Shifts In Precipitation Research Articles

Northward migration of the maximum Indian summer monsoon precipitation during the early–mid-Holocene: Evidence from sporopollen in the Andaman Sea

The Indian summer monsoon (ISM) significantly influences the evolution of the natural environment and the development of human societies in South Asia, however, the spatiotemporal nature of the maximum ISM precipitation remains uncertain. We present the first sedimentary sporopollen record from core ADM-C1 in the southern Andaman Sea, covering the past 11.2 ka to better understand the evolutionary history of the ISM. We use the percentage values of tropical–subtropical broad-leaved tree pollen to indicate regional precipitation. These pollens reached their highest abundances during ∼11–9 cal ka BP, indicating warmest and wettest climatic conditions in the southern Andaman Sea region. The subsequent retreat of the tropical–subtropical broad-leaved forest could reflect a gradual decline in ISM. By comparing numerous ISM precipitation records, we divided these records into two patterns: the timing of maximum ISM precipitation of Pattern 1 records during the early-Holocene (11–9 cal ka BP) and that of Pattern 2 records after 9 cal ka BP. The shift in the maximum ISM precipitation from Pattern 1 to Pattern 2 reflects a northward migration during the early–mid-Holocene, probably induced by the northward migration of the mean position of the Intertropical Convergence Zone (ITCZ). Furthermore, the ∼1.8 ka temporal lag between Patterns 1 and 2 could have resulted from the relatively weak Atlantic Meridional Overturning Circulation, which might have hindered the ITCZ from migrating northward before 9 cal ka BP.

Atmospheric Circulation Patterns Associated with Extreme Precipitation Events in Eastern Siberia and Mongolia

The socioeconomic impacts caused by floods in the south of Eastern Siberia (SES), and the expected increase in precipitation extremes over northern Eurasia, have revealed the need to search for atmospheric circulation patterns that cause extreme precipitation events (EPE) in SES, as well as their changes. We investigate the circulation patterns causing extreme precipitation in SES and Mongolia, by examining the instability and moisture transport associated with potential vorticity (PV) dynamics during two time periods: 1982–1998 and 1999–2019. The EPE were characterized by an increase in instability within the precipitation area, which was compensated by stability around the area, with the East Asian summer monsoon transport being enhanced. PV in the subtropical regions and mid-latitudes has shown the amplification of positive and negative PV anomalies to the southeast and northwest of Lake Baikal, respectively. The PV contours for EPE have shapes of cyclonic wave breaking and cutoff low. EPE accompanied by wave breaking are characterized by strong redistribution areas, with extremely high and low stability and moisture. This can lead to the coexistence of floods and droughts, and in part was the driver of the earlier revealed “seesaw” precipitation mode over Mongolia and SES. We suggest a shift of extreme precipitation to the northwest has occurred, which was probably caused by the wave propagation change.

The influence of the precipitation recycling process on the shift to heavy precipitation over the Tibetan Plateau in the summer

On the Tibetan Plateau (TP), precipitation intensity has shifted to heavy precipitation due to global warming. However, the influence of the precipitation recycling process on this phenomenon remains unknown. Using the Water Accounting Model-2layers (WAM2layers) model and ERA5 reanalysis, this study investigates the contributions of the precipitation recycling process to precipitation shifts over the TP during 1979–2019. The precipitation shift rate was proposed to quantify this process, and the results reveal that the positive precipitation shift (1.384 mm/41 years) over the TP consists of a positive shift over the western TP (5.666 mm/41 years) and a negative shift (−3.485 mm/41 years) over the eastern TP. Considering the source of moisture, either a local source or a remote source, precipitation was decomposed into internal and external cycles of the precipitation recycling process based on the WAM2layers model. Further analysis indicates that the internal cycle (87.2%) contributes more to the shift than the external cycle (12.8%) over the TP. The contributions of the precipitation recycling ratio (PRR) and precipitation amount to the precipitation shift rate induced by the internal cycle were further investigated. The results indicate that PRR changes contribute more to heavy precipitation over the TP, while precipitation amount changes contribute more to light precipitation. The precipitation recycling process contributes to the shift by increasing atmospheric moisture and increasing (decreasing) the dependency on local evaporation in heavy (light) precipitation. Increased dependence of heavy precipitation on evaporation increases the risk of extreme precipitation, and the government should take preventative actions to mitigate these adverse effects.

