1-20 of 57 Results

Article

Bjørn H. Samset

Among the factors that affect the climate, few are as diverse and challenging to understand as aerosols. Minute particles suspended in the atmosphere, aerosols are emitted through a wide range of natural and industrial processes, and are transported around the globe by winds and weather. Once airborne, they affect the climate both directly, through scattering and absorption of solar radiation, and indirectly, through their impact on cloud properties. Combining all their effects, anthropogenic changes to aerosol concentrations are estimated to have had a climate impact over the industrial era that is second only to CO2. Their atmospheric lifetime of only a few days, however, makes their climate effects substantially different from those of well-mixed greenhouse gases. Major aerosol types include sea salt, dust, sulfate compounds, and black carbon—or soot—from incomplete combustion. Of these, most scatter incoming sunlight back to space, and thus mainly cool the climate. Black carbon, however, absorbs sunlight, and therefore acts as a heating agent much like a greenhouse gas. Furthermore, aerosols can act as cloud condensation nuclei, causing clouds to become whiter—and thus more reflecting—further cooling the surface. Black carbon is again a special case, acting to change the stability of the atmosphere through local heating of the upper air, and also changing the albedo of the surface when it is deposited on snow and ice, for example. The wide range of climate interactions that aerosols have, and the fact that their distribution depends on the weather at the time and location of emission, lead to large uncertainties in the scientific assessment of their impact. This in turn leads to uncertainties in our present understanding of the climate sensitivity, because while aerosols have predominantly acted to oppose 20th-century global warming by greenhouse gases, the magnitude of aerosol effects on climate is highly uncertain. Finally, aerosols are important for large-scale climate events such as major volcanoes, or the threat of nuclear winter. The relative ease with which they can be produced and distributed has led to suggestions for using targeted aerosol emissions to counteract global warming—so-called climate engineering.

Article

Global climate models (GCM) are fundamental tools for weather forecasting and climate predictions at different time scales, from intraseasonal prediction to climate change projections. Their design allows GCMs to simulate the global climate adequately, but they are not able to skillfully simulate local/regional climates. Consequently, downscaling and bias correction methods are increasingly needed and applied for generating useful local and regional climate information from the coarse GCM resolution. Empirical-statistical downscaling (ESD) methods generate climate information at the local scale or with a greater resolution than that achieved by GCM by means of empirical or statistical relationships between large-scale atmospheric variables and the local observed climate. As a counterpart approach, dynamical downscaling is based on regional climate models that simulate regional climate processes with a greater spatial resolution, using GCM fields as initial or boundary conditions. Various ESD methods can be classified according to different criteria, depending on their approach, implementation, and application. In general terms, ESD methods can be categorized into subgroups that include transfer functions or regression models (either linear or nonlinear), weather generators, and weather typing methods and analogs. Although these methods can be grouped into different categories, they can also be combined to generate more sophisticated downscaling methods. In the last group, weather typing and analogs, the methods relate the occurrence of particular weather classes to local and regional weather conditions. In particular, the analog method is based on finding atmospheric states in the historical record that are similar to the atmospheric state on a given target day. Then, the corresponding historical local weather conditions are used to estimate local weather conditions on the target day. The analog method is a relatively simple technique that has been extensively used as a benchmark method in statistical downscaling applications. Of easy construction and applicability to any predictand variable, it has shown to perform as well as other more sophisticated methods. These attributes have inspired its application in diverse studies around the world that explore its ability to simulate different characteristics of regional climates.

