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Evaluation of the twenty-first century RCM simulations driven by multiple GCMs over the Eastern Mediterranean-Black Sea region
Abstract
In this study, human-induced climate change over the Eastern Mediterranean–Black Sea region has been analyzed for the twenty-first century by performing regional climate model simulations forced with large-scale fields from three different global circulation models (GCMs). Climate projections have been produced with Special Report on Emissions Scenarios A2, A1FI and B1 scenarios, which provide greater diversity in climate information for future period. The gradual increases for temperature are widely apparent during the twenty-first century for each scenario simulation, but ECHAM5-driven simulation generally has a weaker signal for all seasons compared to CCSM3 simulations except for the Fertile Crescent. The contrast in future temperature change between the winter and summer seasons is very strong for CCSM3-A2-driven and HadCM3-A2-driven simulations over Carpathians and Balkans, 4–5 °C. In addition, winter runoff over mountainous region of Turkey, which feeds many river systems including the Euphrates and Tigris, increases in second half of the century since the snowmelt process accelerates where the elevation is higher than 1,500 m. Moreover, analysis of daily temperature outputs reveals that the gradual decrease in daily minimum temperature variability for January during the twenty-first century is apparent over Carpathians and Balkans. Analysis of daily precipitation extremes shows that positive trend is clear during the last two decades of the twenty-first century over Carpathians for both CCSM3-driven and ECHAM5-driven simulations. Multiple-GCM driven regional climate simulations contribute to the quantification of the range of climate change over a region by performing detailed comparisons between the simulations.
Supplementary resource (1)
... Using the top-down approach as described above, the study area, the Kizilirmak River basin (KRB) has been analyzed by several climate projections and hydrological model analyses. Using a regional climate model (RegCM3) [16], Önol et al. [17] spatially downscaled climate projections from three GCMs under the scenarios of A2, A1FI, and B1, to the end of the 21st century over the Black Sea and eastern Mediterranean regions. Also, using dynamic downscaling methods (RegCM4), a study on the climate projections of the KRB was carried out by the Turkish General Directorate of Water Management under a project on the impact of climate change on water resources in Turkey's rivers [18,19]. ...
... When the region of the KRB is specifically analyzed from the simulation maps in the studies, by 2100, the surface temperatures for all seasons are estimated to increase, according to all emission scenarios and three climate models [16,17]. In addition, the models agree that winter precipitation will increase along the coast of the Black Sea in the basin. ...
This study introduces a novel sensitivity analysis approach to assess the resilience and susceptibility of hydrologic systems to the stresses of climate change, moving away from conventional top-down methodologies. By exploring the hydrological sensitivity of the upper Kızılırmak River basin using the Variable Infiltration Capacity (VIC) hydrologic model, we employed a sensitivity-based approach as an alternative to the traditional Global Climate Model (GCM)-based methods, providing more insightful information for water managers. Considering the consistent projections of increasing temperature over this region in GCMs, the hydrologic system was perturbed to examine gradients of a more challenging climate characterized by warming and drying conditions. The sensitivity of streamflow, snow water equivalent, and evapotranspiration to temperature (T) and precipitation (P) variations under each perturbation or “reference” climate was quantified. Results indicate that streamflow responds to T negatively under all warming scenarios. As the reference climates become drier, streamflow sensitivity to P increases, indicating that meteorological drought impacts on water availability could be exacerbated. These results suggest that there will be heightened difficulty in managing water resources in the region if it undergoes both warming and drying due to the following setbacks: (1) water availability will shift away from the summer season of peak water demand due to the warming effects on the snowpack, (2) annual water availability will likely decrease due to a combination of warming and lower precipitation, and (3) streamflow sensitivity to hydroclimatic variability will increase, meaning that there will be more extreme impacts to water availability. Water managers will need to plan for a larger set of extreme conditions.
... Climate projections revealed a significant warming trend in temperatures, a decrease in precipitation regime, especially in southern latitudes, a decrease in relative humidity, and an increase in heat waves for the period until the end of the 21st century for Türkiye (Akçakaya et al., 2015;Demircan et al., 2017;Eskioglu et al., 2017;Gürkan et al., 2016;Gürkan et al., 2017;Önol et al., 2014;Şen, 2013). Changes in temperature and precipitation factors, vital in crop production, directly affect the productivity and vegetation period suited to the growing region (Bulut, 2015). ...
