Decrease In Winter Precipitation Research Articles

Modelling Floodplain Vegetation Response to Climate Change, Using the Soil and Water Assessment Tool (SWAT) Model Simulated LAI, Applying Different GCM’s Future Climate Data and MODIS LAI Data

Scientists widely agree that anthropogenically driven climate change significantly impacts vegetation growth, particularly in floodplain areas, by altering river flow and flood regimes. This impact will accelerate in the future, according to climate change projections. For example, in Australia, climate change has been attributed to a decrease in winter precipitation in the range of 56% to 72.9% and an increase in summer from 11% to 27%, according to different climate scenarios. This research attempts to understand vegetation responses to climate change variability at the floodplain level. Further, this study is an effort to enlighten our understanding of temporal climate change impacts under different climate scenarios. To achieve these aims, a semi-distributed hydrological model was applied at a sub-catchment level to simulate the Leaf Area Index (LAI). The model was simulated against future time series of climate data according to Global Climate Model (GCM) projections. The time series data underwent a non-parametric Mann–Kendall test to detect trends and assess the magnitude of change. To quantify the model’s performance, calibration and validation were conducted against the Moderate Resolution Imaging Spectroradiometer (MODIS) LAI. The calibration and validation results show Nash–Sutcliffe efficiency (NSE) values of 0.85 and 0.78, respectively, suggesting the model’s performance is very good. The modeling results reveal that the rainfall pattern fluctuates under climate projections within the study site, in which vegetation tends to be more vibrant during the warmer seasons. Moreover, the modeling results highlighted increases in the average projected future winter temperatures, which can help vegetation growth during winter. The results of this study may be employed for sustainable floodplain management, restoration, land-use planning, and policymaking, and help floodplain communities better prepare for and respond to changing flood patterns and related challenges under a future changing climate.

Latest Neogene Paleoclimate Variation in Yunnan, Southwest China, Revealed by Fossil Leaf Physiognomy

AbstractYunnan Province, located in the southeastern margin of the Tibetan Plateau, can provide important information on how climate change was influenced by global cooling. However, its variation patterns in temperature and precipitation during the latest Neogene are not well‐understood. Based on the 357 specimens assigned to 31 morphotypes of plant fossils from the upper Pliocene Ciying Formation in Yiliang County, Yunnan Province, Southwest China, paleoclimate was estimated by Leaf Margin Analysis and Climate Leaf Analysis Multivariate Program. Compared to the present climate, the mean annual temperature and coldest month temperature have not changed significantly since the late Pliocene, whereas the warmest month temperature has decreased significantly. All precipitation‐related parameters have decreased, particularly winter precipitation. Combined with the climatic data of the same period in other areas of Yunnan, the western and eastern Yunnan has shown a similar pattern in temperature variation since the late Pliocene except for central Yunnan; whereas the variation in precipitation does not follow a common law except for a consistent decrease in winter precipitation. Our study reinforced the fact that under the background of global cooling and intensified monsoon systems, different areas of Yunnan exhibit different climatic responses to these changes because of their topographic heterogeneities.

Climate Change Impacts on the Water Resources and Vegetation Dynamics of a Forested Sardinian Basin through a Distributed Ecohydrological Model

Climate change is impacting Mediterranean basins, bringing warmer climate conditions. The Marganai forest is a natural forest protected under the European Site of Community Importance (Natura 2000), located in Sardinia, an island in the western Mediterranean basin, which is part of the Fluminimaggiore basin. Recent droughts have strained the forest′s resilience. A long-term hydrological database collected from 1922 to 2021 shows that the Sardinian forested basin has been affected by climate change since the middle of the last century, associated with a decrease in winter precipitation and annual runoff, reduced by half in the last century, and an increase of ~1 °C in the mean annual air temperature. A simplified model that couples a hydrological model and a vegetation dynamics model for long-term ecohydrological predictions in water-limited basins is proposed. The model well predicted almost one century of runoff observations. Trees have suffered from the recent warmer climate conditions, with a tree leaf area index (LAI) decreasing systematically due to the air temperature and a vapor pressure deficit (VPD) rise at a rate of 0.1 hPa per decade. Future climate scenarios of the HadGEM2-AO climate model are predicting even warmer conditions in the Sardinian forested basin, with less annual precipitation and higher air temperatures and VPD. Using these climate scenarios, we predicted a further decrease in runoff and tree transpiration and LAI in the basin, with a reduction of tree LAI by half in the next century. Although the annual runoff decreases drastically in the worst scenarios (up to 26%), runoff extremes will increase in severity, outlining future scenarios that are drier and warmer but, at the same time, with an increased flood frequency. The future climate conditions undermine the forest’s sustainability and need to be properly considered in water resources and forest management plans.

