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The paper reviews and evaluates a 30-year-long atmospheric CO2 data series measured at the Hegyhátsál tall-tower greenhouse gas monitoring site, a member of the World Meteorological Organization (WMO) Global Atmosphere Watch (GAW), US National Oceanic and Atmospheric Administration (NOAA), and pan-European Integrated Carbon Observation System (ICOS) networks. The paper also gives the technical description of the monitoring system and its changes over time and introduces the environment of the station. This low-elevation (248 m above mean sea level – m a.m.s.l.), mid-continental central European site shows a 3.90 ± 0.83 µmolmol-1 offset relative to the latitudinally representative marine boundary layer reference concentration, presumably due to European net anthropogenic emissions. The long-term trend (2.20 µmolmol-1yr-1) closely follows the global tendencies. In the concentration growth rate, the ENSO effect is clearly detectable with a 6–7-month lag time. The summer diurnal concentration amplitude is slightly decreasing due to the faster-than-average increase in the nighttime concentrations, which is related to the warming climate. The warming climate also caused a 0.96 ± 0.41 dyr-1 advance at the beginning of the summer CO2 -deficit season in the first half of the measurement period, which did not continue later. The summer CO2 -deficit season was extended by 9.0 ± 6.1 d during the measurement period. [ABSTRACT FROM AUTHOR]

The article focuses on the metrics used for comparing greenhouse gases with focus on the Integrated Temperature Change Potential (IGTP). It states that the IGTP and global warming potentials (GWP) are asymptotically equal is the time horizon reaches infinity. It says that the IGTP is equal to the Sustained Global Temperature change Potential (SGTP) under standard assumptions when calculating GWPs.

To develop an accurate measurement network of greenhouse gases, instruments in the field need to be stable and precise and thus require infrequent calibrations and a low consumption of consumables. For about ten years, cavity ring-down spectroscopy (CRDS) analyzers have been available that meet these stringent requirements for precision and stability. Here, we present the results of tests of CRDS instruments in the laboratory (47 instruments) and in the field (15 instruments). The precision and stability of the measurements are studied. We demonstrate that, thanks to rigorous testing, newer models generally perform better than older models, especially in terms of reproducibility between instruments. In the field, we see the importance of individual diagnostics during the installation phase, and we show the value of calibration and target gases that assess the quality of the data. Finally, we formulate recommendations for use of these analyzers in the field. [ABSTRACT FROM AUTHOR]

The knowledge of Green House Gases GHGs fluxes at the air--sea interface at high resolution is crucial to accurately quantify the role of the ocean in the absorption and emission of GHGs. In this paper we present a novel method to reconstruct maps of surface ocean partial pressure of CO2, pCO2, and air--sea CO2 fluxes at super resolution (4 km) using Sea Surface Temperature (SST) and Ocean Colour (OC) data at this resolution, and CarbonTracker CO2 fluxes data at low resolution (110 km). Inference of super-resolution of pCO2, and air--sea CO2 fluxes is performed using novel nonlinear signal processing methodologies that prove efficient in the context of oceanography. The theoretical background comes from the Microcanonical Multifractal Formalism which unlocks the geometrical determination of cascading properties of physical intensive variables. As a consequence, a multiresolution analysis performed on the signal of the so-called singularity exponents allows the correct and near optimal cross-scale inference of GHGs fluxes, as the inference suits the geometric realization of the cascade. We apply such a methodology to the study offshore of the Benguela area. The inferred representation of oceanic partial pressure of CO2 improves and enhances the description provided by CarbonTracker, capturing the small scale variability. We examine different combinations of Ocean Colour and Sea Surface Temperature products in order to increase the number of valid points and the quality of the inferred pCO2 field. The methodology is validated using in-situ measurements by means of statistical errors. We obtain that mean absolute and relative errors in the inferred values of pCO2 with respect to in-situ measurements are smaller than for CarbonTracker. [ABSTRACT FROM AUTHOR]

The realization of national climate change commitments, as agreed through international negotiations, requires local action. However, data is still insufficient to make accurate statements about the scale of urban emissions (UNHABITAT, 2011). The need of comparable emission inventories at city level, including smaller cities, is widely recognized to develop evidence-based policies accounting for the relation between emissions and institutional, socio-economic and demographic characteristics at city level. This paper presents a collection of harmonized greenhouse gases (GHG) emission inventories (the "CoM sample 2013") at municipal level directly computed by the cities and towns that participate in the EU Covenant of Mayors initiative. This is the mainstream European movement of local and regional authorities who voluntarily commit to reduce GHG emissions by 20% or more by 2020. The "CoM sample 2013" (http://edgar.jrc.ec.europa.eu/com/data/index.php? SECURE=123, doi:10.2904/EDGARcom2013) has been carefully checked to ensure its internal consistency and its congruity with respect to internationally accepted guide values for emission factors. Overall, it provides valuable data for the analysis of the heterogeneity of final energy consumption and greenhouse gas emissions of cities. [ABSTRACT FROM AUTHOR]