Climate change, previously considered an environmental problem, has begun to be defined as a climate crisis since its effects intensify faster than previously thought, cause severe economic losses, and threaten food security. Climate indexes have been defined as the primary descriptive indicator to acquire a consistent perspective on observed and projected changes resulting from weather and climatic extremes. In this study, the growing degree days (GDD) index, one of the essential indicators in planning agricultural activities, was examined for wheat (Triticum aestivum), maize (Zea mays), and sunflowers (Helianthus anuus) across Türkiye. The GDD index was examined between 1971 and 2020 for the observed change analysis and between 2023 and 2098 for future projections. Three global climate models and two representative concentration pathways (RCPs), that is, 4.5 and 8.5, were selected to assess climate change impact. The analysis of the entire observed period (1971–2020) indicated a considerable increasing trend in the annual total GDD index for wheat, except in the southeast of Türkiye, and maize and sunflower across the country. Assessment results of the climate projection analysis revealed that there would be increases over 1400 and 2300°C day/year for the RCP4.5 and RCP8.5 scenarios, respectively, for all three crops considered. Additionally, the findings indicated further increases in the southern latitudes of Türkiye. Projection results also confirmed that there will be longer suitable periods for agricultural production, and the crop vegetation periods will be shorter and shift earlier in Türkiyein the future periods.
... The warmer summer temperature in Türkiye has also increased forest fires across the country, destroying 222,384 hectares of forestland from 2010 to 2021 (Memisoglu Baykal, 2023). Some authors projected that these climate change-related impacts would continue in the next few decades due to the ongoing temperature anomalies in the country, with predicted temperature increases between 2 and 6°C (Demircan et al., 2017;Önol et al., 2014). The increasing surface temperature has led to high evaporation rates in the Black Sea that caused intense flooding across the country, particularly in areas bordering the sea (Nuri Balov & Altunkaynak, 2019). ...
Climate change impacts drive warmer winters, reduced snowfall, and forest fires. In 2020, a wildfire scorched about 1508 hectares of black pine (Pinus nigra Arnold) forests in Türkiye. Whether the combined effects of lack of snow and forest fires significantly alter winter soil respiration (Rs) and soil temperature remains poorly understood. A field experiment was conducted in the postfire and undisturbed black pine forests during the winter to quantify Rs rates as affected by lack of snow and forest fire. We applied four treatments: snow‐exclusion postfire (SEPF), snow postfire (SPF), snow‐exclusion‐undisturbed forest (SEUF), and snow undisturbed forest (SUF). The SEPF exhibited the significantly lowest mean Rs rates (0.71 μmol m⁻² s⁻¹) compared to the SPF (1.02 μmol m⁻² s⁻¹), SEUF (1.44 μmol m⁻² s⁻¹), and SUF (1.48 μmol m⁻² s⁻¹). The Rs also showed significant variations with time (p < .0001). However, treatments and time revealed no statistically significant interaction effects (p = .6801). Total winter Rs (January–March) ranged from 4.47 to 4.59 Mt CO2 ha⁻¹ in the undisturbed forest and 2.20 to 3.16 Mt CO2 ha⁻² in the postfire site. The Rs showed a significantly positive relationship (p < .0001) with the soil (0.59) and air (0.46) temperatures and a significantly negative relationship (p = .0017) with the soil moisture (−0.20) at the 5 cm depth. In contrast, the Rs indicated a negative but not statistically significant relationship (p = .0932) with the soil moisture (−0.16) at the 10 cm soil depth. The combined effects of lack of snow and forest fire significantly decreased Rs, thus conserving the soil's organic carbon stocks and reducing the CO2 contribution to the atmosphere. In contrast, a warmer winter significantly increased Rs rates in the undisturbed forest, suggesting an acceleration of soil organic carbon losses and providing positive feedback to climate change.