Impact of Climate Change on Spatio-Temporal Distribution of Glaciers in Western Karakoram Region since 1990: A Case Study of Central Karakoram National Park

Glaciers in the Upper Indus Basin (UIB) in Pakistan are the major source of water, irrigation, and power production for downstream regions. Global warming has induced a substantial impact on these glaciers. In the present study, Landsat images were utilized to evaluate the glaciers for the period from 1990–2020 in the Central Karakoram National Park (CKNP) region to further correlate with climate parameters. The results reveal that glaciers are retreating and the highest (2.33 km2) and lowest (0.18 km2) recession rates were observed for Biafo and Khurdopin glaciers, respectively. However, a minor advancement has also been observed for the period from 1990–2001. More than 80% of glacier recession was recorded between 2009–2020 because mean summer temperature increased at both Skardu and Gilgit meteorological stations, while precipitation decreased at both stations from 2005–2020. The increase in mean summer temperature and decrease in winter precipitation resulted in glacial retreat, which will lead to water scarcity in the future as well as affect the agriculture sector and hydropower production in downstream areas of the Indus River basin.

A multivariate-driven approach for disentangling the reduction in near-natural Iberian water resources post-1980

Abstract. Although the literature still debates how several anthropogenic and natural factors have contributed to the recent streamflow decline in the Iberian Peninsula, a continuing decrease in winter precipitation (WP) has been noticed in this area since the 1980s and has been associated with large-scale atmospheric drivers. This contribution assesses the potential propagation of this WP deficit into water resource variability. For this purpose, the novel “NEar-Natural Water Inflows to REservoirs of Spain” (NENWIRES) dataset was created. The results highlight that higher decreases in winter water inflows (WWIs) are always related to WP reductions. However, while the decline in WP was strongly provoked by the enhancement of the North Atlantic Oscillation index (NAOi) during the study period, WWI reductions could not be essentially linked to the NAOi behaviour in several NENWIRES catchments. Instead, the intensification of drought conditions and forest extension promoted WWI decreases over the target area and aided in understanding why WWI reductions were generally higher than WP decreases. In summary, most humid catchments registered a WWI decline that was mainly promoted by NAOi enhancement, whereas the extension of forest and evapotranspiration increases seem to explain WWI losses in semi-arid environments. This contribution sheds light on the recent debate regarding the magnitude and drivers of water resource decline over southern European regions.

Observed and predicted precipitation variability across Pakistan with special focus on winter and pre-monsoon precipitation.

This study utilises ground, satellite and model data to investigate the observed and future precipitation changes in Pakistan. Pakistan Meteorological Department's (PMD) monthly precipitation data set along with the Tropical Rainfall Measuring Mission (TRMM) monthly dataset TRMM_3B43 (0.25° × 0.25° resolution) and European Centre for Medium-Range Weather Forecasts's (ECMWF) monthly reanalysis product ERA5 have been used to evaluate rainfall trends over the climatic zones of Pakistan through Mann-Kendall test, Sen's slope estimator and innovative trend analysis for the time period 1978-2018. Community Climate System Model (CCSM4) projections have been employed to explore the projected changes in precipitation until 2099. Furthermore, TRMM and CCSM4 projections have been correlated and validated using root mean square error (RMSE) and mean bias error (MBE). There is a good correlation between TRMM and PMD ground observation at all stations of the country for all seasons, with correlation coefficient values ranging from 0.89 (November) to 0.97 (July and August). However, ERA5 monthly precipitation tends to overestimate rainfall in the winter months. The study shows a decreasing trend in winter precipitation in all zones of the country with a significant decrease over western mountains, i.e. zone C of the country. During 2008-2018, a sharp decrease in winter precipitation is observed as compared to the baseline value of 1978-2007 in all climatic zones. Rainy days have also shown a decrease in winter and pre-monsoon seasons. There seems to be a shift in precipitation from winter towards pre-monsoon season as pre-monsoon precipitation in the last 11years increased in all zones except for zone C. Coherently, there is a decrease in an area affected by winter precipitation and an increase in area for pre-monsoon precipitation. Future precipitation estimates from the CCSM4 model for RCP 4.5 and RCP 8.5 overestimate precipitation in most parts of the country for the first 9 observed years (2010-2018) and predict a rise in precipitation by 2099 which is more pronounced in the northern and western Pakistan while a decrease is predicted for the plains of the country, which might have negative consequences for agriculture.

