Climate change impacts on Namibia's natural resources and economy

Climate change is likely to exacerbate the dry conditions already experienced in southern Africa. When rainfall does come, it is likely to be in bursts of greater intensity, leading to erosion and flood damage. However, these predictions have had very little influence on policy in southern African countries. Computable general equilibrium (CGE) model simulations for Namibia indicate that over 20 years, annual losses to the Namibian economy could be up to 5% of GDP, due to the impact that climate change will have on its natural resources alone. This will affect the poorest people the most, with resulting constraints on employment opportunities and declining wages, especially for unskilled labour in rural areas. Namibia must take steps to ensure that all its policies and activities are ‘climate proofed’ and that it has a strategy to deal with displaced farmers and farm workers. The need to mainstream climate change into policies and planning is clear, and it is the responsibility of industrialized nations, who have largely created the problem of climate change, to help Namibia and other vulnerable countries cope with climate change impacts and plan for a climate-constrained future.     

Climate change and global water resources

By 2025, it is estimated that around 5 billion people, out of a total population of around 8 billion, will be living in countries experiencing water stress (using more than 20% of their available resources). Climate change has the potential to impose additional pressures in some regions. This paper describes an assessment of the implications of climate change for global hydrological regimes and water resources. It uses climate change scenarios developed from Hadley Centre climate simulations (HadCM2 and HadCM3), and simulates global river flows at a spatial resolution of 0.5×0.5° using a macro-scale hydrological model. Changes in national water resources are calculated, including both internally generated runoff and upstream imports, and compared with national water use estimates developed for the United Nations Comprehensive Assessment of the Freshwater Resources of the World. Although there is variation between scenarios, the results suggest that average annual runoff will increase in high latitudes, in equatorial Africa and Asia, and southeast Asia, and will decrease in mid-latitudes and most subtropical regions. The HadCM3 scenario produces changes in runoff which are often similar to those from the HadCM2 scenarios — but there are important regional differences. The rise in temperature associated with climate change leads to a general reduction in the proportion of precipitation falling as snow, and a consequent reduction in many areas in the duration of snow cover. This has implications for the timing of streamflow in such regions, with a shift from spring snow melt to winter runoff. Under the HadCM2 ensemble mean scenario, the number of people living in countries with water stress would increase by 53 million by 2025 (relative to those who would be affected in the absence of climate change). Under the HadCM3 scenario, the number of people living in countries with water stress would rise by 113 million. However, by 2050 there would be a net reduction in populations in stressed countries under HadCM2 (of around 69 million), but an increase of 56 million under HadCM3. The study also showed that different indications of the impact of climate change on water resource stresses could be obtained using different projections of future water use. The paper emphasises the large range between estimates of “impact”, and also discusses the problems associated with the scale of analysis and the definition of indices of water resource impact.     

1961-2009年辽河流域气候变化特征及其对水资源的影响

辽河流域是我国七大流域之一,长期以来一直存在水资源严重不足的问题。采用1961-2009年辽河流域境内水文、气象观测数据,研究气象、水文要素历史变化特征,并采用同期和滞后相关分析,建立气象要素与水文要素的最优相关关系。结果表明：辽河流域气候变暖明显,增温幅度远高于全球和中国的同期增温幅度;辽河流域降水量增减趋势不明显,总体上为略减少趋势,但存在明显的少-多-少-多-少5个阶段性变化。辽河流域蒸发量为略减少趋势,春季、夏季是蒸发量较大季节;辽河流域近50年来径流量为减少趋势,经历了偏多-偏少-偏多-偏少4个阶段的变化,最近的1996-2009年经历了年径流量最少阶段,平均年径流量仅为16.2亿 m³,只达到多年平均径流量的58 %、径流量最多年代的32 %。7月、8月是流量最为集中的月份,2个月流量就占到全年的50.24 %,超过全年的一半;辽河流域降水量与径流量有较好的相关关系。在年尺度,径流量与铁岭、法库等周边地区相关系数基本达到0.6左右;在日尺度,日降水量与降水发生后第二日流量相关程度最好,在所有等级上两者相关系数均在0.7以上,在日降水量大于等于25 mm等级上,相关系数最高可达到0.85。     