Article

Michael Howlett and Stuti Rawat

Behavioral science consists of the systematic analysis of processes underlying human behavior through experimentation and observation, drawing on knowledge, research, and methods from a variety of fields such as economics, psychology, and sociology. Because policymaking involves efforts to modify or alter the behavior of policy-takers and centers on the processes of decision-making in government, it has always been concerned with behavioral psychology. Classic studies of decision-making in the field derived their frameworks and concepts from psychology, and the founder of policy sciences, Harold Lasswell, was himself trained as a behavioral political scientist. Hence, it should not be surprising that the use of behavioral science is a feature of many policy areas, including climate change policy. This is given extra emphasis, however, because climate change policymaking and the rise of climate change as a policy issue coincides with a resurgence in behaviorally inspired policy analysis and design brought about by the development of behavioral economics. Thus efforts to deal with climate change have come into being at a time when behavioral governance has been gaining traction worldwide under the influence of works by, among others, Kahneman and Tversky, Thaler, and Sunstein. Such behavioral governance studies have focused on the psychological and cognitive behavioral processes in individuals and collectives, in order to inform, design, and implement different modes of governing. They have been promoted by policy scholars, including many economists working in the area who prefer its insights to those put forward by classical or neoclassical economics. In the context of climate change policy, behavioral science plays two key roles—through its use of behaviorally premised policy instruments as new modes of public policy being used or proposed to be used, in conjunction with traditional climate change policy tools; and as a way of understanding some of the barriers to compliance and policy design encountered by governments in combating the “super wicked problem” of climate change. Five kinds of behavioral tools have been found to be most commonly used in relation to climate change policy: provision of information, use of social norms, goal setting, default rules, and framing. A large proportion of behavioral tools has been used in the energy sector, because of its importance in the context of climate change action and the fact that energy consumption is easy to monitor, thereby facilitating impact assessment.

Article

Benjamin F. Zaitchik

Humans have understood the importance of climate to human health since ancient times. In some cases, the connections appear to be obvious: a flood can cause drownings, a drought can lead to crop failure and hunger, and temperature extremes pose a risk of exposure. In other cases, the connections are veiled by complex or unobserved processes, such that the influence of climate on a disease epidemic or a conflict can be difficult to diagnose. In reality, however, all climate impacts on health are mediated by some combination of natural and human dynamics that cause individuals or populations to be vulnerable to the effects of a variable or changing climate. Understanding and managing negative health impacts of climate is a global challenge. The challenge is greater in regions with high poverty and weak institutions, however, and Africa is a continent where the health burden of climate is particularly acute. Observed climate variability in the modern era has been associated with widespread food insecurity, significant epidemics of infectious disease, and loss of life and livelihoods to climate extremes. Anthropogenic climate change is a further stress that has the potential to increase malnutrition, alter the distribution of diseases, and bring more frequent hydrological and temperature extremes to many regions across the continent. Skillful early warning systems and informed climate change adaptation strategies have the potential to enhance resilience to short-term climate variability and to buffer against negative impacts of climate change. But effective warnings and projections require both scientific and institutional capacity to address complex processes that are mediated by physical, ecological, and societal systems. Here the state of understanding climate impacts on health in Africa is summarized through a selective review that focuses on food security, infectious disease, and extreme events. The potential to apply scientific understanding to early warning and climate change projection is also considered.

Article

Hans von Storch, Katja Fennel, Jürgen Jensen, Kristy A. Lewis, Beate Ratter, Torsten Schlurmann, Thomas Wahl, and Wenyan Zhang

Coasts are those regions of the world where the land has an impact on the state of the sea, and that part of the land is in turn affected by the sea. This land–sea interaction may take various forms—geophysical, biological, chemical, sociocultural, and economic. Coasts are conditioned by specific regional conditions. These unique characteristics result, in heavily fragmented regional and disciplinary research agendas, among them geographers, meteorologists, oceanographers, coastal engineers, and a variety of social and cultural sciences. Coasts are regions where the effects and risks of climate impact societal and ecological life. Such occurrences as coastal flooding, storms, saltwater intrusion, invasive species, declining fish stocks, and coastal retreat and morphological change are challenging natural resource managers and local governments to mitigate these impacts. Societies are confronted with the challenge of dealing with these changes and hazards by developing appropriate cultural practices and technical measures. Key aspects and concepts of these dimensions are presented here and will be examined in more detail in the future to expand on their characteristics and significance.