Drought index predictability for historical and future periods across the Southern plain of Nepal Himalaya.

Drought episodes across the Himalayas are inevitable due to rapidly increasing atmospheric temperatures and uncertainties in rainfall patterns. Tarai of Nepal is a tropical region located in the foothills of the Central Himalaya as a country's food granary with a contribution of over 50% to the entire country's agricultural production. However, there is a lack of detailed studies exploring the spatiotemporal occurrence of drought in these regions under the changing climate. In this study, we used the ensemble of nine climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) under two shared socio-economic pathways (SSPs), namely SSP245 (an intermediate development pathway) and SSP585 (a high development pathway), to assess anticipated drought during the mid-century. We used bias-corrected gridded data from the Worldclim to project drought events by the end of the mid-century based on the historical period (1989-2018). We computed historical and projected Thornthwaite moisture index (TMI) to evaluate soil moisture conditions on a seasonal scale for the Tarai region's Eastern, Central, and Western parts. The model ensemble projected a significant increase in precipitation and temperature for the entire Tarai by the end of mid-century. However, the winter and spring seasons are projected to suffer precipitation deficiency and a temperature rise. Our results indicated that the Eastern Tarai would likely experience a decrease in winter precipitation. We emphasize that the presented spatiotemporal pattern of the MI will be instrumental in addressing the irrigation facility's needs, choice, and rotation of crops under the changing climate scenarios and in improving our mitigation measures and adaptation plans for sustainability of the agriculture in drought-prone areas.

Increased mass loss of glaciers in Volcán Domuyo (Argentinian Andes) between 1962 and 2020, revealed by aerial photos and satellite stereo imagery

AbstractWe present geodetic mass-balance estimates for ten glaciers (22.6 ± 1.1 km2) around Volcán Domuyo between 1962 and 2020 (and 46 glaciers covering 29 ± 1.5 km2 between 1984 and 2020), derived from airborne, ASTER and Pléiades imagery. Overall, we find a slightly negative mass balance (−0.15 ± 0.09 m w.e. a–1) for the entire 1962–2020 time span. A closer inspection of sub-periods reveals, however, an increasingly negative mass balance with time. The Domuyo glaciers shifted from a moderately positive mass balance of +0.28 ± 0.13 m w.e. a–1 between 1962 and 1984, to a strongly negative mass balance of −0.99 ± 0.19 m w.e. a–1 between 2012 and 2020. An increase in summer temperatures and a decrease in winter precipitation during the last four decades are likely drivers of the observed glacier changes. We support this finding by implementing a minimal glacier model, relying solely on monthly precipitation and air temperatures. The mass-balance evolution detected in Volcán Domuyo is consistent with other sites spread across the Central Andes, suggesting rapidly increasing glacier wastage impacts are occurring at a geographically wider scale.

Drier Winters Drove Cenozoic Open Habitat Expansion in North America

AbstractThe shift from denser forests to open, grass‐dominated vegetation in west‐central North America between 26 and 15 million years ago is a major ecological transition with no clear driving force. This open habitat transition (OHT) is considered by some to be evidence for drier summers, more seasonal precipitation, or a cooler climate, but others have proposed that wetter conditions and/or warming initiated the OHT. Here, we use published (n = 2,065) and new (n = 173) oxygen isotope measurements (δ18O) in authigenic clays and soil carbonates to test the hypothesis that the OHT is linked to increasing wintertime aridity. Oxygen isotope ratios in meteoric water (δ18Op) vary seasonally, and clays and carbonates often form at different times of the year. Therefore, a change in precipitation seasonality can be recorded differently in each mineral. We find that oxygen isotope ratios of clay minerals increase across the OHT while carbonate oxygen isotope ratios show no change or decrease. This result cannot be explained solely by changes in global temperature or a shift to drier summers. Instead, it is consistent with a decrease in winter precipitation that increases annual mean δ18Op (and clay δ18O) but has a smaller or negligible effect on soil carbonates that primarily form in warmer months. We suggest that forest communities in west‐central North America were adapted to a wet‐winter precipitation regime for most of the Cenozoic, and they subsequently struggled to meet water demands when winters became drier, resulting in the observed open habitat expansion.