Seedbed not rescue effect buffer the role of extreme precipitation on temperate forest regeneration.

Alterations in global climate via extreme precipitation will have broadscale implications on ecosystem functioning. The increased frequency of drought, coupled with heavy, episodic rainfall are likely to generate impacts on biotic and abiotic processes across aquatic and terrestrial ecosystems. Despite the demonstrated shifts in global precipitation, less is known how extreme precipitation interacts with biophysical factors to control future demographic processes, especially those sensitive to climate extremes such as organismal recruitment and survival. We utilized a field-based precipitation manipulation experiment in 0.1 ha forest canopy openings to test future climate scenarios characterized by extreme precipitation on temperate tree seedling survival. The effects of planting seedbeds (undisturbed leaf litter/organic material vs. scarified, exposed mineral soils), seedling ontogeny, species, and functional traits were examined against four statistically defined precipitation scenarios. Results indicated that seedlings grown within precipitation treatments characterized by heavy, episodic rainfall preceded by prolonged drying responded similarly to drought treatments lacking episodic inputs. Moreover, among all treatment conditions tested, scarified seedbeds most strongly affected seedling survivorship (odds ratio 6.9). Compared with any precipitation treatment, the effect size (predicted probabilities) of the seedbed was more than twice as important in controlling seedling survivorship. However, the interaction between precipitation and seedbed resulted in a 27.9% improvement in survivorship for moisture-sensitive species. Seedling sensitivity to moisture was variable among species, and most closely linked with functional traits such as seed mass. For instance, under dry moisture regimes, survivorship increased linearly with seed mass (log transformed; adjusted R2 = 0.72, p < 0.001), yet no relationship was apparent under wet moisture regimes. Although precipitation influenced survival, extreme rainfall events were not enough to offset moisture deficits nor provide a rescue effect under drought conditions. The relationships reported here highlight the importance of plant seedbeds and species (e.g., functional traits) as edaphic and biotic controls that modify the influence of extreme future precipitation on seedling survival in temperate forests. Finally, we demonstrated the biophysical factors that were most influential to early forest development and that may override the negative effects of increasingly variable precipitation. This work contributes to refinements of species distribution models and can inform reforestation strategies intended to maintain biodiversity and ecosystem function under increasing climate extremes.

Exploiting SMILEs and the CMIP5 Archive to Understand Arctic Climate Change Seasonality and Uncertainty

AbstractArctic Amplification (AA) exhibits a distinct seasonal dependence; it is weakest in boreal summer and strongest in winter. Here, we analyze simulations from single‐model initial‐condition large ensembles and Coupled Model Intercomparison Project Phase 5 to decipher the seasonal evolution of Arctic climate change. Models agree that the annual maximum AA shifts from autumn into winter over the 21st century, accompanied by similar shifts in sea‐ice loss and surface turbulent heat fluxes, whereas the maximum precipitation shifts only into late autumn. However, the exact seasonal timing and magnitude of these shifts are highly uncertain. Decomposing the uncertainty into model structural differences, emission scenarios, and internal variability reveals that model differences dominate the total uncertainty, which also undergo autumn‐to‐winter shifts. We also find that the scenario uncertainty is unimportant for projections of AA. These results highlight that understanding model differences is critical to reducing uncertainty in projected Arctic climate change.

Approaches to Understanding Decadal and Long-Term Shifts in Observed Precipitation Distributions in Victoria, Australia