1961—2009年辽河流域气候变化特征及其对水资源的影响

辽河流域是中国七大流域之一,长期以来一直存在水资源严重不足的问题。采用1961—2009年辽河流域境内水文、气象观测数据,研究气象、水文要素历史变化特征,并采用同期和滞后相关分析,建立气象要素与水文要素的最优相关关系。结果表明：辽河流域气候变暖明显,增温幅度远高于全球和中国的同期增温幅度;辽河流域降水量增减趋势不明显,总体上为略减少趋势,但存在明显的少—多—少—多—少5个阶段性变化。辽河流域蒸发量为略减少趋势,春季、夏季是蒸发量较大季节。近50 a辽河流域径流量为减少趋势,经历了偏多—偏少—偏多—偏少4个阶段的变化,1996—2009年经历了年径流量最少阶段,平均年径流量仅为16.2亿m3,只达到多年平均径流量的58%、径流量最多年代的32%。一年之中,7月和8月径流量最大,两个月径流量占全年的50%。辽河流域降水量与径流量有较好的相关关系。在年尺度,径流量与铁岭、法库等地区降水量相关系数为0.60;在日尺度,日降水量与降水发生后第2日经流量相关程度最好,在所有等级上两者相关系数为0.70或以上;在日降水量大于等于25 mm等级上,相关系数最高为0.85。     

气候变化对水资源影响预估常用指标

正全球气候变暖已成共识。自20世纪50年代至今,全球几乎所有地区都在持续变暖。IPCC第五次评估报告(AR5)显示,全球温度将进一步升高[1]。以1986—2005年为基准,预计全球地表温度在2016—2035年将升高0.3～0.7℃,2081—2100年升高0.3～4.8℃[2]。全球变暖导致一系列环境问题:海洋温度及地球表面温度上升,     

Paper 4. climate change impacts on water resources and possible responses in the mink region

The capacity to supply both instream and offstream water uses under alternative climate conditions and likely future changes in population, technology, and water-using practices are examined through an adaptation of the framework developed in the Second National Water Assessment. Two measures of the adequacy of water supplies - the availability of renewable supplies to provide for withdrawal and instream uses and the relation between desired instream flows and current streamflows - are used to examine the impact of the 1931–1940 analog climate (with and without CO₂ enrichment) on Missouri, Iowa, Nebraska, and Kansas (MINK). The impacts of the analog climate on water supplies are estimated from actual streamflow data and estimates of the differences in reservoir evaporation under the 1931–1940 analog and the 1951–1980 control climates. A modification of the Erosion Productivity Inventory Calculator (EPIC) model is used to estimate the impacts of the analog climate (with and without CO₂ enrichment) on irrigation water use.Water, which is already a scarce resource in the MINK region, would become much scarcer if the climate of the 1930s were to become the norm. Mean assessed total streamflow would drop to 69% of the control climate level for the Missouri River Basin, 71% for the Upper Mississippi, and 93% for the Arkansas. Even in the absence of climate change, MINK will have less water in the year 2030 than it does today because groundwater stocks are being depleted and increased upstream diversions would reduce surface flows into these states. Irrigation and instream uses such as navigation, hydroelectric power production, recreation, and fish and wildlife habitat would be most adversely, impacted by the climate-induced changes in water supplies.     

Climate change and water resources in the Bagmati River Basin,Nepal

This paper characterizes potential hydrological impact of future climate in the Bagmati River Basin, Nepal. For this research, basinwide future hydrology is simulated by using downscaled temperature and precipitation outputs from the Hadley Centre Coupled Model, version 3 (HadCM3), and the Hydrologic Engineering Center's Hydrologic Modeling System (HEC-HMS). It is predicted that temperature may rise maximally during the summer rather than winter for both A2 and B2 Special Report on Emissions Scenarios (SRES) scenarios. Precipitation may increase during the wet season, but it may decrease during other seasons for A2 scenario. For B2 scenario, precipitation may increase during all the seasons. Under the A2 scenario, premonsoon water availability may decrease more in the upper than the middle basin. During monsoons, both upper and middle basins show increased water availability. During the postmonsoon season, water availability may decrease in the upper part, while the middle part shows a mixed trend. Under the B2 scenario, water availability is expected to increase in the entire basin. The analysis of the projected hydrologic impact of climate change is expected to support informed decision-making for sustainable water management.     

Climate change in northern Patagonia: critical decrease in water resources

The current study presents an assessment of the impact of climate change on water yield, one of the main hydrological ecosystem services, in northern Patagonia. The outputs of regional climate models from the CORDEX Project for South America were used to drive the InVEST water yield model. CORDEX regional climate models project for the far future (2071–2100) an increase in temperature higher than 1.5 °C and a precipitation decrease ranging from − 10 to − 30% for the study area. The projected warmer and dryer climate emerges as a robust signal based on model agreement and on consistent physical drivers of these changes. Moreover, both the projected increase in evapotranspiration and the decrease in precipitation contribute to a strong decrease in water yield of around − 20 to − 40% in the headwaters of northern Patagonian watersheds. Comparison of the results in the two basins reveals that the land cover may be considered a buffer of water yield changes and highlights the key role of protected areas in reducing the vulnerability of water resources to climate change.     

