Significant Regional Trends Research Articles

Climate‐Driven Increases in Stream Metal Concentrations in Mineralized Watersheds Throughout the Colorado Rocky Mountains, USA

AbstractIncreasing stream metal concentrations apparently caused by climate warming have been reported for a small number of mountain watersheds containing hydrothermally altered bedrock with abundant sulfide minerals (mineralized watersheds). Such increases are concerning and could negatively impact downstream ecosystem health, water resources, and mine‐site remediation efforts. However, the pervasiveness and typical magnitude of these trends remain uncertain. We aggregated available streamwater chemistry data collected from late summer and fall over the past 40 years for 22 mineralized watersheds throughout the Colorado Rocky Mountains. Temporal trend analysis performed using the Regional Kendall Test indicates significant regional upward trends of ∼2% of the site median per year for sulfate, zinc, and copper concentrations in the 17 streams affected by acid rock drainage (ARD; median pH ≤ 5.5), equivalent to concentrations roughly doubling over the past 30 years. An examination of potential load trends utilizing streamflow data from eight “index gages” located near the sample sites provides strong support for regionally increasing sulfate and metal loads in ARD‐affected streams, particularly at higher elevations. Declining streamflows are likely contributing to regionally increasing concentrations, but increasing loads appear to be on average an equal or greater contributor. Comparison of selected site characteristics with site concentration trend magnitudes shows the highest correlation for mean annual air temperature and mean elevation (R2 of 0.42 and 0.35, respectively, with all others being ≤0.14). Future research on climate‐driven controlling mechanisms should therefore focus on processes such as melting of frozen ground directly linked to site mean temperature and elevation.

Estimating the viscoelastic properties of the human brain at 7 T MRI using intrinsic MRE and nonlinear inversion.

Intrinsic actuation magnetic resonance elastography (MRE) is a phase-contrast MRI technique that allows for in vivo quantification of mechanical properties of the brain by exploiting brain motion that arise naturally due to the cardiac pulse. The mechanical properties of the brain reflect its tissue microstructure, making it a potentially valuable parameter in studying brain disease. The main purpose of this study was to assess the feasibility of reconstructing the viscoelastic properties of the brain using high-quality 7 T MRI displacement measurements, obtained using displacement encoding with stimulated echoes (DENSE) and intrinsic actuation. The repeatability and sensitivity of the method for detecting normal regional variation in brain tissue properties was assessed as secondary goal. The displacement measurements used in this analysis were previously acquired for a separate study, where eight healthy subjects (27 ± 7 years) were imaged with repeated scans (spatial resolution approx. 2 mm isotropic, temporal resolution 75 ms, motion sensitivity 0.35 mm/2π for displacements in anterior-posterior and left-right directions, and 0.7 mm/2π for feet-head displacements). The viscoelastic properties of the brain were estimated using a subzone based non-linear inversion scheme. The results show comparable consistency to that of extrinsic MRE between the viscoelastic property maps obtained from repeated displacement measurements. The shear stiffness maps showed fairly consistent spatial patterns. The whole-brain repeatability coefficient (RC) for shear stiffness was (mean ± standard deviation) 8 ± 8% relative to the mean whole-brain stiffness, and the damping ratio RC was 28 ± 17% relative to the whole-brain damping ratio. The shear stiffness maps showed similar statistically significant regional trends as demonstrated in a publicly available atlas of viscoelastic properties obtained with extrinsic actuation MRE at 50 Hz. The damping ratio maps showed less consistency, likely due to data-model mismatch of describing the brain as a viscoelastic material under low frequencies. While artifacts induced by fluid flow within the brain remain a limitation of the technique in its current state, intrinsic actuation based MRE allow for consistent and repeatable estimation of the mechanical properties of the brain. The method provides enough sensitivity to investigate regional variation in such properties in the normal brain, which is likely sufficient to also investigate pathological changes.

