Shifts in the timing of spring phenology are a central feature of global change research. Long-term observations of plant phenology have been used to track vegetation responses to climate variability but are often limited to particular species and locations and may not represent synoptic patterns. Satellite remote sensing is instead used for continental to global monitoring. Although numerous methods exist to extract phenological timing, in particular start-of-spring (SOS), from time series of reflectance data, a comprehensive intercomparison and interpretation of SOS methods has not been conducted. Here, we assess 10 SOS methods for North America between 1982 and 2006. The techniques include consistent inputs from the 8km Global Inventory Modeling and Mapping Studies Advanced Very High Resolution Radiometer NDVIg dataset, independent data for snow cover, soil thaw, lake ice dynamics, spring streamflow timing, over 16000 individual measurements of ground-based phenology, and two temperature-driven models of spring phenology. Compared with an ensemble of the 10 SOS methods, we found that individual methods differed in average day-of-year estimates by ! 60 days and in standard deviation by ! 20 days. The ability of the satellite methods to retrieve SOS estimates was highest in northern latitudes and lowest in arid, tropical, and Mediterranean ecoregions. The ordinal rank of SOS methods varied geographically, as did the relationships between SOS estimates and the cryospheric/hydrologic metrics. Compared with ground observations, SOS estimates were more related to the first leaf and first flowers expanding phenological stages. We found no evidence for time trends in spring arrival from ground- or model-based data; using an ensemble estimate from two methods that were more closely related to ground observations than other methods, SOS

Intercomparison, interpretation, and assessment of spring phenology in North America estimated from remote sensing for 1982-2006 M I C H A E L A. W H I T E*, K I R S T E N M. DE BEURS w , K A M E L D I D A Nz, D AV I D W. I N O U Y E § ,

Nitrous oxide (N2O), like carbon dioxide, is a long-lived greenhouse gas that accumulates in the atmosphere. Over the past 150 years, increasing atmospheric N2O concentrations have contributed to stratospheric ozone depletion1 and climate change2, with the current rate of increase estimated at 2 per cent per decade. Existing national inventories do not provide a full picture of N2O emissions, owing to their omission of natural sources and limitations in methodology for attributing anthropogenic sources. Here we present a global N2O inventory that incorporates both natural and anthropogenic sources and accounts for the interaction between nitrogen additions and the biochemical processes that control N2O emissions. We use bottom-up (inventory, statistical extrapolation of flux measurements, process-based land and ocean modelling) and top-down (atmospheric inversion) approaches to provide a comprehensive quantification of global N2O sources and sinks resulting from 21 natural and human sectors between 1980 and 2016. Global N2O emissions were 17.0 (minimum-maximum estimates: 12.2-23.5) teragrams of nitrogen per year (bottom-up) and 16.9 (15.9-17.7) teragrams of nitrogen per year (top-down) between 2007 and 2016. Global human-induced emissions, which are dominated by nitrogen additions to croplands, increased by 30% over the past four decades to 7.3 (4.2-11.4) teragrams of nitrogen per year. This increase was mainly responsible for the growth in the atmospheric burden. Our findings point to growing N2O emissions in emerging economies-particularly Brazil, China and India. Analysis of process-based model estimates reveals an emerging N2O-climate feedback resulting from interactions between nitrogen additions and climate change. The recent growth in N2O emissions exceeds some of the highest projected emission scenarios3,4, underscoring the urgency to mitigate N2O emissions.

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A comprehensive quantification of global nitrous oxide sources and sinks

. The Emissions Database for Global Atmospheric Research (EDGAR) compiles
anthropogenic emissions data for greenhouse gases (GHGs), and for multiple air
pollutants, based on international statistics and emission factors. EDGAR data
provide quantitative support for atmospheric modelling and for mitigation
scenario and impact assessment analyses as well as for policy evaluation. The
new version (v4.3.2) of the EDGAR emission inventory provides global
estimates, broken down to IPCC-relevant source-sector levels, from 1970 (the
year of the European Union's first Air Quality Directive) to 2012 (the end
year of the first commitment period of the Kyoto Protocol, KP). Strengths of
EDGAR v4.3.2 include global geo-coverage (226 countries), continuity in time,
and comprehensiveness in activities. Emissions of multiple chemical
compounds, GHGs as well as air pollutants, from relevant sources (fossil fuel
activities but also, for example, fermentation processes in agricultural
activities) are compiled following a bottom-up (BU), transparent and IPCC-compliant methodology. This paper describes
EDGAR v4.3.2 developments with respect to three major long-lived GHGs ( CO2 ,
 CH4 , and N2O ) derived from a wide range of human activities
apart from the land-use, land-use change and forestry (LULUCF) sector and
apart from savannah burning; a companion paper quantifies and discusses
emissions of air pollutants. Detailed information is included for each of the
IPCC-relevant source sectors, leading to global totals for 2010 (in the
middle of the first KP commitment period) (with a 95 % confidence
interval in parentheses): 33.6(±5.9)  Pg CO 2  yr −1 , 0.34(±0.16)  Pg CH 4  yr −1 , and 7.2(±3.7)  Tg N 2 O yr −1 . We provide uncertainty factors in emissions
data for the different GHGs and for three different groups of countries: OECD
countries of 1990, countries with economies in transition in 1990, and the
remaining countries in development (the UNFCCC non-Annex I parties). We
document trends for the major emitting countries together with the European
Union in more detail, demonstrating that effects of fuel markets and
financial instability have had greater impacts on GHG trends than effects of
income or population. These data ( https://doi.org/10.5281/zenodo.2658138 ,
Janssens-Maenhout et al., 2019) are visualised with annual and monthly global emissions grid maps
of 0.1 ∘ × 0.1 ∘ for each source sector.

