Search

Organisations, in the private, public and third sectors, are critical stakeholders and actors in the governance of climate change adaptation. Understanding organisational perceptions of preparedness, risk and response to climate change is important for effective climate adaptation-focused actions and policy design. Our study focuses on two research questions: what factors influence adaptation actions by organisations?, and what do organisations mean by the term ‘adaptation’? To address these, we developed and analysed a national survey of UK-based organisations’ perceptions of adapting to a changing climate, administered in spring 2021 (n = 2,429). Our findings confirm that awareness matters: respondents who reported that their organisation had high levels of concern about climate change risk or threat, and which had greater integration of adaptation within processes, are more likely to take adaptation action. In addition, we find a positive relationship between the occurrence and type of extreme event experienced and increased adaptation action by organisations. However, when asked about specific adaptation measures taken by organisations, examples of mitigation are more frequently mentioned compared to adaptation-type actions. Whether this may signal confusion or conflation of adaptation and mitigation by organisations requires further study. These findings offer critical insights into the perceptions of organisations as pivotal leaders of enacting responses to climate change. A renewed focus on organisational experiences, awareness, attitudes and capacity regarding adaptation can assist in better understanding how organisations can facilitate improved climate-resilient decision-making.

Within research on climate information for decision-making, localized insights on the influences of climate information use remain limited in small and low-income countries. This paper offers an empirical contribution on Caribbean perspectives of climate information use considering current barriers and enablers in the region. We employ thematic analysis of 26 semi-structured interviews with region-focused sectoral experts (including end-users and decision-makers) drawn from climate adaptation, disaster risk reduction, and resilience focused initiatives and institutions. The results reaffirm presence of known barriers, such as the crucial role of finance, but notably we identify a range of interlinked enabling and catalyzing conditions necessary for the effective use of climate information. These conditions include the need for island- and sector- contextualized climate information, the role of international donors, the importance of adequate human resource capacity and presence of loud voices/climate champions, as well as the need for effective political and legislative mandates and for greater co-production. We construct a visualization of respondents' understanding of influencing factor interrelationships. This shows how their heuristics of climate information use for decision-making intricately link with roles for proactive climate champions, and that available finance often reflects donor interests. We end by discussing how these insights can contribute to strategies for more effective climate information use to promote resilience within the region.

Development corridors are linear programmes of infrastructure and agriculture aiming to facilitate rapid socio-economic development. In Africa, they are a major development activity, with 88 underway or planned corridors. Drawing from extensive literature and insights gleaned from a 4 year research programme, this review scrutinizes the impacts of development corridors on people, wildlife and ecosystems in Kenya and Tanzania, proposing solutions to achieve better outcomes. The overarching goal was to discern the principle challenges emerging from the practical execution of the prevailing corridor model. The holistic approach taken, assessing the development corridors paradigm through an integrated ecological, social, and economic lens, provides novel insights that have not been possible using more traditional—siloed—research approaches. Eight key challenge areas are identified: impact assessments processes; coherence across international, national and local planning; governance; inclusivity; equality; impacts on biodiversity and ecosystem services; incorporation of future climate risks; and integrated water resource management. Poorly planned and implemented corridors detrimentally impact livelihoods and ecosystems. They lack a sustainable development vision, detailed social, environmental or climate risk assessments, and develop incrementally in policy and corporate spaces. There is also often a disconnect between investors and recipient governments, with some investors funding what governments request without applying internationally-recognised safeguards, and governments lacking capacity and resources to enforce regulations. We make recommendations for addressing these challenge areas. These aim to enhance impact assessment efficacy; integrate local perspectives into effective and inclusive corridor planning; overcome siloed project development and implementation; anticipate future development projections; and prioritise landscape preservation for enhanced ecosystem services and climate resilience.