... However, applications of dynamic downscaling methods are more complex and take much more time than statistical downscaling methods (Fistikoglu and Okkan 2011;Okkan and Inan 2015a). To determine the potential impacts of climate change on hydro-meteorological variables in Turkey, numerous studies have been conducted using both statistical and dynamic downscaling methods for various regions of the country (Almazroui et al. 2019;Demircan et al. 2017;Durdu 2010;Fujihara et al. 2008;Gorguner, Kavvas, and Ishida 2019;Önol et al. 2014;Inan 2015b, 2015a;Okkan and Inan 2016;Okkan and Kirdemir 2016;Turkes et al. 2020;Yilmaz 2015). In almost all of these studies, it has been concluded that significant changes may occur in the future periods in the hydro-meteorological time series of a different region of Turkey with the effects of climate change. ...
This study compares projected and past seasonal precipitation trends in the Eastern Black Sea Basin, Turkey. Historical data from twelve stations representing the basin during 1981–2010 was used, while statistically downscaled data from two representative concentration pathway scenarios (RCP4.5 and RCP8.5) outputs of the GFDL-ESM2M general circulation model were utilized for 2021–2050. To determine the seasonal trend behaviors of precipitation variables and transitions between consecutive months, the Innovative Polygon Trend Analysis (IPTA) was implemented. Furthermore, the star concept was employed to illustrate the changing sizes between consecutive periods. Both scenarios showed considerable summer and autumn declines at almost all locations, with low seasonal precipitation variability. These scenarios indicated January to be the important month for trend shift, except for Rize, Pazar, and Hopa stations. The formation of several polygons, polygons intersecting, and polygons not forming on the global regression line show that the hydro-climatic cycle might be chaotic.
... The increasing trends in total precipitation and streamflow observed in the Edirne region may be indicative of changes in regional atmospheric circulation patterns. Furthermore, there is evidence that sea surface temperatures have risen in the surrounding seas of Anatolia (Bozkurt and Sen 2011;Önol et al. 2014;MGM 2016). The upward trend in streamflow and precipitation in NW Türkiye may be linked to the increasing sea surface temperatures, air mass temperatures, and moisture-holding capacity of the air masses. ...
Türkiye is one of the countries highly vulnerable to climate change. In this study, we focused on the northwesternmost part of Türkiye, between Edirne-Kalkansogut. We analyzed the long-term climatic data series (70 years) from Edirne Meteorological Station and long-term streamflow gauge data from Tundzha (58 years), Sinanköy (27 years) and Çömlek (30 years) rivers. We performed trend analysis and Thornthwaite water budget analysis to understand the temporal patterns of streamflow and climate. Our findings suggest that annual and seasonal average temperatures, evapotranspiration, water surplus, and total precipitation values decreased between 1952–1986 and increased between 1987–2021. Regression analysis results demonstrated an increase in streamflow values between 1986–2018. Furthermore, statistical analysis has highlighted a weak relationship between temperature/evapotranspiration and streamflow, while a strong relationship was observed between streamflow and precipitation. These climate and surface runoff changes hold the potential to significantly impact natural resources in northwesternmost Türkiye, leading to more frequent extreme precipitation events and more damaging natural hazards. Effective physical planning applications and efficient water management policies are imperative for sustainable hydrological development in this region.
The strong drying expected in the Eastern Mediterranean with climate change could cause mass migration of people already living under water shortages. On the other hand, precipitation is expected to increase toward the region’s north, particularly those along the interior of the eastern Black Sea coasts, which could worsen existing floods. However, this double‐sided adverse phenomenon and its underlying reasons have been investigated by relatively low‐resolution models in the Eastern Mediterranean Black Sea (EMBS) region, where orographic precipitation prevails. This study performs 4 km resolution Weather Research and Forecasting (WRF) model simulations with and without climate change signals retrieved from a CMIP6 GCM ensemble via pseudo‐global‐warming (PGW). The WRF simulations captured the large‐scale dynamics affecting the EMBS fairly well: an anticyclonic low‐level circulation and enhancing subsidence stem from anomalous ridge development over the central Mediterranean in winter (DJF), and a cyclonic low‐level circulation and weakening subsidence rise from heat‐low development over the Eastern Mediterranean in summer (JJA). The resulting picture of future warming and drying over the area generally supports the literature, although new insights emerge in anomalous precipitation increase, especially in the summer season over the Greater Caucasus and nearby regions. Most likely, the warmer‐than‐expected Caspian Sea induces a large increase in specific humidity and, thus, a large moisture source in the lower troposphere and an extension of the heat‐low effect in the mid‐troposphere. In addition, the high‐resolution WRF simulations provide added value over the complex topography of the Caucasian Mountain range for new insights into this region.