Regional climate trend analyses for Aqua MODIS land surface temperatures

ABSTRACT Land surface temperature (LST) is the skin surface temperature of the Earth’s land surface and is an essential climate variable (ECV) that critically characterizes the Earth’s climate and surface energy processes. This is the first regional trend analysis for LST with uncertainties, using a stable LST climate data record suitable for climate trend analyses: the Aqua Moderate Imaging Spectroradiometer (MODIS) dataset (MYDCCI) produced in the European Space Agency (ESA) LST Climate Change Initiative (LST_cci) Project. The quality of the trends is verified here for Western Europe, for which consistent trends per decade of 0.5 K and 0.57 K across daytime and night-time data, respectively. Eight regions representative of a range of biomes and, including the Amazon, Western U.S.A., Greenland, the Sahel, Siberia, China, India, and Australia, have been analysed. Our most significant findings show substantial LST increases for Siberia and the Amazon, as well as evidence of recent increasing trends for the Western U.S.A. Siberia showed the most substantial daytime and night-time changes per decade of +0.87 K and +0.93 K, respectively. Furthermore, the Amazon and Western U.S.A. showed significant daytime LST trend increases of +0.82 K and +0.51 K, respectively. Western Europe and Western U.S.A. show the largest night-time change of +0.57 K and +0.54 K, respectively. India presents an atypical time series with a decreasing daytime and increasing night-time trend per decade of −0.62 K and +0.44 K, respectively, consistent with reported air temperatures. Overall the results show significant positive regional LST trends, against a background of both strong seasonal cycles and intermittent disruptive events, which demonstrate the importance of continued LST observations. The results also incentivize remote sensing science to derive ever more rigorous LST datasets and to continue to investigate emissivity and error correlations to allow improved trend analyses for smaller regions and individual locations.

Spatiotemporal Trends in Near-Natural New Zealand River Flow

Abstract Anthropogenic climate change is affecting rivers worldwide, threatening water availability and altering the risk of natural hazards. Understanding the pattern of regional streamflow trends can help to inform region-specific policies to mitigate and adapt to any negative impacts on society and the environment. We present a benchmark dataset of long, near-natural streamflow records across Aotearoa New Zealand (NZ) and the first nationwide analysis of observed spatiotemporal streamflow trends. Individual records rarely have significant trends, but when aggregated within homogenous hydrologic regions (determined through cluster analyses), significant regional trends emerge. A multitemporal approach that uses all available data for each region and considers trend significance over time reveals the influence of decadal variability in some seasons and regions, and consistent trends in others. Over the last 50+ years, winter streamflow has significantly increased in the west South Island and has significantly decreased in the north North Island; summer streamflow has significantly decreased for most of the North Island; autumn streamflow has generally dried nationwide; and spring streamflow has increased along the west coast and decreased along the east coast. Correlations between streamflow and dynamic and thermodynamic climate indices reveal the dominant drivers of hydrologic behavior across NZ. Consistencies between the observed near-natural streamflow trends and observed changes in circulation and thermodynamic processes suggest possible climate change impacts on NZ hydrology.

Emergency Department Presentations of Acute Primary Angle Closure in the United States from 2008 to 2017.

PurposeAcute primary angle closure (APAC) is an ophthalmologic emergency. Nationwide data on the epidemiology and clinical characteristics of APAC are lacking despite the associated visual morbidity.Patients and MethodsA retrospective cross-sectional study using the Nationwide Emergency Department Sample (NEDS). The NEDS was queried by ICD-9/10 code for cases of APAC presenting to the United States emergency departments over a ten-year period from 2008 to 2017. All identified cases were included to produce nationally representative estimates. Linear regression and seasonality tests were used to identify trends. Reported outcomes include the incidence, demographics, seasonality, and economic impact of APAC regionally and nationwide.ResultsA total of 23,203 APAC-related ED visits were identified. The mean (SD) and median ages were 58.8 (16.2) and 60 years, respectively. Females (59.4%, p < 0.01), those in the lowest income quartile (6983, 30.1%, p < 0.01), and those in the seventh decade of life (5599, 24.1%) presented more frequently with APAC. The incidence of ED presentations within each age group rose with age and increased significantly over the study period (p < 0.01). The Northeast region had the highest average incidence (0.93 per 100,000 population). Significant seasonal variation was seen regionally and nationally (p < 0.01), with the highest average incidence in December and lowest in April. Median inflation adjusted charge per ED visit was $2496.10, and the total inflation adjusted charges equaled $101.5 million.ConclusionThe incidence of APAC-related ED visits continues to rise in the United States. High-risk groups include women, individuals of low socioeconomic status, and those between ages 50 and 70. Significant seasonal and regional trends were observed in ED presentations of APAC.