This research contributes to literature on private sector adaptation, examining business-level adaptation to climate change in the UK wine sector. The research adopts a temporal and relational view of adaptation, through a sector-wide, value chain lens and through considering adaptation to both climate variability and longer-term change. Using the lens of ‘a good year’ and ‘a bad year’ in the sector, we consider the role of extreme events in adaptation decision-making and learning. We focus, unusually, on both opportunities and risks of climate change. Results show businesses increasingly see climate change as an opportunity for the UK wine sector. Yet climate risks remain and propagate along value chains, through supply and demand. This produces winners and losers in ‘good years’ and ‘bad years’, as well as over longer timescales. We find businesses along the value chain take steps to engage in extensive proactive adaptation behaviour, often right from business design and development. Business relationships condition climate risk exposure and adaptive capacity and adaptation decisions within one business can influence risks and opportunities throughout the value chain. Our results also reflect and develop organisational adaptation theories. We find businesses continually refine their adaptation strategies in response to climate variability and extreme events. They enhance adaptation learning by experimenting with new technologies and strategies. Irregular and extreme events can become important focal or tipping points in creative iteration and innovation of adaptation strategies, including for longer-term climate change. Our results stand in contrast to earlier literatures which suggest that businesses consider climate change to be too uncertain, or long-term, to engage in adaptation. Instead, climate change has become a master-narrative within the wine industry, through which sector actors often interpret their experiences and orient their business design and activities. Results indicate a strong dependence on own experience in adaptation decision making, that risks creating adaptation lock-in. We propose a typology of proactive private sector adaptation responses.

Between 1981–2000 and 1999–2018, growing season average temperatures (GST) in the main UK viticulture regions have warmed ~1.0 °C and are now more reliably > 14.0 °C GST. This warming has underpinned the rapid expansion of the UK viticulture sector and its current focus on growing grape varieties for sparkling wine. Near-term (2021–2040) climate change may condition opportunities for further variety and/or wine style changes. Using the latest high-resolution (5 km) ensemble (× 12) of downscaled climate change models for the UK (UK Climate Projections; UKCP18) under Representative Concentration Pathway (RCP) 8.5, we calculate near-term trends and variability in bioclimatic indices (BCIs). We simulate the projected repetition of the UK's highest yielding season —2018— and use an analogue approach to model the 1999–2018 mean growing season temperatures from Pinot noir producing areas of Champagne (France), Burgundy (France) and Baden (Germany) over the UK during 2021–2040. We also project, across the UK for the 2021–2040 period, BCI values of recent high-quality vintage years from Champagne and Burgundy. GST are projected to increase from a 1999–2018 spatial range of 13.0 (minimum threshold)–15.7 °C to a future (2021–2040) range of 13.0–17.0 °C, and Growing Degree Days (GDD) from 850 (minimum threshold)–1267 to 850–1515. Growing season precipitation (GSP) is projected to decline in some UK viticulture areas but is not modelled as a limiting viticulture factor. High inter-annual weather variability is simulated to remain a feature of the UK viticulture climate and early season frost risk is likely to occur earlier. Large areas of the UK are projected to have > 50 % of years within the bioclimatic ranges experienced during the 2018 growing season, indicating potential higher yields in the future. The 1999–2018 mean Champagne, Burgundy and Baden GST and GDD are projected for much of England and some areas in the far south and south-east of Wales during 2021–2040, with significant areas projected to have > 25 % of years within the BCI ranges of top Champagne vintages. These results indicate greater potential for Pinot noir for sparkling wines and shifting suitability to still red wine production. Accounting for changes in variety suitability and wine styles will be essential to maximise opportunities and build resilience within this rapidly expanding wine region.

