model simulations and predictions. The goal of cluster analysis is to provide physical insight into states (and trajectories) that are preferred and also possibly unusually persistent, when such states can be identified and distinguished from the continuous background distribution of geophysical variables. “Preferred” states (or evolutions) are those that are significantly more likely to occur than would be predicted by a suitable background distribution (such as a multivariate Gaussian distribution), while “persistent” states are those with lifetimes distinctly longer than those of the background states. The choice of technique depends to a large extent on its application. For example, the identification of a small number of distinct patterns of the seasonal mean mid-latitude response to large seasonal mean shifts in tropical diabatic heating (perhaps due to the El Niño–Southern Oscillation) can be accomplished with the use of either a partitioning or hierarchical cluster analysis. The partitioning cluster method groups all states (maps of a given variable) into clusters so as to minimize the within-cluster variance, while the hierarchical analysis merges fields into groups based on their similarities. The identification of preferred patterns (whether or not they are tropically forced) on intra-seasonal time scales can also be accomplished in this way. The partitioning approach can easily be adapted to include multiple variables, and to describe tracks of localized features (such as cyclones). A variant of the partitioning cluster analysis, the “self -organizing map” approach, allows for a greater richness in cluster patterns and so can be useful on shorter, weather-related time scales. In either the partitioning or hierarchical analysis, each state (map) is identified uniquely with a given cluster. However, in certain applications it may be desirable to allow a given state to belong to multiple clusters with differing probabilities. In such cases one can estimate the underlying probability distribution function with a mixture model, which is a sum of a (usually small) number of component multivariate Gaussian distributions. The partitioning, hierarchical, and mixture model approaches, applied to a sequence of maps, all have one common feature: the sequencing (order in time) of the maps is not taken into account. This is not the case with the hidden Markov method, an approach that identifies not only preferred states but ones that are also unusually persistent. This approach, based on a simple neural network approach, makes use of an underlying “hidden variable” whose evolution is modeled by a Markov process. Each state is assigned to a number of clusters with a certain probability, but the most likely evolution of states from one cluster to another can be estimated. This approach can be generalized by letting the evolution of the hidden state be governed by a nonstationary multivariate autoregressive factor process. The resulting cluster analysis can then also detect long-term changes in the population of the clusters.


CO₂ in the Atmosphere: Growth and Trends Since 1850  

Michel Ramonet, Abhishek Chatterjee, Philippe Ciais, Ingeborg Levin, Mahesh Kumar Sha, Martin Steinbacher, and Colm Sweeney

Very accurate long-term measurements of atmospheric CO2 concentrationsbi are needed to understand the role of human activities on the greenhouse effect, as well as the interactions between anthropogenic emissions and the natural carbon cycle. Knowledge of the carbon cycle has been acquired through the development describes the development of atmospheric measurement networks and methods for measuring CO2 in the atmosphere, including the measurement of CO2 in air bubbles extracted from ice cores, the emergence of precise in situ measurements at the beginning of the 1960s, and the operational networks now deployed in certain parts of the world. The surface network of atmospheric stations where CO2 is measured, either in air samples or by in situ instrumentation, made up of about 150 monitoring sites, supplemented by airborne measurements on board of research and commercial aircrafts, is coordinated by international projects aimed at guaranteeing a long-term measurement compatibility to within approximately 0.025‰ (0.1 ppm). This level of accuracy is necessary to characterize atmospheric signals such as the long-term trend, which has risen in 60 years from 1 to 2.2 ppm/year, but also the interannual, seasonal, and regional variations of CO2. These atmospheric signals provide unique information about natural biogeochemical cycles and their current disturbance. The additional measurement of radiocarbon in atmospheric CO2, as described in this article, also makes it possible to identify the contribution due to fossil fuel CO2 emissions. The logistics and metrological requirements of in situ measurements mean that the monitoring network only covers the globe very incompletely—hence the importance of satellite observations, which have been developing strongly since their emergence in the early 2000s. Recent space-based CO2 observations make it possible to measure the concentration of CO2 averaged in the atmospheric column with global coverage under cloud-free conditions, providing millions of measurements each year, with a precision that can now reach 1 ppm, thus 10 times less than in situ instrumentation. Similar measurements of total CO2 columns are also made by ground-based remote sensing instruments, at about 100 sites over the world. They provide important reference data to evaluate atmospheric CO2 measurements from satellites and, in combination with in situ measurements of vertical profiles, provide a transfer standard between the satellite measurements and ground-based in situ networks. This article provides an overview of CO2 monitoring programs and what they tell about large-scale biogeochemical change. The perspectives for the development of CO2 observations are important both for surface networks and for space-based observations, with the objective of moving toward the characterization of processes at increasingly fine spatial scales, in particular toward urban emissions.


