Spatial gradient of temperature and potential vegetation feedback across Europe during the late Quaternary

After the last glacial maximum (LGM; 18,000 years. bp) plants migrated onto areas made free by the retreating ice sheets. Pollen records document changes in ecosystems and are an important proxy for the reconstruction of climate parameters. Here, we quantify changes in January temperature (Tjan) over the past 14,000 years using 216 European pollen records. We used functional principal component analysis to evaluate the patterns of change over this period of time. Between 14 and 12 ka, Tjan records show comparable changes across Europe. After this time period, northwest and southeast Europe experienced differing trends in Tjan, trends that became pronounced by 9 ka. The spatial gradient of Tjan records is well-correlated with the overall change from steppe to increasingly diverse forest ecosystems. In particular, differential incorporation of conifer vs. deciduous species into forest ecosystems, based on differential colonization out of refugia, likely resulted in albedo gradients over Europe that affected regional Tjan.     

Probabilistic projections of transient climate change

This paper describes a Bayesian methodology for prediction of multivariate probability distribution functions (PDFs) for transient regional climate change. The approach is based upon PDFs for the equilibrium response to doubled carbon dioxide, derived from a comprehensive sampling of uncertainties in modelling of surface and atmospheric processes, and constrained by multiannual mean observations of recent climate. These PDFs are sampled and scaled by global mean temperature predicted by a Simple Climate Model (SCM), in order to emulate corresponding transient responses. The sampled projections are then reweighted, based upon the likelihood that they correctly replicate observed historical changes in surface temperature, and combined to provide PDFs for 20 year averages of regional temperature and precipitation changes to the end of the twenty-first century, for the A1B emissions scenario. The PDFs also account for modelling uncertainties associated with aerosol forcing, ocean heat uptake and the terrestrial carbon cycle, sampled using SCM configurations calibrated to the response of perturbed physics ensembles generated using the Hadley Centre climate model HadCM3, and other international climate model simulations. Weighting the projections using observational metrics of recent mean climate is found to be as effective at constraining the future transient response as metrics based on historical trends. The spread in global temperature response due to modelling uncertainty in the carbon cycle feedbacks is determined to be about 65–80 % of the spread arising from uncertainties in modelling atmospheric, oceanic and aerosol processes of the climate system. Early twenty-first century aerosol forcing is found to be extremely unlikely to be less than ?1.7 W m^?2. Our technique provides a rigorous and formal method of combining several lines of evidence used in the previous IPCC expert assessment of the Transient Climate Response. The 10th, 50th and 90th percentiles of our observationally constrained PDF for the Transient Climate Response are 1.6, 2.0 and 2.4 °C respectively, compared with the 10–90 % range of 1.0–3.0 °C assessed by the IPCC.     

