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Systemic climate risks, which result from the potential for cascading impacts through inter-related systems, pose particular challenges to risk assessment, especially when risks are transmitted across sectors and international boundaries. Most impacts of climate variability and change affect regions and jurisdictions in complex ways, and techniques for assessing this transmission of risk are still somewhat limited. Here, we begin to define new approaches to risk assessment that can account for transboundary and trans-sector risk transmission, by presenting: (i) a typology of risk transmission that distinguishes clearly the role of climate versus the role of the social and economic systems that distribute resources; (ii) a review of existing modelling, qualitative and systems-based methods of assessing risk and risk transmission; and (iii) case studies that examine risk transmission in human displacement, food, water and energy security. The case studies show that policies and institutions can attenuate risks significantly through cooperation that can be mutually beneficial to all parties. We conclude with some suggestions for assessment of complex risk transmission mechanisms: use of expert judgement; interactive scenario building; global systems science and big data; innovative use of climate and integrated assessment models; and methods to understand societal responses to climate risk. These approaches aim to inform both research and national-level risk assessment.

The threat of climate change is emerging at a time of rapid growth for many economies in sub-Saharan Africa (SSA). Dominant narratives comprising ambitious development plans are common and often based around sectors with strong inter-dependencies that are highly exposed to climate variability. Using document analysis and key informant interviews, this article examines how climate change is addressed in policy, how it is being mainstreamed into water, energy and agriculture sector policies and the extent to which cross-sectoral linkages enable coordinated action. These questions are addressed through a case study of Tanzania, highlighting broader lessons for other developing countries, particularly those in SSA facing similar challenges. The article finds that, while the agriculture and water sectors are increasingly integrating climate change into policies and plans in Tanzania, practical coordination on adaptation remains relatively superficial. Publication of the Tanzania National Adaptation Plan of Action (NAPA) in 2007 marked a step change in the integration of climate change in sectoral policies and plans; however, it may have reinforced a sectoral approach to climate change. Examining the policies for coherence highlights overlaps and complementarities which lend themselves to a coordinated approach. Institutional constraints (particularly structures and resources) restrict opportunities for inter-sectoral action and thus collaboration is confined to ad hoc projects with mixed success to date. The results highlight the need for institutional frameworks that recognize and address these constraints to enable development goals to be pursued in a more sustainable and climate-resilient manner. KEY POLICY INSIGHTS The NAPA has been successful at encouraging climate change mainstreaming into sectoral policies in Tanzania; however, the cross-sectoral collaboration crucial to implementing adaptation strategies remains limited due to institutional challenges such as power imbalances, budget constraints and an ingrained sectoral approach. Collaboration between nexus sectors in Tanzania is largely through ad hoc projects with limited progress on establishing deeper connections to enable collaboration as a process. Regular cross-sectoral planning meetings and consistent annual budgets could provide a platform to enhance cross-sectoral coordination. Plans to develop hydropower and agriculture are prevalent across sub-Saharan Africa. Insights from Tanzania highlight the importance of institutional and policy frameworks that enable cross-sectoral coordination.

Non-technical summary The El Nino event in 2015/2016 was one of the strongest since at least 1950. Through surveys and interviews with key informants, we find businesses in the capital cities of Zambia, Botswana and Kenya experienced major disruption to their activities from El Nino related hydroelectric load shedding, water supply disruption and flooding, respectively. Yet, during the 2015/2016 El Nino, fluctuations in precipitation were not extreme considering the strength of the El Nino event. Results therefore highlight that even fairly moderate precipitation anomalies can contribute to major disruption to economic activity. Addressing the risk of disruption – and supporting the private sector to adapt – is a development priority. Technical summary Drought during the 2015/2016 El Nino amplified disruption to public water supply in Botswana’s capital Gaborone and contributed to unprecedented hydroelectric load shedding across Zambia. In Kenya, moderate precipitation during the El Nino brought localized floods to Nairobi and other areas. Contributing to a sparse literature on firm-level adaptation among micro, small and medium enterprise (MSMEs) in sub-Saharan Africa, through a near-real time assessment we consider MSME experience of this disruption in sectors making substantial contributions to livelihoods and national GDP. Alongside complex and indirect impact pathways that influence total loss and damage, results show varying vulnerability to disruption. Nevertheless, directly after the El Nino event, MSMEs reported water supply disruption, power outages and flooding to be the leading challenge within the business environment in Botswana, Zambia and Kenya respectively. Deeper understanding of vulnerabilities in existing water, energy and urban infrastructure – in the context of increasing urbanisation and a potentially broader range of climate variability – is urgently needed across SSA. This needs to be coupled with public provision of wider enabling conditions – including access to finance – that support private sector adaptation to extreme climate events and associated resource disruption. This paper also identifies clear opportunities to improve climate information services for MSMEs. Social media summary Flooding and water and electricity supply disruption during the 2015/2016 El Nino disrupted business activity in sub-Saharan Africa.

Hydropower comprises a significant and rapidly expanding proportion of electricity production in eastern and southern Africa. In both regions, hydropower is exposed to high levels of climate variability and regional climate linkages are strong, yet an understanding of spatial interdependences is lacking. Here we consider river basin configuration and define regions of coherent rainfall variability using cluster analysis to illustrate exposure to the risk of hydropower supply disruption of current (2015) and planned (2030) hydropower sites. Assuming completion of the dams planned, hydropower will become increasingly concentrated in the Nile (from 62% to 82% of total regional capacity) and Zambezi (from 73% to 85%) basins. By 2030, 70% and 59% of total hydropower capacity will be located in one cluster of rainfall variability in eastern and southern Africa, respectively, increasing the risk of concurrent climate-related electricity supply disruption in each region. Linking of nascent regional electricity sharing mechanisms could mitigate intraregional risk, although these mechanisms face considerable political and infrastructural challenges.