Water resource system planning is complicated by uncertainty on the magnitude and direction of climate change. Therefore, developments such as new infrastructure or changed management rules that would work acceptably well under a diverse set of future conditions (i.e., robust solutions) are preferred. Robust multi-objective optimisation can help identify advantageous system designs which include existing infrastructure plus a selected subset of new interventions. The method evaluates options using simulated water resource performance metrics statistically aggregated to summarise performance over the climate scenario ensemble. In most cases such ‘robustness metrics’ are sensitive to scenarios under which the system performs poorly and so results may be strongly influenced by a minority of unfavorable climate scenarios. Understanding the influence of specific climate scenarios on robust optimised decision alternatives can help better interpret their results. We propose an automated multi-criteria design-under-uncertainty sensitivity analysis formulation that uses multi-objective evolutionary algorithms to reveal robust and efficient designs under different samples of a climate scenario ensemble. The method is applied to a reservoir management problem in the Rufiji River basin, Tanzania, which involves the second largest dam in Africa. We find that solutions optimised for robustness under alternative groups of climate scenarios exhibit important differences. This becomes particularly decision-relevant if analysts and/or decision-makers have differing confidence levels in the relevance of certain climate scenarios. The proposed approach motivates continued research on how climate model credibility should inform climate scenario selection because it demonstrates the influence scenario selection has on recommendations arising from robust optimisation design processes.

West Africa exhibits decadal patterns in the behaviour of droughts and floods, creating challenges for effective water resources management. Proposed drivers of prolonged shifts in hydrological extremes include the impacts of land-cover change and climate variability in the region. However, while future land-degradation or land-use are highly unpredictable, recent studies suggest that prolonged periods of high-flows or increasing flood occurrences could be predicted by monitoring sea-surface temperature (SST) anomalies in the different ocean basins. In this study, we thus examine: i) what ocean basins would be the most suitable for future seamless flood-prediction systems; ii) how these ocean basins affect high-flow extremes (hereafter referred as extreme streamflow); and iii) how to integrate such nonstationary information in flood risk modelling. We first use relative importance analysis to identify the main SST drivers modulating hydrological conditions at both interannual and decadal timescales. At interannual timescales, Pacific Niño (ENSO), tropical Indian Ocean (TIO) and eastern Mediterranean (EMED) constitute the main climatic controls of extreme streamflow over West Africa, while the SST variability in the North and tropical Atlantic, as well as decadal variations of TIO and EMED are the main climatic controls at decadal timescales. Using regression analysis, we then suggest that these SST drivers impact hydrological extremes through shifts in the latitudinal location and the strength of the Intertropical Convergence Zone (ITCZ) and the Walker circulation, impacting the West African Monsoon, especially the zonal and meridional atmospheric water budget. Finally, a nonstationary extreme model, with climate information capturing regional circulation patterns, reveals that EMED SST is the best predictor for nonstationary streamflow extremes, particularly across the Sahel. Predictability skill is, however, much higher at the decadal timescale, and over the Senegal than the Niger catchment. This might be due to stronger impacts of land-use (-cover) and/or catchment properties (e.g. the Inner Delta) on the Niger River flow. Overall, a nonstationary framework for floods can also be applied to drought risk assessment, contributing to water regulation plans and hazard prevention, over West Africa and potentially other parts of the world.

Abstract Global water use for food production needs to be reduced to remain within planetary boundaries, yet the financial feasibility of crucial measures to reduce water use is poorly quantified. Here, we introduce a novel method to compare the costs of water conservation measures with the added value that reallocation of water savings might generate if used for expansion of irrigation. Based on detailed water accounting through the use of a high‐resolution hydrology‐crop model, we modify the traditional cost curve approach with an improved estimation of demand and increasing marginal cost per water conservation measure combination, adding a correction to control for impacts on downstream water availability. We apply the method to three major river basins in the Indo‐Gangetic plain (Indus, Ganges and Brahmaputra), a major global food producing region but increasingly water stressed. Our analysis shows that at basin level only about 10% (Brahmaputra) to just over 20% (Indus and Ganges) of potential water savings would be realized; the equilibrium price for water is too low to make the majority of water conservation measures cost effective. The associated expansion of irrigated area is moderate, about 7% in the Indus basin, 5% in the Ganges and negligible in the Brahmaputra, but farmers' gross profit increases more substantially, by 11%. Increasing the volumetric cost of irrigation water influences supply and demand in a similar way and has little influence on water reallocation. Controlling for the impact on return flows is important and more than halves the amount of water available for reallocation.

