Projected changes in heat wave characteristics in the eastern Mediterranean and the Middle East

According to observed twentieth century temperature trends and twenty-first century climate model projections, the region that encompasses the eastern Mediterranean and the Middle East (EMME) is identified as a climate change hot spot. We extend previous studies by a comprehensive climatology of heat waves in the EMME based on regional climate model simulations for the recent past and the end of the twenty-first century. A percentile-based definition of heat waves is used to account for local climatic conditions. Spatial patterns of several heat wave properties are assessed and associated with atmospheric circulation regimes over specific locations. To cover a range of possible future climates, we use three SRES emission scenarios. According to our results, all indices that characterize heat wave severity will strongly increase compared with the control period of 1961–1990. The northern part of the EMME could be exposed to increased heat wave amplitudes by 6–10 °C, and the southern part may experience 2–3 months more combined hot days and tropical nights. Heat wave peak temperatures will be higher due to the overall mean warming as well as stronger summer anticyclonic conditions. The projected changes will affect human health and the environment in multiple ways and call for impact studies to support the development of adaptation strategies.     

Climate change impacts in the Middle East and Northern Africa (MENA) region and their implications for vulnerable population groups

Regional Environmental Change - The Middle East and North Africa (MENA) region emerges as one of the hot spots for worsening extreme heat, drought and aridity conditions under climate change. A...     

Mid-21st century climate and weather extremes in Cyprus as projected by six regional climate models

We present climate change projections and apply indices of weather extremes for the Mediterranean island Cyprus using data from regional climate model (RCM) simulations driven by the IPCC A1B scenario within the ENSEMBLES project. Daily time-series of temperature and precipitation were used from six RCMs for a reference period 1976–2000 and for 2026–2050 (‘future‘) for representative locations, applying a performance selection among neighboring model grid-boxes. The annual average temperatures of the model ensemble have a ±1.5°C bias from the observations (negative for maximum and positive for minimum temperature), and the models underestimate annual precipitation totals by 4–17%. The climatological annual cycles for the observations fall within the 1σ range of the 6-model average, highlighting the strength of using multi-model output. We obtain reasonable agreement between models and observations for the temperature-related indices of extremes for the recent past, while the comparison is less good for the precipitation-related extremes. For the future, the RCM ensemble shows significant warming of 1°C in winter to 2°C in the summer for both maximum and minimum temperatures. Rainfall is projected to decrease by 2–8%, although this is not statistically significant. Our results indicate the shift of the mean climate to a warmer state, with a relatively strong increase in the warm extremes. The precipitation frequency is projected to decrease at the inland Nicosia and at the coastal Limassol, while the mountainous Saittas could experience more frequent 5–15 mm/day rainfall. In future, very hot days are expected to increase by more than 2 weeks/year and tropical nights by 1 month/year. The annual number of consecutive dry days shows a statistically significant increase (of 9 days) in Limassol. These projected changes of the Cyprus climate may adversely affect ecosystems and the economy of the island and emphasize the need for adaptation strategies.     

The viticultural system and climate change: coping with long-term trends in temperature and rainfall in Roussillon,France

Mediterranean viticulture could suffer from hotter and drier growing seasons over the coming decades. The present article focuses on the wine-producing area Côtes-du-Roussillon-Villages near Perpignan, in southern France. We used observational daily data (1925–2010) from Perpignan weather station and daily outputs (2001–2060) of the regional climate model ARPEGE-RETIC-V4 from Météo-France with scenarios A2, A1B and B1, to assess the exposure of the regional wine system to changes in temperature and precipitation, both in the recent past and the coming decades (1925–2060). Temperatures during the growing season and summer temperature extremes have been increasing continuously since the mid-1980s and are projected to increase faster from the mid-2040s. Precipitation is highly variable and very low in summer, and projections suggest greater uncertainty, and more extreme drought events could be expected. The analysis of climate data was complemented by thirty-two in-depth interviews with local actors of the wine industry to assess the impacts of climate change on their activities and potential adaptive options. Producers reported negative impacts of recent changes in climate in conjunction with a difficult economic situation. Analyses of historical, social and economic backgrounds are important to fully conceptualize the nature and extent of climate change risks in the region. This case study provides important insights into the roles of non-climatic factors in the generation of vulnerability for Mediterranean agricultural systems facing rapid climate change.     