Climate change impacts on water management in the Puget Sound region, Washington State, USA

Climate change is projected to result, on average, in earlier snowmelt and reduced summer flows in the Pacific Northwest, patterns not well represented in historical observations used in water planning. We evaluate the sensitivities of water supply systems in the Puget Sound basin cities of Everett, Seattle, and Tacoma to historical and projected future streamflow variability and water demands. We simulate streamflow for the 2020s, 2040s, and 2080s using the distributed hydrology–soil–vegetation model (DHSVM), driven by downscaled ensembles of climate simulations archived from the 2007 IPCC Fourth Assessment Report. We use these streamflow predictions as inputs to reservoir system models for the three water supply systems. Over the next century, under average conditions all systems are projected to experience declines and eventual disappearance of the springtime snowmelt peak. How these shifts affect management depends on physical characteristics, operating objectives, and the adaptive capacity of each system. Without adaptations, average seasonal drawdown of reservoir storage is projected to increase in all three systems throughout the 21st century. Reliability of all systems in the absence of demand increases is robust through the 2020s however, and remains above 98% for Seattle and Everett in the 2040s and 2080s. With demand increases, however, reliability of the systems in their current configurations and with current operating policies progressively declines through the century.     

The implications of climate policy for the impacts of climate change on global water resources

This paper assesses the implications of climate policy for exposure to water resources stresses. It compares a Reference scenario which leads to an increase in global mean temperature of 4 °C by the end of the 21st century with a Mitigation scenario which stabilises greenhouse gas concentrations at around 450 ppm CO₂e and leads to a 2 °C increase in 2100. Associated changes in river runoff are simulated using a global hydrological model, for four spatial patterns of change in temperature and rainfall. There is a considerable difference in hydrological change between these four patterns, but the percentages of change avoided at the global scale are relatively robust. By the 2050s, the Mitigation scenario typically avoids between 16 and 30% of the change in runoff under the Reference scenario, and by 2100 it avoids between 43 and 65%. Two different measures of exposure to water resources stress are calculated, based on resources per capita and the ratio of withdrawals to resources. Using the first measure, the Mitigation scenario avoids 8-17% of the impact in 2050 and 20-31% in 2100; with the second measure, the avoided impacts are 5-21% and 15-47% respectively. However, at the same time, the Mitigation scenario also reduces the positive impacts of climate change on water scarcity in other areas. The absolute numbers and locations of people affected by climate change and climate policy vary considerably between the four climate model patterns.     

Climate change impacts on wildfires in a Mediterranean environment

We analyse the observed climate-driven changes in summer wildfires and their future evolution in a typical Mediterranean environment (NE Spain). By analysing observed climate and fire data from 1970 to 2007, we estimate the response of fire number (NF) and burned area (BA) to climate trends, disentangling the drivers responsible for long-term and interannual changes by means of a parsimonious Multi Linear Regression model (MLR). In the last forty years, the observed NF trend was negative. Here we show that, if improvements in fire management were not taken into account, the warming climate forcing alone would have led to a positive trend in NF. On the other hand, for BA, higher fuel flammability is counterbalanced by the indirect climate effects on fuel structure (i.e. less favourable conditions for fine-fuel availability and fuel connectivity), leading to a slightly negative trend. Driving the fire model with A1B climate change scenarios based on a set of Regional Climate Models from the ENSEMBLES project indicates that increasing temperatures promote a positive trend in NF if no further improvements in fire management are introduced.     

Climate change impacts on regional rice production in China

Rice (Oryza sativa L.) production is an important contributor to China’s food security. Climate change, and its impact on rice production, presents challenges in meeting China’s future rice production requirements. In this study, we conducted a comprehensive analysis of how rice yield responds to climate change under different scenarios and assessed the associated simulation uncertainties of various regional-scale climate models. Simulation was performed based on a regional calibrated crop model (CERES-Rice) and spatially matched climatic (from 17 global climate models), soil, management, and cultivar parameters. Grain-filling periods for early rice were shortened by 2–7 days in three time slices (2030s, 2050s, and 2070s), whereas grain-filling periods for late rice were shortened by 10–19 days in three time slices. Most of the negative effects of climate change were predicted to affect single-crop rice in central China. Average yields of single-crop rice treated with CO₂ fertiliser in central China were predicted to be reduced by 10, 11, and 11% during the 2030s, 2050s, and 2070s, respectively, compared to the 2000s, if planting dates remained unchanged. If planting dates were optimised, single-crop rice yields were predicted to increase by 3, 7, and 11% during the 2030s, 2050s, and 2070s, respectively. In response to climate changes, early and single-crop rice should be planted earlier, and late rice planting should be delayed. The predicted net effect would be to prolong the grain-filling period and optimise rice yield.     