Amidst increasing interest in multi-stakeholder partnerships (MSPs) in climate discourse, this paper identifies four rationales for why MSPs may be particularly suited to supporting adaptation from existing literatures. With a focus on MSPs that seek to support adaptation among micro, small and medium enterprises (SMEs) in Kenya, we then investigate the extent to which this potential is being realised in practice, through interviews with partners engaged in the design and implementation of MSPs. This allows us to examine some of the opportunities, challenges and distributional risks that may result from employing MSPs to support adaptation. We find that through action and investment from donors and the public sector in areas such as research, data access, relationship building, training and capacity building, access to finance and business incubation, MSPs can enable a wide range of private sector actors to deliver adaptation resources to SMEs. Beneficiaries include small-scale SMEs in agricultural value chains in remote regions, that could otherwise fall outside of market inclusion. As such, respondents in this research typically considered MSPs to present an exciting opportunity to plug gaps in adaptation and development finance. Further analysis, however, suggests that dependence on market mechanisms for delivering adaptation resources means that MSPs risk excluding the poorest groups, exposing businesses to new risks and reproducing existing inequalities. Additionally, MSPs often remain heavily dependent on donor-led organisations for both resources and momentum. In Kenya, opportunities to develop more integrated responses to supporting the adaptive capacity of SMEs are being missed through a disconnect between the practice of MSPs and national public sector development frameworks and institutions.

Abstract Many river basins in the Global South are undergoing rapid development with major implications for the interdependent water‐energy‐food‐environmental (WEFE) “nexus” sectors. A range of views on the extent to which such natural‐human systems should be developed typically exists. The perceived best investments in river basins depend on how one frames the planning problem. Therefore, we propose an approach where the best possible (optimized) implementations of different river basin development scenarios are assessed by comparing their WEFE sector trade‐offs. We apply the approach to Tanzania's Rufiji river basin, an area with multiple WEFE interdependencies and high development potential (irrigation and hydropower) and ecosystem services. Performance indicators are identified through stakeholder consultation and describe WEFE sector response under scenarios of river basin development. Results show considerable potential exists for energy and irrigation expansion. Designs that prioritize energy production adversely affect environmental performance; however, part of the negative impacts can be minimized through release rules designed to replicate the natural variability of flow. The reliability of monthly energy generation is more sensitive to environmental‐oriented management than the cumulative annual energy production. Overall results highlight how sectoral trade‐offs change depending on the extent of development, something that may be difficult to regulate in the future, and that there are important basin‐scale interdependencies. Benefits and limitations of the approach and its application are discussed.

This perspective explores how climate services may potentially incorporate information emerging from the new science of interannual-to-decadal (I2D) climate prediction. The geographic focus is the Sahel region of West Africa, which has demonstrated prediction advances for rainfall on the I2D timescale, and vulnerability to climate hazards. The perspective draws on reviews of predictability and applications in the region and a national workshop in Sudan to explore applications. Decadal prediction is an emerging capability, to date being undertaken primarily as a learning process. However, for the multi-year forecast information, we identify a number of new dimensions that challenge product design and user uptake. Current experiments often present forecasts as the average conditions for a target first year, and then subsequent set of years raising a question of what a forecast of mean average conditions for years 2–5 represents in terms of climate to expect, and how annual updates to multi-year forecasts may be produced and communicated. Stakeholder consultations highlighted some of the concerns noted for existing seasonal forecasts, but now translated into terms for multi-year information, such as confidence in information, need for research on temporal downscaling (which may now include information on the risks of climate anomalies in the individual years that make up the forecast period), capacity development, and that communities would need to be convinced about effectiveness, alongside careful communication, especially in the context of multi-year planning. This perspective captures one of the first learning case studies on how I2D prediction may be explored in a given region, a first step towards climate services development that integrate I2D information.