In southern Africa, the connections between climate and the water-energy-food nexus are strong. Physical and socioeconomic exposure to climate is high in many areas and in crucial economic sectors. Spatial interdependence is also high, driven for example, by the regional extent of many climate anomalies and river basins and aquifers that span national boundaries. There is now strong evidence of the effects of individual climate anomalies, but associations between national rainfall and Gross Domestic Product and crop production remain relatively weak. The majority of climate models project decreases in annual precipitation for southern Africa, typically by as much as 20% by the 2080s. Impact models suggest these changes would propagate into reduced water availability and crop yields. Recognition of spatial and sectoral interdependencies should inform policies, institutions and investments for enhancing water, energy and food security. Three key political and economic instruments could be strengthened for this purpose; the Southern African Development Community, the Southern African Power Pool, and trade of agricultural products amounting to significant transfers of embedded water.

Decision‐Making Under Uncertainty (DMUU) approaches have been less utilized in developing countries than developed countries for water resources contexts. High climate vulnerability and rapid socioeconomic change often characterize developing country contexts, making DMUU approaches relevant. We develop an iterative multi‐method DMUU approach, including scenario generation, coproduction with stakeholders and water resources modeling. We apply this approach to explore the robustness of adaptation options and pathways against future climate and socioeconomic uncertainties in the Cauvery River Basin in Karnataka, India. A water resources model is calibrated and validated satisfactorily using observed streamflow. Plausible future changes in Indian Summer Monsoon (ISM) precipitation and water demand are used to drive simulations of water resources from 2021 to 2055. Two stakeholder‐identified decision‐critical metrics are examined: a basin‐wide metric comprising legal instream flow requirements for the downstream state of Tamil Nadu, and a local metric comprising water supply reliability to Bangalore city. In model simulations, the ability to satisfy these performance metrics without adaptation is reduced under almost all scenarios. Implementing adaptation options can partially offset the negative impacts of change. Sequencing of options according to stakeholder priorities into Adaptation Pathways affects metric satisfaction. Early focus on agricultural demand management improves the robustness of pathways but trade‐offs emerge between intrabasin and basin‐wide water availability. We demonstrate that the fine balance between water availability and demand is vulnerable to future changes and uncertainty. Despite current and long‐term planning challenges, stakeholders in developing countries may engage meaningfully in coproduction approaches for adaptation decision‐making under deep uncertainty., Key Points An iterative approach combining qualitative and quantitative methods is used to assess robustness of adaptation options and pathwaysPerformance criteria for the Cauvery River Basin in Karnataka are not satisfied under almost all scenarios with or without adaptationA coproduction approach helps target stakeholder priorities in the hydrological modeling and design of long‐term adaptation pathways

The international community's support for adaptation in developing countries has proliferated through numerous complementary funding mechanisms. A range of serious practical issues are emerging, however, as adaptation moves from theory and international negotiation to implementation. We identify three areas deserving greater scrutiny: in-country priorities, entry points and delivery systems, and provide recommendations for improving adaptation practice. These concerns, if not addressed, have the potential to hamper attempts at effective delivery and to increase the vulnerability of intended beneficiaries of the adaptation agenda.

Next year Global Environmental Change will have been in existence for 25 years. This year sees a major change in the journal's editors, as Neil Adger and Kate Brown depart after a decade of leadership. As of January, four individuals have joined Declan Conway (London School of Economics, UK) as the new editorial team: Jon Barnett (University of Melbourne, Australia), Michele Betsill (Colorado State University, US), Louis Lebel (Chiang Mai University, Thailand) and Karen Seto (Yale University, US). This change does not signal a major shift in the journal's directions and scope. It does, however, provide an opportunity to reflect on the past and identify emerging frontiers in research on global environmental change, at least as reflected in the pages of this journal. We will use Global Environmental Change's anniversary next year to lay out our vision and plans for the future of the journal; here we reflect on some of the key contributions to understanding processes of global environmental change.

Responses to climate change in transboundary river basins are believed to depend on national and sub-national capacities as well as the ability of co-riparian nations to communicate, coordinate, and cooperate across their international boundaries. We develop the first framework for assessing transboundary adaptive capacity. The framework considers six dimensions of transboundary river basins that influence planning and implementation of adaptation measures and represents those dimensions using twelve measurable indicators. These indicators are used to assess transboundary adaptive capacity of 42 basins in the Middle East, Mediterranean, and Sahel. We then conduct a cluster analysis of those basins to delineate a typology that includes six categories of basins: High Capacity, Mediated Cooperation, Good Neighbour, Dependent Instability, Self-Sufficient, and Low Capacity. We find large variation in adaptive capacity across the study area; basins in Western Europe generally have higher capacities to address the potential hazards of climate change. Our basin typology points to how climate change adaptation policy interventions would be best targeted across the different categories of basins.

Diversity of both social networks and livelihood sources plays a central role in determining the sustainability of natural resource use and resilience of social–ecological systems, not least in resource-dependent economies. Yet the types of social capital and characteristics of diversity are not well understood. Here we examine social capital and livelihood diversification strategies in dynamic lakeshore social–ecological systems in Uganda adapting to climate variability and change. Water and land use data are used to explain lake system variations and lakeshore people's livelihood responses in terms of adaptive cycles and examine how system resilience changes over time in response to climatic and other stresses. Interview and household survey data are used to explain household adaptations to climate variability based on livelihood diversification and social capital and to determine which adaptations were dominant during different stages of adaptive cycles. Results show that households adapt to climate va...

There are strong interdependencies between water use in agriculture and energy consumption as water saving technologies can require increased pumping and pressurizing. The Chinese Government includes water efficiency improvement and carbon intensity reduction targets in the 12th Five-Year Plan (5YP. 2011–2015), yet the links between energy use and irrigation modernization are not always addressed in policy targets. Here we build an original model of the energy embedded in water pumping for irrigated agriculture and its related processes. The model is based on the physical processes of irrigation schemes and the implication of technological developments, comprising all processes from extraction and conveyance of water to its application in the field. The model uses data from government sources to assess policy targets for deployment of irrigation technologies, which aim to reduce water application and contribute to adaptation of Chinese agriculture to climate change. The consequences of policy targets involve co-beneficial outcomes that achieve water and energy savings, or trade-offs in which reduced water application leads to increasing greenhouse gas (GHG) emissions. We analyze irrigation efficiency and energy use in four significant provinces and nationally, using scenarios based on the targets of the 12th 5YP. At the national scale, we find that expansion of sprinklers and micro-irrigation as outlined in the 5YP would increase GHG emissions from agricultural water use, however, emissions decrease in those provinces with predominant groundwater use and planned expansion of low-pressure pipes. We show that the most costly technologies relate to trade-offs, while co-benefits are generally achieved with less expensive technologies. The investment cost per area of irrigation technology expansion does not greatly affect the outcome in terms of water, but in terms of energy the most expensive technologies are more energy-intensive and produce more emissions. The results show that water supply configuration (proportion of surface to groundwater) largely determines the potential energy savings from reductions in water application. The paper examines the importance of fertigation and highlights briefly some policy implications.