Abstract Over the past century, precipitation totals in Australia’s southeastern state of Victoria have shown multidecadal variability without clear trends. This has impacted agriculture, water security, ecosystem services, and flood hazards. Hydrological and meteorological evidence suggests that Victorian precipitation regimes have changed since the beginning of the Millennium Drought in 1997. Until now, Victorian precipitation intensity distributions have not been assessed in detail. We assess the time-varying aspect of observed precipitation intensity distributions by identifying temporal shifts in Victorian precipitation and using those different epochs to assess multidecadal changes in precipitation characteristics. We used 788 manual rain gauges and 49 automatic weather stations to analyze subdaily-to-multiday precipitation distributions from 1900 to 2020 for three Victorian regions and four seasons. Distributions are significantly different for the three epochs (1900–45, 1946–96, and 1997–2020). We summarized precipitation distributions by categorizing precipitation intensities, calculating histograms, and fitting gamma distributions. This study provides evidence that Victorian precipitation distributions have shifted over decades and that distributions depend on regional and seasonal differences. Recent precipitation declines are mostly due to decreasing light and moderate precipitation, despite increasing heavy precipitation. Heavy precipitation has shown a tendency to increase in frequency since 1997. Increases were greatest for 6-h springtime and summertime precipitation in northern Victoria and wintertime precipitation in southern and eastern Victoria. Observed precipitation distributions show changes that are consistent with climate projections. To better understand processes driving observed and projected changes to precipitation distributions globally, interdecadal shifts, seasonal variations, and regional climates need to be considered. Significance Statement Our research investigated how different rainfall intensities have contributed to changing rainfall totals over the last century in Victoria, Australia. This is important because different rainfall intensities have various impacts on farms, rivers, catchments, and infrastructure. In Victoria, we found three multidecade periods with different average rainfall intensity distributions. Early-twentieth-century rainfall is close to the observed average, 1946–96 was very wet, and 1997–2020 was drier. Recent years were drier because of fewer light and moderate rainfall events. Changes in heavy rainfall depend on the season and subregional factors. This may indicate that weather processes have changed. Decreasing light-to-moderate rainfall intensities will affect stakeholders by decreasing soil moisture, runoff, and streamflow.

The impact of climate change on mandarin production in Dumtoed Chewa Chiwog under Samtse Dzongkhag

Climate change which refers to a long-term shift in temperature, precipitation, wind patterns, and other elements of the Earth's climate system has a significant impact on agricultural practices across the world. Climate change has caused a notable impact on Bhutan, an agriculturally reliant nation, particularly affecting the production of mandarin, a crucial cash crop in the southern regions of the country. The study explored the impact of climate change on mandarin production in Dumtoed Chewa Chiwog under Samtse Dzongkhag. Employing the mixed methods research approach the study explored community perception of the impact of climate change on mandarin production, identified the impact of climate change on the production of mandarin, and explored the adaptations to reduce the impact of climate change on mandarin production in their locality. The study revealed that farmers are increasingly vulnerable to climate change. Erratic rainfall, rise in temperature, storms, drying soil moisture, and the emergence of new diseases and pests attributed to climate change have declined both the quality and quantity of their mandarin production, ultimately resulting in decreased income levels for farmers. While local indigenous practices have proven effective in safeguarding mandarin plants, there is a need to strengthen the resilience of mandarin cultivators against the influence of climate change. This can be achieved through policy support, raising awareness, and the provision of training.

Asymmetric responses of biocrust respiration to precipitation manipulation under a changing semiarid climate

