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In equatorial East Africa, glaciers still exist on Mount Kenya, Kilimanjaro, and Ruwenzori. The decreasing ice extent has been documented by field reports since the end of the 19th century and a series of mappings. For Mount Kenya, the mappings are of 1947, 1963, 1987, 1993, and 2004, with more detailed mappings of Lewis Glacier in 1934, 1958, 1963, 1974, 1978, 1982, 1985, 1986, 1990, and 1993. For Kilimanjaro, the sequence is 1912, 1953, 1976, 1989, and 2000. For Ruwenzori (for which information is more scarce), the information is from 1906, 1955, and 1990. Photographs are valuable complementary evidence. At Lewis Glacier on Mount Kenya, measurements of mass budget and ice flow have been conducted over decades. The climatic forcing of ice recession in East Africa at the onset in the 1880s was radiationally controlled, affecting the most exposed locations. Later warming caused further ice shrinkage, except on the summit plateau of Kilimanjaro, above the freezing level. Whereas the ice recession in the Ecuadorian Andes and New Guinea began in the middle of the 19th century, plausibly caused by warming, the late onset in East Africa should be appreciated in the context of large-scale circulation changes evidenced by the historical ship observations in the equatorial Indian Ocean.
Precipitation levels in southern Africa exhibit a marked east–west gradient and are characterized by strong seasonality and high interannual variability. Much of the mainland south of 15°S exhibits a semiarid to dry subhumid climate. More than 66 percent of rainfall in the extreme southwest of the subcontinent occurs between April and September. Rainfall in this region—termed the winter rainfall zone (WRZ)—is most commonly associated with the passage of midlatitude frontal systems embedded in the austral westerlies. In contrast, more than 66 percent of mean annual precipitation over much of the remainder of the subcontinent falls between October and March. Climates in this summer rainfall zone (SRZ) are dictated by the seasonal interplay between subtropical high-pressure systems and the migration of easterly flows associated with the Intertropical Convergence Zone. Fluctuations in both SRZ and WRZ rainfall are linked to the variability of sea-surface temperatures in the oceans surrounding southern Africa and are modulated by the interplay of large-scale modes of climate variability, including the El Niño-Southern Oscillation (ENSO), Southern Indian Ocean Dipole, and Southern Annular Mode.
Ideas about long-term rainfall variability in southern Africa have shifted over time. During the early to mid-19th century, the prevailing narrative was that the climate was progressively desiccating. By the late 19th to early 20th century, when gauged precipitation data became more readily available, debate shifted toward the identification of cyclical rainfall variation. The integration of gauge data, evidence from historical documents, and information from natural proxies such as tree rings during the late 20th and early 21st centuries, has allowed the nature of precipitation variability since ~1800 to be more fully explored.
Drought episodes affecting large areas of the SRZ occurred during the first decade of the 19th century, in the early and late 1820s, late 1850s–mid-1860s, mid-late 1870s, earlymid-1880s, and mid-late 1890s. Of these episodes, the drought during the early 1860s was the most severe of the 19th century, with those of the 1820s and 1890s the most protracted. Many of these droughts correspond with more extreme ENSO warm phases.
Widespread wetter conditions are less easily identified. The year 1816 appears to have been relatively wet across the Kalahari and other areas of south central Africa. Other wetter episodes were centered on the late 1830s–early 1840s, 1855, 1870, and 1890. In the WRZ, drier conditions occurred during the first decade of the 19th century, for much of the mid-late 1830s through to the mid-1840s, during the late 1850s and early 1860s, and in the early-mid-1880s and mid-late 1890s. As for the SRZ, markedly wetter years are less easily identified, although the periods around 1815, the early 1830s, mid-1840s, mid-late 1870s, and early 1890s saw enhanced rainfall. Reconstructed rainfall anomalies for the SRZ suggest that, on average, the region was significantly wetter during the 19th century than the 20th and that there appears to have been a drying trend during the 20th century that has continued into the early 21st. In the WRZ, average annual rainfall levels appear to have been relatively consistent between the 19th and 20th centuries, although rainfall variability increased during the 20th century compared to the 19th.
Water, not temperature, governs life in West Africa, and the region is both temporally and spatially greatly affected by rainfall variability. Recent rainfall anomalies, for example, have greatly reduced crop productivity in the Sahel area. Rainfall indices from recent centuries show that multidecadal droughts reoccur and, furthermore, that interannual rainfall variations are high in West Africa. Current knowledge of historical rainfall patterns is, however, fairly limited. A detailed rainfall chronology of West Africa is currently only available from the beginning of the 19th century. For the 18th century and earlier, the records are still sporadic, and an interannual rainfall chronology has so far only been obtained for parts of the Guinea Coast. Thus, there is a need to extend the rainfall record to fully understand past precipitation changes in West Africa.