This paper examines the challenges and opportunities for Non-Governmental Organisations (NGOs) to integrate climate change adaptation into development projects, focusing on the potential contribution of community-generated information. The research, undertaken with agricultural NGO FARM-Africa, centres upon subsistence farming communities in the Kenyan Districts of Mwingi and Kitui, where a succession of droughts has blighted agricultural production in recent years. Discussions with FARM-Africa staff highlight how recent climate variability and possibly climate change, is already affecting project-level operations. In particular, the interaction between the secondary impacts of climate hazards and livelihood responses presents a challenge to local staff as there is no obvious means of reflecting the complexity of local experiences and impacts within project planning processes. In response, drawing upon discussions with Farmer Groups, a matrix for each community was developed comprising environmental, soci...

This paper identifies over 50 000 patents filed worldwide in various water-related technologies between 1990 and 2010, distinguishing between those related to availability (supply) and conservation (demand) technologies. Patenting activity is analysed – including inventive activity by country and technology, international diffusion of such water-related technologies, and international collaboration in technology development. Three results stand out from our analysis. First, although inventive activity in water-related technologies has been increasing over the last two decades, this growth has been disproportionately concentrated on supply-side technologies. Second, whilst 80% of water-related invention worldwide occurs in countries with low or moderate water scarcity, several countries with absolute or chronic water scarcity are relatively specialized in water efficiency technologies. Finally, although we observe a positive correlation between water scarcity and local filings of water patents, some countries with high water availability, in particular Switzerland or Norway, nevertheless appear as significant markets for water-efficiency technologies. This suggests that drivers other than local demand, like regulation and social and cultural factors, play a role in explaining the global flows of technologies. And finally, the extent to which innovation is "internationalised" shows some distinct patterns relative to those observed for innovation in technologies in general.

Climate change is projected to increase annual Nile river flow; importantly, year-to-year variability is also expected to increase markedly. More variable flows could present a challenge for consistent water resource provision in this region.

This paper reviews research on African climate from the major Sahel droughts in the early 1970s to current interest in improving the use of climate science within societal decision-making processes. During the last decade, and particularly since the mid-2000s, the development community has begun to engage seriously with the issue of climate change and its implications for the world's poor. This has led to a growing interaction with the climate research community. Recent climate literature is used to explore four research themes and identify knowledge gaps and areas with potential to adapt climate research for development needs. The first theme considers the development and use of seasonal forecasts and their portrayal by some as a relative success story, but with important skill limitations and need for much greater interaction with users. Forecast use is set within a wider context of generally low scientific understanding of the drivers of Africa's high climate variability and low research capacity. The second theme addresses the main influences on African climate variability and their response to climate change; high levels of uncertainty for future rainfall in some regions where remote influences are poorly resolved in global climate models. The third theme summarizes key elements of climate impacts research and shows a situation of rather ad hoc case studies and little engagement with decision-makers. Recent studies reveal an important move to couple more effectively impacts research with adaptation by focusing on the near future and drawing on current climate–society relationships. The fourth theme looks at the emerging evidence of anthropogenic climate change and secondary effects on African environments and, apart from widespread warming, shows an equivocal situation with evidence for anthropogenic ocean warming affecting regional rainfall. Detection is hampered by data availability and high levels of background variability. Finally, three emergent issues are discussed: (1) reflection on African climate research capacity and international collaboration suggests it is timely to review experiences from recent climate programs in Africa; (2) attempts to untangle climate signals from within complex livelihood systems face significant methodological challenges. These include the need to reconcile scientific observations and local perceptions and to clarify views that may over-simplify climate–society interactions, to avoid construction of a crisis narrative on Africa and climate change; (3) the challenge of linking climate science with decision-making to inform adaptation. Demand for information and confidence often exceeds what climate science can realistically achieve in many parts of Africa. WIREs Clim Change 2011 2 428–450 DOI: 10.1002/wcc.115 For further resources related to this article, please visit the WIREs website

Africa is widely held to be highly vulnerable to future climate change and Ethiopia is often cited as one of the most extreme examples. With this in mind we seek to identify entry points to integrate short- to medium-term climate risk reduction within development activities in Africa, drawing from experiences in Ethiopia. To achieve this we employ a range of data and methods. We examine the changing nature of climate risks using analysis of recent climate variability, future climate scenarios and their secondary impacts. We assess the effects of climate variability on agricultural production and national GDP. Entry points and knowledge gaps in relation to mainstreaming climate risks in Ethiopia are identified using the Government's plan for poverty reduction. We end with a case study incorporating climate risks through drought insurance within the current social protection programme in Ethiopia, which provides support to 8.3 million people. Rainfall behaviour in Ethiopia shows no marked emergent changes and future climate projections show continued warming but very mixed patterns of rainfall change. Economic analysis highlights sensitivities within the economy to large-scale drought, however, while the effects are clear in major drought years in other years the relationship is weak. For social protection fairly small positive and negative effects on the number of recipients and frequency of cash payments during drought occur under the extreme range of climate model rainfall projections (2020s). Our analysis highlights several important challenges and opportunities for addressing climate risks. Challenges primarily relate to the large uncertainties in climate projections for parts of Africa, a weak evidence base of complex, often non-deterministic, climate–society interactions and institutional issues. Opportunities relate to the potential for low-regrets measures to reduce vulnerability to current climate variability which can be integrated with relatively modest effort within a shift in Africa from a disaster-focused view of climate to a long-term perspective that emphasises livelihood security and vulnerability reduction.

