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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.
Julie Doyle, Nathan Farrell, and Michael K. Goodman
Since the mid-2000s, entertainment celebrities have played increasingly prominent roles in the cultural politics of climate change, ranging from high-profile speeches at UN climate conferences, and social media interactions with their fans, to producing and appearing in documentaries about climate change that help give meaning to and communicate this issue to a wider audience. The role afforded to celebrities as climate change communicators is an outcome of a political environment increasingly influenced by public relations and attuned toward the media’s representation of political ideas, policies, and sentiments. Celebrities act as representatives of mass publics, operating within centers of elite political power. At the same time, celebrities represent the environmental concerns of their audiences; that is, they embody the sentiments of their audiences on the political stage. It is in this context that celebrities have gained their authority as political, social, and environmental “experts,” and the political performances of celebrities provide important ways to engage electorates and audiences with climate change action.
More recently, celebrities offer novel engagements with climate change that move beyond scientific data and facilitate more emotional and visceral connections with climate change in the public’s everyday lives. Contemporary celebrities, thus, work to shape how audiences and publics ought to feel about climate change in efforts to get them to act or change their behaviors. These “after data” moments are seen very clearly in Leonardo DiCaprio’s documentary Before the Flood. Yet, with celebrities acting as our emotional witnesses, they not only might bring climate change to greater public attention, but they expand their brand through neoliberalism’s penchant for the commoditization of everything including, as here, care and concern for the environment. As celebrities build up their own personal capital as eco-warriors, they create very real value for the “celebrity industrial complex” that lies behind their climate media interventions. Climate change activism is, through climate celebrities, rendered as spectacle, with celebrities acting as environmental and climate pedagogues framing for audiences the emotionalized problems and solutions to global environmental change. Consequently, celebrities politicize emotions in ways that that remain circumscribed by neoliberal solutions and actions that responsibilize audiences and the public.
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.
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.
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.
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.”
John T. Allen
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.
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.
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.
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.