The main challenge when investigating historical rainfall variability in West Africa is the scarcity of detailed and continuous data. Readily available meteorological data barely covers the last century, whereas in Europe and the United States for example, the data sometimes extend back two or more centuries. Data availability strongly correlates with the historical development of West Africa. The strong oral traditions that prevailed in the pre-literate societies meant that only some of the region’s history was recorded in writing before the arrival of the Europeans in the 16th century. From the 19th century onwards, there are, therefore, three types of documents available, and they are closely linked to the colonization of West Africa. These are: official records started by the colonial governments continuing to modern day; regular reporting stations started by the colonial powers; and finally, temporary nongovernmental observations of various kinds. For earlier periods, the researcher depends on noninstrumental observations found in letters, reports, or travel journals made by European slave traders, adventurers, and explorers. Spatially, these documents are confined to the coastal areas, as Europeans seldom ventured inland before the mid-1800s. Thus, the inland regions are generally poorly represented. Arabic chronicles from the Sahel provide the only source of information, but as historical documents, they include several spatiotemporal uncertainties. Climate researchers often complement historical data with proxy-data from nature’s own archives. However, the West African environment is restrictive. Reliable proxy-data, such as tree-rings, cannot be exploited effectively. Tropical trees have different growth patterns than trees in temperate regions and do not generate growth rings in the same manner. Sediment cores from Lake Bosumtwi in Ghana have provided, so far, the best centennial overview when it comes to understanding precipitation patterns during recent centuries. These reveal that there have been considerable changes in historical rainfall patterns—West Africa may have been even drier than it is today.
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.
Storms are characterized by high wind speeds; often large precipitation amounts in the form of rain, freezing rain, or snow; and thunder and lightning in the case of a thunderstorm. Many different types exist, ranging from tropical cyclones and large storms of the mid-latitudes to small polar lows, medicanes (Mediterranean tropical cyclones), thunderstorms, and tornadoes. They can lead to extreme weather events such as storm surges, flooding, high snow quantities, and bushfires. Storms often pose a threat to human lives and properties, agriculture, forestry, shipping, and offshore and onshore industries. Thus it is of great interest to gain knowledge about changes in storm frequency and intensity. Future storm predictions are important and they depend to a great extent on the evaluation of changes in wind statistics of the past. For reliable statistics, long and homogeneous time series extending over at least several decades are needed. But wind measurements are frequently influenced by changes in the synoptic station, its location or surroundings, instruments, and measurement practice. These factors deteriorate the homogeneity of wind records. Storm indices derived from sea level pressure measurements are less prone to such changes as pressure does not show very large spatial variability in contrast to wind speed. Long-term historical pressure measurements exist that enable us to deduce changes in storminess for more than the last 140 years. But storm records are not just compiled from measurement data; they may also be inferred from climate model data. The first numerical weather forecasts were performed in the 1950s. These predictions served as a basis for the development of atmospheric circulation models, which constituted the first generation of climate models or general circulation models. Soon afterward, model data were analyzed for storm events, and cyclone tracking algorithms were programmed. Climate models nowadays have reached high resolution and reliability and can be run not just for the past, but also for future emission scenarios to provide possible future changes of storm activity.
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 communication in Japan is characterized by governmental campaigns for carbon dioxide emission reduction and mass media coverage of international events on climate change issues. A series of governmental campaigns included “Cool Biz,” “Warm Biz,” and “Team Minus 6%” for the Kyoto protocol; “Challenge 25” for the Hatoyama initiative; “Fun to Share” and “Cool Choice” for the new mid-term Greenhouse gas emissions reduction target of 26%. Those campaigns are popular among public. As for media coverage of international events on climate change issues, one of the biggest events was the COP3 in Kyoto, in 1997; another is the release of AR5 from 2006 to early 2007, and following events of the G8 summits of Heiligendamm, Germany in 2007, and of Toyako, Japan in 2008.
Until now, not much attention has been paid to climate change communication research, as social scientists seldom join research projects concerning climate change science. But recent severe weather, such as stronger or early-season typhoons, heavier rainfalls, early arrival of spring (e.g., earlier bloom of cherry blossoms), and the bleaching of coral reefs bring awareness not only to the general public but also to social scientists. Lack of participation by social scientists in climate change communication research has meant a very narrow range of communication with the public. Experts try to “teach” the science of climate change, and actions such as “50 easy things for tackling global warming,” but it seems those are not what ordinary people want to know. Furthermore, there seems to be no debate on what climate change will bring us, what kinds of energy we should choose, who might be more vulnerable. Debate on ethical issues, justice issues, and sharing of responsibility will be need to be part of future climate change communication.