Dendrochronology is developing outside temperate and boreal regions. Over the past decade substantial progress has been made in Mediterranean and wet tropical regions. However, research in dry tropical regions, notably those of sub-Saharan Africa, has remained fragmentary. Here, we try to identify the unique challenges and opportunities of dendrochronology in the dry tropics. First, we briefly review the status of dendrochronology outside temperate and boreal regions with an emphasis on sub- Saharan Africa. Subsequently, we focus upon one of those areas where dendrochronology in the dry tropics is at the forefront of scientific advance: Ethiopia. A detailed review of tree ring studies in the lowlands and highlands highlights the complexity of ring formation and made us identify four major types of growth ring expression: anatomically notdistinct rings, multiple rings per year, annual rings and multiple missing rings. This complex tree growth behaviour is associated with large-scale variations in precipitation regime (unimodal to multimodal) and relatively small-scale variations in tree sensitivity to water availability. Literature results are used to develop a scheme that can be used to predict differences in growth ring formation along gradients in these two factors. Because of the exceptional growth sensitivity of and the importance of local site conditions (topography, biological factors, etc.) for most trees sampled, those growing at the limits of their ecological amplitude are prone to possess multiple rings per year or multiple missing rings. In such circumstances, site selection should not always take place at the limits of the ecological amplitude of a species, but may sometimes have to be diverted to more mesic environments. Successful studies are now appearing, such as those reporting correlations between tree ring chronologies and Blue Nile river flows.

Climate scenarios from a regional climate model are used to drive crop and water simulation models underpinned by the IPCC A2 and B2 socio-economic development pathways to explore water availability for agriculture in China in the 2020s and 2040s. Various measures of water availability are examined at river basin and provincial scale in relation to agricultural and non-agricultural water demand and current and planned expansions to the area under irrigation. The objectives are to understand the influences of different drivers on future water availability to support China's food production. Hydrological simulations produce moderate to large increases in total water availability in response to increases in future precipitation. Total water demand increases nationally and in most basins, but with a decreasing share for agriculture due primarily to competition from industrial, domestic and municipal sectors. Crop simulations exhibit moderate to large increases in irrigation water demand which is found to be highly sensitive to the characteristics of daily precipitation in the climate scenarios. The impacts of climate change on water availability for agriculture are small compared to the role of socio-economic development. The study identifies significant spatial differences in impacts at the river basin and provincial level. In broad terms water availability for agriculture declines in southern China and remains stable in northern China. The combined impacts of climate change and socio-economic development produce decreases in future irrigation areas, especially the area of irrigated paddy rice. Overall, the results suggest that there will be insufficient water for agriculture in China in the coming decades, due primarily to increases in water demand for non-agricultural uses, which will have significant implications for adaptation strategies and policies for agricultural production and water management.

A conceptual water balance model is applied in a distributed structure to model monthly river flow in tributaries of two very large river systems which exhibit non-stationary behaviour, the Parana in South America and the Niger in West Africa. The approach utilises global data sets of rainfall and potential evaporation (PE) time series and soil available water capacity at 0.5 degree latitude and longitude resolution. River flow data for tributaries ranging in size from 631 to 71 510 km(2) for the period 1931-1990 (Parana) and 1950-1989 (Niger) are used to calibrate and validate the model. The results show varying degrees of model performance during both the calibration and validation procedure. The analysis highlights some interesting issues pertaining to the development and application of water balance models such as sensitivity of model performance and parameter values to input data sets, particularly the method chosen to estimate PE. The paper ends with an analysis of prolonged fluctuation in flow characteristics exhibited by both rivers after the early 1970s, associated with fluctuation in rainfall regime and possibly change in land use or land cover. Between 1931-1971 and 1972-1990 Parana river flows increased by similar to 28% (rainfall increase similar to 5%) and between 1950-1969 and 1970-1989 Niger river flows decreased by similar to 34% (rainfall decrease similar to 14%).

This paper reviews current knowledge of the potential impacts of climate change on water resources in Africa and the possible limits, barriers or opportunities for adaptation to climate change in internationally-shared river basins. Africa faces significant challenges to water resources management in the form of high variability and regional scarcity, set within the context of generally weak institutional capacity. Management is further challenged by the transboundary nature of many of its river basins. Climate change, despite uncertainty about the detail of its impacts on water resources, is likely to exacerbate many of these challenges. River basins, and the riparian states that share them, differ in their capacities to adapt. Without appropriate cooperation adaptation may be limited and uneven. Further research to examine the factors and processes that are important for cooperation to lead to positive adaptation outcomes and the increased adaptive capacity of water management institutions is s...

We assessed the effect of greenhouse gas-induced climate change, as well as the direct fertilization effect of CO2, on rice yields and production in China. Our methodology coupled the regional climate model PRECIS (Providing Regional Climates for Impacts Studies) with the CERES (Crop Environment Resources Synthesis) rice crop model to simulate current (1961-1990) and future (2011-2100) rice yields and production under A2 and B2 climate change scenarios. The movement of rice-producing areas to more favorable climatic conditions was also considered. Results demonstrate that simulated future rice yields decrease without the CO2 fertilization effect and increase in some areas and time slices with it. Yield variability measured by the coefficient of variation exhibits increases in both scenarios, with the largest increases under A2. Due to favorable climatic conditions, single rice cropping may expand further north in China, and double rice cropping may move to the northern portion of the Yangtze River basin. China's potential rice production is projected to increase in the future, due to the CO2 fertilization effect and shifts in rice-producing areas. Three rice cultiva- tion regions (Sichuan basin, Yangtze River basin, and Huang-huaihai plain) are identified as highly sensitive to future climate change if no adaptation measures are implemented, due to yield decreases and large increases in production variability.

Ecological citizenship presents a normative account of how citizens should conduct their lives, reducing their environmental impact. Little research has characterised ecological citizenship in practice or in the context of climate change. Q methodology is applied to a case study in Canada to scrutinise how individuals respond to climate change. The results identify four factors – the communitarian, the systemist, the sceptic and the economist – three of which suggest strongly that participants act on perceived individual responsibility for climate change. Practising ecological citizenship motivates individuals' responses to climate change. The actions taken suggest that behavioural change is the result of a complex negotiation between living standards, knowledge of causes of and contributions to climate change, and perceived intensity of greenhouse gas emission. The practice of ecological citizenship involves individuals' actions as voters and consumers, and concerns the power and justice implications of ...