Statistical downscaling for climate change projections in the Mediterranean region: methods and results

Besides dynamical downscaling by regional climate models, statistical downscaling (SD) is a major tool to derive climate change projections on regional or even local scales. For the Mediterranean area, an increasing number of downscaling studies based on different statistical techniques have been published in the last two decades with a broad range of sometimes differing results relating to different variables and regional domains. This paper gives a short review of these Mediterranean downscaling studies mainly considering the following two aspects: (1) what kind of progress has been realized in this field since the early 1990s? The review addresses the inclusion of extremes in downscaling assessments, the development of probabilistic approaches, the extension of predictor sets, the use of ensembles for both dynamical model simulations and statistical model assessments, the consideration of non-stationarities in the predictor–predictand relationships, and some advances related to synoptic downscaling. (2) What are the main regional climate change signals in the Mediterranean area, considering agreed and controversial points also with respect to dynamical models? Best accordance among future projections can be found in seasonal temperatures with lower rates of warming in winter and spring, and, in most cases, higher ones in summer and autumn. Different results are obtained for the intra-annual range of extreme temperatures, but high-temperature conditions are generally expected to increase. Regarding seasonal precipitation, predominant reductions are indicated for spring, summer, and autumn. For winter, however, projections are distinctly different (GCMs: rainfall decrease; RCMs: increase only in the northernmost parts of the Mediterranean region; SD: widespread increases in the northern and western parts in several studies). Different results are obtained for rainfall extremes, but the entire precipitation distribution tends to shift towards higher and lower values. Apart from some sub-regional deviations, there is a predominant increase in future dry period durations. For near-surface winds, only a few studies are available, and they project some decline mainly for the winter season.     

Projecting ozone-related mortality in East China

BackgroundThe concentrations of ozone (O₃) in China are increasing, especially in East China, but its future trends and potential health impacts remain to be explored.ObjectivesThe objective was to assess future trends in O₃ concentrations and related premature death in East China between 2005 and 2030.MethodsFirst, a global chemical transport model (MIROC-ESM-CHEM) and regional chemical transport modelling system (including the Weather Research and Forecasting model and the Community Multiscale Air Quality model) were combined to estimate daily O₃ concentrations in 2005 and 2030 in East China under the “current legislation” (CLE) and “maximum technically feasible reduction” (MFR) scenarios which were applied globally. O₃ concentrations were then linked with population projections, mortality projections, and O₃-mortality associations to estimate changes in O₃-related mortality in East China.ResultsThe annual mean O₃ concentration was projected to increase in East China between 2005 and 2030 under the CLE scenario, while decrease under the MFR scenario. Under the CLE scenario, O₃-attributable health burden could increase by at least 40,000 premature deaths in East China, without considering the population growth. Under the MFR scenario, the health burden could decrease by up to 260,000 premature deaths as a result of the reduction in O₃ concentration with a static population. However, when the population growth was considered, O₃-attributable health burden could increase by up to 46,000 premature deaths in East China under the MFR scenario.ConclusionsThe results suggest that the health burden attributable to O₃ may increase in East China in 2030.     