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.
In the mid-1950s, the geophysicist Norman Phillips computed a general circulation model on John von Neumann’s IAS computer at the Institute for Advanced Studies (IAS) at Princeton. His two-level quasi-geostrophic model predicted the main global circulation patterns for one hemisphere and the poleward transport of energy. Phillips’ computations are considered to be the very first climate simulation and the crucial experiment for testifying that numerical flow can represent large-scale dynamic patterns of the atmosphere. It is high-speed computing, as Phillips pointed out in his conclusion, which will overcome the main obstacle of meteorology, namely the difficulty of solving the nonlinear hydrodynamic equations. Thus, computations will advance the physical understanding of the atmosphere.
Simulation as the numerical approach to scientific problems requires not only high-speed computing, but also a view of meteorology as dynamical meteorology, which was developed in the late 19th and early 20th centuries. Originating as a way to address the problem of weather forecasting, the dynamical approach turned meteorology into the physics of the atmosphere. This view detached the experience of climates into average weather, defined by the World Meteorological Organization as the mean and variability of relevant quantities of variables such as temperature, precipitation, or wind over a period of time of at least 30 years. Today, simulated climate has become a prominent topic in public discourse due to the environmental and societal problem of anthropogenic climate change. However, understanding climate and simulation requires understanding the three major transformations of meteorology: from weather to climate, from synopsis to numerics, and from measurements to projections.
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.
Kenshi Baba, Masahiro Matsuura, Taiko Kudo, Shigeru Watanabe, Shun Kawakubo, Akiko Chujo, Hiroharu Tanaka, and Mitsuru Tanaka
The latest climate change adaptation strategies adopted by local governments in Japan are discussed. A nationwide survey demonstrates several significant findings. While some prefectures and major cities have already begun to prepare adaptation strategies, most municipalities have yet to consider such strategies. This gap must be considered when studying the climate adaptation strategies of local governments in Japan, as municipal governments are crucial to the implementation of climate adaptation strategies due to high diversity in climate impacts and geographical conditions among municipalities within each prefecture in Japan. Key challenges for local governments in preparing adaptation strategies are the lack of expert knowledge and experience in the field of climate change adaptation, and compartmentalization of government bureaus. To address these issues, an interview study of six model prefectures in the SI-CAT (Social Implementation Program on Climate Change Adaptation Technology) project by the MEXT (Ministry of Education, Culture, Sports, Science and Technology) was conducted in order to understand the details of challenges raised by adaptation among local governments in Japan. The survey results reveal that local government officials lack information regarding impact projections and tools for evaluating policy options, even though some of them recognize some of the impacts of climate change on rice crop, vegetable, and fruit production. In addition, different bureaus, such as agriculture, public health, and disaster prevention, focus on different outcomes of climate change due to their different missions. As this is the inherent nature of bureaucratic organizations, a new approach for encouraging collaboration among them is needed. The fact that most of the local governments in Japan have not yet assessed the local impacts of climate change, an effort that would lay the groundwork for preparing adaptation strategies, suggests the importance of cyclical co-design that facilitates the relationship between climatic technology such as climate models and impact assessment and local governments’ needs so that the technology developments clarify the needs of local government, while those needs in turn nurture the seeds of technology.
Climate and carbon cycle are tightly coupled on many time scales, from the interannual to the multimillennial. Observation always shows a positive feedback between climate and the carbon cycle: elevated atmospheric CO2 leads to warming, but warming is expected to further release of carbon to the atmosphere, enhancing the atmospheric CO2 increase. Earth system models do represent these climate–carbon cycle feedbacks, always simulating a positive feedback over the 21st century; that is, climate change will lead to loss of carbon from the land and ocean reservoirs. These processes partially offset the increases in land and ocean carbon sinks caused by rising atmospheric CO2. As a result, more of the emitted anthropogenic CO2 will remain in the atmosphere. There is, however, a large uncertainty on the magnitude of this feedback. Recent studies now help to reduce this uncertainty. On short, interannual, time scales, El Niño years record larger-than-average atmospheric CO2 growth rate, with tropical land ecosystems being the main drivers. These climate–carbon cycle anomalies can be used as emerging constraint on the tropical land carbon response to future climate change. On a longer, centennial, time scale, the variability of atmospheric CO2 found in records of the last millennium can be used to constrain the overall global carbon cycle response to climate. These independent methods confirm that the climate–carbon cycle feedback is positive, but probably more consistent with the lower end of the comprehensive models range, excluding very large climate–carbon cycle feedbacks.