Indicators of Climate Warming in Minnesota: Lake ICE Covers and Snowmelt Runoff

Records of hydrologic parameters, especially those parameters that are directly linked to air temperature, were analyzed to find indicators of recent climate warming in Minnesota, USA. Minnesota is projected to be vulnerable to climate change because of its location in the northern temperate zone of the globe. Ice-out and ice-in dates on lakes, spring (snowmelt) runoff timing, spring discharge values in streams, and stream water temperatures recorded up to the year 2002 were selected for study. The analysis was conducted by inspection of 10-year moving averages, linear regression on complete and on partial records, and by ranking and sorting of events. Moving averages were used for illustrative purposes only. All statistics were computed on annual data. All parameters examined show trends, and sometimes quite variable trends, over different periods of the record. With the exception of spring stream flow rates the trends of all parameters examined point toward a warming climate in Minnesota over the last two or three decades. Although hidden among strong variability from year to year, ice-out dates on 73 lakes have been shifting to an earlier date at a rate of −0.13 days/year from 1965 to 2002, while ice-in dates on 34 lakes have been delayed by 0.75 days/year from 1979 to 2002. From 1990 to 2002 the rates of change increased to −0.25 days/year for ice-out and 1.44 days/year for ice-in. Trend analyses also show that spring runoff at 21 stream gaging sites examined occurs earlier. From 1964 to 2002 the first spring runoff (due to snowmelt) has occurred −0.30 days/year earlier and the first spring peak runoff −0.23 days/year earlier. The stream water temperature records from 15 sites in the Minneapolis/St Paul metropolitan area shows warming by 0.11^∘C/year, on the average, from 1977 to 2002. Urban development may have had a strong influence. The analysis of spring stream flow rates was inconclusive, probably because runoff is linked as much to precipitation and land use as to air temperature. Ranking and sorting of annual data shows that a disproportionately large number of early lake ice-out dates has occurred after 1985, but also between 1940 and 1950; similarly late lake ice-in has occurred more frequently since about 1990. Ranking and sorting of first spring runoff dates also gave evidence of earlier occurrences, i.e. climate warming in late winter. A relationship of changes in hydrologic parameters with trends in air temperature records was demonstrated. Ice-out dates were shown to correlate most strongly with average March air temperatures shifting by −2.0 days for a 1^°C increase in March air temperature. Spring runoff dates also show a relationship with March air temperatures; spring runoff dates shift at a rate of −2.5 days/1^°C minimum March air temperature change. Water temperatures at seven river sites in the Minneapolis/St Paul metropolitan area show an average rise of 0.46^°C in river temperature/1^°C mean annual air temperature change, but this rate of change probably includes effects of urban development. In conclusion, records of five hydrologic parameters that are closely linked to air temperature show a trend that suggests recent climate warming in Minnesota, and especially from 1990 to 2002. The recent rates of change calculated from the records are very noteworthy, but must not be used to project future parameter values, since trends cannot continue indefinitely, and trend reversals can be seen in some of the long-term records.     

Coupling climate change with hydrological dynamic in Qinling Mountains, China

This study intends to disclose orographic effects on climate and climatic impacts on hydrological regimes in Qinling Mountains under global change background. We integrate a meteorological model (MM5 model, PSU/NCAR, 2005) and a hydrological model (SWAT model, 2005) to couple hydrological dynamic with climate change in Qinling Mountains. Models are calibrated and validated based on the simulation of different combined schemes. Following findings were achieved. Firstly, Qinling Mountains dominantly influence climate, and hydrological process in Weihe River and upper Hanjiang River. Results show that Qinling Mountains lead to a strong north–south gradient precipitation distribution over Qinling Mountains due to orographic effects, and it reduces precipitation from 10–25 mm (December) to 55–80 mm (August) in Weihe River basin, and adds 25–50 mm (December) or 65–112 mm (August) in upper Hanjiang River basin; evapotranspiration (ET) decrease of 21% in Weihe River (August) and increase 10.5% in upper Hanjiang River (July). The Qinling Mountains reduce water yields of 23.5% in Weihe River, and decrease of 11.3% in upper Hanjiang River. Secondly, climate change is responsible for the changes of coupling effects of rainfall, land use and cover, river flow and water resources. It shows that average temperature significantly increased, and precipitation substantially reduced which leads to hydrological process changed greatly from 1950 to 2005: temperature increased and precipitation decreased, climate became drier in the past two decades (1980–2005), high levels of precipitation exists in mid-1950, mid-1970, while other studied periods are in low level states. The inter-annual variation in water yield correlates with surface runoff with an R ² value of 0.63 (Weihe River) and 0.87 (upper Hanjiang River). It shows that variation of annual precipitation was smaller than that of seasonal precipitation.     

The contribution of snow condition trends to future ground climate

Global climate models predict that terrestrial northern high-latitude snow conditions will change substantially over the twenty-first century. Results from a Community Climate System Model simulation of twentieth and twenty-first (SRES A1B scenario) century climate show increased winter snowfall (+10–40%), altered maximum snow depth (?5 ± 6 cm), and a shortened snow-season (?14 ± 7 days in spring, +20 ± 9 days in autumn). By conducting a series of prescribed snow experiments with the Community Land Model, we isolate how trends in snowfall, snow depth, and snow-season length affect soil temperature trends. Increasing snowfall, by countering the snowpack-shallowing influence of warmer winters and shorter snow seasons, is effectively a soil warming agent, accounting for 10–30% of total soil warming at 1 m depth and ~16% of the simulated twenty-first century decline in near-surface permafrost extent. A shortening snow season enhances soil warming due to increased solar absorption whereas a shallowing snowpack mitigates soil warming due to weaker winter insulation from cold atmospheric air. Snowpack deepening has comparatively less impact due to saturation of snow insulative capacity at deeper snow depths. Snow depth and snow-season length trends tend to be positively related, but their effects on soil temperature are opposing. Consequently, on the century timescale the net change in snow state can either amplify or mitigate soil warming. Snow state changes explain less than 25% of total soil temperature change by 2100. However, for the latter half of twentieth century, snow state variations account for as much as 50–100% of total soil temperature variations.     