/pdf/edgar-v4-3-2-global-atlas-of-the-three-major-greenhouse-gas-2gk63ff6n7.pdf

EDGAR v4.3.2 Global Atlas of the three major greenhouse gas emissions for the period 1970–2012

https://works.bepress.com/chaoqun_lu/21/download/

Model estimates of net primary productivity, evapotranspiration, and water use efficiency in the terrestrial ecosystems of the southern United States during 1895–2007

The change in spring phenology is recognized to exert a major influence on carbon balance dynamics in temperate ecosystems. Over the past several decades, several studies focused on shifts in spring phenology; however, large uncertainties still exist, and one understudied source could be the method implemented in retrieving satellite-derived spring phenology. To account for this potential uncertainty, we conducted a multimethod investigation to quantify changes in vegetation green-up date from 1982 to 2010 over temperate China, and to characterize climatic controls on spring phenology. Over temperate China, the five methods estimated that the vegetation green-up onset date advanced, on average, at a rate of 1.3 ± 0.6 days per decade (ranging from 0.4 to 1.9 days per decade) over the last 29 years. Moreover, the sign of the trends in vegetation green-up date derived from the five methods were broadly consistent spatially and for different vegetation types, but with large differences in the magnitude of the trend. The large intermethod variance was notably observed in arid and semiarid vegetation types. Our results also showed that change in vegetation green-up date is more closely correlated with temperature than with precipitation. However, the temperature sensitivity of spring vegetation green-up date became higher as precipitation increased, implying that precipitation is an important regulator of the response of vegetation spring phenology to change in temperature. This intricate linkage between spring phenology and precipitation must be taken into account in current phenological models which are mostly driven by temperature.

/pdf/changes-in-satellite-derived-spring-vegetation-green-up-date-5dq5je5wqp.pdf

Changes in satellite‐derived spring vegetation green‐up date and its linkage to climate in China from 1982 to 2010: a multimethod analysis

China has experienced a rapid land-use/cover change (LUCC) during the 20th Century, and this process is expected to continue in the future. How LUCC has affected water resources across China, however, remains uncertain due to the complexity of LUCC-water interactions. In this study, we used an integrated Dynamic Land Ecosystem Model (DLEM) in conjunction with spatial data of LUCC to estimate the LUCC effects on the magnitude, spatial and temporal variations of evapotranspiration (ET), runoff, and water yield across China. Through comparisons of DLEM results with other model simulations, field observations, and river discharge data, we found that DLEM model can adequately catch the spatial and seasonal patterns of hydrological processes. Our simulation results demonstrate that LUCC led to substantial changes in ET, runoff, and water yield in most of the China's river basins during the 20th Century. The temporal and spatial patterns varied significantly across China. The largest change occurred during the second half century when almost all of the river basins had a decreasing trend in ET and an increasing trend in water yield and runoff, in contrast to the inclinations of ET and declinations of water yield in major river basins, such as Pearl river basin, Yangtze river basin, and Yellow river basin during the first half century. The increased water yield and runoff indicated alleviated water deficiency in China in the late 20th Century, but the increased peak flow might make the runoff difficult to be held by reservoirs. The continuously increasing ET and decreasing water yield in Continental river basin, Southwest river basin, and Songhua and Liaohe river basin implied regional water deficiency. Our study in China indicates that deforestation averagely increased ET by 138 mm/year but decreased water yield by the same amount and that reforestation averagely decreased ET by 422 mm/year since most of deforested land was converted to paddy land or irrigated cropland. In China, cropland-related land transformation is the dominant anthropogenic force affecting water resources during the 20th Century. On national average, cropland expansion was estimated to increase ET by 182 mm/year while cropland abandonment decreased ET by 379 mm/year. Our simulation results indicate that urban sprawl generally decreased ET and increased water yield. Cropland managements (fertilization and irrigation) significantly increased ET by 98 mm/year. To better understand LUCC effects on China's water resources, it is needed to take into account the interactions of LUCC with other environmental changes such as climate and atmospheric composition. © 2008 American Water Resources Association.

Effects of land-use and land-cover change on evapotranspiration and water yield in China during 1900-2000

Nitrous oxide (N2O) is an important greenhouse gas and also an ozone-depleting substance that has both natural and anthropogenic sources. Large estimation uncertainty remains on the magnitude and spatiotemporal patterns of N2O fluxes and the key drivers of N2O production in the terrestrial biosphere. Some terrestrial biosphere models have been evolved to account for nitrogen processes and to show the capability to simulate N2O emissions from land ecosystems at the global scale, but large discrepancies exist among their estimates primarily because of inconsistent input datasets, simulation protocol, and model structure and parameterization schemes. Based on the consistent model input data and simulation protocol, the global N2O Model Intercomparison Project (NMIP) was initialized with 10 state-of-the-art terrestrial biosphere models that include nitrogen (N) cycling. Specific objectives of NMIP are to 1) unravel the major N cycling processes controlling N2O fluxes in each model and identify the unc...

/pdf/the-global-n2o-model-intercomparison-project-2egsvtsyft.pdf

The Global N2O Model Intercomparison Project

Aim We intend to characterize and understand the spatial and temporal patterns of vegetation phenology shifts in North America during the period 1982–2006.

PAPER Extension of the growing season due to delayed autumn over mid and high latitudes in North America during

United States. National Aeronautics and Space Administration (Land Cover and Land Use Change Program NNX08AL73G)

Guangsheng Chen

Papers

Effects of land-use and land-cover change on evapotranspiration and water yield in China during 1900-2000

The Global N2O Model Intercomparison Project

PAPER Extension of the growing season due to delayed autumn over mid and high latitudes in North America during

Spatial and temporal patterns of CO[subscript 2] and CH[subscript 4] fluxes in China's croplands in response to multifactor environmental changes