River basin rainfall series and extensive river flow records are used to characterize and improve understanding of spatial and temporal variability in sub-Saharan African water resources during the last century. Nine major international river basins were chosen for examination primarily for their extensive, good quality flow records. A range of statistical descriptors highlight the substantial variability in rainfall and river flows [e.g., differences in rainfall (flows) of up to −14% (−51%) between 1931–60 and 1961–90 in West Africa], the marked regional differences, and the modest intraregional differences. On decadal time scales, sub-Saharan Africa exhibits drying across the Sahel after the early 1970s, relative stability punctuated by extreme wet years in East Africa, and periodic behavior underlying high interannual variability in southern Africa. Central Africa shows very modest decadal variability, with some similarities to the Sahel in the adjoining basins. No consistent signals in rainfall and river flows emerge across the whole of the region. An analysis of rainfall–runoff relationships reveals varying behavior including strong but nonstationary relationships (particularly in West Africa); many basins with marked variations (temporal and spatial) in strength; weak, almost random behavior (particularly in southern Africa); and very few strong, temporally stable relationships. Twenty-year running correlations between rainfall and river flow tend to be higher during periods of greater rainfall station density; however, there are situations in which weak (strong) relationships exist even with reasonable (poor) station coverage. The authors conclude for sub-Saharan Africa that robust identification and attribution of hydrological change is severely limited by data availability, conflicting behavior across basins/regions, low signal-to-noise ratios, sometimes weak rainfall–runoff relationships, and limited quantification of the magnitude and effects of land use change.

Crop models have been used extensively to assess the impacts of environmental change, but few studies have evaluated their performance at the regional scale. Here, we evaluate the performance of CERES-Wheat (Triticum aestivum L.) in simulating regional spatial and temporal characteristics of wheat production in China. The model uses genetic coefficients of representative cultivars within relatively homogeneous Agro Ecological Zones on a 50- by 50-km grid resolution with supported soil and daily weather inputs. Simulated maturity dates and yields are compared with observations (1998-2000) at 141 experimental agricultural stations, and with county-scale census yields (1980-2000). The model is evaluated with respect to its ability to capture the regional and temporal patterns of yield, measured by statistics including relative root mean square error (RMSE) and the index of agreement (d). Results show that the model captures the spatial patterns of yield variability reasonably well when compared to observed field data (RMSE% = 22.8% and d = 0.85) and census data (RMSE% = 27.0% and d = 0.76). Simulation of interannual variability in national production is very good (RMSE% = 8.2%, and d = 0.85). In spatial terms, simulation of variability varies considerably; good results are achieved in some of the main wheat planting areas, but not in others. The paper ends with a discussion of likely reasons for these differences in performance.

Crop simulation models are widely used to assess the impacts of and adaptation to climate change in relation to agricultural production. However, a substantial mismatch often exists between the spatial and temporal scale of available data and the requirements of crop simulation models. Conventional model calibration methods which concentrate on a model's performance at plot scale cannot be used for large scale regional simulation (especially for climate change impacts assessments), given the limited observed data and the iterative calibration needed. One primary purpose of regional simulation is to predict the spatial yield variation and temporal yield fluctuation. This purpose could be fulfilled through model input calibration in which the objective of the calibration focuses on spatial or temporal agreement between simulated and observed values. This study examines the performance of CERES-Rice at the regional scale across China using a cross calibration process based on limited experiment data, agroecological zones (AEZ) and 50 km × 50 km grid scale geographical database. Model performance is evaluated using rice yields from experimental sites at the plot scale, and/or observed yield data at the county scale. Results suggest: the CERES-Rice model was able to simulate the site-specific rice production with good performance in most of China, with a root mean square error (RMSE) = 991 kg ha −1 and a relative RMSE = 14.9% for yield across China. The cross calibration process, in which AEZ-scale parameter values were derived, gave a relative bigger bias to yield estimation, with a RMSE = 1485 kg ha −1 and a relative RMSE = 22.5%, but achieved a reasonable agreement with observed maturity day and yield at spatial scale. The bias rose further if this cross calibrated model was used to simulate the real farmer rice yields at a regional scale, with a RMSE = 2191 kg ha −1 and relative RMSE = 34% across China. The pattern of yield variation was captured spatially by the model in most of the rice planting areas, but not temporally. The sources of uncertainties were analyzed for both plot scale and regional scale simulation. This calibration process could be incorporated into climate change integrated assessment and adaptation assessment, especially for those developing counties with limited observed data.

Climate data for studies within the SWURVE (Sustainable Water: Uncertainty, Risk and Vulnerability in Europe) project, assessing the risk posed by future climatic change to various hydrological and hydraulic systems were obtained from the regional climate model HadRM3H, developed at the Hadley Centre of the UK Met Office. This paper gives some background to HadRM3H; it also presents anomaly maps of the projected future changes in European temperature, rainfall and potential evapotranspiration (PET, estimated using a variant of the Penman formula). The future simulations of temperature and rainfall, following the SRES A2 emissions scenario, suggest that most of Europe will experience warming in all seasons, with heavier precipitation in winter in much of western Europe (except for central and northern parts of the Scandinavian mountains) and drier summers in most parts of western and central Europe (except for the north-west and the eastern part of the Baltic Sea). Particularly large temperature anomalies (>6°C) are projected for north-east Europe in winter and for southern Europe, Asia Minor and parts of Russia in summer. The projected PET displayed very large increases in summer for a region extending from southern France to Russia. The unrealistically large values could be the result of an enhanced hydrological cycle in HadRM3H, affecting several of the input parameters to the PET calculation. To avoid problems with hydrological modelling schemes, PET was re-calculated, using empirical relationships derived from observational values of temperature and PET.