Global climate change is expected to cause both increased and reduced precipitation in the next decades, especially in drylands with semi-arid climates. Biocrusts are an essential soil surface cover in global drylands, and they strongly influence most soil properties and support fundamental ecosystem functions, especially soil carbon (C) cycling. Nevertheless, the response patterns and mechanisms of biocrust respiration rate (Rs) to precipitation changes remain uncertain under changing semi-arid climates. In our study, a field experiment for biocrusts with natural precipitation (CK) and six levels of precipitation manipulation (–50 %, –30 %, –10 %, +10 %, +30 %, and +50 % of CK) were conducted from 2019 to 2021 in a semi-arid climate region of the northern Chinese Loess Plateau. We continuously measured the biocrust Rs of all the treatments in the growing seasons, and the fundamental properties of biocrusts and their temperature and water content at 5 cm depth were also measured. Our results showed that the increased precipitation inhibited biocrust Rs, while moderately reduced precipitation stimulated biocrust Rs. As compared with the CK, the precipitation manipulations of +10 %, +30 %, and +50 % decreased biocrust Rs by 8.9 %, 15.3 %, and 22.1 %, respectively, while the treatments of –10 % and –30 % increased biocrust Rs by 25.5 % and 8.0 %, respectively. However, the precipitation manipulation of –50 % suppressed biocrust Rs by 19.3 %. More importantly, the responses of biocrust Rs to precipitation changes were negative and asymmetric, which indicated a higher sensitivity of biocrust Rs to reduced precipitation in comparison to increased precipitation. Moreover, the increased precipitation (+10 % to + 50 %) raised soil water content (by 29.7 %–55.0 %), moss biomass (by 12.5 %–50.0 %), and organic matter content (by 11.3 %–12.4 %). In contrast, the reduced precipitation (–10 % to –30 %) decreased soil water content (by 5.2 %–17.6 %) and moss biomass (by 12.5 %–25.8 %). The structural equation modeling analysis showed that the responses of biocrust Rs to precipitation manipulation were mainly and directly influenced by soil temperature and biocrust properties. Although soil water content did not have a direct significant effect on biocrust Rs, it indirectly influenced biocrust Rs by affecting the fundamental properties of soil and biocrusts. Consequently, the changed soil properties and biocrust characteristics caused by precipitation shifts aggravated the negative responses of biocrust Rs to precipitation manipulation. Our findings emphasize that biocrusts have a negative and asymmetric response of Rs to precipitation changes, implying that the intensified precipitation variation in semi-arid regions caused by global climate change in future may positively affect the stability of soil C stocks contributed by biocrusts and thus reduce soil C efflux in drylands.

Watershed memory amplified the Oroville rain-on-snow flood of February 2017.

Mountain snowpacks are transitioning to experience less snowfall and more rainfall as the climate warms, creating more persistent low- to no-snow conditions. This precipitation shift also invites more high-impact rain-on-snow (ROS) events, which have historically yielded many of the largest and most damaging floods in the western United States. One such sequence of events preceded the evacuation of 188,000 residents below the already-damaged Oroville Dam spillway in February 2017 in California's Sierra Nevada. Prior studies have suggested that snowmelt during ROS dramatically amplified reservoir inflows. However, we present evidence that snowmelt may have played a smaller role than previously documented (augmenting terrestrial water inputs by 21%). A series of hydrologic model experiments and subdaily snow, soil, streamflow, and hydrometeorological measurements demonstrate that direct, "passive" routing of rainfall through snow, and increasingly efficient runoff driven by gradually wetter soils can alternatively explain the extreme runoff totals. Our analysis reveals a crucial link between frequent winter storms and a basin's hydrologic response-emphasizing the role of soil moisture "memory" of within-season storms in priming impactful flood responses. Given the breadth in plausible ROS flood mechanisms, this case study underscores a need for more detailed measurements of soil moisture along with in-storm changes to snowpack structure, extent, energy balance, and precipitation phase to address ROS knowledge gaps associated with current observational limits. Sharpening our conceptual understanding of basin-scale ROS better equips water managers moving forward to appropriately classify threat levels, which are projected to increase throughout the mid-21st century.

Influence of the North Kazakhstan Plains Weather on the Productivity of the Spring Soft Wheat

Spring soft wheat is a primary agricultural crop of North Kazakhstan, the growing process of which is done in harsh weather conditions due to the fact, that early spring drought and the biggest rainfalls at the end of June and beginning of July, are normal in the region. Due to this fact, scientists and producers have mistakenly believed that in the Northern region, spring wheat should be sown later, adjusting the main phase of plant development “tillering – stem elongation” under the maximum summer rainfalls. The research aims to establish the dependence of spring wheat yield on the amount of spring-summer rainfall at different sowing periods. The following methods were used in the research: field method, methods of clustering, variation, correlation and dispersion analysis. Analysis of observations from 2012-2021 showed that years with an early-spring drought and mid-summer maximum rainfalls were less than one-third of ten and about 60% were years with no spring drought, although the maximum rainfall period was shifted to the June month. However, only one year (10%) was characterized by a severe spring drought and a shift of summer rainfalls to August. The highest yield (26.9 c/ha) of the studied wheat species was observed in years with an atmospheric precipitation shift at the beginning of the summer period and early sowing date. During years of early spring drought with the biggest rainfall in mid-summer, relatively high yields (20.5 cwt/ha) are observed in the later sowing dates. The practical value of the research is determined by the fact, that in Northern Kazakhstan the sowing dates of spring wheat are not closely tied to the calendar dates and depend significantly on the climatic conditions of the region and the weather conditions that prevailed in the spring and summer period of a specific year

Frog body size responses to precipitation shift from resource-driven to desiccation-resistant as temperatures warm.