Industry Payments to Adult Reconstruction-Trained Orthopedic Surgeons: An Analysis of the Open Payments Database From 2014 to 2019.

In recent time, there has been an increased push toward transparency in industry funding toward physicians. The Physician Payments Sunshine Act called for the creation of the Open Payments Database managed by the Centers for Medicare & Medicaid Services. To our knowledge, there have been no studies evaluating the trends in payments among adult reconstruction fellowship-trained orthopedic surgeons. The purpose of this study is to investigate trends in all payments to adult reconstruction-trained orthopedic surgeons from 2014 to 2019. Secondary outcomes included evaluating trends in yearly subpayment categories, regional variations, as well as characterizing the top 5 industry companies. A review of the Centers for Medicare & Medicaid Services Open Payments Database was performed to identify all payments to adult reconstruction-trained orthopedic surgeons. A total of 94,265 payments were made to 4911 surgeons accounting for a total of $258,865,231.20 during the study period. Our primary outcome was to assess the trend in median payment per year to individual surgeons. Secondary outcomes included evaluating payment trends with respect to subtype, location as defined by United States Census regions, as well as specifics concerning the top 5 companies. Over the study period, there was a nonsignificant increasing trend in median payment per surgeon (r= 0.49, P= .096). However, there was also a significantly increasing trend in the number of payments per year (r= 0.83, P= .014), as well as the number of surgeons receiving payments (r= 0.88, P= .019). With respect to subcategory payments, there were significantly increasing trends in the median payment per surgeon for education (1054%, r= 0.942, P < .001) and entertainment/food and beverage expenses (20.2%, r= 0.49, P= .020), as well as a significantly decreasing trend for median honoraria payments per surgeon (20.2%, r=-0.04, P= .005). No significant regional trends were identified. Of the top 5 companies, one demonstrated a significantly decreasing trend in median payment per surgeon (21.6%, r=-0.109, P < .001), whereas the others remained unchanged. In this study, we found a nonsignificant increasing trend in payments to adult reconstruction-trained surgeons as well as an increasing number of surgeons receiving payments. There were increasing trends in median payment per surgeon for education and entertainment expenses, but a decreasing trend for honoraria payments. No significant regional trends were identified. The majority of the top 5 companies had nonsignificant trends in their payments. Further studies are needed to characterize the disclosure of payments and the impact of industry payments on clinical outcomes. IV.

Molecular surveillance of antimalarial partner drug resistance in sub-Saharan Africa: a spatial-temporal evidence mapping study