While climate change is a global phenomenon, the activities that contribute to climate change and its impacts are inherently local. Accumulating evidence within national and UN Intergovernmental Panel on Climate Change (IPCC) assessments (IPCC, 2013 and 2014), special reports (IPCC, 2012) and from recent extreme events indicates that all countries have elements of society, economy and environment that are vulnerable to a variable and changing climate. According to the IPCC, global surface temperature change for the end of the twenty-first century is likely to exceed 1.5°C relative to pre-industrial levels, with warming projected to continue beyond 2100. Warming and precipitation changes will be much more pronounced at different locations (IPCC, 2013). Continued variability, shifts in seasons, and climate extremes – such as heat waves and more frequent and intense precipitation events – will continue to cause harm. Climate change manifests through two different time dimensions: those over the long-term and those that occur abruptly. While it is easier to investigate the potential impacts of climate hazards and extreme weather events (acute hazards such as typhoons, heat spells or severe storms that last only for a short period), slow-onset events (long-term, gradual changes to an area’s average precipitation, temperature and seasons) such as drought and sea level can be just as detrimental or beneficial as the more flashy events. These types of changes can exceed thresholds, sensitivities and coping mechanisms for a group of people or system, and cause a cascade of impacts detrimental or beneficial to other groups or systems. The impacts of these projected changes are expected to be many and serious for both natural and human systems. The core systems (e.g. agriculture, electricity generation and water, among others) upon which humanity depends for livelihoods, safety and well-being are exposed and sensitive to being affected by climate variability1 and change. Around the world, socio-economic development has sometimes increased vulnerability. This is due to increasing demographic pressures and ageing populations, as well as resource-use pressures and previous policy choices made in pursuit of economic growth and development. This chapter provides an overview of current ideas and practices around adaptation planning processes, as well as the movement from these to develop adaptation policies and actions.

Water management is a central responsibility of civil society. Major questions persist regarding practice, policy, and the underlying evidence and methods to inform both. Over the next 3 weeks, Science presents essays invited to debate key issues in freshwater research and management. This week: local versus global. When, and to what extent, should a global viewpoint replace, or work in tandem with, enduring localized perspectives?

Numerous factors are associated with poverty and underdevelopment in Africa, including climate variability. Rainfall, and climate more generally, are implicated directly in the United Nations “Millennium Development Goals” to eradicate extreme poverty and hunger, and reduce child mortality and incidence of diseases such as malaria by the target date of 2015. But, Africa is not currently on target to meet these goals. We pose a number of questions from a climate science perspective aimed at understanding this background: Is there a common origin to factors that currently constrain climate science? Why is it that in a continent where human activity is so closely linked to interannual rainfall variability has climate science received little of the benefit that saw commercialization driving meteorology in the developed world? What might be suggested as an effective way for the continent to approach future climate variability and change? We make the case that a route to addressing the challenges of climate change in Africa rests with the improved management of climate variability. We start by discussing the constraints on climate science and how they might be overcome. We explain why the optimal management of activities directly influenced by interannual climate variability (which include the development of scientific capacity) has the potential to serve as a forerunner to engagement in the wider issue of climate change. We show this both from the perspective of the climate system and the institutions that engage with climate issues. We end with a thought experiment that tests the benefits of linking climate variability and climate change in the setting of smallholder farmers in Limpopo Province, South Africa.

Egypt is almost totally dependent upon water that originates from the upstream headwaters of the Nile in the humid Ethiopian and East African highlands. Analysis of rainfall and river flow records during the 20th century demonstrates high levels of interannual and interdecadal variability. This is experienced locally and regionally in the headwater regions of the Nile and internationally through its effects on downstream Nile flows in Sudan and Egypt. Examples of climate variability are presented from areas in the basin where it exerts a strong influence on society; the Ethiopian highlands (links with food security), Lake Victoria (management of non-stationary lake levels) and Egypt (exposure to interdecadal variability of Nile flows). These examples reveal adaptations across various scales by individuals and institutions acting alongside other social and economic considerations. Water resources management in the downstream riparian Egypt has involved institutional level reactive adaptations to prolonged periods of low and high Nile flows. Observed responses include the establishment of more robust contingency planning and early warning systems alongside strategic assessment of water use and planning in response to low flows during the 1980s. In the 1990s high flows have enabled Egypt to pursue opportunistic policies to expand irrigation. These policies are embedded in wider socio-political and economic considerations but increase Egypt's exposure and sensitivity to climate driven fluctuations in Nile flows. Analysis of climate change projections for the region shows there is no clear indication of how Nile flows will be affected because of uncertainty about future rainfall patterns in the basin. In many instances the most appropriate entry point for adaptation to climate change will be coping with climate variability and will play out against the certainty of looming national water scarcity in Egypt due to rapid population growth and its possible exacerbation by water demands from upstream riparians.

A detailed historical reconstruction and analysis is presented of the longest record of climate observations for Ethiopia, from 1898 to 2002 in Addis Ababa. Prior to 1951 the record comprises rainfall and minimum and maximum temperatures recorded in different locations by different observers. The rainfall series is complete except for 1899 and 1900, but the temperature series are very incomplete. Using documentary evidence, we attempt as far as is possible to establish the origins of all the pre-1951 observations. Rainfall observations originate from at least six different sites. After establishment of an Ethiopian meteorological department in 1951 the records are complete and, to our understanding, originate from the same location, the Addis Ababa Observatory (AAO). A revised rainfall series for 1898-1950 is derived using observations from sites with the longest records. The minimum and maximum temperature records show evidence of statistically significant inhomogeneities. Homogeneity tests on the full rainfall record (the revised series plus AAO) show it is reliable, with evidence of minor but not statistically significant breaks in the record before establishment of the AAO. Some, but not all, breaks can be accounted for using the historical information. Analysis of the records shows increasing trends in annual minimum and maximum temperatures from 1951 to 2002 (0.4 °C/decade and 0.2 °C/decade, respectively). There is little trend in rainfall from 1901-50, 1951-2002 and 1901-2002, dry years do not correspond with known drought years elsewhere in Ethiopia, and interannual variability is poorly correlated with another long rainfall series in Ethiopia (Gore), Blue Nile river flows and the southern oscillation index. This suggests strongly that the record for Addis Ababa should not be used as a proxy for conditions in Ethiopia, particularly the more drought-prone areas to the north and east. We conclude that the temperature series are suspect but that the full rainfall record is useful for analysis of long-term rainfall conditions in Addis Ababa.