Climate change threatens biodiversity in a range of ways, including changing animal body sizes. Despite numerous examples of size declines related to increasing temperatures, patterns of size change are not universal, suggesting that one or more primary mechanisms impacting size change are unknown. Precipitation is likely to influence the size different from and in conjunction with changes in temperature, yet tests of the interaction between these variables are rare. In this study, we show that a crossover interaction between temperature and precipitation impacts the body size of frogs as the climate warms. Using more than 3000 museum frog specimens from Borneo and climate records spanning more than 100 years, we found that frogs are larger in wet conditions than in dry conditions at cool temperatures, suggesting that resource availability determines body size at colder temperature. Conversely, frogs are larger in dry conditions than in wet conditions at warm temperatures, resulting in a crossover to desiccation resistance as the main determinant of body size as climates warm. Our results demonstrate that global warming can alter the impact of precipitation on life-history traits. We suggest that increased attention be paid to such interactive effects of climate variables, to identify complex mechanisms driving climate-induced size changes.

Climate change information over Fenno-Scandinavia produced with a convection-permitting climate model

This paper presents results from high-resolution climate change simulations that permit convection and resolve mesoscale orography at 3-km grid spacing over Fenno-Scandinavia using the HARMONIE-Climate (HCLIM) model. Two global climate models (GCMs) have been dynamically down-scaled for the RCP4.5 and RCP8.5 emission scenarios and for both near and far future periods in the 21st century. The warmer and moister climate conditions simulated in the GCMs lead to changes in precipitation characteristics. Higher precipitation amounts are simulated in fall, winter and spring, while in summer, precipitation increases in northern Fenno-Scandinavia and decreases in the southern parts of the domain. Both daily and sub-daily intense precipitation over Fenno-Scandinavia become more frequent at the expense of low-intensity events, with most pronounced shifts in summer. In the Scandinavian mountains, pronounced changes occur in the snow climate with a shift in precipitation falling as snow to rain, reduced snow cover and less days with a significant snow depth. HCLIM at 3-km grid spacing exhibits systematically different change responses in several aspects, e.g. a smaller shift from snow to rain in the western part of the Scandinavian mountains and a more consistent decrease in the urban heat island effect by the end of the 21st century. Most importantly, the high-resolution HCLIM shows a significantly stronger increase in summer hourly precipitation extremes compared to HCLIM at the intermediate 12-km grid spacing. In addition, an analysis of the statistical significance of precipitation changes indicates that simulated time periods of at least a couple of decades is recommended to achieve statistically robust results, a matter of important concern when running such high-resolution climate model experiments. The results presented here emphasizes the importance of using “convection-permitting” models to produce reliable climate change information over the Fenno-Scandinavian region.

Records of Monsoon Variability in the Rain-shadow Zone of Western Maharashtra, Based on Multi-proxy Studies of Deposits in Two Historical Tanks

Global climate change is the predominant socio-economic, environmental and political issue confronting the mankind in the 21st century. The humanity in future is likely to depend upon the realistic assessment of the present climate and reasonably accurate prediction of the future climate change. This requires better understanding of the dominant characteristics of past climates. Lakes and tanks located in the semi-arid and arid regions are particularly suitable for palaeoclimatic studies, because of their high sensitivity to shifts in precipitation. The present study has been carried out using multi-proxies (e.g., textural, geochemical, mineral magnetic and charophytes studies) of sediments of two historical tanks namely, Bhatodi (~450 yrs old) and Mastani (~270 yrs old), from the rain-shadow zone of Western Maharashtra to understand the nature of monsoon variability in the catchment area of the tanks. The multi-proxy analyses of 4-5m thick sediment sections have revealed that with the exception of some minor sedimentary units in the middle, the lake sediments are by and large similar. This implies only short-term, subtle to modest changes in the rainfall and runoff conditions in the catchment area during the last 2-3cm. There is no evidence a major shift in monsoon rainfall conditions in the rain-shadow zone.