Molecular markers for antimalarial drug resistance can be used to rapidly monitor the emergence and spatial distribution of resistance to artemisinin-based combination therapies (ACTs). Little has been done to analyse molecular surveillance efforts or to assess surveillance coverage. This study aimed to develop an evidence map to characterise the spatial-temporal distribution and sampling methodologies of drug resistance surveillance in sub-Saharan Africa, specifically focusing on markers associated with ACT partner drugs. By use of a systematic search, we identified studies that reported data on the following mutations associated with ACT partner drug resistance: pfmdr1 Asn86Tyr, Tyr184Phe, Asp1246Tyr, and copy number variation and pfcrt Lys76Thr, with sample collection occurring in sub-Saharan Africa between Jan 1, 2004, and Dec 31, 2018, corresponding to the uptake of ACTs. For each identified study, we extracted information on its sampling and laboratory methods, author and publication affiliations, years of sampling and of publication, geographic coordinates of the study sites, and prevalence of the partner drug resistance-associated markers. We used linear models to test whether urbanicity, population density, and endemicity were predictors of drug resistance survey sites and linear regressions to identify associations between the number of resistance surveys within a given country and the at-risk malaria population in 2010, the per-capita GDP in 2010, and the mean amount of funding directed to malaria and to determine trends in marker prevalence over time. For country case studies with three or more datapoints, we assessed global spatial autocorrelation using Moran's I. Our search yielded 254 studies encompassing 492 year-specific and location-specific surveys from 35 malaria-endemic countries, the most complete set of molecular partner drug surveillance data to date. We observed a median time lag of 3·1 years (95% CI 1·0-7·7) from final sample acquisition to publication. 22 (49%) of the 44 countries in the study region conducted, on average, one or fewer studies every 3 years. The locations of surveillance sites were positively associated with urbanicity (p<0·0001), and the abundance of country-level data was associated with reported donor funding in 2004-18 (p=0·0011) and local government funding in 2004-09 (p=0·014). Nearly all molecular markers displayed significant regional trends over time and global spatial autocorrelation in space. For selected countries with more widespread coverage of surveillance data, some markers also displayed spatial heterogeneity. In most sub-Saharan countries, molecular data on antimalarial resistance might not be representative of the temporal and geographic heterogeneity of partner drug resistance, and likely do not represent the true spatially dependent distribution of partner drug resistance. Our results highlight several inefficiencies that can be improved upon to develop more accurate data landscapes, including the expansion of sentinel surveillance systems, syndemic usage of research samples, and increased participation in reporting published and unpublished data to centralised platforms.

Observed Changes in Temperature and Precipitation Extremes Over the Yarlung Tsangpo River Basin during 1970–2017

Twenty-five climate indices based on daily maximum and minimum temperature and precipitation at 15 meteorological stations were examined to investigate changes in temperature and precipitation extremes over the Yarlung Tsangpo River Basin (1970–2017). The trend-free prewhitening (TFPW) Mann–Kendall test and Pettitt’s test were used to identify trends and abrupt changes in the time series, respectively. The results showed widespread significant changes in extreme temperature indices associated with warming, most of which experienced abrupt changes in the 1990s. Increases in daily minimum and maximum temperature were detected, and the magnitude of daily minimum temperature change was greater than that of the daily maximum temperature, revealing an obvious decrease in the diurnal temperature range. Warm days and nights became more frequent, whereas fewer cold days and nights occurred. The frequency of frost and icing days decreased, while summer days and growing season length increased. Moreover, cold spell length shortened, whereas warm spell length increased. Additionally, changes in the precipitation extreme indices exhibited much less spatial coherence than the temperature indices. Spatially, mixed patterns of stations with positive and negative trends were found, and few trends in the precipitation extreme indices at individual stations were statistically significant. Generally, precipitation extreme indices showed a tendency toward wetter conditions, and the contribution of extreme precipitation to total precipitation has increased. However, no significant regional trends and abrupt changes were detected in total precipitation or in the frequency and duration of precipitation extremes.

Can an ensemble climate simulation be used to separate climate change signals from internal unforced variability?

The contribution of internal unforced variability to climate change is explored using a 100-member ensemble climate simulation for the period 1850–2005. The ensemble simulation is based on the Max Planck Institute for Meteorology climate model, ECHAM6, where all members have been exposed to the identically same radiative forcing. The range of global mean surface temperature warming over the 1850–2005 period, based on all members, is 0.65–1.10 °C. The distribution of the global mean surface temperature about the ensemble mean has a standard deviation (StD) of ~ 0.14 °C which slowly decreases in time. Regionally, the largest decrease in the ensemble StD occurs in the Northern Hemisphere winter. Comparing the temporal StD with that from the observed HadCRUT4 surface temperature data indicates that the majority of the ensemble members have a larger temporal StD than the observations suggesting that the model simulations might overestimate the variance. There are clear random 20-year linear trends in global mean surface temperature anomalies as well as significant regional 50-year linear trends. Even with an ensemble mean warming trend, typical of the early twenty-first century, a global hiatus in temperature of 20 years duration is possible to occur by chance. The results support the view that observed decadal and multi-decadal anomalies in the twentieth century were significantly influenced by internal processes of the climate system. This is particularly the case for the observed global warming trend of 1910–1940 and the global cooling trend of 1940–1970. Global mean precipitation hardly increases with time in the ensemble simulations, but in agreement with theory regional changes occur, with increasing precipitation in polar regions and in some tropical areas. In the subtropics there are reductions in precipitation. Long-lasting regional anomalies of significant amplitudes occur by chance in the ensemble integration.