This paper summarizes currently available data on greenhouse gas (GHG) emissions from African natural and agricultural lands, outlines the knowledge gaps and suggests future directions and strategies for GHG emission studies. GHG emission data were collected from 73 studies conducted in 22 countries in sub-Saharan Africa (SSA). Soil GHG emissions from African natural terrestrial systems ranged from 3.3 to 57.0 Mg carbon dioxide (CO2) ha-1 yr-1, -4.8 to 3.5 kg methane (CH4) ha-1 yr-1 and -0.1 to 13.7 kg nitrous oxide (N2O) ha-1 yr-1. Soil physical and chemical properties, rewetting, vegetation type, forest management and land-use changes were all found to be important factors affecting soil GHG emissions. Greenhouse gas emissions from African aquatic systems ranged from 5.7 to 232.0 Mg CO2 ha-1 yr-1, -26.3 to 2741.9 kg CH4 ha-1 yr-1 and 0.2 to 3.5 kg N2O ha-1 yr-1 and were strongly affected by discharge. Soil GHG emissions from African croplands ranged from 1.7 to 141.2 Mg CO2 ha-1 yr-1, -1.3 to 66.7 kg CH4 ha-1 yr-1and 0.05 to 112.0 kg N2O ha-1 yr-1 and the N2O emission factor (EF) ranged from 0.01 to 4.1%. Incorporation of crop residues or manure with inorganic fertilizers resulted in significant changes in GHG emissions but these were different for CO2 and N2O. Soil GHG emissions in vegetable gardens ranged from 73.3 to 132.0 Mg CO2 ha-1 yr-1 and 53.4 to 177.6 kg N2O ha-1 yr-1 and N2O EFs ranged from 3 to 4%. Soil CO2 and N2O emissions from agroforestry were 38.6 Mg CO2 ha-1 yr-1 and 0.2 to 26.7 kg N2O ha-1 yr-1, respectively. Improving fallow with nitrogen (N)-fixing trees increased CO2 and N2O emissions compared to conventional croplands and type and quality of plant residue is likely to be an important control factor affecting N2O emissions. Throughout agricultural lands, N2O emissions slowly increased with N inputs below 150 kg N ha-1 yr-1 and increased exponentially with N application rates up to 300 kg N ha-1 yr-1. The lowest yield-scaled N2O emissions were reported with N application rates ranging between 100 and 150 kg N ha-1. Overall, total CO2 equivalent (eq) emissions from African natural and agricultural lands were 56.9 ± 12.7 Pg CO2 eq yr-1 and natural and agricultural lands contributed 76.3 and 23.7%, respectively. Additional GHG emission measurements throughout Africa agricultural and natural lands are urgently required to reduce uncertainty on annual GHG emissions from the different land uses and identify major control factors and mitigation options on emissions. There is also a need to develop a common strategy for addressing this data gap that may involve identifying priorities for data acquisition, utilizing appropriate technologies, and establishing networks and collaboration. [ABSTRACT FROM AUTHOR]

Total column water vapour product from the Global Ozone Monitoring Experiment-2 on board Metop-A and Metop-B satellites (GOME-2/Metop-A and GOME-2/Metop-B) produced by the Satellite Application Facility on Ozone and Atmospheric Chemistry Monitoring (O3M SAF) is compared with co-located radiosonde and Global Positioning System (GPS) observations. The comparisons are performed using recently reprocessed data by the GOME Data Processor (GDP) version 4.7. The comparisons are performed for the period of January 2007-July 2013 (GOME- 2A) and from December 2012 to July 2013 (GOME-2B). Radiosonde data are from the Integrated Global Radiosonde Archive (IGRA) maintained by National Climatic Data Center (NCDC) and screened for soundings with incomplete tropospheric column. Ground-based GPS observations from COSMIC/SuomiNet network are used as the second independent data source. Good general agreement between GOME-2 and the ground-based observations is found. The median relative difference of GOME-2 to radiosonde observations is -2.7% for GOME-2A and -0.3% for GOME-2B. Against GPS observations, the median relative differences are 4.9 and 3.2% for GOME-2A and B, respectively. For water vapour total columns below 10 kgm-2, large wet biases are observed, especially against GPS observations. Conversely, at values above 50 kgm-2, GOME-2 generally underestimates both ground-based observations. [ABSTRACT FROM AUTHOR]

The column-averaged dry-air mole fractions of carbon dioxide and methane (XCO2 and XCH4) have been retrieved from Greenhouse gases Observing SATellite (GOSAT) Short-Wavelength InfraRed (SWIR) observations. XCO2 and XCH4 retrieved using the version 01.xx retrieval algorithm showed large negative biases and standard deviations (-8.85 ppm and 4.75 ppm for XCO2 and -20.4 ppb and 18.9 ppb for XCH4, respectively) compared with data of the Total Carbon Column Observing Network (TCCON). Multiple reasons for these error characteristics (e.g. solar irradiance database, handling of aerosol scattering) are identified and corrected in a revised version of the retrieval algorithm (version 02.xx). The improved retrieval algorithm shows much smaller biases and standard deviations (-1.48 ppm and 2.10 ppm for XCO2 and -6.0 ppb and 12.5 ppb for XCH4, respectively) than the version 01.xx. Also, the number of postscreened measurements is increased especially at northern mid- and high-latitudinal area. [ABSTRACT FROM AUTHOR]

The article focuses on a study which aims at analyzing the role of multi-spectral measurements for a gas and aerosol retrieval parameters from the Thermal and Near infrared Sensor for carbon Observation-Fourier Transform Spectrometer (TANSO-FTS). It discusses the advantage of the Greenhouse gases Observing SATellite (GOSAT) mission in measuring spectral ranges and shows the accuracy of the model in the retrieval of gases and aerosol granulometry.