Effect difference of climate change and urbanization on extreme precipitation over the Guangdong-Hong Kong-Macao Greater Bay Area

Increasing extreme precipitation caused by climate change and human activities may have severe consequences on people's lives and property. In this study, the effect difference of urbanization, climate change and their compound effect on the annual and seasonal extreme precipitation under various Shared Socioeconomic Pathways are investigated using a convection-permitting (4 km) Weather Research and Forecasting model in the mega urban agglomeration. The enhancement effects of urbanization and climate change on extreme precipitation are also compared in the near future (2021–2050) and far future (2071–2100) periods of various Shared Socioeconomic Pathways-Representative Concentration Pathways (SSP-RCP) emission scenarios. The Guangdong-Hong Kong-Macao Greater Bay Area (GBA), a subtropical coastal world-class urban agglomeration in China, is taken as a representative in this study. The results indicate that, annual extreme and total precipitation will be more intensive and more frequent at regional scale along with rising long-lived greenhouse gas (LLGHG) concentration, while future urbanization exacerbates precipitation at local scale. Urban-induced total precipitation increases in the downwind areas and some urban areas of urban agglomeration, but still slightly decreases (all below 1.5%) over the entire study area. And more robust and stronger urban-induced signal in extreme precipitation characteristic is found in and around the urban areas where the total precipitation increases, as seen with an increase of >20% in amount and day number. In the compound scenarios, the interaction between urban and LLGHGs on precipitation was nonlinear and can be better explored by using convective permitting simulations. While urbanization can amplify or dampen local to regional precipitation, increased concentration of LLGHGs still make regional precipitation shift toward a general enhancement. Urbanization still has an impact on spatial distribution of precipitation despite a warming background climate. Additionally, seasonal heterogeneity of precipitation will be enhanced in all the future scenarios, especially in the future urbanization scenarios. The enhancement of urbanization (increase by about 42.1%, 38.0%, 14.0% in the precipitation amount, days and intensity respectively) on summer extreme precipitation change is greater than that of low-level LLGHG concentration (same as above, but increase by about 38.7%, 35.4%, 13.4%), despite their different mechanisms in altering extreme precipitation. The dominant factor of extreme precipitation varies with urbanization level and the LLGHG concentration. More attention should be paid to urban-induced precipitation changes under sustainable development scenarios with low-level LLGHG concentration.

Influence of multiple global change drivers on plant invasion: Additive effects are uncommon.

Invasive plants threaten biodiversity and cause huge economic losses. It is thought that global change factors (GCFs) associated with climate change (including shifts in temperature, precipitation, nitrogen, and atmospheric CO2) will amplify their impacts. However, only few studies assessed mixed factors on plant invasion. We collated the literature on plant responses to GCFs to explore independent, combined, and interactive effects on performance and competitiveness of native and invasive plants. From 176 plant species, our results showed that: (1) when native and invasive plants are affected by both independent and multiple GCFs, there is an overall positive effect on plant performance, but a negative effect on plant competitiveness; (2) under increased precipitation or in combination with temperature, most invasive plants gain advantages over natives; and (3) interactions between GCFs on plant performance and competitiveness were mostly synergistic or antagonistic. Our results indicate that native and invasive plants may be affected by independent or combined GCFs, and invasive plants likely gain advantages over native plants. The interactive effects of factors on plants were non-additive, but the advantages of invasive plants may not increase indefinitely. Our findings show that inferring the impacts of climate change on plant invasion from factors individually could be misleading. More mixed factor studies are needed to predict plant invasions under global change.