Trends in extreme temperature and precipitation indices for the Caribbean small islands: Trinidad and Tobago

Trends in extreme temperature and rainfall were analyzed for two Caribbean islands in close proximity: Tobago (Crown Point) and Trinidad (Piarco) for the most recent period 1985–2015 using daily data. Most annual extreme temperature indices at Crown Point show no significant warming. However, warming at Crown Point manifests during the wet season and strongly in September. In contrast, most extreme temperature indices at Piarco show significant warming trends on annual and seasonal scales as well as for most months. Extreme precipitation indices show few trends. For Crown Point, trends indicate an increase in annual precipitation totals and extremely wet days were observed, whereas no significant trends in annual indices were found for Piarco. The greatest 5-day rainfall amounts were found to increase during the dry season at both sites. When compared to previous regional studies, this specific territory approach highlights that most indices with no significant regional trends also do not show trends at the local scale. Furthermore, differences in trends between these two nearby sites, 80 km apart, indicate that there is a spatial variation in warming trends.

Regional Acidification Trends in Florida Shellfish Estuaries: a 20+ Year Look at pH, Oxygen, Temperature, and Salinity

Increasing global CO2 and local land use changes coupled with increased nutrient pollution are threatening estuaries worldwide. Local changes of estuarine chemistry have been documented, but regional associations and trends comparing multiple estuaries latitudinally have not been evaluated. Rapid climate change has impacted the annual and decadal chemical trends in estuaries, with local ecosystem processes enhancing or mitigating the responses. Here, we compare pH, dissolved oxygen, temperature, and salinity data from 10 Florida shellfish estuaries and hundreds of shellfish bed stations. Over 80,000 measurements, spanning from 1980 to 2008, taken on Atlantic Ocean and West Florida coast showed significant regional trends of consistent pH decreases in 8 out of the 10 estuaries, with an average rate of decrease on the Gulf of Mexico side estuaries of Florida of 7.3 × 10−4 pH units year−1, and average decrease on the Atlantic Coast estuaries of 5.0 × 10−4 pH units year−1. The rates are approximately 2–3.4 times slower than observed in pH decreases associated with ocean acidification in the Atlantic and Pacific. Other significant trends observed include decreasing dissolved oxygen in 9 out of the 10 estuaries, increasing salinity in 6 out of the 10, and temperature increases in 3 out of the 10 estuaries. The data provide a synoptic regional view of Florida estuary trends which reflect the complexity of changing climate and coastal ocean acidification superimposed on local conditions. These data provide context for understanding, and interpreting the past and predicting future of regional water quality health of shellfish and other organisms of commercial and ecological significance along Florida’s coasts.

Satellite microwave assessment of Northern Hemisphere lake ice phenology from 2002 to 2015

Abstract. A new automated method enabling consistent satellite assessment of seasonal lake ice phenology at 5 km resolution was developed for all lake pixels (water coverage ≥ 90 %) in the Northern Hemisphere using 36.5 GHz H-polarized brightness temperature (Tb) observations from the Advanced Microwave Scanning Radiometer for EOS and Advanced Microwave Scanning Radiometer 2 (AMSR-E/2) sensors. The lake phenology metrics include seasonal timing and duration of annual ice cover. A moving t test (MTT) algorithm allows for automated lake ice retrievals with daily temporal fidelity and 5 km resolution gridding. The resulting ice phenology record shows strong agreement with available ground-based observations from the Global Lake and River Ice Phenology Database (95.4 % temporal agreement) and favorable correlations (R) with alternative ice phenology records from the Interactive Multisensor Snow and Ice Mapping System (R = 0.84 for water clear of ice (WCI) dates; R = 0.41 for complete freeze over (CFO) dates) and Canadian Ice Service (R = 0.86 for WCI dates; R = 0.69 for CFO dates). Analysis of the resulting 12-year (2002–2015) AMSR-E/2 ice record indicates increasingly shorter ice cover duration for 43 out of 71 (60.6 %) Northern Hemisphere lakes examined, with significant (p &lt; 0.05) regional trends toward earlier ice melting for only five lakes. Higher-latitude lakes reveal more widespread and larger trends toward shorter ice cover duration than lower-latitude lakes, consistent with enhanced polar warming. This study documents a new satellite-based approach for rapid assessment and regional monitoring of seasonal ice cover changes over large lakes, with resulting accuracy suitable for global change studies.