Variations in cereal crop phenology in Spain over the last twenty-six years (1986–2012)

Over recent years, the Iberian Peninsula has witnessed an increase both in temperature and in rainfall intensity, especially in the Mediterranean climate area. Plant phenology is modulated by climate, and closely governed by water availability and air temperature. Over the period 1986–2012, the effects of climate change on phenology were analyzed in five crops at 26 sites growing in Spain (southern Europe): oats, wheat, rye, barley and maize. The phenophases studied were: sowing date, emergence, flag leaf sheath swollen, flowering, seed ripening and harvest. Trends in phenological response over time were detected using linear regression. Trends in air temperature and rainfall over the period prior to each phenophase were also charted. Correlations between phenological features, biogeographical area and weather trends were examined using a Generalized Lineal Mixed Model approach. A generalized advance in most winter-cereal phenophases was observed, mainly during the spring. Trend patterns differed between species and phenophases. The most noticeable advance in spring phenology was recorded for wheat and oats, the “Flag leaf sheath swollen” and “Flowering date” phenophases being brought forward by around 3 days/year and 1 day/year, respectively. Temperature changes during the period prior to phenophase onset were identified as the cause of these phenological trends. Climate changes are clearly prompting variations in cereal crop phenology; their consequences could be even more marked if climate change persists into the next century. Changes in phenology could in turn impact crop yield; fortunately, human intervention in crop systems is likely to minimize the negative impact.     

Temporal and geographical variation in the onset of climatological spring in Northeast China

Indications of earlier onset of spring have been observed in behavior of diverse animal and plant species in the Northern Hemisphere in response to recent climate warming. Knowledge of changes in the spring onset is a critical requirement for understanding ecosystem adaption to climate change, especially for agricultural regions. In this study, we present a climatological approach for detecting the temporal and spatial variability in onset of spring with particular emphasis on how they vary along geographical parameters. Yearly dates for spring onset were computed for 71 climate stations in Northeast China based on daily surface air temperature records. These analyses were conducted for the two study periods (1960–2004 and 1979–2004). We also examined the boundary shifts of spring onset for three selected dates between the periods of 1960–1978 and 1979–2004. The results showed that advancement of spring onset was more pronounced for the period of 1979–2004 than for the period of 1960–2004 (4.0 vs. 2.2 days/decade). For the 22 stations where the spring advancement was statistically significant in the two periods, the mean rate of advancement was ?0.6 days/decade during the period of 1960 to 1978. The trends of advancement of spring onset decreased with both increasing latitude and altitude up to 300 m above sea level, and these geographical effects were clearer during 1979–2004. Analysis of boundary shifts of three specific dates revealed that the spring onset has moved to higher latitudes for each date with an average shift of about 1° of latitude (about 110 km). Our results suggest that attempts to address how ecosystems will adapt to spring advancement associated with climate warming should consider the differences in response rates and geographical effects across the study area.     

Modeling soil thermal and hydrological dynamics and changes of growing season in Alaskan terrestrial ecosystems