Rewetting of temperate continental cutover peatlands generally implies the creation of flooded areas, which are - dependent on water depth - colonized by helophytes such as Eriophorum angustifolium, Carex spp., Typha latifolia or Phragmites australis. Reeds of Typha and Phragmites are reported to be large sources of methane, but data on net CO2 uptake are contradictory for Typha and rare for Phragmites. This paper describes the effect of vegetation, water level and nutrient conditions on greenhouse gas (GHG) emissions for representative vegetation types along water level gradients at two rewetted cutover fens (mesotrophic and eutrophic) in Belarus. Greenhouse emissions were measured with manual chambers in weekly to few - weekly intervals over a two years period and interpolated by modelling. All sites had negligible nitrous oxide exchange rates. Most sites were carbon sinks and small GHG sources. Methane emissions were generally associated with net ecosystem CO2 uptake. Small sedges were minor methane emitters and net CO2 sinks, while Phragmites australis sites released large amounts of methane and sequestered very much CO2. Variability of both fluxes increased with site productivity. Floating mats composed of Carex tussocks and Typha latifolia were a source for both methane and CO2. We conclude that shallow, stable flooding is a better measure to arrive at low GHG emissions than deep flooding, and that the risk of high GHG emissions consequent on rewetting is larger for eutrophic than for mesotrophic peatlands. [ABSTRACT FROM AUTHOR]

This study presents results from the European Centre for Medium-Range Weather Forecasts (ECMWF) carbon dioxide (CO2) analysis system where the atmospheric CO2 is controlled through the assimilation of column-average dry-air mole fractions of CO2 (XCO2) from the Greenhouse gases Observing Satellite (GOSAT). The analysis is compared to a free run simulation and they are both evaluated against XCO2 data from the Total Carbon Column Observing Network (TCCON). We show that the assimilation of the GOSAT XCO2 product from the Bremen Optimal Estimation DOAS (BESD) algorithm during the year 2013 provides XCO2 fields with an improved station-to-station bias deviation of 0.7 parts per million (ppm) compared to the free run (1.4 ppm) and an improved estimated precision of ∼ 1 ppm compared to the used GOSAT data (3.4 ppm). We also show that the analysis has skill for synoptic situations in the vicinity of frontal systems where the GOSAT retrievals are sparse due to cloud contamination. We finally computed the 10 day forecast from each analysis at 00:00 UTC. Compared to its own analysis the CO2 forecast shows synoptic skill for the largest scale weather patterns even up to day 5 according to the anomaly correlation coefficient. [ABSTRACT FROM AUTHOR]

The article focuses on the measurement of the short-wavelength infrared (SWIR) spectrum through the Thermal And Near-infrared Sensor for carbon Observation-Fourier Transform Spectrometer5 (TANSO-FTS) onboard Greenhouse gases Observing SATellite (GOSAT). It states that radiometric accuracy of the measurement influences the accuracy of the greenhouse gas concentrations that have been retrieved. It explores the evaluation of the radiometric degradation of TANSO-FTS from on-orbit solar calibration.

The article presents a study that demonstrates the capabilities of Parallel Offline Radiative Transfer (PORT) model in diagnosing radiative forcing. It states that the model separates the radiation code from the Community Atmosphere Model (CAM4) in the Community Earth System Model (CESM1). It also notes that the model can effectively provide accurate computation of radiative forcing from doubling of carbon dioxide from the ozone concentration.

To assess the responses of nitrogen and greenhouse gas emissions to pan-European changes in land cover, land management and climate, an integrated dynamic model, INTEGRATOR, has been developed. This model includes both simple process-based descriptions and empirical relationships, and uses detailed GIS-based environmental and farming data in combination with various downscaling methods. This paper analyses the propagation of uncertainties in model inputs and model parameters to outputs of INTEGRATOR, using a Monte Carlo analysis. Uncertain model inputs and parameters were represented by probability distributions, while spatial correlation in these uncertainties was taken into account by assigning correlation coefficients at various spatial scales. The uncertainty propagation was analysed for the emissions of NH3, N2O and NOx and N leaching to groundwater and N surface runoff to surface water for the entire EU27 and for individual countries. Results show large uncertainties for N leaching and N runoff (relative errors of ~19% for Europe as a whole), and smaller uncertainties for emission of N2O, NH3 and NOx (relative errors of ~12%). Uncertainties for Europe as a whole were much smaller compared to uncertainties at Country level, because errors partly cancelled out due to spatial aggregation. [ABSTRACT FROM AUTHOR]

The article presents a study which measures ground-based high-resolution fourier transform spectrometers through carbon dioxide and methane aircraft measurements. The study also compares the aforementioned measurements to Greenhouse Gases Observing Satellite (GOSAT) data measurement. It also gives details of the measurement instruments onboard the aircraft and ground sites.