Multi-GCM projections of future drought and climate variability indicators for the Mediterranean region

Future climate conditions for the Mediterranean region based on an ensemble of 16 Global Climate Models are expressed and mapped using three approaches, giving special attention to the intermodel uncertainty. (1) The scenarios of mean seasonal temperature and precipitation agree with the projections published previously by other authors. The results show an increase in temperature in all seasons and for all parts of the Mediterranean with good intermodel agreement. Precipitation is projected to decrease in all parts and all seasons (most significantly in summer) except for the northernmost parts in winter. The intermodel agreement for the precipitation changes is lower than for temperature. (2) Changes in drought conditions are represented using the Palmer Drought Severity Index and its intermediate Z-index product. The results indicate a significant decrease in soil moisture in all seasons, with the most significant decrease occurring in summer. The displayed changes exhibit high intermodel agreement. (3) The climate change scenarios are defined in terms of the changes in parameters of the stochastic daily weather generator calibrated with the modeled daily data; the emphasis is put on the parameters, which affect the diurnal and interdiurnal variability in weather series. These scenarios indicate a trend toward more extreme weather in the Mediterranean. Temperature maxima will increase not only because of an overall rise in temperature means, but partly (in some areas) because of increases in temperature variability and daily temperature range. Increased mean daily precipitation sums on wet days occurring in some seasons, and some parts of the Mediterranean may imply higher daily precipitation extremes, and decreased probability of wet day occurrence will imply longer drought spells all across the Mediterranean.     

Impacts of climate change on the distribution of species and communities in the Chilean Mediterranean ecosystem

The Mediterranean region of Chile is considered a biodiversity hot spot. An increase in temperature and decrease in precipitation, as projected for the end of this century by global circulation models, would likely change the distribution of the sclerophyllous thorny shrubland and woodland. In order to assess those potential impacts, the MAXENT algorithm was used to project potential changes in the distribution of the Mediterranean ecosystem. Ecological niche models were fitted and used to project the potential distribution of these forest ecosystems by the end of the century. Projections were made using data from the PRECIS model for the A2 and B2 climate change scenarios and two strategies of occupancy: free migration and non-migration. Distribution models of sclerophyllous, woodland and shrubland performed accurately representing current species’ distribution. When we assume non-migration responses under climate change scenarios, results reveal a decrease in the distribution area for all the species. The areas where the highest reduction in a suitable environment was found are located along the coastline, where higher temperature increases have been projected. For native ecosystems from the Andean Range region, such as communities dominated by thorny species, a stable habitat was found, associated with a higher adaptation capability to future climatic projections. Hence, in the future, buffer zones originated by “topo-climatic” conditions might play a key role in protecting Central Chile biodiversity.     

Mediterranean cyclones and windstorms in a changing climate

Changes in the frequency and intensity of cyclones and associated windstorms affecting the Mediterranean region simulated under enhanced Greenhouse Gas forcing conditions are investigated. The analysis is based on 7 climate model integrations performed with two coupled global models (ECHAM5 MPIOM and INGV CMCC), comparing the end of the twentieth century and at least the first half of the twenty-first century. As one of the models has a considerably enhanced resolution of the atmosphere and the ocean, it is also investigated whether the climate change signals are influenced by the model resolution. While the higher resolved simulation is closer to reanalysis climatology, both in terms of cyclones and windstorm distributions, there is no evidence for an influence of the resolution on the sign of the climate change signal. All model simulations show a reduction in the total number of cyclones crossing the Mediterranean region under climate change conditions. Exceptions are Morocco and the Levant region, where the models predict an increase in the number of cyclones. The reduction is especially strong for intense cyclones in terms of their Laplacian of pressure. The influence of the simulated positive shift in the NAO Index on the cyclone decrease is restricted to the Western Mediterranean region, where it explains 10–50 % of the simulated trend, depending on the individual simulation. With respect to windstorms, decreases are simulated over most of the Mediterranean basin. This overall reduction is due to a decrease in the number of events associated with local cyclones, while the number of events associated with cyclones outside of the Mediterranean region slightly increases. These systems are, however, less intense in terms of their integrated severity over the Mediterranean area, as they mostly affect the fringes of the region. In spite of the general reduction in total numbers, several cyclones and windstorms of intensity unknown under current climate conditions are identified for the scenario simulations. For these events, no common trend exists in the individual simulations. Thus, they may rather be attributed to long-term (e.g. decadal) variability than to the Greenhouse Gas forcing. Nevertheless, the result indicates that high-impact weather systems will remain an important risk in the Mediterranean Basin.     