Globally, semi-arid lands (SALs) are home to approximately one billion people, including some of the poorest and least food secure. These regions will be among the hardest hit by the impacts of climate change. This article urges governments and their development partners to put SAL inhabitants and their activities at the heart of efforts to support adaptation and climate resilient development, identifying opportunities to capitalize on the knowledge, institutions, resources and practices of SAL populations in adaptation action.

Making climate-resilient planning and adaptation decisions is, in part, contingent on the use of climate information. Growing attention has been paid to the “usability gap” and the need to make information both useful and useable to decision-makers. Less attention has, however, been paid to the factors that determine whether, once created, useful and useable information is then actually used. In this Perspectives piece, we outline a framework that puts together the pieces necessary to close the “usability gap” – highlighting not only what is required to make information useful and useable, but also what is required to ensure that useful and useable information is actually used. Creating useful information is subject to understanding and being able to deliver metrics that address identified needs in a range of decision-making contexts. Creating useable information requires legitimate and credible information that is visualised and communicated in ways that are accessible and understandable. The framework highlights traditionally under-recognized enablers necessary to promote effective use of the growing availability of useful and useable climate information in decision-making; supportive institutions, appropriate policy frameworks, capacity of individuals and agency to make decisions. Whilst this is not enough in itself to effect information use, we argue that greater focus on these enablers can re-balance the activities promoted through climate services and increase the likelihood of successful use. We illustrate the framework with case examples of co-producing climate information for the tea and water sectors in sub-Saharan Africa.

Study region: The Rufiji basin, East Africa. Study focus: Rapid advances in global hydrological model (GHM) resolution, model features, and in situ and remotely sensed datasets are driving progress towards local relevance and application. Despite their increasing use, however, evaluation of local hydrological performance of GHMs is rare. In this paper, we examine the performance of a well-known GHM (LPJmL, recently modified to ∼9 km resolution) with and without modest steps to regionalise the model. We consider the Rufiji river basin, an economically important medium-size basin in eastern Africa. New hydrological insights for the region: Our results indicate that the unmodified GHM does provide a reasonable first approximation of spatial variability in mean flow conditions, but scores rather poorly on seasonal and inter-annual variability. For the model to achieve levels of performance indicators comparable with bespoke modelling, modifications to model inputs, additional runoff delay and wetland parameterization were required. The largest improvements are associated with adjustments in precipitation and enhanced runoff delay. With the modified version, as a proof of concept, we show that a well-known drying trend in a major tributary of the Rufiji can be explained by implementing irrigation abstractions in the model. Overall, the results suggest that with limited and fairly simple modification GHMs can be regionalised to allow their use for scenario testing and further exploration of key local processes in basins with limited observational data. Keywords: LPJmL, Global hydrological model, Regionalization, Rufiji, Irrigation abstractions, Water resources, Stiegler’s Gorge

Climate change adaptation is unavoidable, particularly in developing countries where the adaptation deficit is often larger than in developed countries. Robust Decision Making (RDM) approaches are considered useful for supporting adaptation decision making, yet case study applications in developing countries are rare. This review paper examines the potential to expand the geographical and sectoral foci of RDM as part of the repertoire of approaches to support adaptation. We review adaptation decision problems hitherto relatively unexplored, for which RDM approaches may have value. We discuss the strengths and weaknesses of different approaches, suggest potential sectors for application and comment on future directions. We identify that data requirements, lack of examples of RDM in actual decision-making, limited applicability for surprise events, and resource constraints are likely to constrain successful application of RDM approaches in developing countries. We discuss opportunities for RDM approaches to address decision problems associated with urban socio-environmental and water-energy-food nexus issues, forest resources management, disaster risk management and conservation management issues. We examine potential entry points for RDM approaches through Environmental Impact Assessments and Strategic Environmental Assessments, which are relatively well established in decision making processes in many developing countries. We conclude that despite some barriers, and with modification, RDM approaches show potential for wider application in developing country contexts.