Climate change impacts on water management and irrigated agriculture in the Yakima River Basin, Washington, USA

The Yakima River Reservoir system supplies water to ~180,000 irrigated hectares through the operation of five reservoirs with cumulative storage of ~30% mean annual river flow. Runoff is derived mostly from winter precipitation in the Cascade Mountains, much of which is stored as snowpack. Climate change is expected to result in earlier snowmelt runoff and reduced summer flows. Effects of these changes on irrigated agriculture were simulated using a reservoir system model coupled to a hydrological model driven by downscaled scenarios from 20 climate models archived by the 2007 Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. We find earlier snowmelt results in increased water delivery curtailments. Historically, the basin experienced substantial water shortages in 14% of years. Without adaptations, for IPCC A1B global emission scenarios, water shortages increase to 27% (13% to 49% range) in the 2020s, to 33% in the 2040s, and 68% in the 2080s. For IPCC B1 emissions scenarios, shortages occur in 24% (7% to 54%) of years in the 2020s, 31% in the 2040s and 43% in the 2080s. Historically unprecedented conditions where senior water rights holders suffer shortfalls occur with increasing frequency in both A1B and B1 scenarios. Economic losses include expected annual production declines of 5%–16%, with greater probabilities of operating losses for junior water rights holders.     

气候变化对长江上游径流影响预估

利用第五次国际耦合模式比较计划(CMIP5)中5个气候模式在3种典型浓度路径(RCPs)下的预估结果驱动SWAT水文模型,预估了21世纪气候变化对长江上游年径流量、季节分配以及极端径流的影响。结果表明：预估的长江上游平均气温呈显著上升趋势,21世纪末较当前(1986—2005年)升高1.5~5.5℃,降水总体呈增加趋势,在21世纪30年代后高于当前气候平均值,21世纪末相对于当前增加5%~15%。流域内气候变化存在明显空间差异,金沙江和岷沱江流域气温升高和降水增加幅度均大于流域平均值。预估的长江上游年径流量及各月平均径流均有增加趋势,在21世纪30年代后高于当前多年平均值,21世纪中期增加4%~8%,21世纪末增加10%~15%。预估的径流年内分布的均匀性有所增加,但年际变化明显增大,极端旱涝事件的频率和强度明显增加。预估的各子流域径流变化对气候变化的响应也存在差异,金沙江和岷沱江流域年径流量、年际变化和年内分布变化小,对气候变化的响应表现为低敏感;嘉陵江流域、乌江流域和长江上游干流径流增加幅度大,同时极端丰枯出现的频率和程度增加显著,是气候变化响应的敏感区域。     

Climate change impacts on fish catch in the world fishing grounds

Climate change impacts on fish catch in the major fishing areas in the world oceans using a new method for forecasting of fish catch is presented with probability statements. The data on historical behaviour of surface water temperature and fish catches were analyzed and processed to assess the dynamics of spatial temperature distribution and fish catches for the world oceans. An analysis shows that the species diversity of fish catch does not change significantly with time and hence the total fish catch was used as the main dynamic variables, practically without loss of information about the dynamic properties of the system. A predictor was constructed to predict the dynamics of fish catch for new values of four moments for a future temperature distribution and the predictor’s power was estimated with a probability statement. Based on the predicted temperatures for the years 2000–2100, the fish catches in the Pacific, Atlantic and Indian Oceans have been predicted with a probability statement.     

Climate change: impacts on electricity markets in Western Europe

This paper studies some impacts of climate change on electricity markets, focusing on three climate effects. First, demand for electricity is affected because of changes in the temperature. Second, changes in precipitation and temperature have impact on supply of hydro electric production through a shift in the inflow of water. Third, plant efficiency for thermal generation will decrease because the temperature of water used to cool equipment increases. To find the magnitude of these partial effects, as well as the overall effects, on Western European energy markets, we use the multi-market equilibrium model LIBEMOD. We find that each of the three partial effects changes the average electricity producer price by less than 2%, while the net effect is an increase of only 1%. The partial effects on total electricity supply are small, and the net effect is a decrease of 4%. The greatest effects are found for Nordic countries with a large market share for reservoir hydro. In these countries, annual production of electricity increases by 8%, reflecting more inflow of water, while net exports doubles. In addition, because of lower inflow in summer and higher in winter, the reservoir filling needed to transfer water from summer to winter is drastically reduced in the Nordic countries.     