Temperature and precipitation changes in Extensive Hexi Region, China, 1960-2011

Global climate change has been evident in many places worldwide. This study provides a better understanding of the variability and changes in frequency, intensity, and duration of temperature, precipitation, and climate extremes in the Extensive Hexi Region, based on meteorological data from 26 stations. The analysis of average, maximum, and minimum temperatures revealed that statistically significant warming occurred from 1960 to 2011. All temperature extremes displayed trends consistent with warming, with the exception of coldest-night temperature (TNn) and coldest-day temperature (TXn), which were particularly evident in high-altitude areas and at night. Amount of precipitation and number of rainy days slowly increased with no significant regional trends, mainly occurring in the Qilian Mountains and Hexi Corridor. The significance of changes in precipitation extremes during 1960-2011 was high, but the regional trends of maximum 5-day precipitation (RX5day), the average precipitation on wet days (SDⅡ), and consecutive wet days (CWD) were not significant. The variations in the studied parameters indicate an increase in both the extremity and strength of precipitation events, particularly in higher-altitude regions. Furthermore, the contribution from very wet precipitation (R95) and extremely wet precipitation (R99) to total precipitation also increased between 1960 and 2011. The assessment of these changes in temperature and precipitation may help in developing better management practices for water resources. Future studies in the region should focus on the impact of these changes on runoffs and glaciers.

Antarctic station‐based seasonal pressure reconstructions since 1905: 2. Variability and trends during the twentieth century

AbstractThe Antarctic seasonal station‐based pressure reconstructions evaluated in our companion paper are evaluated here to provide additional knowledge on Antarctic pressure variability during the twentieth century. In the period from 1905 to 1956, we find that the Hadley Centre gridded sea level pressure data set compared the best with our reconstructions, perhaps due to similar methods to estimate pressure without direct observations. The primary focus on the twentieth century Antarctic pressure variability was in summer and winter, as these were the seasons with the highest reconstruction skill. In summer, there is considerable interannual variability that was spatially uniform across all of Antarctica. Notable high pressure anomalies were found in the summers of 1911/1912 and 1925/1926; both summers correspond to negative phases of the Southern Annular Mode as well as El Niño events in the tropical Pacific. In addition, negative summer pressure trends during the last ~40 years across all of Antarctica are unique in the context of 30 year trends throughout the entire twentieth century, suggesting a strong component of anthropogenic forcing on the recent summer trends. In contrast, mean winter pressure is less variable from year to year during the early twentieth century, and there is less similarity between the pressure variations along the Antarctic Peninsula compared to the rest of the continent. No significant pressure trends were found consistently across all Antarctica (although some significant regional trends can be identified), and low‐frequency, multidecadal‐scale variability appears to dominate the historical pressure variations in this season.