Abundant evidence indicates the growing season has been changed in the Alaskan terrestrial ecosystems in the last century as climate warms. Reasonable simulations of growing season length, onset, and ending are critical to a better understanding of carbon dynamics in these ecosystems. Recent ecosystem modeling studies have been slow to consider the interactive effects of soil thermal and hydrological dynamics on growing season changes in northern high latitudes. Here, we develop a coupled framework to model these dynamics and their effects on plant growing season at a daily time step. In this framework, we (1) incorporate a daily time step snow model into our existing hydrological and soil thermal models and (2) explicitly model the moisture effects on soil thermal conductivity and heat capacity and the effects of active layer depth and soil temperature on hydrological dynamics. The new framework is able to well simulate snow depth and soil temperature profiles for both boreal forest and tundra ecosystems at the site level. The framework is then applied to Alaskan boreal forest and tundra ecosystems for the period 1923–2099. Regional simulations show that (1) for the historical period, the growing season length, onset, and ending, estimated based on the mean soil temperature of the top 20 cm soils, and the annual cycle of snow dynamics, agree well with estimates based on satellite data and other approaches and (2) for the projected period, the plant growing season length shows an increasing trend in both tundra and boreal forest ecosystems. In response to the projected warming, by year 2099, (1) the snow-free days will be increased by 41.0 and 27.5 days, respectively, in boreal forest and tundra ecosystems and (2) the growing season lengths will be more than 28 and 13 days longer in boreal forest and tundra ecosystems, respectively, compared to 2010. Comparing two sets of simulations with and without considering feedbacks between soil thermal and hydrological dynamics, our analyses suggest coupling hydrological and soil thermal dynamics in Alaskan terrestrial ecosystems is important to model ecosystem dynamics, including growing season changes.     

A study on the role of land-atmosphere coupling on the south Asian monsoon climate variability using a regional climate model

The spatial and temporal trends of 11 (7) temperature (precipitation) extreme indices are examined for the Loess Plateau Region (LPR) and its southeast and northwest sub-regions based on daily observations at 214 meteorological stations. Results show widespread significant warming trends for all the temperature extremes except for the diurnal temperature range (DTR) and the lowest daily maximum temperature in each year (TXn) during 1961–2010. When regionally averaged, a significant warming trend is detected for all the indices except for DTR and TXn in the past 50 years. Compared with the entire LPR, a significant warming trend is detected for all the indices except for DTR and TXn over the southeast sub-region of LPR; while it is observed for all the indices over the northwest. The trends for these indices are generally stronger in the northwest than in the southeast in the past 50 years. In contrast, for precipitation indices, only a small percentage of areas show significant drying or wetting trends and, when regionally averaged, none of them displays significant trends during the past 50 years. On the sub-regional scale, however, a larger percentage of areas show significant drying trends for precipitation indices generally over the southeast relative to the entire LPR, and noticeably, the sub-regional average heavy precipitation (R10mm) and wet day precipitation (PRCPTOT) display significant decreasing trends during the past 50 years; whereas only a slightly larger percentage of areas show significant wetting trends for these indices over the northwest compared with the entire LPR, and when sub-regionally averaged, none of the indices have significant trends during the past 50 years.     

Climate trends of the North American prairie pothole region 1906–2000

The Prairie Pothole Region (PPR) is unique to North America. Its millions of wetlands and abundant ecosystem goods and services are highly sensitive to wide variations of temperature and precipitation in time and space characteristic of a strongly continental climate. Precipitation and temperature gradients across the PPR are orthogonal to each other. Precipitation nearly triples from west to east from approximately 300 mm/year to 900 mm/year, while mean annual temperature ranges from approximately 1°C in the north to nearly 10°C in the south. Twentieth-century weather records for 18 PPR weather stations representing 6 ecoregions revealed several trends. The climate generally has been getting warmer and wetter and the diurnal temperature range has decreased. Minimum daily temperatures warmed by 1.0°C, while maximum daily temperatures cooled by 0.15°C. Minimum temperature warmed more in winter than in summer, while maximum temperature cooled in summer and warmed in winter. Average annual precipitation increased by 49 mm or 9%. Palmer Drought Severity Index (PDSI) trends reflected increasing moisture availability for most weather stations; however, several stations in the western Canadian Prairies recorded effectively drier conditions. The east-west moisture gradient steepened during the twentieth century with stations in the west becoming drier and stations in the east becoming wetter. If the moisture gradient continues to steepen, the area of productive wetland ecosystems will shrink. Consequences for wetlands would be especially severe if the future climate does not provide supplemental moisture to offset higher evaporative demand.     