This focus collection on resilience to climate shocks in the tropics draws together 16 papers that predominantly examine the impacts of, and responses to, the 2015/2016 El Niño-Southern Oscillation event, in a range of contexts. This introductory synthesis contextualises the collection of papers by reviewing important concepts and highlighting some important insights that emerge from the collection. The papers in this collection collectively highlight: the value of longitudinal and interdisciplinary research in understanding both the roots of, and responses to, resilience challenges; the critical interaction between climatic and land-use changes; and the ways in which governance arrangements underpin societal decision-making across a range of scales and contexts to shape resilience.

We quantify the heavily oil-dominated WEF nexus in three Gulf Cooperation Council (GCC) countries (Kuwait, Qatar and Saudi Arabia) across spatial scales and over time, using available empirical data at the national level, and explore the exposure to nexus stresses (groundwater depletion) in other countries through virtual water trade. At the domestic scale, WEF trade-offs are fairly limited; while all sectors require considerable amounts of energy, the requirements for water and food production are modest compared to other uses. At the international scale, revenues from oil exports in the GCC allow the region to compensate for low food production and scarce water availability. This dependency is dynamic over time, increasing when oil prices are low and food prices are high. We show how reducing domestic trade-offs can lead to higher exposure internationally, with rice imports originating in regions where groundwater is being depleted. However, Saudi Arabia’s increased wheat imports, after reversing its food self-sufficiency policy, have had limited effects on groundwater depletion elsewhere. Climate change mitigation links the WEF nexus to the global scale. While there is great uncertainty about future international climate policy, our analysis illustrates how implementation of measures to account for the social costs of carbon would reduce the oil and gas revenues available to import food and desalinate water in the GCC.

In a Perspective, Hannah Nissan and Declan Conway discuss the implications of uncertainty about projected impacts of climate change on health.

The El Niño event in 2015/2016 was one of the strongest since at least 1950. Through surveys and interviews with key informants, we found businesses in the capital cities of Zambia, Botswana and Kenya experienced major disruption to their activities from El Niño related hydroelectric load shedding, water supply disruption and flooding, respectively. Yet, during the 2015/2016 El Niño, fluctuations in precipitation were not extreme considering the strength of the El Niño 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.

Knowledge about regional and local climate change can inform climate risk assessments and adaptation decisions. However, estimates of future precipitation change at the regional and local level are deeply uncertain for many parts of the world. A novel methodology was developed that uses climate processes and expert elicitation to build narratives of future regional precipitation change. The narratives qualitatively describe physically plausible evolutions of future regional climate substantiated by climate processes. This method is applied to the Indian Summer Monsoon, focusing on the Cauvery River Basin in Karnataka, Southern India. Six climate narratives are constructed as a function of two drivers prioritised by the experts: moisture availability over the Arabian Sea and strength of the low-level westerly flow. The narratives describe how future precipitation could change until the 2050s and which climate processes and anthropogenic factors could influence this evolution. Analysis using observed (Global Precipitation Climatology Centre) and re-analysis (ERA20 and Interim) data shows the experts’ judgement on key drivers fits well with empirical relationships. The expert elicited drivers explain 70% of the variance in peak monsoon precipitation (July and August) over the Western Ghats between 1979−2013 (using ERA Interim). The study shows that through expert elicitation, process-based narratives enable climate scientists to characterise and communicate elements of deep uncertainty in future precipitation change. Expert judgment techniques need be more widely applied to characterise uncertainty in regional and local climate change.