Ocean colour estimates of particulate organic carbon reservoirs in the global ocean – revisited

We have examined 16 years (1998–2013) of particulate organic carbon (POC) concentrations derived from remotely sensed ocean colour. POC concentrations vary spatially from more than 300 mg m−3 in the northern North Atlantic in summer to about 20 mg m−3 in the oligotrophic South Pacific (16-year global average = 67.7 mg m−3). The seasonal variability is weak at lower latitudes and stronger at higher latitudes. The annual mean surface POC concentrations show statistically significant regional trends (p < 0.05, 95% confidence level), and are decreasing in the North Atlantic and North Pacific and increasing in the South Pacific and Southern Oceans. The global trend is not significant. The 16-year global average water column POC biomass integrated over the euphotic depth, the mixed layer depth, or based on a combination of these two depths is estimated to be about 3.97, 3.92, and 5.03 g m−2, respectively. Water column integrated biomass shows different spatial and seasonal patterns than the surface POC concentrations, and is increasing in many ocean regions. Globally averaged POC biomass is also increasing. At the same time ocean colour data indicate a decrease in the global oceanic productivity (PP). This means that there is a negative trend in the ratio of PP to POC biomass almost everywhere in the ocean. Such a decrease could indicate that the biological pump in the ocean is weakening, but longer time series of the ocean colour data are needed to confirm this observation.

Carbon and nitrogen dynamics of native &amp;lt;i&amp;gt;Leymus chinensis&amp;lt;/i&amp;gt; grasslands along a 1000 km longitudinal precipitation gradient in northeastern China

Abstract. Understanding how ecosystem carbon (C) and nitrogen (N) cycles respond to the variability of precipitation can help us assess the effects of global climate change on terrestrial ecosystem structure and function. We investigated the contributions of aboveground biomass, litter, root, soil and microbial communities to ecosystem C and N processes at 14 sites along a 1000 km precipitation gradient in native Leymus chinensis grasslands of northeastern China. The results show that aboveground biomass C and N increased gradually, while no significant regional trends in litter and root biomass were found with increasing mean annual precipitation (MAP) along the gradient. Soil respiration increased first and then decreased from the dry to mesic sites, which could be ascribed to the relative changes in temperature, soil fungal : bacterial biomass and N availability. Surprisingly, N mineralization varied only slightly along the gradient, likely due to the decreases of soil organic matter quality (i.e., C : N). Stepwise regression models indicated regional soil C and N content positively correlated with MAP and clay content. Overall, C and N sequestration increased 3.2- and 1.8-fold with increasing MAP in terms of C and N storage in aboveground biomass, roots, litter and soil. It was concluded from the current study that regional precipitation variability strongly influences ecosystem C and N dynamics. The ecosystem C and N sequestration are primarily modulated by annual precipitation and soil texture, while the C and N turnover are largely controlled by microbial community composition, temperature and soil quality in L. chinensis grasslands across the large-scale precipitation gradient.

Model-simulated trend of surface carbon monoxide for the 2001–2010 decade

Abstract. We present decadal trend estimates of surface carbon monoxide (CO) simulated using the atmospheric chemistry general circulation model ECHAM5/MESSy (EMAC; ECHAM5 and MESSy stand for fifth-generation European Centre Hamburg general circulation model and Modular Earth Submodel System, respectively) based on the emission scenarios Representative Concentration Pathways (RCP) 8.5 for anthropogenic activity and Global Fire Emissions Database (GFED) v3.1 for biomass burning from 2001 through 2010. The spatial distribution of the modeled surface CO is evaluated with monthly data from the Measurements Of Pollution In The Troposphere (MOPITT) thermal infrared product. The global means of correlation coefficient and relative bias for the decade 2001–2010 are 0.95 and −4.29%, respectively. We also find a reasonable correlation (R = 0.78) between the trends of EMAC surface CO and full 10-year monthly records from ground-based observation (World Data Centre for Greenhouse Gases, WDCGG). Over western Europe, eastern USA, and northern Australia, the significant decreases in EMAC surface CO are estimated at −35.5 ± 5.8, −59.6 ± 9.1, and −13.7 ± 9.5 ppbv decade−1, respectively. In contrast, the surface CO increases by +8.9 ± 4.8 ppbv decade−1 over southern Asia. A high correlation (R = 0.92) between the changes in EMAC-simulated surface CO and total emission flux shows that the significant regional trends are attributed to the changes in primary and direct emissions from both anthropogenic activity and biomass burning.