Contribution of winter precipitation to tree growth persists until the late growing season in the Karakoram of northern Pakistan

Identifying the influence of seasonal source water on tree growth is essential to understand the effect of climate change on forest dynamics. However, due to the lack of available long-term monitoring studies, little is known on how long moisture originating from winter precipitation influences tree growth in the following growing season. Herein, we developed a tree-ring latewood oxygen isotope (δ18OLW) chronology from the Karakoram (1955–2013) in northern Pakistan. We investigated whether winter climate signals are incorporated in the δ18OLW and how long winter precipitation through soil moisture contributed to tree growth during the growing season. Significant correlations were found between δ18OLW with both, winter to spring (January–May) temperature (r = 0.43, p < 0.05) and summer (July–August) precipitation (Local: r = −0.38, p < 0.05; Moisture source region: r = −0.44, p < 0.05). As shown by the cross-spectrum and commonality analysis, the climate signals in the δ18OLW are frequency-dependent. Winter temperature signals stored in the δ18OLW variations dominate at low frequencies more than 7 years (59% variance explained), while the summer precipitation signals dominate variations with higher frequencies shorter than 7 years (47% variance explained). Further analysis using reanalysis data shows that the growing season soil moisture at root depth (10–40 cm) is more strongly related to winter precipitation than to summer rainfall. Winter precipitation formed as ground snow provides root-zone soil moisture and tree growth via snowmelt during the growing season. Our study highlights that winter precipitation is the dominant water source contributing to Karakoram tree growth until the late growing season. Given the possibility of a decrease in winter precipitation under climate change in the Karakoram region, local forest is potentially threatened by the declining water supply during the growing season.

Climate Change: Droughts and Increasing Desertification in the Middle East, with Special Reference to Iraq

Climate change impacts on Earth’s atmosphere have caused drastic changes in the environment of most regions of the world. The Middle East region ranks among the worst affected of these regions. This has taken forms of increasing atmospheric temperatures, intensive heat waves, decreased and erratic precipitation and general decline in water resources; all leading to frequent and longer droughts, desertification and giving rise to intensive and recurrent (SDS). The present conditions have led to increasing emissions of (GHG) in the earth atmosphere. All future projections especially those using (IPCC) models and emission scenarios indicate that the Middle East will undergo appreciable decrease in winter precipitation with increasing temperature until the end of this century both of which are inductive to increased dryness and desertification. Iraq as one of the countries of this region and due to its geographical location, its dependence mostly on surface water resources originating from neighboring countries, long years of neglect and bad land management put it in the most precarious and unstable position among the other countries of the region. Modelling studies have shown that Iraq is suffering now from excessive dryness and droughts, increasing loss of vegetation cover areas, increasing encroachment of sand dunes on agricultural lands, in addition to severe and frequent (SDS). These negative repercussions and their mitigations require solutions not on the local level alone but collective cooperation and work from all the countries of the region.

Analysis of the Effect of Climate Change on Flood Flows of Kemer Ağva River, Antalya

The environment and atmosphere are largely polluted due to increased urbanization, especially greenhouse gases from industrial and residential areas, and the trend of warming air on a global scale is increasing. In the event that global climate change persists for many years, it is expected that there may be significant increases in the severity, frequency and activity of hydrological natural disasters such as floods caused by these events, as well as extreme weather events. In recent years, Turkey has seen an increase in summer temperatures caused by climate change, a decrease in winter precipitation, and sudden and heavy rains and flood. Especially in the Western Mediterranean basin, heavy rainfall and flood events have started to be seen frequently due to climatic changes. In this study, current flood flow rates in Antalya Kemer Agva Stream and flood flow rates of 2050, 2075 and 2100 projections of HadGEM2-ES, MPI-ESM-MR and CNRM CM 5.1 climate models outputs were determined according to RCP 4.5 and RCP 8.5 scenarios. With this study, it has been revealed that the flood flows in the Kemer Agva basin will increase in the period until 2050 compared to the current situation, and will decrease in the periods of 2075 and 2100.