Article

Philipp Schmidt-Thomé

Climate change adaptation is the ability of a society or a natural system to adjust to the (changing) conditions that support life in a certain climate region, including weather extremes in that region. The current discussion on climate change adaptation began in the 1990s, with the publication of the Assessment Reports of the Intergovernmental Panel on Climate Change (IPCC). Since the beginning of the 21st century, most countries, and many regions and municipalities have started to develop and implement climate change adaptation strategies and plans. But since the implementation of adaptation measures must be planned and conducted at the local level, a major challenge is to actually implement adaptation to climate change in practice. One challenge is that scientific results are mainly published on international or national levels, and political guidelines are written at transnational (e.g., European Union), national, or regional levels—these scientific results must be downscaled, interpreted, and adapted to local municipal or community levels. Needless to say, the challenges for implementation are also rooted in a large number of uncertainties, from long time spans to matters of scale, as well as in economic, political, and social interests. From a human perspective, climate change impacts occur rather slowly, while local decision makers are engaged with daily business over much shorter time spans. Among the obstacles to implementing adaptation measures to climate change are three major groups of uncertainties: (a) the uncertainties surrounding the development of our future climate, which include the exact climate sensitivity of anthropogenic greenhouse gas emissions, the reliability of emission scenarios and underlying storylines, and inherent uncertainties in climate models; (b) uncertainties about anthropogenically induced climate change impacts (e.g., long-term sea level changes, changing weather patterns, and extreme events); and (c) uncertainties about the future development of socioeconomic and political structures as well as legislative frameworks. Besides slow changes, such as changing sea levels and vegetation zones, extreme events (natural hazards) are a factor of major importance. Many societies and their socioeconomic systems are not properly adapted to their current climate zones (e.g., intensive agriculture in dry zones) or to extreme events (e.g., housing built in flood-prone areas). Adaptation measures can be successful only by gaining common societal agreement on their necessity and overall benefit. Ideally, climate change adaptation measures are combined with disaster risk reduction measures to enhance resilience on short, medium, and long time scales. The role of uncertainties and time horizons is addressed by developing climate change adaptation measures on community level and in close cooperation with local actors and stakeholders, focusing on strengthening resilience by addressing current and emerging vulnerability patterns. Successful adaptation measures are usually achieved by developing “no-regret” measures, in other words—measures that have at least one function of immediate social and/or economic benefit as well as long-term, future benefits. To identify socially acceptable and financially viable adaptation measures successfully, it is useful to employ participatory tools that give all involved parties and decision makers the possibility to engage in the process of identifying adaptation measures that best fit collective needs.

Article

Historic discussions of climate often suggested that it caused societies to have certain qualities. In the 19th-century, imperial representations of the world environment frequently “determined” the fate of peoples and places, a practice that has frequently been used to explain the largest patterns of political rivalry and the fates of empires and their struggles for dominance in world politics. In the 21st century, climate change has mostly reversed the causal logic in the reasoning about human–nature relationships and their geographies. The new thinking suggests that human decisions, at least those made by the rich and powerful with respect to the forms of energy that are used to power the global economy, are influencing future climate changes. Humans are now shaping the environment on a global scale, not the other way around. Despite the widespread acceptance of the 2015 Paris Agreement on climate-change action, numerous arguments about who should act and how they should do so to deal with climate change shape international negotiations. Differing viewpoints are in part a matter of geographical location and whether an economy is dependent on fossil-fuels revenue or subject to increasingly severe storms, droughts, or rising sea levels. These differences have made climate negotiations very difficult in the last couple of decades. Partly in response to these differences, the Paris Agreement devolves primary responsibility for climate policy to individual states rather than establish any other geopolitical arrangement. Apart from the outright denial that humanity is a factor in climate change, arguments about whether climate change causes conflict and how security policies should engage climate change also partly shape contemporary geopolitical agendas. Despite climate-change deniers, in the Trump administration in particular, in the aftermath of the Paris Agreement, climate change is understood increasingly as part of a planetary transformation that has been set in motion by industrial activity and the rise of a global fossil-fuel-powered economy. But this is about more than just climate change. The larger earth-system science discussion of transformation, which can be encapsulated in the use of the term “Anthropocene” for the new geological circumstances of the biosphere, is starting to shape the geopolitics of climate change just as new political actors are beginning to have an influence on climate politics.