Climate change and the food production system: impacts and adaptation in China

China has received a lot of attention from both the scientific and policy community in its ability to maintain selfreliance in food supply (Verburg et al. 2000; Yang and Li 2000; Yu et al. 2012). Advances in technology and changing agronomic practices have been responsible for significant increases in food production in China over past several decades (Xiong et al. 2012). Yet, since the 1980s, the unprecedented growth of both the economy and the population has led to a decrease in the area of cropland (Deng et al. 2006; He et al. 2013). The growing competition for land, water, and energy, and the overexploitation of fisheries, seriously impairs the production of food. Global environmental change, particularly climate change, makes the situation more challenging. Changes in climate may have implications for climate-sensitive systems such as agriculture, forestry, and other natural resources (Wu et al. 2011; Verburg et al. 2013). China is among the most affected countries by climate change (Ye et al. 2012). Continuous measurements from meteorological stations show that there is a strong warming of China over the past five decades and the temperature has increased by 1.2 C since 1960, which is much higher than the overall rate of global surface temperature change (Piao et al. 2010). Although there is no observed significant longterm trend in country-average precipitation since 1960, there are significant regional precipitation trends. The drier regions of northeastern China (including North China and Northeast China) are receiving less and less precipitation in summer and autumn (a 12 % decline since 1960). By contrast, the wetter region of southern China is experiencing more rainfall during both summer and winter. As for future projections, climate models tell us unambiguously that the warming trend will continue, and China’s average temperature is estimated to increase further by 1–5 C by 2100. This acceleration in temperature warming and its associated changes in precipitation have affected agriculture and food production in China. One of the greatest challenges for China in the twenty-first century will be to ensure that the food supply sustainably meets the needs of the population despite the necessary adaptations to climate change. Meeting this task will require technical and institutional innovations that increase food production and facilitate adaptation to changing climatic conditions. Climate change affects agriculture and the food production system in many ways (Godfray et al. 2011). Changes in climatic variables drive changes in overall food production through interacting effects on crop yields and crop areas. Although there has been much research to investigate the impacts of climate change on crop/food production (Barry and Cai 1996; Chen et al. 2013; Li et al. 2011, 2005; Piao et al. 2010; Wang et al. 2009; Zhang and Huang 2012), these studies are generally either focused on a single aspect of the interactions between climate change and food production or are performed in specific small regions. This causes some inconsistency in assessment results of climate change impacts, and well-recognized conclusions are therefore unavailable (Yang et al. 2013). W. Wu H. Tang Key Laboratory of Agri-Informatics, Ministry of Agriculture of China, Beijing 100081, China e-mail: wuwenbin@caas.cn

A Review of Enrico Moretti's The New Geography of Jobs

Why is prosperity distributed so unevenly across America's metropolitan areas? While population growth has gone disproportionately towards the Sunbelt, high-skill areas have experienced the strongest income growth since 1970. Gaps between more and less educated areas were modest forty years ago, but they have become quite large, and far larger than would be predicted solely by the general rise in the returns to skill. Unemployment rates during the recent recession were also strongly correlated with area level education. This essay reviews Enrico Moretti's The New Geography of Jobs, which both describes and explains these significant regional trends. (JEL I32, J24, R12, R23, R32)

Trends in observable passive solar design strategies for existing homes in the U.S.

Passive design strategies are among the most cost-effective methods to reduce energy consumption in buildings. However, the prevalence of these strategies in existing U.S. homes is not well understood. To help address this issue, this research evaluated a nationally-representative sample of 1000 existing homes distributed geographically across the U.S. Using satellite images, each building was evaluated for three passive design strategies: orientation, roof color, and level of shading. Several statistically significant regional trends were identified. For example, existing homes in the High Plains, Ohio Valley, Northwest, and Southern regions show a statistically significant trend towards orientation in the East–West direction, an effective passive design strategy. Less intuitively, in terms of what would seem to be optimal passive design, buildings in the High Plains and Ohio Valley generally have lighter roof colors than buildings in the warmer Southwest region. At the national level, no statistically significant trends were found towards the passive design strategies evaluated. These trends give us no reason to believe they were a major consideration in the design of existing homes. Policy measures and education may be required to take advantage of the opportunity for cost-effective energy savings through more widespread passive solar design.