The impact of summer temperatures and heatwaves on mortality and morbidity in Perth,Australia 1994–2008

Climate change projections have drawn attention to the risks of extreme heat and the importance of public health interventions to minimise the impact. The city of Perth, Western Australia, frequently experiences hot summer conditions, with recent summers showing above average temperatures. Daily maximum and minimum temperatures, mortality, emergency department (ED) presentations and hospital admissions data were acquired for Perth for the period 1994 to 2008. Using an observed/expected analysis, the temperature thresholds for mortality were estimated at 34–36 °C (maximum) and 20 °C (minimum). Generalised estimating equations (GEEs) were used to estimate the percentage increase in mortality and morbidity outcomes with a 10 °C increment in temperature, with adjustment for air pollutants. Effect estimates are reported as incidence rate ratios (IRRs). The health impact of heatwave days (three or more days of ≥ 35 °C) was also investigated. A 9.8% increase in daily mortality (IRR 1.098; 95%CI: 1.007–1.196) was associated with a 10 °C increase in maximum temperature above threshold. Total ED presentations increased by 4.4% (IRR 1.044; 95%CI: 1.033–1.054) and renal-related ED presentations by 10.2% (IRR 1.102; 95%CI: 1.071–1.135) per 10 °C increase in maximum temperature. Heatwave days were associated with increases in daily mortality and ED presentations, while total hospital admissions were decreased on heatwave days. Public health interventions will be increasingly important to minimise the adverse health impacts of hot weather in Perth, particularly if the recent trend of rising average temperatures and more hot days continues as projected.     

Climate change and variability in Sub-Saharan Africa: a review of current and future trends and impacts on agriculture and food security

Sub-Saharan Africa has been portrayed as the most vulnerable region to the impacts of global climate change because of its reliance on agriculture which is highly sensitive to weather and climate variables such as temperature, precipitation, and light and extreme events and low capacity for adaptation. This article reviews evidence on the scope and nature of the climate change challenge; and assesses the impact of climate change on agriculture and food security in Sub-Saharan Africa. From the review, it is apparent that the climate in Africa is already exhibiting significant changes, evident by changes in average temperature, change in amount of rainfall and patterns and the prevalence of frequency and intensity of weather extremes. The review also revealed that although uncertainties exist with regards to the magnitude of impacts, climate will negatively affect agricultural production in Sub-Saharan Africa. Specifically, as result of current and expected climate change, the area suitable for agriculture, the length of growing seasons and yield potential, particularly along the margins of semi-arid and arid areas, are expected to decrease. These impacts will affect all components of food security: food availability, food accessibility, food utilisation and food stability and hence increase the risk of hunger in the region. The review thus confirms the general consensus that Sub-Saharan Africa is the most vulnerable region to climate change. It suggests that, policymakers and development agencies should focus on formulating and implementing policies and programmes that promote farm level adaptation strategies currently being practiced by farmers across the region.     

Freshwater stress on small island developing states: population projections and aridity changes at 1.5 and 2 °C

Small island developing states (SIDS) face multiple threats from anthropogenic climate change, including potential changes in freshwater resource availability. Due to a mismatch in spatial scale between SIDS landforms and the horizontal resolution of global climate models (GCMs), SIDS are mostly unaccounted for in GCMs that are used to make future projections of global climate change and its regional impacts. Specific approaches are required to address this gap between broad-scale model projections and regional, policy-relevant outcomes. Here, we apply a recently developed methodology that circumvents the GCM limitation of coarse resolution in order to project future changes in aridity on small islands. These climate projections are combined with independent population projections associated with shared socioeconomic pathways (SSPs) to evaluate overall changes in freshwater stress in SIDS at warming levels of 1.5 and 2 °C above pre-industrial levels. While we find that future population growth will dominate changes in projected freshwater stress especially toward the end of the century, projected changes in aridity are found to compound freshwater stress for the vast majority of SIDS. For several SIDS, particularly across the Caribbean region, a substantial fraction (~?25%) of the large overall freshwater stress projected under 2 °C at 2030 can be avoided by limiting global warming to 1.5 °C. Our findings add to a growing body of literature on the difference in climate impacts between 1.5 and 2 °C and underscore the need for regionally specific analysis.     