Article

Glaciers are probably the most obvious features of Earth’s changing climate. They enable one to see the effects of a warming or a cooling of the atmosphere by landscape changes on time scales short enough to be perceived or recognized by humans. However, the relationship between a retreating and advancing glacier and the climate is not linear, as glacier flow can filter the direct signal of the climate. Thus, glaciers can advance during periods of warming or, vice versa, retreat during periods of cooling. In fact, it is the mass change of the glacier (i.e., the mass balance) that directly links the glacier reaction to an atmospheric signal. The mechanism-based understanding of the relationship between the changing climate and glacier reaction received important and significant momentum from the science of the Alpine region. This strong momentum from the Alps has to do with the well-established science tradition in Europe in the 19th and beginning of the 20th century, which resulted in a series of important inventions to measure climate and glacier properties. Even at that time, knowledge was gained that is still valid in the early 21st century (e.g., the climate is changing and fluctuating; glacier changes are caused by changing climate; and the ice age was the result of shifting climate). Above all others, Albrecht Penck and Eduard Brückner were the key scientists in this blossoming era of glacier climatology. Interest in a better understanding of the relationship of climate to glaciers was not only driven by curiosity, but also by several impacts of glaciers on human life in the Alps. Investigations of climate–glacier relationships in the Alps began with the expiration of the Little Ice Age (LIA) period when glaciers were particularly large but began to retreat significantly. Observations of post-LIA glacier front positions showed a sharp decline after their maximum extent in about 1850 until the turn of the 19th to 20th centuries, when they began to grow and advance again. They were also forming a prominent moraine around 1920, which was, however, far behind the 1850 extent. Interestingly, climate time series of the post LIA period show a general long-term cooling of summer temperatures and several decades of precipitation deficit in the second half of the 19th century. Thus, the retreat forced by climate changes cannot be simply explained by increasing air temperatures, though calibrated glacier mass balance models are able to simulate this period quite well. Additional effects related to the albedo could be a source for a better understanding. From 1920 onward, the climate moved into a period of warm and high-sunshine summers, which peaked in the 1940s until 1950. Glaciers started again to melt strongly and related discharges of pro-glacial rivers were exceptionally high during this period as glaciers were still quite large and the available energy for melt from radiation was enhanced. With the shift of the Atlantic meridional overturning (AMO), which is an important driver of European climate, into a negative mode in the 1960s, the mass balances of Alpine glaciers experienced more and more positive mass balance years. This finally resulted in a period of advancing glaciers and the development of frontal moraines around 1980 for a large number of glaciers. Thereafter, from 1980 onward, Alpine glaciers moved into an era of continuous negative mass balances and particularly strong retreat. The anthropogenic forcing from greenhouse gases together with global brightening and the increase of anticyclonic weather types in summer moved the climate and thus the mass balances of glaciers into a state far away from equilibrium. Given available scenarios of future climate, this retreat will continue and, even under the optimistic RCP2.6 scenario, glaciers (as derived from model simulations for the future) will not return to an equilibrium mass balance before the end of the 21st century. According to a glacier inventory for the European Alps from Landsat Thematic Mapper scenes of 2003, published by Paul and coworkers in 2011, the total surface of all glaciers and ice patches in the European Alps in 2003 was 2,056 km² (50% in Switzerland, 19% in Italy, 18% in Austria, 13% in France, and <1% in Germany). Generally, the reaction of Alpine glaciers to climate perturbations is rather well understood. For the glaciers of the Alps, important processes of glacier changes are related to the surface energy balance during the ablation season when radiation is the primary source of energy for snow and ice melt. Other ablation processes, such as sublimation and internal and basal ablation, are small compared to surface melt. This specificity enables the use of simple temperature-based models to simulate the mass balance of glaciers sufficiently well. Besides atmospheric forcing of glacier mass balance, glacier flow (which is related to englacial temperature distribution) plays a role, in particular, for observed front position changes of glaciers. Glaciers are continuously adapting their size to the climate, which could work much faster for smaller glaciers compared to large valley glaciers of the Alps having a response time of about 100 years.