Oscillatory dynamics do not mask linear trends in the timing of ice breakup for Northern Hemisphere lakes from 1855 to 2004

Our analyses partition the relative influence of progressive climate change and large-scale climate drivers that can be associated with the Quasi-Biennial Oscillation (QBO), El Niño Southern Oscillation (ENSO), North Atlantic Oscillation (NAO), solar sunspot cycle, and multi-decadal oscillations on lake ice breakup dates for thirteen Northern Hemisphere lakes. Oscillatory dynamics explain 26 % of the total variance in the time series compared with 15 % for linear trends, leaving 60 % unexplained and likely attributable, in part, to local weather. Significant oscillatory dynamics include frequencies in 2–3 year periods (9.4 % of the total variance), 3–6 year periods (8.2 %), 10–12 year periods (1.6 %) and various multidecadal periods (0.4–1.3 %). All 13 study lakes, although widely scattered in the Northern Hemisphere, had similar oscillatory dynamics and linear trends, emphasizing that global processes influence lake ice breakup locally. We illustrate that while quasi-periodic dynamics associated with large-scale climate drivers are important, they do not mask the clear evidence for progressive climate change.     

Historical and potential changes of precipitation and temperature of Alberta subjected to climate change impact: 1900–2100

We investigated changes to precipitation and temperature of Alberta for historical and future periods. First, the Mann-Kendall test and Sen’s slope were used to test for historical trends and trend magnitudes from the climate data of Alberta, respectively. Second, the Special Report on Emissions Scenarios (SRES) (A1B, A2, and B1) of CMIP3 (Phase 3 of Coupled Model Intercomparison Project), projected by seven general circulation models (GCM) of the Intergovernmental Panel on Climate Change (IPCC) for three 30 years periods (2020s, 2050s, and 2080s), were used to evaluate the potential impact of climate change on precipitation and temperature of Alberta. Third, trends of projected precipitation and temperature were investigated, and differences between historical versus projected trends were estimated. Using the 50-km resolution dataset from CANGRD (Canadian Grid Climate Data), we found that Alberta had become warmer and somewhat drier for the past 112 years (1900–2011), especially in central and southern Alberta. For observed precipitation, upward trends mainly occurred in northern Alberta and at the leeward side of Canadian Rocky Mountains. However, only about 13 to 22 % of observed precipitation showed statistically significant increasing trends at 5 % significant level. Most observed temperature showed significant increasing trends, up to 0.05 °C/year in DJF (December, January, and February) in northern Alberta. GCMs’ SRES projections indicated that seasonal precipitation of Alberta could change from ?25 to 36 %, while the temperature would increase from 2020s to 2080s, with the largest increase (6.8 °C) in DJF. In all 21 GCM-SRES cases considered, precipitation in both DJF and MAM (March, April, and May) is projected to increase, while temperature is consistently projected to increase in all seasons, which generally agree with the trends of historical precipitation and temperature. The SRES A1B scenario of CCSM3 might project more realistic future climate for Alberta, where its water resources can become more critical in the future as its streamflow is projected to decrease continually in the future.     

Climate change in Bangladesh: a spatio-temporal analysis and simulation of recent temperature and rainfall data using GIS and time series analysis model

In this paper, temperature and rainfall data series were analysed from 34 meteorological stations distributed throughout Bangladesh over a 40-year period (1971 to 2010) in order to evaluate the magnitude of these changes statistically and spatially. Linear regression, coefficient of variation, inverse distance weighted interpolation techniques and geographical information systems were performed to analyse the trends, variability and spatial patterns of temperature and rainfall. Autoregressive integrated moving average time series model was used to simulate the temperature and rainfall data. The results confirm a particularly strong and recent climate change in Bangladesh with a 0.20 °C per decade upward trend of mean temperature. The highest upward trend in minimum temperature (range of 0.80–2.4 °C) was observed in the northern, northwestern, northeastern, central and central southern parts while greatest warming in the maximum temperature (range of 1.20–2.48 °C) was found in the southern, southeastern and northeastern parts during 1971–2010. An upward trend of annual rainfall (+7.13 mm per year) and downward pre-monsoon (?0.75 mm per year) and post-monsoon rainfall (?0.55 mm per year) trends were observed during this period. Rainfall was erratic in pre-monsoon season and even more so during the post-monsoon season (variability of 44.84 and 85.25 % per year, respectively). The mean forecasted temperature exhibited an increase of 0.018 °C per year in 2011–2020, and if this trend continues, this would lead to approximately 1.0 °C warmer temperatures in Bangladesh by 2020, compared to that of 1971. A greater rise is projected for the mean minimum (0.20 °C) than the mean maximum (0.16 °C) temperature. Annual rainfall is projected to decline 153 mm from 2011 to 2020, and a drying condition will persist in the northwestern, western and southwestern parts of the country during the pre- and post-monsoonal seasons.     