The world’s climate is changing and will continue to change into the coming century at rates projected to be unprecedented in recent human history. The risks associated with these changes are real but highly uncertain. Societal vulnerability to the risks associated with climate change may exacerbate ongoing social and economic challenges, particularly for those parts of societies dependent on resources that are sensitive to changes in climate. Risks are apparent in agriculture, fisheries and many other components that constitute the livelihood of rural populations in developing countries. In this paper we explore the nature of risk and vulnerability in the context of climate change and review the evidence on present-day adaptation in developing countries and on coordinated international action on future adaptation. We argue that all societies are fundamentally adaptive and there are many situations in the past where societies have adapted to changes in climate and to similar risks. But some sectors are more sensitive and some groups in society more vulnerable to the risks posed by climate change than others. Yet all societies need to enhance their adaptive capacity to face both present and future climate change outside their experienced coping range. The challenges of climate change for development are in the present. Observed climate change, present-day climate variability and future expectations of change are changing the course of development strategies - development agencies and governments are now planning for this adaptation challenge. The primary challenge, therefore, posed at both the scale of local natural resource management and at the scale of international agreements and actions, is to promote adaptive capacity in the context of competing sustainable development objectives.

This study investigates the climatological variables responsible for fluctuations in Lake Victoria levels, in particular the causal mechanism responsible for a major anomaly that occurred in 1961. A Lake Victoria rainfall series (LVRS) correlates significantly (5%) with Lake Victoria levels and is utilized for subsequent analysis of rainfall variability. Relationships between annual and seasonal (March–May and October–December (OND)) LVRS and a number of tropical and extra-tropical series were analyzed. The results illustrate the dominance of the El Nino–Southern Oscillation phenomenon in modulating LVRS. The greatest correlation is found between LVRSOND and the Southern Oscillation index (r = −0.39, significant at the 1% level), although the relationship is non-linear over the course of the century. Velocity potential χ is employed as the principal diagnostic variable. Seasonal composite maps and empirical orthogonal function (EOF) analysis of Indian Ocean region χ-fields are utilized to test the hypothesis that an Indian Ocean Walker cell is responsible for the anomalous 1961 rainfall episode. Subsequent analysis leads to the rejection of this hypothesis. EOF analysis of OND 200 hPa χ-fields reveals a number of modes of tropical variability. EOF analysis of the Indian Ocean basin illustrates the emergence of a meridional circulation directed over the Indian Ocean (EOF5). This time series correlates significantly with LVRSOND (r = −0.40, 1% level), although the spatial pattern only explains a small proportion (2.35%) of the total variance. χ analysis for OND over the broader tropical region reveals significant relationships (5%) between OND EOF3* and July–September Sahel rainfall for the preceding season and subsequent year. This relationship may assist future long-lead seasonal forecast schemes for the Sahel region. Copyright © 2003 Royal Meteorological Society.

This paper explores the use of synoptic-scale predictor variables to downscale both high- and low-frequency components of daily precipitation at sites across the British Isles. Part I investigates seasonal and inter-annual variations in three weather generator parameters with respect to concurrent variations in a North Atlantic Oscillation (NAO) index and area-average sea surface temperature (SST) anomalies. Marked spatial gradients were found in the strength of the associated correlation fields using rainfall data for the period 1961–90. For example, the persistence of winter wet-spells was most strongly correlated with the NAO index in NW Scotland, and the persistence of autumn dry-spells with SST anomalies in SE England. At such locations, North Atlantic conditioning accounted for over 40% of the inter-annual variability of precipitation occurrence. In Part II, three downscaling models were compared using independent daily precipitation data for sites located in the regions of strongest North Atlantic forcing. The parameters of Model M were implicitly conditioned by three regional airflow indices; the parameters of Model X were explicitly conditioned by either the NAO index or SST anomalies and daily vorticity; and the parameters of Model U (a three-parameter stochastic rainfall model) were unconditional. Overall, the conditional models displayed greater skill for monthly rainfall statistics relative to Model U (the control), but still did not completely remove overdispersion. On comparing Models M and X, it was evident that explicit conditioning did bestow additional advantages for the chosen sites and seasons of greatest forcing. However, further research is required to determine the generality of these results for other regions and periods of the rainfall record. Copyright © 2002 John Wiley & Sons, Ltd.

The relationship between the climatic characteristics of a river basin and its hydrological response is very well understood. River flow is the synthesis of a broad range of phenomena such as rainfall, evapotranspiration, vegetation, soil, and geomorphological characteristics. This paper analyzes the Uruguay River in terms of its flow variability and the possible influences of the El Nino/Southern Oscillation (ENSO) phenomenon over a transition region between the subtropical and the mid-latitude regimes. A number of relationships were found between the warm, cold and neutral ENSO phases and the maximum floods of the Uruguay river. The conclusion of this work enhances knowledge of the climatic characteristics of the Uruguay river basin, and it may also be useful for flood forecasting.

A variety of different methods have been proposed for downscaling large-scale General Circulation Model (GCM) output to the time and space scales required for climate impact studies. Using weather types to achieve this goal provides greater understanding of the problems that are involved compared to the many “black box” techniques that have been proposed. Analyses using Lamb weather types, counts of weather fronts and air flow indices over the British Isles show strong relationships with daily rainfall characteristics such as the probability and amount of rainfall. Three versions of a weather type method are described for generating daily rainfall series. Two methods use an objective scheme to classify daily circulation types over the British Isles along the lines of Lamb's subjective classification. The third method is based on user-defined categories of vorticity. Each method categorises rainfall events according to whether the previous day was wet or dry. All three methods successfully reproduce the monthly means, persistence and interannual variability of two daily rainfall time series during a validation period. A significant advantage of using vorticity is that it is a continuous variable and is strongly related to the probability of rainfall and the magnitude of rainfall events. The paper ends with a discussion of the issues relevant to the application of this method to the development of climate scenarios from GCMs.

Asia's mega-deltas are densely populated and face multiple stressors including upstream development and sea-level rise. Adapting to these challenges requires difficult choices between hard and soft responses set within a strongly political context.