Modelling climate change impact on water resources of the Upper Indus Basin

Abstract Climate change has implications for water resources by increasing temperature, shifting precipitation patterns and altering the timing of snowfall and glacier melt, leading to shifts in the seasonality of river flows. Here, the Soil &amp; Water Assessment Tool was run using downscaled precipitation and temperature projections from five global climate models (GCMs) and their multi-model mean to estimate the potential impact of climate change on water balance components in sub-basins of the Upper Indus Basin (UIB) under two emission (RCP4.5 and RCP8.5) and future (2020–2050 and 2070–2100) scenarios. Warming of above 6 °C relative to baseline (1974–2004) is projected for the UIB by the end of the century (2070–2100), but the spread of annual precipitation projections among GCMs is large (+16 to −28%), and even larger for seasonal precipitation (+91 to −48%). Compared to the baseline, an increase in summer precipitation (RCP8.5: +36.7%) and a decrease in winter precipitation were projected (RCP8.5: −16.9%), with an increase in average annual water yield from the nival–glacial regime and river flow peaking 1 month earlier. We conclude that predicted warming during winter and spring could substantially affect the seasonal river flows, with important implications for water supplies.

Climate and environmental reconstruction of the Epipaleolithic Mediterranean Levant (22.0–11.9 ka cal. BP)

This study presents, for the first time, an environmental reconstruction of a sequence spanning nearly the entire Mediterranean Epipaleolithic (∼22.0–11.9 ka cal. BP). The study is based on a well-dated, high-resolution pollen record recovered from the waterlogged archaeological site Jordan River Dureijat (JRD), located on the banks of Paleolake Hula. JRD's continuous sequence enabled us to build a pollen-based paleoclimate model providing a solid background for the dramatic cultural changes that occurred in the region during this period. Taxonomic identification of the waterlogged wood assemblage collected from JRD was used to fine-tune the paleoenvironmental reconstruction. The chronological framework is based on radiocarbon dating and the typology of archaeological findings. The LGM (∼22–19 ka cal. BP) was found to be the coldest period of the sequence, marked by a distinct decrease in the reconstructed January temperatures of up to 5°C lower than today, while mean annual precipitation was only slightly lower than the present-day average (∼450 vs. 515 mm, respectively). The wettest and warmest period of the record was identified between ∼14.9 and 13.0 ka cal. BP, with maximum values of 545 mm mean annual precipitation reached at ∼14.5 ka cal. BP. This time interval is synchronized with the global warm and moist Bølling-Allerød interstadial as well as with the onset of the Natufian culture and the emergence of sedentism in the Levant. The Younger Dryas began around 12.9 ka cal. BP and was identified as an exceptional period by the JRD sequence with low temperatures and minimal climatic seasonality contrast: an increase in rain contribution during spring, summer, and autumn was documented concurrently with a significant decrease in winter precipitation. The detailed vegetation and climatological reconstruction presented in this study serves as backdrop to seminal events in human history: the transition from small nomadic groups of hunter-gatherers to the sedentary villages of the Natufian, eventually transitioning to the agricultural, complex communities of the Neolithic.

Impacts of dynamic and thermal forcing by the Tibetan Plateau on the precipitation distribution in the Asian arid and monsoon regions

The dynamic and thermal effects of the Tibetan Plateau (TP) on the precipitation in the Asian arid and monsoon regions were investigated using three numerical experiments—one using real topography, one with the whole TP removed, and one with sensible heat turned off over the TP. The results show that there are strong seasonal and regional differences in the dynamic and thermal effects of the TP on the precipitation in the Asian arid regions. The dynamic effect dominated the decrease in winter precipitation by blocking the westerly, while the thermal effect dominated the decrease in summer precipitation due to the TP-induced compensation downdraft in Central Asia and arid East Asia. The thermal effect dominated and accounted for 60% of the decrease in summer precipitation in West Asia. The results also show that both the dynamic and thermal effects of TP exhibit a more salient influence on the East Asian monsoon region than the South Asian monsoon region. The thermal effect dominated and accounted for 40% of the increase in summer precipitation due to intensification of the summer monsoon, while the dynamic effect dominated and accounted for 80% of the decrease in winter precipitation due to the northeast wind anomaly in the northern East Asian monsoon region. The anomalous wind can reach to the coast of South China and form frontal precipitation in the southern East Asian monsoon region in winter. The thermal effect dominated and accounted for 80% of the increase in precipitation in the pre-monsoon period due to intensification of the Asian summer monsoon.