Temporal and spatial variability of precipitation in southern Africa is particularly high. The associated drought and flood risks, combined with a largely rain-fed agriculture, pose a challenge for water and food security in the region. As regional collaboration strengthens through the Southern Africa Development Community and trade with other regions increases, it is thus important to understand both how climate variability affects agricultural productivity and how food trade (regional and extra-regional) can contribute to the region's capacity to deal with climate-related shocks. We combine global hydrological model simulations with international food trade data to quantify the water resources embedded in international food trade in southern Africa and with the rest of the world, from 1986–2011. We analyze the impacts of socio-economic changes and climatic variability on agricultural trade and embedded water resources during this period. We find that regional food trade is efficient in terms of water use but may be unsustainable because water-productive exporters, like South Africa, rely on increasingly stressed water resources. The role of imports from the rest of the world in the region's food supply is important, in particular during severe droughts. This reflects how trade can efficiently redistribute water resources across continents in response to a sudden gap in food production. In a context of regional and global integration, our results highlight opportunities for improved water-efficiency and sustainability of the region's food supply via trade.

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.

Extreme heat stress during the crop reproductive period can be critical for crop productivity. Projected changes in the frequency and severity of extreme climatic events are expected to negatively impact crop yields and global food production. This study applies the global crop model PEGASUS to quantify, for the first time at the global scale, impacts of extreme heat stress on maize, spring wheat and soybean yields resulting from 72 climate change scenarios for the 21st century. Our results project maize to face progressively worse impacts under a range of RCPs but spring wheat and soybean to improve globally through to the 2080s due to CO _2 fertilization effects, even though parts of the tropic and sub-tropic regions could face substantial yield declines. We find extreme heat stress at anthesis (HSA) by the 2080s (relative to the 1980s) under RCP 8.5, taking into account CO _2 fertilization effects, could double global losses of maize yield ( Δ Y = −12.8 ± 6.7% versus − 7.0 ± 5.3% without HSA), reduce projected gains in spring wheat yield by half ( Δ Y = 34.3 ± 13.5% versus 72.0 ± 10.9% without HSA) and in soybean yield by a quarter ( Δ Y = 15.3 ± 26.5% versus 20.4 ± 22.1% without HSA). The range reflects uncertainty due to differences between climate model scenarios; soybean exhibits both positive and negative impacts, maize is generally negative and spring wheat generally positive. Furthermore, when assuming CO _2 fertilization effects to be negligible, we observe drastic climate mitigation policy as in RCP 2.6 could avoid more than 80% of the global average yield losses otherwise expected by the 2080s under RCP 8.5. We show large disparities in climate impacts across regions and find extreme heat stress adversely affects major producing regions and lower income countries.

There is increasing evidence of crop yield response to recent global warming, yet there is poor understanding of the relative contributions of different climatic variables to changes in crop production. Using a spatially calibrated crop model with cultivars and crop inputs held constant for the year 2000, we simulate idealized national cereal production during the period 1961–2010 under different combinations of observed climate and CO _2 forcings. With increasing CO _2 and all climate forcings, production shows a slight and insignificant change (−0.9% between 1961 and 2010); however, without CO _2 the combined climate forcings decrease production (−8.6%). Changing one climate variable at a time, whilst holding the other variables constant at 1961 values, observed warming has virtually no overall effect on production (0.01%), precipitation decreases it by 1.2% and radiation decreases it by 7.0%. The effects are management and crop dependent, with decreasing radiation responsible for reduced irrigated crop production, and precipitation for variability in rain-fed crop production. Rice is the most sensitive crop, with the largest decline (−12.4%) in simulated production. Wheat shows reduced yield (−9.7%) owing to climate factors, whilst offset by CO _2 fertilization (overall change 0.9%). Maize shows insignificant change (−1.2%) and moderate increase in production (2.6%), respectively. These model results suggest that decreasing radiation due to increasing aerosol concentration and other atmospheric pollutants has had a greater effect on crop production than warming trends in China. This underscores the need for crop–climate studies to resolve better the effects of radiation on crop yield and examine climate model projections of radiation in greater detail.