Drought impacts on hydrology and water quality under climate change

The Intergovernmental Panel on Climate Change (IPCC) has predicted that droughts are projected to affect global hydrology and water quality in varying ways, resulting in a considerable challenge to water availability for society, environment, and ecosystems. This study employed the Soil and Water Assessment Tool to evaluate how drought affects hydrology and water quality in the Miyun Reservoir watershed, coupled with bias-corrected climate projections in the Representative Concentration Pathway 8.5 scenario, accommodating the intercoupling effects of precipitation shifts and rising temperatures. The standardized precipitation index (SPI), standardized runoff index (SRI), and standardized soil moisture index (SSWI) were used to characterize meteorological, hydrological, and agricultural droughts that occur in the different phases in the hydrological cycle. Climate change had the most significant impact on agricultural drought. SSWI were projected to considerably increase in intensity, frequency, and duration in most subbasins by up to 15 %, 55 %, and 45 %, respectively, and showed a strong correlation with meteorological and hydrological droughts (correlation coefficients r = 0.54, 0.57, and 0.60 with SPI for the baseline, near future and far future periods, and 0.91, 0.87, and 0.89 with SRI for the three periods, respectively). Hydrological components, sediment export, and nutrient loss were highly correlated with changes in drought indexes, with r ranging between −0.68 and 0.34 in the near future period and −0.62 and 0.53 in the far future period. Drought conditions of surface runoff and soil water dominated the changes in sediment export, and hydrological drought was the major cause for reduced nutrient loads. In addition to drought impacts, the synergistic effects of increasing precipitation and rising temperature led to a certain degree of increase in sediment and nutrient exports. The results of this study emphasize the need to enhance the resilience of watershed systems to the predicted increases in the intensity, frequency, and duration of droughts.

Effects of drought on grassland phenology depend on functional types.

Shifts in flowering phenology are important indicators of climate change. However, the role of precipitation in driving phenology is far less understood compared with other environmental cues, such as temperature. We use a precipitation reduction gradient to test the direction and magnitude of effects on reproductive phenology and reproduction across 11 plant species in a temperate grassland, a moisture-limited ecosystem. Our experiment was conducted in a single, relatively wet year. We examine the effects of precipitation for species, functional types, and the community. Our results provide evidence that reduced precipitation shifts phenology, alters flower and fruit production, and that the magnitude and direction of the responses depend on functional type and species. For example, early-blooming species shift toward earlier flowering, whereas later-blooming species shift toward later flowering. Because of opposing species-level shifts, there is no overall shift in community-level phenology. This study provides experimental evidence that changes in rainfall can drive phenological shifts. Our results additionally highlight the importance of understanding how plant functional types govern responses to changing climate conditions, which is relevant for forecasting phenology and community-level changes. Specifically, the implications of divergent phenological shifts between early- and late-flowering species include resource scarcity for pollinators and seed dispersers and new temporal windows for invasion.

Large-scale climate response to regionally confined extratropical cooling: effect of ocean dynamics

This study investigates the effect of ocean dynamics on the tropical climate response to localized radiative cooling over three northern extratropical land regions using hierarchical model simulations that vary in the degree of ocean coupling. Without ocean dynamics, the tropical climate response is independent of the extratropical forcing location, characterized by a southward tropical precipitation shift with a high degree of zonal symmetry, a reduced zonal sea surface temperature gradient along the equatorial Pacific, and the eastward-shifted Walker circulation. When ocean dynamical adjustments are allowed, the zonal-mean tropical precipitation shift is damped primarily via Eulerian-mean ocean heat transport. The oceanic damping effect is strongest (weakest) for North Asian (American) cooling, associated with the largest (smallest) Eulerian-mean ocean heat transport across the equatorial Pacific. The cross-equatorial ocean heat transport in the Pacific is anchored to the North Pacific subtropical high, the response of which can be inferred from the corresponding slab ocean simulations. Hence, the slab ocean simulations provide useful a priori prediction for oceanic damping efficiency. Ocean dynamics also modulates the spatial pattern of climate response in a distinct manner depending on the zonal distribution of imposed forcing. North Asian forcing induces a pronounced eastern equatorial Pacific cooling extending to the western basin, accompanying the westward shifted Walker circulation. European forcing causes cooling confined to the eastern equatorial Pacific and strengthens the Walker circulation. The tropical precipitation response in these two cases exhibits large zonal variations with a high degree of equatorial symmetry, being essentially uncorrelated with the corresponding slab ocean simulations. By contrast, North American forcing induces a sufficiently strong inter-hemispheric contrast in the tropical Pacific SST response, due to the relatively weak oceanic damping effect, producing a weaker but spatially similar tropical response to that in the slab ocean simulation. This study demonstrates that the effect of ocean dynamics in modulating the tropical climate response depends on the extratropical forcing location. The results are relevant for understanding the distinct climate response induced by aerosols from different continental sites.