Current and future suitability areas of kermes oak (<Emphasis Type="Italic">Quercus coccifera</Emphasis> L.) in the Levant under climate change

Quercus coccifera L. (Kermes oak) is an evergreen oak, typical of the maquis in the eastern and south-eastern part of the Mediterranean. It occurs almost continuously along the Syrian–Lebanese coast up to 1500 m and is more scattered inland, up to the arid southernmost area of Petra in Jordan. Human impact and global warming both strongly affect the natural distribution of the species, thus leading to a widespread forest fragmentation in the whole region. In this study, we investigate the current bioclimatic range of Kermes oak and forecast which areas are potentially most suitable over the course of the twenty-first century. Ecological niche modelling was used to retrieve the environmental envelope of the species according to 23 topographic and climate variables. Five algorithms and three general circulation models were applied to provide the potential distribution of Kermes oak at the present time and project it to the future. Results showed a current suitability area in the Middle East extending from NW of Syria, rather continuously along the Lebanese coasts and inland up to the Mediterranean western slopes of Palestine and the Golan area (Israel), encompassing the Jordan Valley towards Dana and Wadi Rum (Jordan), with an isolated patch in Jabal Al-Arab (South Syria). Future scenarios depict a significant fragmentation and restriction of Kermes oak range, especially in the north of Syria and Golan, with a general shifting in altitude. This information may be useful in helping the foresters to cope with the challenge of climate changes by identifying the most suitable areas climatically effective for successful ecosystem restoration and management, including reforestation programmes.     

An integrated assessment of climate change impacts for Greece in the near future

Climate changes in the Mediterranean region, related to a significant increase in temperature and changes in precipitation patterns, can potentially affect local economies. Agriculture and tourism are undoubtedly the most important economic sources for Greece and these may be more strongly affected by changing future climate conditions. Climate change and their various negative impacts on human life are also detected in their environment; hence this study deals with implications, caused by changing climate, in urban and forest areas. Potential changes for the mid-twenty-first century (2021–2050) are analysed using a high-resolution regional climate model. This paper presents relevant climatic indices, indicative for potential implications which may jeopardise vital economic/environmental sectors of the country. The results provide insights into particular regions of the Greek territory that may undergo substantial impacts due to climate change. It is concluded that the duration of dry days is expected to increase in most of the studied agricultural regions. Winter precipitation generally decreases, whereas an increase in autumn precipitation is projected in most areas. Changing climate conditions associated with increased minimum temperatures (approximately 1.3°C) and decreased winter precipitation by 15% on average suggest that the risk for forest fires is intensified in the future. In urban areas, unpleasantly high temperatures during day and night will increase the feeling of discomfort in the citizens, while flash floods events are expected to occur more frequently. Another impact of climate change in urban regions is the increasing energy demand for cooling in summer. Finally, it was found that continental tourist areas of the Greek mainland will more often face heatwave episodes. In coastal regions, increased temperatures especially at night in combination with high levels of relative humidity can lead to conditions that are nothing less than uncomfortable for foreigners and the local population. In general, projected changes associated with temperature have a higher degree of confidence than those associated with precipitation.     