Impact of ENSO-Related Climate Anomalies on Crop Yields in the U.S.

Historical daily thermal and precipitation data from selected stations across the United States are composited into climate scenarios for the three phases of ENSO: Warm Events (El Niño), Cold Events (El Viejo or La Niña), and Neutral. Using these scenarios, yields of 7 field crops were simulated using the EPIC biophysical model during the one-year period coincident with maximum SST anomalies in the equatorial Pacific. The response of simulated agricultural productivity to the ENSO-related climate-variability parameters, is presented. A sensitivity calculation confirms the relevance of precipitation totals/medians and suggests ENSO-related yields are sensitive to changes in statistical properties characterizing precipitation distribution and occurrence. Results are spatially dependent, with the southwest and northern plains regions indicating the highest sensitivity to the inclusion of additional precipitation characteristics. The southeast yields are not as sensitive. The yield deviations (expressed as normalized differences to neutral yields) associated with the two extreme ENSO phases (Warm Events and Cold Events) are spatially and crop dependent with ranges up to ±120%. The largest yield deviations are in the south, southwest, and northern plains. Overall, Cold Events demonstrate larger impacts in the southern regions and Warm Events have a larger impact in the north. Additionally, the notion that climate anomalies associated with Cold and Warm Events and subsequent impacts on yields should be of opposite sign (i.e., linear) is not valid in many regions. For the eastern half of the U.S., modeled yield deviations under Warm Event conditions are nearly all less than neutral. Conversely, in the western half, results are more mixed. Under Cold Event conditions, yields in the east are enhanced in the south, but worsened in the north; while in the western half, yields have decreased in general. The results highlight the critical role of climate and production-related data on station or county levels in quantifying the impact of ENSO climate anomalies on yields. Both the diverse nature of the ENSO-related yield deviations as well as their sensitivity to monthly frequency distribution and occurrence characteristics imply that ENSO-related seasonal precipitation forecasts might be beneficial for agricultural application only if details were provided regarding not only totals, but also predicted changes in temporal and spatial variability of a more comprehensive suite of characteristics.     

Climate change impacts on sugarcane attainable yield in southern Brazil

This study evaluated the effects of climate change on sugarcane yield, water use efficiency, and irrigation needs in southern Brazil, based on downscaled outputs of two general circulation models (PRECIS and CSIRO) and a sugarcane growth model. For three harvest cycles every year, the DSSAT/CANEGRO model was used to simulate the baseline and four future climate scenarios for stalk yield for the 2050s. The model was calibrated for the main cultivar currently grown in Brazil based on five field experiments under several soil and climate conditions. The sensitivity of simulated stalk fresh mass (SFM) to air temperature, CO₂ concentration [CO₂] and rainfall was also analyzed. Simulated SFM responses to [CO₂], air temperature and rainfall variations were consistent with the literature. There were increases in simulated SFM and water usage efficiency (WUE) for all scenarios. On average, for the current sugarcane area in the State of São Paulo, SFM would increase 24 % and WUE 34 % for rainfed sugarcane. The WUE rise is relevant because of the current concern about water supply in southern Brazil. Considering the current technological improvement rate, projected yields for 2050 ranged from 96 to 129 t?ha^?1, which are respectively 15 and 59 % higher than the current state average yield.     

Projected global climate change impact on water temperatures in five north central U.S. streams

The effect of projected global climate change due to a doubling of atmospheric CO₂ on water temperatures in five streams in Minnesota was estimated using a deterministic heat transport model. The model calculates heat exchange between the atmosphere and the water and is driven by climate parameters and stream hydrologic parameters. The model is most sensitive to air temperature and solar radiation. The model was calibrated against detailed measurements to account for seasonally variable shading and wind sheltering. Using climate projections from the GISS, GFDL and OSU GCMs as input; stream temperature simulations predict a warming of freely flowing river reaches by 2.4 °C to 4.7 °C when atmospheric CO₂ doubles. In small shaded streams water temperatures are predicted to rise by an additional 6 °C in summer if trees along stream banks should be lost due to climate change or other human activities (e.g. logging). These projected water temperature changes have significant consequences for survival and growth of fishes. Simulation with the complete heat budget equations were also used to examine simplified water temperature/air temperature correlations.