This paper evaluates the performance of a multirotor uncrewed aircraft and AirCore system (UAAS) for measuring vertical profiles of wind velocity (speed and direction) and the mole fractions of methane (CH 4) and carbon dioxide (CO 2) , and it presents a use case that combines UAAS measurements and dispersion modeling to quantify CH 4 emissions from a dairy farm. To evaluate the atmospheric sensing performance of the UAAS, four field deployments were performed at three locations in the San Joaquin Valley of California where CH 4 hotspots were observed downwind of dairy farms. A comparison of the observations collected on board the UAAS and an 11 m meteorological tower show that the UAAS can measure wind velocity trends with a root mean squared error varying between 0.4 and 1.1 m s -1 when the wind magnitude is less than 3.5 m s -1. Findings from UAAS flight deployments and a calibration experiment also show that the UAAS can reliably resolve temporal variations in the mole fractions of CH 4 and CO 2 occurring over periods of 10 s or longer. Results from the UAAS and dispersion modeling use case further demonstrate that UAASs have great potential as low-cost tools for detecting and quantifying CH 4 emissions in near real time. [ABSTRACT FROM AUTHOR]

To mitigate the impact of greenhouse gas (GHG) and air pollutant emissions, it is of utmost importance to understand where emissions occur. In the real world, atmospheric pollutants are produced by various human activities from point sources (e.g. power plants and industrial facilities) but also from diffuse sources (e.g. residential activities and agriculture). However, as tracking all these single sources of emissions is practically impossible, emission inventories are typically compiled using national-level statistics by sector, which are then downscaled at the grid-cell level using spatial information. In this work, we develop high-spatial-resolution proxies for use in downscaling the national emission totals for all world countries provided by the Emissions Database for Global Atmospheric Research (EDGAR). In particular, in this paper, we present the latest EDGAR v8.0 GHG, which provides readily available emission data at different levels of spatial granularity, obtained from a consistently developed GHG emission database. This has been achieved through the improvement and development of high-resolution spatial proxies that allow for a more precise allocation of emissions over the globe. A key novelty of this work is the potential to analyse subnational GHG emissions over the European territory and also over the United States, China, India, and other high-emitting countries. These data not only meet the needs of atmospheric modellers but can also inform policymakers working in the field of climate change mitigation. For example, the EDGAR GHG emissions at the NUTS 2 level (Nomenclature of Territorial Units for Statistics level 2) over Europe contribute to the development of EU cohesion policies, identifying the progress of each region towards achieving the carbon neutrality target and providing insights into the highest-emitting sectors. The data can be accessed at 10.2905/b54d8149-2864-4fb9-96b9-5fd3a020c224 specifically for EDGAR v8.0 (Crippa et al., 2023a) and 10.2905/D67EEDA8-C03E-4421-95D0-0ADC460B9658 for the subnational dataset (Crippa et al., 2023b). [ABSTRACT FROM AUTHOR]

Low-centre polygonal terrain developing within gentle sloping surfaces and lowlands in the high Arctic have a potential to retain snowmelt water in their bowl-shaped centre and as such are considered high latitude wetlands. Such wetlands in the continuous permafrost regions have an important ecological role in an otherwise generally arid region. In the valley of the glacier C-79 on Bylot Island (Nunavut, Canada), thermal erosion gullies are rapidly eroding the permafrost along ice wedges affecting the integrity of the polygons by breaching and collapsing the surrounding rims. While intact polygons were characterized by a relative homogeneity (topography, snow cover, maximum active layer thaw depth, ground moisture content, vegetation cover), eroded polygons had a non-linear response for the same elements following their perturbation. The heterogeneous nature of disturbed terrains impacts active layer thickness, ground ice aggradation in the upper portion of permafrost, soil moisture and vegetation dynamics, carbon storage and terrestrial green-house gas emissions. [ABSTRACT FROM AUTHOR]

Ponds and lakes are widespread across the rapidly changing permafrost environments. Aquatic systems play an important role in global biogeochemical cycles, especially in greenhouse gas (GHG) exchanges between terrestrial systems and the atmosphere. The source, speciation and emission of carbon released from permafrost landscapes are strongly influenced by local specific conditions rather than general environmental setting. This study reports on GHG ages and emission rates from aquatic systems on Bylot Island in the eastern Canadian Arctic. Dissolved and ebullition gas samples were collected during the summer season from different types of water bodies located in a highly dynamic periglacial valley: polygonal ponds, collapsed ice-wedge trough ponds, and larger lakes overlying unfrozen soils (talik). The results showed strikingly different ages and fluxes depending on aquatic system types. Polygonal ponds were net sinks of dissolved CO2, but variable sources of dissolved CH4. They presented the highest ebullition fluxes, one or two orders of magnitude higher than from other ponds and lakes. Trough ponds appeared as substantial GHG sources, especially when their edges were actively eroding. Both types of ponds produced modern to hundreds of years old (< 550 yr BP) GHG, even if trough ponds could contain much older carbon (> 2000 yr BP) derived from freshly eroded peat. Lakes had small dissolved and ebullition fluxes, however they released much older GHG, including millennium-old CH4 (up to 3500 yr BP) sampled from lake central areas. Acetoclastic methanogenesis dominated at all study sites and there was minimal, if any, methane oxidation in gas emitted through ebullition. These findings provide new insights on the variable role of permafrost aquatic systems as a positive feedback mechanism on climate. [ABSTRACT FROM AUTHOR]