Article

The topic of climate change and migration attracts a strong following from the media and produces an increase in academic literature and reports from international governmental institutions and NGOs. It poses questions that point to the core of social and environmental developments of the 21st century, such as environmental and climate justice as well as North–South relations. This article examines the main features of the debate and presents a genealogy of the discussion on climate change and migration since the 1980s. It presents an analysis of different framings and lines of argument, such as the securitization of climate change and connections to development studies and adaptation research. This article also presents methodological and conceptual questions, such as how to conceive interactions between migration and climate change. As legal aspects have played a crucial role since the beginning of the debate, different legal strands are considered here, including soft law and policy-oriented approaches. These approaches relate to questions of voluntary or forced migration and safeguarding the rights of environmental migrants. This article introduces theoretical concepts that are prompted by analyzing climate change as an “imaginative resource” and by questioning power relations related to climate-change discourses, politics, and practices. This article recommends a re-politicization of the debate, questions the often victimizing, passive picture of the “drowning” climate-change migrant, and criticizes alarmist voices that can trigger perceived security interests of countries of the Global North. Decolonizing and critical perspectives analyze facets of the debate that have racist, depoliticizing, or naturalizing tendencies or exoticize the “other.”

Article

The response of severe thunderstorms to a changing climate is a rapidly growing area of research. Severe thunderstorms are one of the largest contributors to global losses in excess of USD $10 billion per year in terms of property and agriculture, as well as dozens of fatalities. Phenomena associated with severe thunderstorms such as large hail (greater than 2 cm), damaging winds (greater than 90 kmh−1), and tornadoes pose a global threat, and have been documented on every continent except Antarctica. Limitations of observational records for assessing past trends have driven a variety of approaches to not only characterize the past occurrence but provide a baseline against which future projections can be interpreted. These proxy methods have included using environments or conditions favorable to the development of thunderstorms and directly simulating storm updrafts using dynamic downscaling. Both methodologies have demonstrated pronounced changes to the frequency of days producing severe thunderstorms. Major impacts of a strongly warmed climate include a general increase in the length of the season in both the fall and spring associated with increased thermal instability and increased frequency of severe days by the late 21st century. While earlier studies noted changes to vertical wind shear decreasing frequency, recent studies have illustrated that this change appears not to coincide with days which are unstable. Questions remain as to whether the likelihood of storm initiation decreases, whether all storms which now produce severe weather will maintain their physical structure in a warmer world, and how these changes to storm frequency and or intensity may manifest for each of the threats posed by tornadoes, hail, and damaging winds. Expansion of the existing understanding globally is identified as an area of needed future research, together with meaningful consideration of both the influence of climate variability and indirect implications of anthropogenic modification of the physical environment.

Article

In South Africa, one of the world’s most carbon-intense economies and a society marked by gross social inequality, climate change is not a popular topic. As of 2018, more than half of the population had never heard of climate change and only one in five South Africans believed that human activities lead to global warming. The communication of climate change in South Africa is influenced by the notorious inequality that the country still suffers decades after the apartheid regime has ended. Few South Africans are able to live a life in prosperity and security on par with life in industrialized nations, more than half of the population are considered poor, almost a third of the population are chronically unemployed, and many work for carbon-intense industries. The country’s prevalent inequality and its economic dependency on coal influence the way climate change is communicated and interpreted. Environmental NGOs, journalists, and scientists frequently set communication cues on climate change. However, their messages are largely circulated in newspapers catering to an urban and educated readership and resonate less with people living in rural areas or those who rely on employment in the coal and mining sector. In South Africa, most people hear about climate change in mass media, but journalists frequently lack the resources and training necessary to investigate climate change stories or to interact with local scientists. Environmental NGOs, in contrast, provide easily comprehendible communication cues for unspecialized journalists and often share similar worldviews and demographic backgrounds with dedicated environmental reporters. However, because Black South Africans are underrepresented among environmental journalists and because many affordable local newspapers cannot afford to hire specialized reporters, climate change is covered mostly in high-quality English-language outlets to which most people have no access. Moreover, environmental NGOs are frequently accused of prioritizing abstract ecological concerns, like climate change, over the interests of the South Africans workers, a sentiment that is informed by the country’s history of racial injustice. Counterintuitively, living in a coal area is associated with higher climate change awareness and belief, likely because coal companies and trade unions conduct awareness-raising programs among their workers and because many residents experience the adverse impact of coal mining and combustion firsthand.