CO2 in the Surface Ocean  

Peter Landschützer

The global ocean comprises a significant sink for human-emitted carbon dioxide, yet many different processes are at play, causing strong spatial and temporal variations in the distribution of the sea surface pCO2 and the resulting air-sea CO2 fluxes. While dominated by the temperature-driven solubility, physical transport and biogeochemistry, the increase in the sea surface CO2 partial pressure over the past decades is closely following the increase in atmospheric CO2, resulting in a decreasing pH and decreasing saturation states of calcite and aragonite minerals. Despite the increasing abundance of novel data interpolation tools, e.g. based on machine learning, the heterogeneous distribution of CO2 in the surface ocean requires a dense observing network to reconstruct global change.


Cognitive Biases, Non-Rational Judgments, and Public Perceptions of Climate Change  

Lisa Zaval and James F. M. Cornwell

In recent years, scientists have identified cognitive processes that short-circuit our deliberative faculties. In the domain of climate change in particular, a number of psychological barriers and biases may disrupt typical discourse and reflection and may even prevent those who are aware of climate change from taking action to mitigate or reduce its impact. These processes include the use of heuristic versions of calculation-based decisions to reduce processing load, which can make climate change judgments responsive to situational factors in the immediate decision context. Recent research in the decision sciences provides insight into how common biases in judgment inhibit rational deliberation about climate change, which may lead to the gap between society’s recognition of environmental problems and society’s frequent failure to address them appropriately. These insights involve the finite nature of human attention and cognitive resources, the complex interactions of personal experience and emotion, the challenges that uncertainty and risk place on behavior, and the profoundly social nature of human action. Understanding these barriers and systematic biases have led to a set of potential interventions, which demonstrate how practitioners can put research insights into practice in order to address a variety of sustainability challenges. One important direction for these interventions involves changing the decision context in ways that account for decision bias (e.g., using green defaults) and triggering more adaptive decisions as a result.


Communicating about Biodiversity, Public Engagement, and Climate Change  

Mikko Rask and Richard Worthington

The term public engagement (PE) refers to processes that provide a distinct role for citizens or stakeholder groups in policymaking. Such engagement is distinctive because it aims to create opportunities for mutual learning among policymakers, scientists, stakeholders, and members of the public. In so doing, PE involves a particular type of voice in public debate and policymaking that is different from more established discourses, such as those expressed through official policymaking channels, scientific institutions, civil society activists, or the public media. By the early 1970s, PE had emerged in the context of an overall democratization movement in Western societies through such innovations as the “citizen jury” in the United States and “planning cells” in Germany. Today, it is often more pragmatically motivated, such as in the European Commission, where PE is seen as a tool for responsible research and innovation that helps to anticipate and assess potential implications and societal expectations of research and innovation, as well as to design more inclusive and sustainable research policies. The first global PE processes in history were created to incorporate citizen voices into United Nations (UN) conventions on biodiversity and climate change. Building on theories of deliberative democracy and tested PE practices, a new World Wide Views process was developed to provide informed and considered input from ordinary citizens to the 2009 UN climate summit. This and subsequent World Wide Views (WWViews) deliberations have demonstrated that PE may potentially open up policy discourses that are constricted and obfuscated by organized interests. A telling example is provided by the World Wide Views on Climate and Energy deliberation held on June 5, 2015, where nearly 10,000 ordinary citizens gathered in 76 countries to consider and express their views on the issues to be addressed at the UN climate summit in Paris later that year. In a noteworthy departure from prevailing media and policy discourses, two-thirds of the participating citizens saw measures to fight climate change as “mostly an opportunity to improve our quality of life,” while only a quarter saw them as “mostly a threat to our quality of life,” a result that was consistent across high-, middle-, and low-income countries. Recent research on PE has indicated that when effectively implemented, such processes can increase the legitimacy, quality, and capacity of decision-making. Earlier aspirations for broader impacts, such as the democratization of policymaking at all levels, are now less prominent but arguably indispensable for achieving both immediate and longer-range goals. The relatively new concept of a deliberative system captures this complexity by moving beyond the narrow focus on single PE events encountered in much research to date, recognizing that single events rarely affect the course of policymaking. The evolving prospects for PE in biodiversity and climate change policy, therefore, can be seen as requiring ongoing improvements in the capacities of the deliberative system.