The global extent of agriculture demands a thorough understanding of the ways it impacts the Earth system through both the modification of the physical and biological characteristics of the landscape as well as through emissions of greenhouse gases and aerosols. People use fire to manage cropland and pasture in many parts of the world, impacting both the timing and amount of fire. So far, much previous research into how these land uses affect fire regimes has either focused on individual small regions or global patterns at annual or decadal scales. Moreover, because pasture is not mapped globally at high resolution, the amount of fire associated with pasture has never been quantified as it has for cropland. The work presented here resolves the effects of agriculture - including pasture - on fire on a monthly basis for regions across the world, using globally gridded data on fire activity and land use at 0.25° resolution. The first global estimate of pasture-associated fire reveals that it accounts for over 40% of annual burned area. Cropland, generally assumed to reduce fire occurrence, is shown to enhance or suppress fire at different times of year within individual regions. These results bridge important gaps in the understanding of how agriculture and associated management practices influence vegetation fire, enabling the next generation of vegetation and Earth system models more realistically incorporate these anthropogenic effects. [ABSTRACT FROM AUTHOR]

Three years of greenhouse gases measurements, obtained using a gas chromatograph (GC) system located at the Puy de Dôme station at 1465 ma.s.l. in Central France are presented. The GC system was installed in 2010 at Puy de Dôme and was designed for automatic and accurate semi-continuous measurements of atmospheric carbon dioxide, methane, nitrous oxide and sulfur hexafluoride mole fractions. We present in detail the instrumental set up and the calibration strategy, which together allow the GC to reach repeatabilities of 0.1 µmol mol-1, 1.2, 0.3 nmol mol-1 and 0.06 pmol mol-1 for CO2, CH4, N2O and SF6, respectively. Comparisons of the atmospheric time series with those obtained using other instruments shown that the GC system meets the World Meteorological Organization recommendations. The analysis of the three-year atmospheric time series revealed how the planetary boundary layer height drives the mole fractions observed at a mountain site such as Puy de Dôme where air masses alternate between the planetary boundary layer and the free troposphere. Accurate long-lived greenhouse gases measurements collocated with 222Rn measurements as an atmospheric tracer, allowed us to determine the CO2, CH4 and N2O emissions in the catchment area of the station. The derived CO2 surface flux revealed a clear seasonal cycle with net uptake by plant assimilation in the spring and net emission caused by the biosphere and burning of fossil fuel during the remainder of the year. We calculated a mean annual CO2 flux of 1150 t(CO2) km-2. The derived CH4 and N2O emissions in the station catchment area were 5.6 t(CH4)km-2 yr-1 and 1.5 t(N2O)km-2 yr-1, respectively. Our derived annual CH4 flux is in agreement with the national French inventory, whereas our derived N2O flux is five times larger than the same inventory. [ABSTRACT FROM AUTHOR]

Several low resolution spectrometers were used to investigate the CO2 and CH4 emissions of the megacity Berlin. Before and after the campaign the instruments were tested side-by-side. An excellent level of agreement and stability was found between the different spectrometers: the drifts in XCO2 and XCH4 are within 0.005 and 0.035%, respectively. The instrumental line shape characteristics of all spectrometers were found to be close to nominal. Cross-calibration factors for XCH4 and XCO2 were established for each spectrometer. An empirical airmass correction factor has been applied. As a last calibration step, using a co-located TCCON spectrometer as a reference, a common factor has been derived for the low-resolution campaign spectrometers, which ensures that the records are compatible to the WMO in-situ scale. Finally as a first result of the Berlin campaign we show the excellent agreement of ground pressure values obtained from total column measurements and in situ records. [ABSTRACT FROM AUTHOR]

A new coastal background site has been established for observations of greenhouse gases (GHGs) in the central Namib Desert at Gobabeb, Namibia. The location of the site was chosen to provide observations for a data-poor region in the global sampling network for GHGs. Semi-automated, continuous measurements of carbon dioxide, methane, nitrous oxide, carbon monoxide, atmospheric oxygen, and basic meteorology are made at a height of 21ma.g.l., 50 km from the coast at the northern border of the Namib Sand Sea. Atmospheric oxygen is measured with a differential fuel cell analyzer (DFCA). Carbon dioxide and methane are measured with an early-model cavity ring-down spectrometer (CRDS); nitrous oxide and carbon monoxide are measured with an off-axis integrated cavity output spectrometer (OA-ICOS). Instrument-specific water corrections are employed for both the CRDS and OA-ICOS instruments in lieu of drying. The performance and measurement uncertainties are discussed in detail. As the station is located in a remote desert environment, there are some particular challenges, namely fine dust, high diurnal temperature variability, and minimal infrastructure. The gas handling system and calibration scheme were tailored to best fit the conditions of the site. The CRDS and DFCA provide data of acceptable quality when base requirements for operation are met, specifically adequate temperature control in the laboratory and regular supply of electricity. In the case of the OA-ICOS instrument, performance is significantly improved through the implementation of a drift correction through frequent measurements of a working tank. [ABSTRACT FROM AUTHOR]