The resilience of annual vegetation primary production subjected to different climate change scenarios

We examined if climate change in two dry ecosystems—Mediterranean (DME) and Semiarid (SAE)—would cause substantial reduction in the production of annual vegetation. Field measurements and computer simulations were used to examine the following six climate change scenarios: (1) rainfall amount reduction; (2) increases of 10 % in annual evaporation rate and 5 % in annual temperature; (3) increase in magnitude of rainfall events, accompanied by reductions in frequency and seasonal variation; (4) postponement of the beginning of the first rainfall event of the growing season; (5) long dry spells during the growing season; and (6) early ending of the growing season. The results revealed the following outcomes. a) Reduction by 5–35 % in annual rainfall amount did not significantly affect productivity in the DME, but a large (25–35 %) decrease in rainfall would change vegetation productivity in the SAE and lead to a patchier environment. b) Similar results were observed: when temperature and evaporation rate were increased; when the magnitude of rainfall events increased but their frequency decreased; and during a long mid-season dry spell. c) In both ecosystems, changes in the temporal distribution of rainfall, especially at the beginning of the season, caused the largest reduction in productivity, accompanied by increased patchiness. d) Long-term data gathered during the last three decades indicated that both environments exhibited high resilience of productivity under rainfall variability. These results imply that the response of dry ecosystems to climate change is not characterized by a dramatic decrease in productivity. Moreover, these ecosystems are more resilient than expected, and their herbaceous productivity might undergo drastic changes only under more severe scenarios than those currently predicted in the literature.     

Observational estimate of climate sensitivity from changes in the rate of ocean heat uptake and comparison to CMIP5 models

Climate sensitivity is estimated based on 0–2,000 m ocean heat content and surface temperature observations from the second half of the 20th century and first decade of the 21st century, using a simple energy balance model and the change in the rate of ocean heat uptake to determine the radiative restoration strength over this time period. The relationship between this 30–50 year radiative restoration strength and longer term effective sensitivity is investigated using an ensemble of 32 model configurations from the Coupled Model Intercomparison Project phase 5 (CMIP5), suggesting a strong correlation between the two. The mean radiative restoration strength over this period for the CMIP5 members examined is 1.16 Wm^?2K^?1, compared to 2.05 Wm^?2K^?1 from the observations. This suggests that temperature in these CMIP5 models may be too sensitive to perturbations in radiative forcing, although this depends on the actual magnitude of the anthropogenic aerosol forcing in the modern period. The potential change in the radiative restoration strength over longer timescales is also considered, resulting in a likely (67 %) range of 1.5–2.9 K for equilibrium climate sensitivity, and a 90 % confidence interval of 1.2–5.1 K.     

Recent land cover changes on the Tibetan Plateau: a review

This paper reviews the land cover changes on the Tibetan Plateau during the last 50 years partly caused by natural climate change and, more importantly, influenced by human activities. Recent warming trends on the plateau directly influence the permafrost and snow melting and will impact on the local ecosystem greatly. Human activities increased rapidly on the plateau during the last half century and have significant impacts on land use. Significant land cover changes on the Tibetan Plateau include permafrost and grassland degradation, urbanization, deforestation and desertification. These changes not only impact on local climate and environment, but also have important hydrological implications for the rivers which originate from the plateau. The most noticeable disasters include the flooding at the upper reaches of Yangtze River and droughts along the middle and lower reaches of Yellow River. Future possible land cover changes under future global climate warming are important but hard to assess due to the deficits of global climate model in this topographically complex area. Integrated investigation of climate and ecosystems, including human-beings, are highly recommended for future studies.     