Article

Joseph E. Uscinski, Karen Douglas, and Stephan Lewandowsky

An overwhelming percentage of climate scientists agree that human activity is causing the global climate to change in ways that will have deleterious consequences both for the environment and for humankind. While scientists have alerted both the public and policy makers to the dangers of continuing or increasing the current rate of carbon emission, policy proposals intended to curb carbon emission and thereby mitigate climate change have been resisted by a notable segment of the public. Some of this resistance comes from those not wanting to incur costs or change energy sources (i.e., the carbon-based energy industry). Others oppose policies intended to address climate change for ideological reasons (i.e., they are opposed to the collectivist nature of the solutions usually proposed). But perhaps the most alarming and visible are those who oppose solutions to climate change because they believe, or at least claim to believe, that anthropogenic climate change is not really happening and that climate scientists are lying and their data is fake. Resistance, in this latter case, sometimes referred to as climate “skepticism” or “denialism,” varies from region to region in strength but worldwide has been a prominent part of a political force strong enough to preclude both domestic and global policy makers from making binding efforts to avert the further effects of anthropogenic climate change. For example, a 2013 poll in the United States showed that almost 40% believed that climate change was a hoax. Climate skeptics suggest the well-publicized consensus is either manufactured or illusory and that some nefarious force—be it the United Nations, liberals, communists, or authoritarians—want to use climate change as a cover for exerting massive new controls over the populace. This conspiracy-laden rhetoric—if followed to its logical conclusion—expresses a rejection of scientific methods, scientists, and the role that science plays in society. Skeptic rhetoric, on one hand, may suggest that climate skepticism is psychological and the product of underlying conspiratorial thinking, rather than cognitive and the product of a careful weighing of scientific evidence. On the other hand, it may be that skeptics do not harbor underlying conspiratorial thinking, but rather express their opposition to policy solutions in conspiratorial terms because that is the only available strategy when arguing against an accepted scientific consensus. This tactic of calling into question the integrity of science has been used in other scientific debates (e.g., the link between cigarette smoking and cancer). Opinion surveys, however, support the view that climate change denialism is driven at least partially by underlying conspiratorial thinking. Belief in climate change conspiracy theories also appears to drive behaviors in ways consistent with the behaviors of people who think in conspiratorial terms: Climate change conspiracy theorists are less likely to participate politically or take actions that could alleviate their carbon footprint. Furthermore, some climate skeptics reject studies showing that their skepticism is partially a product of conspiratorial thinking: They believe such studies are themselves part of the conspiracy.

Article

Tim Rayner and Andrew Jordan

The European Union (EU) has long claimed, with some justification, to be a leader in international climate policy. Its policy activities in this area, dating from the early 1990s, have had enormous influence within and beyond Europe. The period since ca. 2000 in particular has witnessed the repeated emergence of policies and targets that are increasingly distinct from national ones and sometimes globally innovative. They encompass a wide array of instruments (e.g., market-based, informational, voluntary, as well as regulatory). Policy development has been motivated by a mixture of concerns: to avoid national differences in policy causing distortions of the EU’s internal market; to enhance the domestic legitimacy of the wider project of European integration; to improve energy security; and to increase economic competitiveness through “ecological modernization.” Climate policy has also offered a means to enhance the standing of the EU as a global actor. The EU has, in general, been influential in international negotiations, for example, in its promotion of the 2°C warming limit and advocacy of emission reduction “targets and timetables.” In turn, its own policy has been shaped by developments at global level, as with the surprisingly enthusiastic adoption of the “flexible mechanism” of emissions trading. However, it is becoming increasingly apparent that acute challenges to policy coherence and effectiveness—applying to emerging policy on adaptation, as well as mitigation—lie ahead in a Europe that is more polarized between its more environmentally conscious Member States and those in central and eastern Europe who have extracted significant concessions to protect their fossil fuel–intensive sectors. Although the Paris Agreement of 2015 offers an important opportunity to “ratchet up” the ambition of EU policy, it is proving to be a difficult one to seize.