Planetary boundary layer (PBL) CO2 mole fraction data are needed by transport models and carbon budget models as both input and reference for validation. The height of in situ CO2 mole fraction measurements is usually different from that of the model levels where the data are needed; data from short towers, in particular, are dificult to utilize in atmospheric models that do not simulate the surface layer well. Tall tower CO2 mole fraction measurements observed at heights ranging from to 115ma.g.l. at a rural site in Hungary and regular airborne vertical mole fraction profile measurements (136 vertical profiles) above the tower allowed us to estimate how well a tower of a given height could estimate the CO2 mole fraction above the tower in the PBL. The statistical evaluation of the height-dependent bias between the real PBL CO2 mole fraction profile (measured by the aircraft) and the measurement at a given elevation above the ground was performed separately for the summer and winter half years to take into account the different dynamics of the lower troposphere and the different surface CO2 flux in the dif15 ferent seasons. The paper presents: (1) how accurately the vertical distribution of CO2 in the PBL can be estimated from the measurements on the top of a tower of height H, (2) how tall a tower would be needed for the satisfaction of different requirements on the accuracy of the estimation of the CO2 vertical distribution, (3) how accurate a CO2 vertical distribution estimation can be expected from the existing towers; and (4) how much improvement can be achieved in the accuracy of the estimation of CO2 vertical distribution applying the virtual tall tower concept. [ABSTRACT FROM AUTHOR]

Clouds play a crucial role in the Earth's radiative budget, yet their climate feedbacks are poorly understood. The advent of space-borne high resolution spectrometers probing the O² A-band, such as the GOSAT and OCO-2 satellites, could make it possible to simultaneously retrieve several cloud parameters that play a vital role in the Earth's radiative budget, thereby allowing a reduction of the corresponding uncertainty due to clouds. In this work, the hyperspectral, polarimetric response of the O² A-band to mainly three important cloud parameters, viz., optical thickness, top height and droplet size has been studied, revealing a different sensitivity to each for the varying atmospheric absorption strength within the A-band. Cloud optical thickness finds greatest sensitivity in both intensity and polarization measurements at non-absorbing wavelengths. Cloud height had a negligible effect on intensity measurements at nonabsorbing wavelengths, but finds maximum sensitivity at an intermediate absorption strength, which increases with cloud height. The same is found to hold for cloud geometric thickness, except that the sensitivity is weaker. Sensitivity to droplet size is generally weaker than to cloud optical thickness to top height at non-absorbing wavelengths and diminishes further with increasing absorption strength. It has been shown that significantly more information on droplet size can be drawn from multiangular measurements. Our results show that, in the absence of sunglint, the backscatter direction is richer in information on droplet size, especially in the glory and rainbow regions. It has been shown that I and Q generally have differing sensitivities to cloud parameters. Thus, accurate measurements of both orthogonal components /h and Iv (as in GOSAT) are expected to contain more information than measurements of only /, /h or /v (as in the case of OCO-2). [ABSTRACT FROM AUTHOR]

Ozone, an important greenhouse gas, has the largest climate forcing in the tropopause region, meaning that knowledge of long-term ozone changes in the upper troposphere/ lower stratosphere (UTLS) is particularly important. Here, we perform a 16 yr comparison (1994–2009) of UTLS ozone measurements from balloon-borne ozonesondes and MOZAIC (measurements of ozone, water vapor, carbon monoxide and nitrogen oxides by in-service Airbus aircraft). The analysis uses trajectories computed from ERA-Interim wind fields to find matches between the two measurement platforms. Ozonesonde data quality is most critical in the UTLS, where natural variability is high, particularly close to the tropopause. On average, at the 28 launch sites considered, ozone mixing ratios measured by the sondes exceed MOZAIC data by 5– 15 %, with differences being smaller in the LS than in the UT at many launch sites. For most sites, sondes and MOZAIC data are in close agreement after 1998. Before 1998 ozone mixing ratios measured by the Brewer–Mast (BM) sondes and Electrochemical Concentration Cell (ECC) sondes are systematically (up to 20%) higher than the MOZAIC UV photometers. The reason for this large difference remains unclear. Results also show that after 1998 large background current signals may affect ozonesonde performance, limiting the determination of reliable ozone trends in the UTLS. Sonde measurements appear to be insensitive to changing the type of ECC ozonesonde, provided the cathode sensing solution strength remains unchanged. Only Scoresbysund (Greenland) showed systematically higher readings after changing from Science Pump Corporation sondes to ENSCI Corporation sondes, while keeping a 1.0% KI cathode electrolyte. This suggests that ECC sondes, provided their background current and sensing solutions are properly monitored, are robust and reliable tools for ozone trend studies in the UTLS. [ABSTRACT FROM AUTHOR]