Understanding global sea levels: past, present and future

The coastal zone has changed profoundly during the 20th century and, as a result, society is becoming increasingly vulnerable to the impact of sea-level rise and variability. This demands improved understanding to facilitate appropriate planning to minimise potential losses. With this in mind, the World Climate Research Programme organised a workshop (held in June 2006) to document current understanding and to identify research and observations required to reduce current uncertainties associated with sea-level rise and variability. While sea levels have varied by over 120 m during glacial/interglacial cycles, there has been little net rise over the past several millennia until the 19th century and early 20th century, when geological and tide-gauge data indicate an increase in the rate of sea-level rise. Recent satellite-altimeter data and tide-gauge data have indicated that sea levels are now rising at over 3 mm year⁻¹. The major contributions to 20th and 21st century sea-level rise are thought to be a result of ocean thermal expansion and the melting of glaciers and ice caps. Ice sheets are thought to have been a minor contributor to 20th century sea-level rise, but are potentially the largest contributor in the longer term. Sea levels are currently rising at the upper limit of the projections of the Third Assessment Report of the Intergovernmental Panel on Climate Change (TAR IPCC), and there is increasing concern of potentially large ice-sheet contributions during the 21st century and beyond, particularly if greenhouse gas emissions continue unabated. A suite of ongoing satellite and in situ observational activities need to be sustained and new activities supported. To the extent that we are able to sustain these observations, research programmes utilising the resulting data should be able to significantly improve our understanding and narrow projections of future sea-level rise and variability.     

夏季南亚高压年代际变化及其对长江中下游降水的影响

夏季南亚高压对我国长江中下游旱涝分布有重要影响,为深入认识长江中下游夏季降水年代际演变规律和机理,提高其短期气候预测水平,利用1960~2015年NCEP/NCAR再分析资料和地面气象站降水资料,分析夏季南亚高压年代际变化及其对长江中下游降水的影响。结果表明：夏季南亚高压强度、面积、南界、东伸脊点、西伸脊点和脊线均存在显著的年代际变化,长江中下游夏季降水也有明显年代际转折,南亚高压脊线与长江中下游夏季降水相关最好,呈显著负相关。夏季南亚高压脊线年代际偏南期,南亚高压偏大偏强,长江中下游高层气流强,且形成发散;副高增强西伸,印度有稳定低压存在,长江中下游处于副高西北侧和西风槽前,盛行西南风,与北方来的偏西气流汇合;低层风场有明显切变和辐合,从孟湾、南海输送来的水汽在长江中下游辐合上升,导致降水偏多。1990s初至2000s初,夏季南亚高压年代际减弱西撤,副高减弱东撤,但由于两个高压减弱程度较小,长江中下游夏季降水仍偏多。     

Spatially differentiated management-revised discharge scenarios for an integrated analysis of multi-realisation climate and land use scenarios for the Elbe River basin

A spatially differentiated, management-revised projection of natural water availability up to 2053 was requested for a basin-wide scenario study about the impact of global change in the Elbe River basin. Detailed discharge and weather information of the recent years 1951–2003 were available for model calibration and validation. However, the straightforward “classic” approach of calibrating a hydrological model on observed data and running it with a climate scenario could not be taken, because most observed river runoffs in Central Europe are modified by human management. This paper reports how the problem was addressed and how a major projection bias could be avoided. The eco-hydrological model SWIM was set up to simulate the discharge dynamics on a daily time step. The simulation area of 134,890?km2 was divided into 2,278 sub-basins that were subdivided into more than 47,500 homogeneous landscape units (hydrotopes). For each hydrotope, plant growth and water fluxes were simulated while river routing calculation was based on the sub-basin structure. The groundwater module of SWIM had to be extended for accurate modelling of low flow periods. After basin-scale model calibration and revisions for known effects of lignite mining and water management, evapotranspiration and groundwater dynamics were adjusted individually for more than 100 sub-areas largely covering the entire area. A quasi-natural hydrograph was finally derived for each sub-area taking into account management data for the years 2002 (extremely wet) and 2003 (extremely dry). The validated model was used to access the effect of two climate change scenarios consisting of 100 realisations each and resembling temperature increases of 2 and 3?K, respectively. Additionally, four different land use scenarios were considered. In all scenario projections, discharge decreases strongly: The observed average discharge rate in the reference period 1961–1990 is 171?mm/a, and the scenario projections for the middle of the twenty-first century give 91–110?mm/a, mainly depending on the climate scenario. The area-averaged evapotranspiration increases only marginally within the scenario period, e.g., from about 570 to about 580?mm/a for the temperature increase of 2?K, while potential evapotranspiration increases considerably from about 780 to more than 900?mm/a. Both discharge and evapotranspiration changes vary strongly within the basin, correlating with elevation. The runoff coefficient that globally decreases from 0.244 to 0.160 in the 2?K scenario is locally governed primarily by land use; 68% of the variance of the decreases can be attributed to this factor.     