An assessment of the projected changes in precipitation extremes for the 21st century is presented here for Greece and its individual administrative regions. The analysis relies on an ensemble of high-resolution Regional Climate Model (RCM) simulations following various Representative Concentration Pathways (RCP2.6, RCP4.5, and RCP8.5). The simulated changes in future annual total precipitation (PRTOT) under the examined scenarios are generally negative but statistically non-robust, except towards the end of the century (2071–2100) over high-altitude mountainous regions in Western Greece, Peloponnese, and Crete under RCP8.5. The pattern of change in the number of very heavy precipitation days (R20) is linked to the respective pattern of the PRTOT change with a statistically robust decrease of up to −5 days per year only over parts of the high-altitude mountainous regions in Western Greece, Peloponnese, and Crete for 2071–2100 under RCP8.5. Contrasting the future tendency for decrease in total precipitation and R20, the changes in the intensity of precipitation extremes show a tendency for intensification. However, these change patterns are non-robust for all periods and scenarios. Statistical significance is indicated for the highest 1-day precipitation amount in a year (Rx1day) for the administrative regions of Thessaly, Central Greece, Ionian Islands, and North Aegean under RCP8.5 in 2071–2100. The changes in the contribution of the wettest day per year to the annual total precipitation (RxTratio) are mainly positive but non-robust for most of Greece and all scenarios in the period 2021–2050, becoming more positive and robust in 2071–2100 for RCP8.5. This work highlights the necessity of taking into consideration high-resolution multi-model RCM estimates in future precipitation extremes with various scenarios, for assessing their potential impact on flood episodes and the strategic planning of structure resilience at national and regional level under the anticipated human-induced future climate change.
Türkiye turizminin, başta deniz turizmi olmak üzere, tüm türleriyle,
belirgin bir biçimde iklim değişikliğinden etkileneceği ve bunun büyük
oranda olumsuz olacağı kuvvetle muhtemeledir. Bunun için iki kritik tavır önemlidir: İlki halihazırda olası senaryolara göre ulusal çapta turizm için önlemlerin alınarak iklim değişikliğine uyum çabalarının organize edilmesi; diğeri ise tüm dünyada genel ve özel olarak turizmden kaynaklanan karbon salınımını azaltmaya yönelik çalışmalara dahil olunmasıdır. Çalışmaların, önümüzdeki dönemlerde ortaya çıkan ya da revize edilen yeni durumlara ve senaryolara göre dinamik bir biçimde devam etmesi gerektiği açıktır
Son yıllarda etkisini giderek artıran küresel iklim değişikliği, artık insanlığın önlem alması ve uyum çabalarını artırması gereken bir problem haline gelmiştir. Daha uzun süre maruz kalınan sıcak hava dalgaları, sıcak hava dalgaları ile birlikte sıklığı giderek artan orman yangınları, kuraklık, şiddetli yağışlar, sel ve heyelan olayları iklimsel parametrelerdeki farklılaşmaların en belirgin göstergeleridir. İklim değişikliğinin Dünya’nın farklı alanlarında farklı sonuçları ortaya çıksa da, Türkiye’nin içinde bulunduğu Akdeniz Havzası bu değişikliklerden en fazla etkilenmesi beklenen sahalardandır. Türkiye'nin sıcaklık ve yağış iklim değişkenleri üzerine gelecek öngörüsü sunmak ve olası farklılaşmaları belirlemek çalışmanın amacını oluşturmaktadır. Bilimsel kuruluşlar tarafından geliştirilen modeller ve uygulanan emisyon senaryoları, gelecekte yaşanabilecek olası değişikliklerin tahmini için önemli metotlardır. Araştırmada Coupled Model Intercomparison Project Phase 5 (CMIP5) projesi kapsamında yer alan modellere ve senaryolara ait çoklu model ortalaması kullanılmıştır. Analizlere dahil edilen emisyon senaryoları RCP4.5 ve RCP8.5’tir. Çalışmaya ait analizler Google Earth Engine bulut işletim sistemi ile gerçekleştirilmiş ve ArcGIS 10.4 programı ile haritalanmıştır. Yapılan analizler sonucunda 2005-2040 döneminde Türkiye, bugünkü ortalamalara göre daha sıcak günler ile karşı karşıya kalacaktır. Maksimum sıcaklık ortalamalarındaki artış trendi daha kuvvetlidir. Akdeniz kıyılarında görülen iklim şartları ilerleyen yıllarda etki sahasını Ege ve Marmara bölgelerine doğru genişletecektir. Doğu Anadolu Bölgesi’nde minimum sıcaklık ortalamalarında daha kuvvetli artışlar yaşanacaktır. Yağış miktarlarında Akdeniz-Ege kıyıları ve iç bölgelerde azalma, Doğu Karadeniz kıyılarında kısmen artışlar görülecektir. Genel olarak bütün Türkiye arazisinin ortalama yağışı dikkate alındığında, pozitif ya da negatif yönde bir eğilim mevcut değildir.