A Climate Pattern-Scaling Model (CPSM) that simulates global patterns of climate change, for a prescribed emissions scenario, is described. A CPSM works by quantitatively establishing the statistical relationship between a climate variable at a specific location (e.g. daily maximum surface temperature, Tmax) and one or more predictor time series (e.g. global mean surface temperature, Tglobal) - referred to as the "training" of the CPSM. This training uses a regression model to derive fit-coefficients that describe the statistical relationship between the predictor time series and the target climate variable time series. Once that relationship has been determined, and given the predictor time series for any greenhouse gas (GHG) emissions scenario, the change in the climate variable of interest can be reconstructed - referred to as the "application" of the CPSM. The advantage of using a CPSM rather than a typical atmosphere-ocean global climate model (AOGCM) is that the predictor time series required by the CPSM can usually be generated quickly using a simple climate model (SCM) for any prescribed GHG emissions scenario and then applied to generate global fields of the climate variable of interest. The training can be performed either on historical measurements or on output from an AOGCM. Using model output from 21st century simulations has the advantage that the climate change signal is more pronounced than in historical data and therefore a more robust statistical relationship is obtained. The disadvantage of us20 ing AOGCM output is that the CPSM training might be compromised by any AOGCM inadequacies. For the purposes of exploring the various methodological aspects of the CPSM approach, AOGCM output was used in this study to train the CPSM. These investigations of the CPSM methodology focus on monthly mean fields of daily temperature extremes (Tmax and Tmin). Key conclusions are: (1) overall, the CPSM trained on simulations based on the Representative Concentration Pathway (RCP) 8.5 emissions scenario is able to reproduce AOGCM simulations of Tmax and Tmin based on predictor time series from an RCP 4.5 emissions scenario; (2) access to hemisphere average land and ocean temperatures as predictors improves the variance that can be explained, particularly over the oceans; (3) regression model fit-coefficients derived from individual simulations based on the RCP 2.6, 4.5 and 8.5 emissions scenarios agree well over most regions of the globe (the Arctic is the exception); (4) training the CPSM on concatenated time series from an ensemble of simulations does not result in fit-coefficients that explain significantly more of the variance than an approach that weights results based on single simulation fits; and (5) the inclusion of a linear time dependence in the regression model fit-coefficients improves the variance explained, primarily over the oceans. [ABSTRACT FROM AUTHOR]

Transformations of dissolved organic matter (DOM) in boreal lakes lead to large greenhouse gas emissions as well as substantial carbon storage in sediments. Using novel molecular characterization approaches and photochemical degradation experiments we studied how seasonal patterns in water column stratification affected the DOM in a Swedish lake under late winter and early summer conditions. Dissolved organic carbon (DOC) concentrations were consistently higher above the sediment when compared to surface waters. Solely photobleaching could not explain this difference in DOC because the lake was covered by 40 cm thick ice during late winter sampling and still showed the same DOC trend. The differences in the molecular diversity between surface water DOM in winter and summer were consistent with summertime photobleaching/decarboxylation reactions and a possible bacterial consumption of photo-products. Additional photodegradation experiments using simulated sunlight showed a production of highly oxidized organic molecules and low molecular weight compounds in all late winter samples and also in the deep water sample in summer. In the surface summer DOM sample, few such molecules were produced during the photodegradation experiments confirming that DOM was already photobleached prior to the experiments. This study suggests that photobleaching, and therefore also the ice cover during winter plays a central role in surface DOM structural dynamics with important differences in the molecular composition of DOM between surface and deep boreal lake waters. The release of DOC from boreal lake sediments likely also contribute to this pattern. Photochemical degradation of DOM may be more extensive following ice-out and water column turnover when non-light exposed and thereby photosensitive DOM is photo-mineralized. Hence, the yearly DOM photo-mineralization may be greater than inferred from studies of recently light exposed DOM. [ABSTRACT FROM AUTHOR]

We present evidence of temporal variation in nitrous oxide (N2O) concentrations in the bottom waters of the northern Gulf of Mexico (nGOM) hypoxic zone. The analysis is based on a conceptual model simulating N2O biogeochemical processes in conjunction with water-column O2 levels, derived from summer Texas-Louisiana shelf-wide hydrographic data for twenty Julys between 1985 and 2007. The mean modeled nGOM N2O concentration was 7.7±6.7 nmol L-1, and was significantly correlated with the areal extent of hypoxia. Our modeling analysis indicates that the nGOM is a persistent summer source of N2O, and nitrification is a primary factor leading to its production in this region. Based on the ongoing increase in the areal extent of hypoxia in the nGOM, we conclude that N2O emission from this environmentally stressed region will continue to increase into the future contributing to the global increase in greenhouse gases. [ABSTRACT FROM AUTHOR]