Spatial patterns of temperature, precipitation, and settlement dynamics on the Iberian Peninsula during the Chalcolithic and the Bronze Age

In light of recent climate changes, it is important to also gain knowledge about the spatial manifestation of past climate events and their potential impact on ancient societies across a wide range of different scenarios. Following this approach, we compare compilations of seasonal (winter and summer) as well as annual precipitation and temperature changes to a measure of human activity based on AMS 14C data of settlement sites from the Iberian Peninsula during the Chalcolithic and the Bronze Age – a period of major social turnover. Palaeoclimatic reconstructions show a long-term decrease in winter precipitation between 6000 and 3000 cal. BP (4050–1050 BCE). Superimposed to this long-term aridification trend was the 4.2 ka BP climate event, which manifested itself as a period of abrupt decrease in summer precipitation and/or an elongation of the summer dry period, but probably with constant winter precipitation from 4000 to 3800 cal. BP (2050–1850 BCE), particularly affecting the southeast of the Iberian Peninsula. Additionally, a winter cooling event across the Iberian Peninsula and its marginal seas occurred between 4400 and 4000 cal. BP (2450–2050 BCE) coinciding with Bond Event 3. By comparing human activities to the changes in seasonal and annual precipitation, new insight is gained into the causal relationships between climatic and social dynamics in the past. We show that winter precipitation potentially played a major role for the societies during the Chalcolithic and the Bronze Age of the southern Iberian Peninsula. While the El Argar culture at the south-eastern Iberian Peninsula boomed in spite of enhanced summer drought associated to the 4.2 ka BP climate event, decreasing winter precipitation was potentially contributing to a demographic decline in the southwest after 4800 cal. BP (2850 BCE) as well as to the bust of the El Argar culture in the southeast after 3600 cal. BP (1650 BCE) by limiting the agricultural strategies.

Impact of Climate Change and Adaptation Measures on Transhumance Herding System in Gatlang, Rasuwa

Climate change impact is global and Nepal is no exception, posing vulnerability for different communities and regions. Transhumance herding is the culture and identity of indigenous settlement in Himalayan region where herders follow vertical transhumance herding as a part of subsistence mixed agriculture system for their livelihood. It differs from nomadism in terms of its periodicity, regularity, and mobility. This study confers the impacts of climate change and adaptation on transhumance herders in Gatlang of Rasuwa District. Focus Group Discussion, Key Informant Interview, and Questionnaire survey were carried out covering herder’s perception toward climatic variability, changes in the biophysical indicator, its impact and adaptation strategies. Data were analyzed using descriptive statistics, weighted mean, and Index of Usefulness of Practice for Adaptation (IUPA) tools. This study showed increase in mean average temperature (0.0202°C), increase in monsoon precipitation (2.1 mm) and decrease in winter precipitation (0.5 mm). Seasonal movement of livestock was mainly guided for adjusting temperature. The observed changes in biophysical indicator were diverse with shrinking grazing lands as most agreed statements followed by low crop productivity and faster melting of snow in rangeland. Herders perceived different adaptation strategies where reserving some grazing areas scored highest IUPA ranking followed by seasonal movement, storage of grass/hay, and so on. Though transhumance itself is one of the adaptation strategy against climate change people were not aware about changing monsoon precipitation and following same seasonal calendar as before which have affected livestock. These observations suggested that herders were unaware of the underlying cause and its impacts on the system which needed to be monitored scientifically.

Intensified hydroclimatic regime in Korean basins under 1.5 and 2°C global warming