This paper describes the development and validation of a water balance model of the Upper Blue Nile in Ethiopia. A major requirement of any modelling attempt is the availability of climatic and hydrological data. However, for the Upper Blue Nile, only a limited number of observation sites are available over a very large area. As a result, the model described here is a grid-based water balance model which requires limited data inputs, few parameters and runs on a monthly time-step. Climate is dominated by the influence of elevation in the river basin. Estimates of potential evapotranspiration (PE) and rainfall are predicted for 10-minute resolution grid cells for input to the model. These estimates are based on multiple regression models using latitude, longitude and elevation. In the basin, annual mean PE and rainfall range, with increasing elevation, from 1800 mm to 1200 mm and 924 mm to 1845 mm, respectively. In the model, vegetation cover is not explicitly treated and soil characteristics are ...

The purpose of this book is to present an overview of the latest research, policy, practitioner, academic and international thinking on water security—an issue that, like water governance a few years ago, has developed much policy awareness and momentum with a wide range of stakeholders. As a concept it is open to multiple interpretations, and the authors here set out the various approaches to the topic from different perspectives. Key themes addressed include: - Water security as a foreign policy issue - The interconnected variables of water, food, and human security - Dimensions other than military and international relations concerns around water security - Water security theory and methods, tools and audits. The book is loosely based on a masters level degree plus a short professional course on water security both given at the University of East Anglia, delivered by international authorities on their subjects. It should serve as an introductory textbook as well as be of value to professionals, NGOs, and policy-makers.

This paper describes the application of hydrologic models of the Blue Nile and Lake Victoria sub-basins to assess the magnitude of potential impacts of climate change on Main Nile discharge. The models are calibrated to simulate historical observed runoff and then driven with the temperature and precipitation changes from three general circulation model (GCM) climate scenarios. The differences in the resulting magnitude and direction of changes in runoff highlight the inter-model differences in future climate change scenarios. A 'wet' case, 'dry' case and composite case produced +15 (+12), -9 (-9) and + 1(+7) per cent changes in mean annual Blue Nile (Lake Victoria) runoff for 2025, respectively. These figures are used to estimate changes in the availability of Nile water in Egypt by making assumptions about the runoff response in the other Nile sub-basins and the continued use of the Nile Waters Agreement. Comparison of these availability scenarios with demand projections for Egypt show a slight surplus ...

The relationships between regional daily precipitation time series in the British Isles and 3 indices of air flow are examined with a view to assessing their potential for use in GCM downscaling. These indices, calculated from daily grid-point sea-level pressure data, are as follows: total shear vorticity, a measure of the degree of cyclonicity; strength of the resultant flow; and angular direction of flow. The 3 indices, particularly vorticity, exert a strong control over daily precipitation characteristics such as the probability and amount of precipitation. There are significant regional differences in the relationships with precipitation, particularly between the England and Wales series and the Scotland and Northern Ireland series. Comparison of the relationships between air flow indices and regional and 2 single site precipitation series in England shows they are similar, although at the site-scale local factors may play an important role in affecting the relationships with the indices. Two models for generating daily precipitation series from vorticity are presented and evaluated by their ability to reproduce the following characteristics of precipitation over an independent validation period: annual totals and interannual variability, wet day probability and spell duration, and size of daily precipitation amounts. Model 1 is based on empirical relationships between vorticity and precipitation. Model 2 is based on user-defined categories of vorticity. The results for 2 sites (Durham and Kempsford) show that both models reproduce key characteristics of the observed daily precipitation series. Differences in model structure and number of parameters affect their accuracy in simulating the interannual variability and daily characteristics of precipitation. The air flow indices represent a significant advantage over traditional weather types because they are continuous variables. Previous downscaling techniques have relied upon classification techniques that impose artificial boundaries to define classes that may contain a wide range of conditions and no information about the intensity of development of the weather system concerned. As the 3 air flow indices are the basic determinants for describing the day's weather in many parts of the world, there is significant potential to apply this technique to other such regions. An example is shown of the relationships between daily precipitation in Switzerland and the air flow indices. The models may also be applied to the development of future daily precipitation scenarios using the coarse-scale output of GCM pressure fields.

This chapter addresses changes in weather and climate events relevant to extreme impacts and disasters. An extreme (weather or climate) event is generally defined as the occurrence of a value of a weather or climate variable above (or below) a threshold value near the upper (or lower) ends (‘tails’) of the range of observed values of the variable. Some climate extremes (e.g., droughts, floods) may be the result of an accumulation of weather or climate events that are, individually, not extreme themselves (though their accumulation is extreme). As well, weather or climate events, even if not extreme in a statistical sense, can still lead to extreme conditions or impacts, either by crossing a critical threshold in a social, ecological, or physical system, or by occurring simultaneously with other events. A weather system such as a tropical cyclone can have an extreme impact, depending on where and when it approaches landfall, even if the specific cyclone is not extreme relative to other tropical cyclones. Conversely, not all extremes necessarily lead to serious impacts. [3.1] Many weather and climate extremes are the result of natural climate variability (including phenomena such as El Nino), and natural decadal or multi-decadal variations in the climate provide the backdrop for anthropogenic climate changes. Even if there were no anthropogenic changes in climate, a wide variety of natural weather and climate extremes would still occur. [3.1] A changing climate leads to changes in the frequency, intensity, spatial extent, duration, and timing of weather and climate extremes, and can result in unprecedented extremes. Changes in extremes can also be directly related to changes in mean climate, because mean future conditions in some variables are projected to lie within the tails of present-day conditions. Nevertheless, changes in extremes of a climate or weather variable are not always related in a simple way to changes in the mean of the same variable, and in some cases can be of opposite sign to a change in the mean of the variable. Changes in phenomena such as the El Nino-Southern Oscillation or monsoons could affect the frequency and intensity of extremes in several regions simultaneously.

Substantial fluctuations in precipitation and runoff have occurred over the Nile Basin in recent decades. Ten-year mean flows of the Blue Nile (Khartoum gauge) during the 20th century have ranged from 42.2 to 56.7 km3 and for the White Nile (Malakal gauge) from 25.5 to 36.9 km3. These fluctuations have been responsible for changes in decade-mean Main Nile discharge of up to ± 20% which have had important consequences for water resource management in both Egypt and Sudan.