Impacts of climate change on August stream discharge in the Central-Rocky Mountains

In the snowmelt dominated hydrology of arid western US landscapes, late summer low streamflow is the most vulnerable period for aquatic ecosystem habitats and trout populations. This study analyzes mean August discharge at 153 streams throughout the Central Rocky Mountains of North America (CRMs) for changes in discharge from 1950–2008. The purpose of this study was to determine if: (1) Mean August stream discharge values have decreased over the last half-century; (2) Low discharge values are occurring more frequently; (3) Climatic variables are influencing August discharge trends. Here we use a strict selection process to characterize gauging stations based on amount of anthropogenic impact in order to identify heavily impacted rivers and understand the relationship between climatic variables and discharge trends. Using historic United States Geologic Survey discharge data, we analyzed data for trends of 40–59 years. Combining of these records along with aerial photos and water rights records we selected gauging stations based on the length and continuity of discharge records and categorized each based on the amount of diversion. Variables that could potentially influence discharge such as change in vegetation and Pacific Decadal Oscillation (PDO) were examined, but we found that that both did not significantly influence August discharge patterns. Our analyses indicate that non-regulated watersheds are experiencing substantial declines in stream discharge and we have found that 89% of all non-regulated stations exhibit a declining slope. Additionally our results here indicate a significant (α?≤?0.10) decline in discharge from 1951–2008 for the CRMs. Correlations results at our pristine sites show a negative relationship between air temperatures and discharge and these results coupled with increasing air temperature trends pose serious concern for aquatic ecosystems in CRMs.     

Improved estimation of average warming trend of China from 1951–2010 based on satellite observed land-use data

This paper provides new evidence of regional warming trends from local Chinese observations covering the period 1951–2010. We used satellite-derived land data and weighted urban and rural temperature records (a weighted method) and estimate the regional warming trend, which involves natural climate change and human impact. The annual warming rate over the whole of China is 0.21?±?0.02 °C/decade. The seasonal warming is 0.30?±?0.05 °C/decade (Winter), 0.24 °C?±?0.03 °C/decade (Spring); 0.16?±?0.02 °C/decade (Summer) and 0.21?±?0.03 °C/decade (Autumn). The mean warming trend is lower than previous estimates (e.g. NMIC, CRU-China) using un-weighted methods (arithmetic average of all records). The warming difference between the weighted and un-weighted accounts for 27 % (12 %) of the NMIC (CRU-China) un-weighted estimate on the total warming. This indicates that previous estimations overestimated a regional warming trend. The differences can be partly attributed to the weighting of the urban effect which is taken into consideration in this study, resulting in a much slower temperature increase. Spatially, the northern part of China shows a larger difference than the south especially for winter and spring. We argue that it is of importance to take into consideration the influence of urban land-use change to improve the physical understanding of surface warming in China over past decades.     

Climate change affecting temperature and aridity zones: a case study in Eastern Inner Mongolia, China from 1960–2008

Recent climate change is substantially affecting the spatial pattern of geographical zones, and the temporal and spatial inconsistency of climatic warming and drying patterns contributes to the complexity of the shifting of temperature and aridity zones. Eastern Inner Mongolia, China, located in the interface region of different biomes and ecogeographic zones, has experienced dramatic drying and warming over the past several decades. In this study, the annual accumulated temperature above 10 °C (AAT10) and the aridity index, two key indicators in geographical regionalization, are used to assess warming and drying processes and track the movements of temperature and aridity zones from 1960 to 2008. The results show a significant warming at the regional level from 1960 to 2008 with an AAT10 increase rate of 7.89 °C·d/year (p?<?0.001) in Eastern Inner Mongolia, while the drying trend was not significant during this period. Spatial heterogeneity of warming and drying distributions was also evident. Analysis of warming and drying via piecewise regression revealed two separate, specific trends between the first 31 years (1960–1990) and the subsequent 18 years (1991–2008). Generally, mild warming and very slight wetting occurred prior to 1990, while after 1991 both warming and drying were significant and enhanced. Continuous warming drove a northward shift of temperature zones from the 1960s to 2000s, while aridity zones displayed enhanced temporal and spatial variability. Climate change effects on temperature and aridity zones imply that the patterns of cropping systems, macro-ecosystems, and human land use modes are potentially undergoing migration and modification due to climate change.