Communicating about Biofuels and Climate Change  

Michael A. Cacciatore

Biofuels are produced from biomass, which is any organic matter that can be burned or otherwise used to produce heat or energy. While not a new technology—biofuels have been around for well over 100 years—they are experiencing something of a renaissance in the United States and other countries across the globe. Today, biofuels have become the single most common alternative energy source in the U.S. transportation sector with billions of gallons of the fuel produced annually. The expansion of the bio-based economy in recent years has been intertwined with mounting concerns about environmental pollution and the accumulation of carbon dioxide (CO2) in the earth’s atmosphere. In the United States, for example, biofuels mandates have been championed as key to solving not only the country’s increasing energy demand problems and reliance on foreign oil, but also growing fears about global climate change. Of course, the use of biomass and biofuels to combat global climate change has been highly controversial. While proponents argue that biofuels burn cleaner than gasoline, research has suggested that any reductions in CO2 emissions are offset by land use considerations and the energy required in the biofuels-production process. How publics perceive of climate change as a problem and the use of biomass and biofuels as potential solutions will go a long way toward determining the policies that government’s implement to address this issue.


Communicating about Carbon Capture and Storage  

Amanda Boyd

Carbon capture and storage (CCS) has emerged as a potential strategy for reducing greenhouse gas (GHG) emissions. It involves the capture of carbon dioxide (CO2) emissions from large point source emitters, such as coal-fired power plants. The CO2 is transported to a storage location, where it is isolated from the atmosphere in stable underground reservoirs. CCS technology has been particularly intriguing to countries that utilize fossil fuels for energy production and are seeking ways to reduce their GHG emissions. While there has been an increase in technological development and research in CCS, some members of the public, industry, and policymakers regard the technology as controversial. Some proponents see CCS as a climate change mitigation technology that will be essential to reducing CO2 emissions. Others view CCS as an environmentally risky, complex, and expensive technology that is resource-intensive, promotes the continued extraction of fossil fuels, and competes with renewable energy investments. Effective communication about CCS begins with understanding the perceptions of the general public and individuals living in the communities where CCS projects are sited or proposed. Most people may never live near a CCS site, but may be concerned about risks, such as the cost of development, environmental impacts, and competition with renewable energy sources. Those who live near proposed or operational projects are likely to have a strong impact on the development and deployment of CCS. Individuals in locally affected communities may be more concerned about disruptions to sense of place, impact on jobs or economy, or effect on local health and environment. Effective communication about the risks and benefits of CCS has been recognized as a critical factor in the deployment of this technology.


Communicating about Carbon Taxes and Emissions Trading Programs  

Erick Lachapelle

In debates surrounding policy options for mitigating greenhouse gas (GHG) emissions, economists of various political stripes are near unanimous in their advocacy of putting a price on carbon, whether through a tax or emissions trading program. Due to the visible costs imposed on industry and consumers, however, these policies have been resisted by carbon-intensive industries and by an ideologically divided public, producing incentives for vote-seeking politicians to avoid implementing comprehensive and stringent carbon prices within their own borders. In this highly politicized environment, and considering the more recent diffusion of market-based instruments across political jurisdictions around the world, researchers have sought to identify the conditions most favorable to implementing carbon taxes and cap-and-trade programs, the correlates of public support for these policies, and the extent to which different communication strategies may help build public support. How do experts, political leaders, and members of the public understand these policy instruments, and what specific approaches have been most successful in persuading policy makers and the public to support a price on carbon? In places that have yet to implement a carbon price, what can communication strategists learn from existing research and the experience of other jurisdictions where such policies have been successfully implemented? In places where carbon taxes or carbon cap-and-trade programs exist, how are the benefits of these policies best communicated to ensure the durability of carbon pricing policies over time?