Plant Abiotic and Biotic Stress Alleviation: From an Endophytic Microbial Perspective.

Plant abiotic and biotic stresses can change plant-pest synergism by augmenting host plant vulnerability to pests and lessening competitive capability with weed plants. Climate change, such as a shift in precipitation, intensifies the damaging effects of stresses, undesirably impacting plant growth and survival. However, we have yet to reach a clear answer as the outcome usually depends on complex interactions and agro-climatic conditions. To alleviate plant stresses, more in-depth work is required to elucidate the underlying mechanisms and exploit thereof. In this review, we have confined ourselves to the domain of the role played by endophytic microorganisms to alleviate plant stress. In contrast, some biotic stresses may alter plant response to abiotic stress factors. Hence, methodical analyses are indispensable for understanding the effect of abiotic and biotic stress conditions on crop development and agronomic production. Endophytic microbes have drawn interest owing to their plant growth stimulating attributes and valuable performances related to plant responses under abiotic and biotic stress environments. Endophytes produce secondary metabolites to defend the host plant under stressful climatic conditions and against phytopathogens. Understanding plant resilience mechanisms will assist in the commercialized biotechnological development of endophytes in crop improvement. There is still much scope to explore factors and elucidate mechanisms that result in unquestionably recognized beneficial effects of endophytes. This review article bridges the gap mentioned and focuses on the role played by endophytes in plant development and their stimulating diverse mechanisms for tolerating diverse abiotic and biotic stresses in the host.

Carbon Fluxes during Dansgaard–Oeschger Events as Simulated by an Earth System Model

Abstract The Community Earth System Model with marine and terrestrial biogeochemistry is configured to simulate glacial climate. The integration shows transitions from warm to cold states—interstadials to stadials—and back. The amplitude of the associated Greenland and Antarctica temperature changes and the atmospheric CO2 signal are consistent with ice-core reconstructions, and so are the time lags between termination of a stadial, Antarctic temperature reversal, and the decline of the atmospheric CO2 concentration (for brevity’s sake simply referred to as CO2 from here on). The present model results stand out because the transitions occur spontaneously (without forcing changes like hosing) and because they reproduce the observed features above in a configuration that uses the same parameterizations as climate simulations for the present day (i.e., no retuning has been done). During stadials, precipitation shifts lead to reduced growth on land, which dominates the CO2 increase; the ocean acts as a minor carbon sink during the stadials. After the end of the stadials, however, the sudden reversal of the stadial anomalies in temperature, wind, and precipitation turns the ocean into a carbon source, which accounts for the continued rise of CO2 for several hundred years into the interstadial. The simulations also provide a novel possible interpretation for the observed correlation between CO2 and Antarctic temperature: rather than both being controlled by Southern Ocean processes, they are both controlled by the North Atlantic Ocean, and most of the extra CO2 may not be of Southern Hemisphere origin. If the stadials are prolonged through North Atlantic hosing, the upper ocean comes to an equilibrium, and the CO2 response is dominated by a single process: reduced export production in the North Atlantic as result of the collapsed overturning circulation. This is in contrast to the unforced simulation where the net ocean carbon flux anomaly is the sum of several regional responses of both signs and similar magnitudes. Reducing the aeolian iron deposition by half, to account for the observed reduction of Southern Hemisphere dust fluxes during stadials, reduces biological productivity and export production so that the Southern Ocean emerges as an important carbon source, at least for the three centuries up until a new equilibrium for the upper ocean is reached. Significance Statement The last ice age featured millennial-scale oscillations in CO2 and temperature, the latter being anticorrelated between Greenland and Antarctica. This is often referred to as the bipolar seesaw. Here, an Earth system model is described that reproduces these signals, and its results are used to explain the observed correlation between temperature and CO2. In contrast to previous idealized studies it is found that all ocean basins and the land each contribute equally to the CO2 signal.