AbstractThis study assesses the potential changes in regional hydroclimates over South Korea in response to 1.5 and 2.0°C of global warming above preindustrial levels based on multimodel ensemble projections forced by a representative concentration pathway (RCP4.5) scenario. The meteorological inputs, which are derived from five global climate models after removing systematic bias using quantile mapping, are fed into a distributed hydrological model, the variable infiltration capacity model, to estimate the hydrologic responses to different levels of greenhouse gas concentrations in future periods. The changes in seasonal mean precipitation differ between monsoon and intermonsoon seasons. An increase in summer precipitation and a decrease in winter precipitation commonly occur under 1.5 and 2.0°C of global warming, resulting in intensified precipitation seasonality. However, changes in spring and fall precipitation show opposite change signals or relatively little robustness (as measured by model agreement) in response to different degrees of warming. Spatial and seasonal changes in precipitation are directly transferred to runoff patterns, increasing the disparity between wet and dry seasons. Global warming also leads to changes in the distributions of daily precipitation and streamflow, and the projected changes systematically involve an increase in high‐intensity precipitation and a decrease in relatively low‐intensity precipitation. This behaviour tends to be amplified under 2.0°C in comparison to 1.5°C of global warming, with potential implications for increased water stress under a much warmer climate. More importantly, under 2.0°C of global warming, the magnitude of extremes such as the annual maximum day flow in Korean basins is likely to be enhanced. This study demonstrates that changes in precipitation characteristics can explicitly modulate runoff and subsequently streamflow patterns, suggesting positive benefits of half a degree less warming in terms of the frequency and intensity of extreme streamflow.

Cold and dry outbreaks in the eastern Mediterranean 3200 years ago

Abstract Can climate affect societies? This question, of both past and present importance, is encapsulated by the major socioeconomic crisis that affected the Mediterranean 3200 yr ago. The demise of the core civilizations of the Aegean and eastern Mediterranean during the Late Bronze Age and the early Iron Age (Dark Ages) is still controversial because it raises the question of climate-change impacts on ancient societies. Although evidence for this climate shift has gradually gained currency, recent attempts to quantify its magnitude remain equivocal. Here we focus on the northern Levant (coastal Syria) where the economic, political, and cultural changes were particularly acute. We quantify past climate changes and find that mean annual temperatures attained anomalies of − 2.3 ± 0.3 °C to − 4.8 ± 0.4 °C compared to present-day conditions. Rainfall regimes displayed an important shift in seasonality, with a 40% decrease in winter precipitation. A 300 yr period of dry and cool climate started ∼3200 yr ago and was coeval with deep social changes in the eastern Mediterranean. These “Little Ice Age”–type conditions affected harvests, leading to severe food shortages that probably aggravated the sociopolitical tensions. This crisis highlights the fragility of societies, both past and present, to major climate-change episodes and their broader consequences.

Warming temperatures are impacting the hydrometeorological regime of Russian rivers in the zone of continuous permafrost

Abstract. Large Arctic river basins experience substantial variability in climatic, landscape, and permafrost conditions. However, the processes behind the observed changes at the scale of these basins are relatively poorly understood. While most studies have been focused on the “Big 6” Arctic rivers – the Ob', Yenisey, Lena, Mackenzie, Yukon, and Kolyma – few or no assessments exist for small and medium-sized river basins, such as the Yana and Indigirka River basins. Here, we provide a detailed analysis of streamflow data from 22 hydrological gauges in the Yana and Indigirka River basins with a period of observation ranging from 35 to 79 years up to 2015. These river basins are fully located in the zone of continuous permafrost. Our analysis reveals statistically significant (p&lt;0.05) positive trends in the monthly streamflow time series during the autumn–winter period for most of the gauges. The streamflow increases in a stepwise pattern (post-1981) for 17 out of 22 gauges in September (average trend value for the period of record is 58 % or 9.8 mm) and 15 out of 22 gauges in October (61 % or 2.0 mm). The positive trends are seen in 9 out of 19 rivers that do not freeze in November (54 %, 0.4 mm) and 6 out of 17 rivers that do not freeze in December (95 %, 0.15 mm). Precipitation is shown to decrease in late winter by up to 15 mm over the observational period. Additionally, about 10 mm of precipitation that used to fall as snow at the beginning of winter now falls as rain. Despite the decrease in winter precipitation, no decrease in streamflow has been observed during the spring freshet in May and June in the last 50 years (from 1966); moreover, five gauges show an increase of 86 % or 12.2 mm in spring floods via an abrupt change in 1987–1993. The changes in spring freshet start date are identified for 10 gauges; the earlier onset in May varies from 4 to 10 d over the observational period. We conclude that warmer temperatures due to climate change are impacting the hydrological regime of these rivers via changes in precipitation type (rain replacing snow). Other factors, such as the melting of permafrost, glaciers, and aufeis or changes in groundwater conditions, are likely to contribute as well; however, no direct observations of these changes are available. The changes in streamflow can have a significant impact on the ecology of the zone of continuous permafrost, while the increasing freshwater fluxes to the Arctic Ocean can impact the Arctic thermohaline circulation.