High-resolution regional climate simulations driven by NCEP-reanalysis for the eastern Mediterranean (EM) region covering 48 yr (1961-2008) are used to examine the coastal effects over the EM region. The present study uses the ICTP-RegCM3 to downscale to a 10 km resolution over the EM with a 50 km driving nest. The high-resolution simulation captures strong temperature gradients as a result of resolving the steep topography over the eastern Black Sea and Mediterranean coasts of Turkey, as well as the Ionian coast of Greece. In terms of the validation based on the coastal meteorological stations, the annual temperature bias in the high-resolution simulation is <0.7 degrees C for the Black Sea and Mediterranean regions over Turkey and the same bias is 1 C in the 50 km simulation. Moreover, the model is able to capture the observed warming trend in summer temperatures during the last 5 decades. In terms of the precipitation simulation, the error in the 10 km simulation (17%) over the Black Sea region is much lower than that in the 50 km simulation (42%) when considering coastal meteorological stations. In addition, existence of many small islands over the EM domain is another unresolved challenge for climate simulations. The small islands tend to be overwhelmed by the influence of sea-surface temperature, and local climate effects related to topography are suppressed in 10 km temperature simulations. However, the precipitation error in the 10 and 50 km simulations based on the island stations (Crete, Rhodes and Cyprus) over the EM domain are 12 and 24%, respectively. In terms of the cross-section analysis comparing model elevation to simulated precipitation, the implementation of high-resolution simulation illustrates the importance of modeling the complex terrain over the eastern Black Sea and Mediterranean coasts of Turkey, as the precipitation error was reduced to 7 and 18%, respectively.
This study investigates the effects of projected climate change on snow
water availability in the Euphrates-Tigris basin using the Variable
Infiltration Capacity (VIC) macro scale hydrologic model and a set of
regional climate-change outputs from 13 global circulation models (GCMs)
forced with two greenhouse gas emission scenarios for two time periods
in the 21st century (2050 and 2090). The hydrologic model produces a
reasonable simulation of seasonal and spatial variation in snow cover
and associated snow water equivalent (SWE) in the mountainous areas of
the basin, although its performance is poorer at marginal snow cover
sites. While there is great variation across GCM outputs influencing
snow water availability, the majority of models and scenarios suggest a
significant decline (between 10 and 60 percent) in available snow water,
particularly under the aggressive A2 climate change scenario and later
in the 21st century. The changes in SWE are more stable when multi-model
ensemble GCM outputs are used to minimize inter-model variability,
suggesting a consistent and significant decrease in snow-covered areas
and associated water availability in the headwaters of the Euphrates
Tigris basin. Detailed analysis of future climatic conditions point to
the combined effects of reduced precipitation and increased temperatures
as primary drivers of reduced snowpack. Results also indicate a more
rapid decline in snow cover in the lower elevation zones than the higher
areas in a changing climate. The simulated changes in snow water
availability have important implications for the future of water
resources and associated hydropower generation and land-use management
and planning in a region already ripe for interstate water conflict.