Communicating About Clean Energy and Efficiency Policies  

Matthew A. Shapiro, Toby Bolsen, and Anna McCaghren Fleming

Public opinion plays a central role in determining the feasibility of efforts to transform energy systems in the coming years, yet scholarship on communication effects and public opinion about clean energy and energy efficiency seems to have expanded only relatively recently. There is a growing body of work that explores how targeted and strategically framed messages affect individuals’ beliefs and motivations to act on matters affecting household energy choices as well as energy policies. One must attend particularly to the principal communication-based factors that shape the public’s understanding of clean energy sources and promote efficiencies in energy use. To better understand the communication vehicles for improving both household energy efficiency and conservation, two research foci are most relevant: (1) field experiments that primarily assess how household energy consumption shifts after receiving energy consumption reports and (2) surveys/laboratory experiments that focus on the nuances of energy-related communications, paying particular attention to the role of politics and ideology. This bimodal classification of clean energy and efficiency communication research genres is not exhaustive but can be synthesized into two major contributions. First, providing households with information about specific benefits that would result from a greater reliance on clean energy may increase support for its development and move individuals toward energy efficiency outcomes; however, exposure to counter-messages that emphasize costs associated with clean energy and the associated policies can negate the effects of pro-clean energy messages. Second, there is still no reprieve from the politicization of energy, and thus the role of partisanship and motivated reasoning must be accounted for when assessing how individuals modify their decision-making processes regarding energy efficiency.


Communicating About Climate Change, Natural Gas Development, and “Fracking”: U.S. and International Perspectives  

Christopher E. Clarke, Dylan Budgen, Darrick T.N. Evensen, Richard C. Stedman, Hilary S. Boudet, and Jeffrey B. Jacquet

The impacts associated with unconventional natural gas development (UGD) via hydraulic fracturing have generated considerable controversy and introduced terms such as “fracking” into the public lexicon. From a climate change perspective, transitioning from fossil fuels to renewable sources in order to potentially avoid the worst consequences of a warming planet will need to also consider the climate implications of increased UGD and natural gas use that follows. Specifically, how much greenhouse gas is emitted as natural gas is extracted, transported, and consumed relative to other energy sources? Is UGD a “cleaner” energy source? Compared to what? Does it postpone or “bridge” the transition from fossil fuels to renewable energy? Public perception of UGD’s climate impacts not only reflect individual attitudes but broader social discourse among stakeholder groups. Understanding these perceptions, their psychological and social factors antecedents, and how to engage audiences on this topic will play a key role in UGD’s long-term trajectory, especially as it relates to climate change. An added challenge is that most public opinion studies specific to UGD’s climate impacts (and indeed UGD in general) are limited to the United States, Canada, and a few countries in Europe and Africa, with other parts of the world entirely absent. Nonetheless, the studies that do exist highlight several common themes. In particular, UGD tends to be viewed as cleaner relative to fossil fuels because of the belief it produces less carbon emissions as a result of natural gas extraction and consumption. However, it tends to be viewed as dirtier relative to renewables amid the belief that it increases carbon emissions. This finding complements research showing that natural gas occupies a middle ground between renewables and other fossil fuels in terms of acceptance. Moreover, the extent UGD serves as a bridge energy source remains contentious, with some arguing that it and the natural gas it produces complement fossil fuels and facilitates a transition to renewables, while others claim that UGD entrenches society’s continued reliance on the former. Overall, despite the contentious nature of these issues, UGD’s climate impacts appear less salient across countries than other health, environmental, and economic impacts, perhaps because they are psychologically distant and difficult to experience directly. Amid efforts to convey the public health risks associated with a changing climate, we believe that emphasizing the public health dimensions of UGD’s climate impacts can potentially make them more psychologically tangible. Positively framed messages emphasize that reducing carbon emissions tied to both unconventional natural gas extraction and natural gas consumption (relative to other fossil fuels) and thus mitigating the resultant climate change that follows benefits public health. Conversely, negatively framed messages emphasize that increasing carbon emissions (relative to renewables) and thus amplifying the resultant climate change adversely affects public health. At present, though, there is little evidence as to how these messages affect the perceived connection between UGD’s climate impacts and public health and, in turn, support for UGD versus other energy types. Nor is it clear how these outcomes may vary across countries based on public sentiment toward UGD and climate change along with a variety of psychological and social factors that influence such sentiment. Data available for some countries offers tantalizing scenarios, but we remain limited due to the lack of social science research in countries outside the United States and a handful of others. We call for cross-national comparative studies that include places where UGD—and social science research on it—is still maturing.