Article

Konrad Ott and Frederike Neuber

The means to combat dangerous anthropogenic climate change constitutes a portfolio. Beside abatement of greenhouse gas emissions, this portfolio entails adaptation to changing climate conditions, and so-called climate engineering measures. The overall portfolio has to be judged on technical, economic, and moral grounds. This requires an in-depth understanding of the moral aspects of climate engineering options. Climate engineering (CE) is a large-scale intentional intervention either in carbon cycles (carbon dioxide removal; CDR) or in solar radiation (solar radiation management; SRM). The ethical discourse on climate engineering has gained momentum since the 2010s. The set of arguments pro and contra specific CE technologies constitute a vast landscape of discourse. Single arguments must be analyzed with scrutiny according to their ethical background, their normative premises, their inferential logic, and their practical and political consequences. CE ethics, then, has a threefold task: (a) it must suppose a solid understanding of different CE technologies and their risks; (b) it has to analyze the moral arguments that speak in favor or against specific CE technologies; and (c) it has to assess the impacts of accepting or rejecting specific arguments for the overall climate portfolio’s design. The global climate portfolio differs from ordinary investment portfolios since stakes are huge, moral values in dispute, risks and uncertainties pervasive, and collective decision-making urgent. Any argument has implications of how to design the overall portfolio best. From an ethical perspective, however, one must reflect upon the premises and inferential structures of the arguments as such. Analysis of arguments and mapping them logically can be seen as core business of CE ethics. Highly general arguments about CE usually fall short, since the diverse features of individual technologies may not be addressed by overarching arguments that necessarily homogenize different technologies. It can be stated with confidence that the moral profiles of CDR and SRM are highly different. Every single deployment scheme ought to be judged specifically, for it is a huge difference to propose SRM as a substitute for abatement, or to embed it within a comprehensive climate portfolio including abatement and adaptation, where SRM will be used sporadically and only for a matter of decades.

Article

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.

Article

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.

Article

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.

Article

The relationship between scientific experts and news media producers around issues of climate change has been a complicated and often contentious one, as the slow-moving and complex story has frequently challenged, and clashed with, journalistic norms of newsworthiness, speed, and narrative compression. Even as climate scientists have become more concerned by their evidence-based findings involving projected risks, doubts and confusion over communications addressing those risks have increased. Scientists increasingly have been called upon to speak more clearly and forcefully to the public through news media about evidence and risks—and to do so in the face of rapidly changing news media norms that only complicate those communications. Professional science and environment journalists—whose ranks have been thinned steadily by media industry financial pressures—have meanwhile come under more scrutiny in terms of their understanding; accuracy; and, at times, perceived bias. A number of important organizations have recognized the need to educate and empower a broad range of scientists and journalists to be more effective at communicating about the complexities of climate science and about the societal and economic impacts of a warming climate. For example, organizations such as Climate Communication have been launched to support scientists in their dealings with media, while the United Nations Intergovernmental Panel on Climate Change itself has continued to focus on the communication of climate science. The Earth Journalism Network, Society of Environmental Journalists, Poynter Institute, and the International Center for Journalists have worked to build media capacity globally to cover climate change stories. Efforts at Stanford University, the University of Oxford, Massachusetts Institute of Technology, Harvard University, and the University of Rhode Island sponsor programming and fellowships that in part help bolster journalism in this area. Through face-to-face workshops and online efforts, The Yale Project on Climate Change Communication has sought to link the media and science communities. Meanwhile, powerful, widely read sites and blogs such as “Dot Earth,” hosted by the New York Times, Climate Central, Real Climate, The Conversation, and Climate Progress have fostered professional dialogue, greater awareness of science, and called attention to reporting and communications issues. Journalists and scientists have had ongoing conversations as part of the regular publication and reporting processes, and professional conferences and events bring the two communities together. Issues that continue to animate these discussions include conveying the degree to which climate science can be said to be “settled” and how to address uncertainty. Through some of these capacity-building efforts, news media have become increasingly aware of audience dynamics including how citizens respond to pessimistic reports, or “doom and gloom,” versus solutions-oriented reports. Professional dialogue has also revolved around the ethical dimensions of conveying a story at the level of global importance. Still, with issues of climate change communication on display for more than two decades now, certain tensions and dynamics persist. Notably, journalists seek clarity from scientists, while climate change experts and advocates for and against taking climate action often continue to demand that journalists resist the temptation to oversimplify or hype the latest empirical findings, while at the same time urging that journalists do not underestimate potential climate risks.