While the changes in the frequency and intensity of snow-bearing
circulation systems or the interannual variability related to climate
were not considered, the simulated changes in snow water availability
presented here are likely to be indicative of climate change impacts on
the water resources of the Euphrates-Tigris basin.
Projected climate change over Turkey has been analyzed by using the reference (1961–1990) and future (2071–2100) climate simulations produced by ICTP-RegCM3. Since examining Turkey as a single region could be misleading due to the existence of complex topography and different climatic regions, Turkey has been separated into seven climatic regions to evaluate the surface temperature and precipitation changes. Comparison of the reference simulation with observations was made spatially by using a monthly gridded data set and area-averaged surface data compiled from 114 meteorological stations for each climatic region of Turkey. In the future simulation, warming over Turkey’s climatic regions is in the range of 2–5 °C. Summer warming over western regions of Turkey is 3 °C higher than the winter warming. During winter, in the future simulation, precipitation decreases very significantly over southeastern Turkey (24 %), which covers most of the upstream of Euphrates and Tigris river basin. This projected decrease could be a major source of concern for Turkey and the neighboring countries. Our results indicate that a significant increase (48 %) in the autumn season precipitation is simulated over southeastern Turkey, which may help to offset the winter deficit and therefore reduce the net change during the annual cycle.
This study investigates the effects of projected climate change on snow water availability in the Euphrates-Tigris basin using the Variable Infiltration Capacity (VIC) macro scale hydrologic model and a set of regional climate-change outputs from 13 global circulation models (GCMs) forced with two greenhouse gas emission scenarios for two time periods in the 21st century (2050 and 2090). The hydrologic model produces a reasonable simulation of seasonal and spatial variation in snow cover and associated snow water equivalent (SWE) in the mountainous areas of the basin, although its performance is poorer at marginal snow cover sites. While there is great variation across GCM outputs influencing snow water availability, the majority of models and scenarios suggest a significant decline (between 10 and 60 percent) in available snow water, particularly under the high-impact A2 climate change scenario and later in the 21st century. The changes in SWE are more stable when multi-model ensemble GCM outputs are used to minimize inter-model variability, suggesting a consistent and significant decrease in snow-covered areas and associated water availability in the headwaters of the Euphrates-Tigris basin. Detailed analysis of future climatic conditions point to the combined effects of reduced precipitation and increased temperatures as primary drivers of reduced snowpack. Results also indicate a more rapid decline in snow cover in the lower elevation zones than the higher areas in a changing climate but these findings also contain a larger uncertainty. The simulated changes in snow water availability have important implications for the future of water resources and associated hydropower generation and land-use management and planning in a region already ripe for interstate water conflict. While the changes in the frequency and intensity of snow-bearing circulation systems or the interannual variability related to climate were not considered, the simulated changes in snow water availability presented here are likely to be indicative of climate change impacts on the water resources of the Euphrates-Tigris basin.
Satellite retrievals of surface evaporation and precipitation from the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data (HOAPS-3) dataset are used to document the distribution of evaporation, precipitation, and freshwater flux over the Mediterranean and Black Seas. An analysis is provided of the major scales of temporal and spatial variability of the freshwater budget and the atmospheric processes responsible for the water flux changes. The satellite evaporation fluxes are compared with fields from three different reanalysis datasets [40-yr ECMWF Re-Analysis (ERA-40), ERA-Interim, and NCEP].
The results show a water deficit in the Mediterranean region that averages to about 2.4 mm day−1 but with a significant east–west asymmetry ranging from 3.5 mm day−1 in the eastern part to about 1.1 mm day−1 in the western part of the basin. The zonal asymmetry in the water deficit is driven by evaporation differences that are in turn determined by variability in the air–sea humidity difference in the different parts of the Mediterranean basin. The Black Sea freshwater deficit is 0.5 mm day−1, with maxima off the northern coast (0.9 mm day−1) that are attributed to both evaporation maxima and precipitation minima there.