1998年长江大洪水与大气环流和海温异常分析

概述了引起１９９８年长江大洪水的雨情,从天气气候角度分析了１９９８年长江流域降水异常偏多的原因。指出了最直接的原因是副高移动的反常,特别７月１５日以后副高突然南撤南海季风爆发晚,南亚和东亚季风强度偏弱、夏季赤道辐合带偏弱热带地区台风生成少、生成时间晚,     

Vulnerability of the power sector of Bangladesh to climate change and extreme weather events

Rise in temperature and annual precipitation, changes in seasonal rainfall patterns, more frequent and severe extreme weather events, and increased salinity in river water have been observed in Bangladesh in the recent years. Rising temperature will elevate total power consumption and peak power demand especially during the pre-monsoon hot summer season, reduce power plant efficiency and transformer lifetime, and increase the transmission loss. More frequent and severe extreme weather events may cause more disruption in power generation and distribution, and more damage of power infrastructure. Lower river flow in dry season may cause water scarcity in power plants and hamper the production. Increased salinity in river water due to sea level rise may lead to corrosion and leakages in power plants located in the coastal region of Bangladesh. A diversified, decentralized, and climate resilient power system can reduce negative impacts of climate change on power sector of Bangladesh. Adaptation and mitigation strategies must be incorporated in the planning and development of new power systems and the reformation of existing power systems of Bangladesh.     

“一带一路”国家天然气投资绩效评价及其改进路径

运用超效率数据包络分析(SE-DEA)方法,综合考虑目标国资源现状、政治因素、经济技术、社会条件、市场体制和国际合作情况,构建天然气投资绩效评价线性规划模型,并以2003—2013年中国对"一带一路"国家的天然气投资绩效均值进行聚类,结合规模报酬和投入要素的影子价格分析,提出目标国天然气投资绩效改进路径。结果显示:(1)中国对中亚及北亚、东南亚和南亚的天然气投资普遍处于中高效区,对独联体、中东欧洲和西亚北非地区的天然气投资普遍处于中低效区。(2)高效区国家自2012年起投资绩效处于规模报酬不变阶段,技术水平和国家经济对天然气贸易的依赖程度是影响投资绩效的关键因素。(3)中效区国家投资绩效大多处于规模报酬递增阶段,从2013年起总储量、人文地理和与中国油气合作状况成为影响中效区投资绩效的关键因素。(4)低效区国家投资绩效处于规模报酬递增阶段,国家经济对天然气贸易的依赖程度和技术水平要素是影响低效区投资绩效的关键因素;此外,对于处于低效区的中亚国家资源现状是影响投资绩效的另一关键因素,政治因素则是中东欧洲和独联体国家的关键因素,东南亚和南亚地区的投资关键因素则包含社会条件。这意味着,中国要提高在"一带一路"区域的天然气投资绩效,就要针对不同地区投资现状制定改进策略。对于高效区和低效区的中亚国家,未来中国要加强同目标国政府间的沟通,达成"以技术换气条款";对中效区和低效区的中东欧洲、独联体国家可采用与油气企业合作方式降低合作风险;对低效区的东南亚和南亚国家,可签订天然气长期贸易合同。