Article

Ishani Mukherjee and Michael Howlett

Policy communication and the resulting influence that information has on policy decision-makers is an especially pertinent topic when it comes to problems of climate change. Notorious for its complexity, uncertainty, and divergence of viewpoints, climate change has earned the title of being the major “wicked” or “super-wicked” problem of our times. A proliferation of expertise, interests, and capacities mark the climate change policymaking landscape and this density of players warrants an advanced framework to understand the ways in which the variety of climate-pertinent knowledge is communicated to policymakers. Moving beyond undifferentiated “two-communities” models of knowledge utilization in policymaking which limit the discussion to the bilateral interactions between knowledge experts or “producers” and information “consumers” of the public sector, this article explores the concept of a policy advisory system, which embodies the different sets of influence that various policy actors can have during policy decision-making and how communication between and among actors is a significant aspect of climate change policymaking. The concept of policy advisory systems is an important new development in the policy studies literature and one that is analytically very applicable to climate policy contexts. Suitably generalizable across representative policy settings, policy advisory systems are comprised of distinct groups of actors who are engaged in the definition of policy problems, the articulation of policy solutions, or the matching of policy problems to solutions. We explore how individual members of these separate sets of actors—namely the epistemic community, which is occupied in discourses about policy problems; the instrument constituencies which define policy instruments; and the advocacy coalitions which compete to have their choice of policy alternatives adopted—interact and communicate with policymakers across climate change policy activities.

Article

Scientific agreement on climate change has strengthened over the past few decades, with around 97% of publishing climate scientists agreeing that human activity is causing global warming. While scientific understanding has strengthened, a small but persistent proportion of the public actively opposes the mainstream scientific position. A number of factors contribute to this rejection of scientific evidence, with political ideology playing a key role. Conservative think tanks, supported with funding from vested interests, have been and continue to be a prolific source of misinformation about climate change. A major strategy by opponents of climate mitigation policies has been to cast doubt on the level of scientific agreement on climate change, contributing to the gap between public perception of scientific agreement and the 97% expert consensus. This “consensus gap” decreases public support for mitigation policies, demonstrating that misconceptions can have significant societal consequences. While scientists need to communicate the consensus, they also need to be aware of the fact that misinformation can interfere with the communication of accurate scientific information. As a consequence, neutralizing the influence of misinformation is necessary. Two approaches to neutralize misinformation involve refuting myths after they have been received by recipients (debunking) or preemptively inoculating people before they receive misinformation (prebunking). Research indicates preemptive refutation or “prebunking” is more effective than debunking in reducing the influence of misinformation. Guidelines to practically implement responses (both preemptive and reactive) can be found in educational research, cognitive psychology, and a branch of psychological research known as inoculation theory. Synthesizing these separate lines of research yields a coherent set of recommendations for educators and communicators. Clearly communicating scientific concepts, such as the scientific consensus, is important, but scientific explanations should be coupled with inoculating explanations of how that science can be distorted.