The trend analysis of the freshwater budget shows that the freshwater deficit increases in the 1988–2005 period. The prominent increase in the eastern part of the basin is present in the satellite and all three reanalysis datasets. The water deficit is due to increases in evaporation driven by increasing sea surface temperature, while precipitation does not show any consistent trends in the period. Similarly, in the Black Sea, trends in the freshwater deficit are mainly due to evaporation, although year-to-year variability is due to precipitation patterns.
In this study, the potential role of global warming in modulating the future climate over the eastern Mediterranean (EM) region has been investigated. The primary vehicle of this investigation is the Abdus Salam International Centre for Theoretical Physics Regional Climate Model version 3 (ICTP-RegCM3), which was used to downscale the present and future climate scenario simulations generated by the NASA's finite-volume GCM (fvGCM). The present-day (1961-90; RF) simulations and the future climate change projections (2071-2100; A2) are based on the Intergovernmental Panel on Climate Change (IPCC) greenhouse gas (GHG) emissions. During the Northern Hemispheric winter season, the general increase in precipitation over the northern sector of the EM region is present both in the fvGCM and RegCM3 model simulations. The regional model simulations reveal a significant increase (10%-50%) in winter precipitation over the Carpathian Mountains and along the east coast of the Black Sea, over the Kackar Mountains, and over the Caucasus Mountains. The large decrease in precipitation over the southeastern Turkey region that recharges the Euphrates and Tigris River basins could become a major source of concern for the countries downstream of this region. The model results also indicate that the autumn rains, which are primarily confined over Turkey for the current climate, will expand into Syria and Iraq in the future, which is consistent with the corresponding changes in the circulation pattern. The climate change over EM tends to manifest itself in terms of the modulation of North Atlantic Oscillation. During summer, temperature increase is as large as 7°C over the Balkan countries while changes for the rest of the region are in the range of 3°-4°C. Overall the temperature increase in summer is much greater than the corresponding changes during winter. Presentation of the climate change projections in terms of individual country averages is highly advantageous for the practical interpretation of the results. The consistence of the country averages for the RF RegCM3 projections with the corresponding averaged station data is compelling evidence of the added value of regional climate model downscaling.
Abstract The Community Climate System Model version 3 (CCSM3) has recently been developed and released to the climate community. CCSM3 is a coupled climate model with components representing the atmosphere, ocean, sea ice, and land surface connected by ...
Hydro-climatic effects of future climate change in the Euphrates-Tigris Basin are investigated using dynamically downscaled outputs of different GCM (ECHAM5, CCSM3 and HadCM3) - emissions scenario (A1FI, A2 and B1) simulations. The suite of simulations (total five) enables an analysis taking into account the A2 emission scenario simulations of three different GCMs and another analysis based on the three different emissions scenario (A1FI, A2 and B1) simulations of one GCM (CCSM3). All scenario simulations indicate winter surface temperature increases in the entire basin, however, the increase is larger in the highlands. The greatest increase in the annual temperature by the end of century belongs to the CCSM3 A1FI simulation with an increment of 6.1 oC in the highlands. There is a broad agreement amongst the simulations in terms of the winter precipitation decrease in the highlands and northern parts and increase in the southern parts of the basin. A remarkable impact of warming could be seen on the snow water equivalent in the highlands where each simulation points out statistically significant decreases ranging from 55% (lower emissions) to 87% (higher emissions). Statistically significant declines (25 to 55%) are found for the annual surface runoff of the main headwaters area. Moreover, significant temporal shifts to earlier days (between 18 and 39 days depending on the scenario) are projected to occur in the surface runoff timing in the headwaters region. Projected annual surface runoff changes in all simulations suggest that the territories of Turkey and Syria within the basin are most vulnerable to climate change as they will experience significant decreases in the annual surface runoff. Eventually, however, the downstream countries, especially Iraq, may suffer more as they rely primarily on the water released by the upstream countries. The substantial changes in the hydro-climate of the basin, therefore, are likely to increase the challenges associated with the management of several dam reservoirs and hydropower plants in the basin in addition to causing further impacts on physical and biological components of the ecosystems along these rivers.