The Total Carbon Column Observing Network (TCCON) has been established to provide ground-based remote sensing measurements of the column-average dry air mole fractions of key greenhouse gases. To ensure the network wide consistency, biases between Fourier Transform spectrometers at different sites have to be well controlled. In this study we investigate a fundamental correction scheme for errors in the sampling of the interferogram. This is a two-step procedure in which the laser sampling error (LSE) is quantified using a subset of suitable interferograms and then used to re-sample all the interferograms in the timeseries. Timeseries of measurements acquired at the TCCON sites Izaña and Lauder are used to demonstrate the method. At both sites the sampling error histories show changes in LSE due to instrument interventions. Estimated LSE are in good agreement with sampling errors inferred from lamp measurements of the ghost to parent ratio (Lauder). The LSE introduce retrieval biases which are minimised when the interferograms are resampled. The original timeseries of Xair and XCO2 at both sites show discrepancies of 0.2-0.5% due to changes in the LSE associated with instrument interventions or changes in the measurement sample rate. After resampling discrepancies are reduced to 0.1% at Lauder and 0.2% at Izaña. In the latter case, coincident changes in interferometer alignment may also contribute to the residual difference [ABSTRACT FROM AUTHOR]

A profound understanding of temporal and spatial variabilities of CO2, CH4 and N2O fluxes between terrestrial ecosystems and the atmosphere is needed to reliably quantify these fluxes and to develop future mitigation strategies. For managed grassland ecosystems, temporal and spatial variabilities of these three greenhouse gas (GHG) fluxes are due to environmental drivers as well as to fertilizer applications, grazing and cutting events. To assess how these affect GHG fluxes at Swiss grassland sites, we studied three sites along an altitudinal gradient that corresponds to a management gradient: from 400ma.s.l. (intensively managed) to 1000ma.s.l. (moderately intensive managed) to 2000 ma.s.l. (extensively managed). Temporal and spatial variabilities of GHG fluxes were quantified along small-scale transects of 16 static soil chambers at each site. We then established functional relationships between drivers and the observed fluxes on diel and annual time scales. Furthermore, spatial variabilities and their effect on representative site-specific mean chamber GHG fluxes were assessed using geostatistical semivariogram approaches. All three grasslands were N2O sources, with mean annual fluxes ranging from 0.15 to 1.28 nmol m-2 s-1. Contrastingly, all sites were net CH4 sinks, with uptake rates ranging from -0.56 to -0.15 nmol m-2 s-1. Mean annual respiration losses of CO2, as measured with opaque chambers, ranged from 5.2 to 6.5 µmol m-2 s-1. While the environmental drivers and their respective explanatory power for N O emissions differed considerably among the three grasslands (adjusted r² ranging from 0.19 to 0.42), CH4 and CO2 fluxes were much better constrained (adjusted r² ranging from 0.41 to 0.83), in particular by soil water content and air temperature, respectively. Throughout the year, spatial heterogeneity was particularly high for N2O and CH4 fluxes. We found permanent hot spots for N2O emissions and CH4 up- take at the extensively managed site. Including these hot spots in calculating the mean chamber flux was essential to obtain a representative mean flux for this ecosystem. At the intensively managed grassland, management effects clearly dominated over effects of environmental drivers on N2O fluxes. For CO2 and CH4, the importance of management effects did depend on the status of the vegetation. [ABSTRACT FROM AUTHOR]

The article discusses the study which assesses the cavity ring-down spectroscopy (CRDS) CO2CH4CO/H2O analyzer performance operating on an aircraft. The study used the CRDS analyzer to describe the system for making greenhouse gas measurements. Results show that the stability is not affected by pressure or temperature variation.

The Eastern Tropical Pacific (ETP) is believed to be one of the largest marine sources of the greenhouse gas nitrous oxide (N2O). Future N2O emissions from the ETP are highly uncertain because oxygen minimum zones are expected to expand, affecting both regional production and consumption of N2O. Here we assess three primary uncertainties in how N2O may respond to changing O2 levels: (1) the relationship between N2O production and O2 (is it linear or exponential at low O2 concentrations?), (2) the cutoff point at which net N2O production switches to net N2O consumption (uncertainties in this parameterization can lead to differences in model ETP N2O concentrations of more than 20%), and (3) the rate of net N2O consumption at low O2. Based on the MEMENTO database, which is the largest N2O dataset currently available, we find that N2O production in the ETP increases linearly rather than exponentially with decreasing O2. Additionally, net N2O consumption switches to net N2O production at -10 µM O2, a value in line with recent studies that suggest consumption occurs on a larger scale than previously thought. N2O consumption is on the order of 0.129mmol N2O myr-3 yr-1 in the Peru--Chile Undercurrent. Based on these findings, it appears that recent studies substantially overestimated N2O production in the ETP. In light of expected deoxygenation, future N2O production is still uncertain, but due to higher-than-expected consumption levels, it is possible that N2O concentrations may decrease rather than increase as oxygen minimum zones expand. [ABSTRACT FROM AUTHOR]

The article presents a study which focuses on the development of an integrated flask sample collection system for greenhouse gas (GHG) measurements. It is inferred that GHG measurements are essential in understanding the carbon cycle, climate change and air quality problems. A detailed description on the process of air collection with the flask sampling system is provided.

The article describes the operational level 1 algorithms in producing the spectral radiance from the acquired interferogram. It also describes the on-orbit characteristics and calibrations of the thermal and near infrared sensor for carbon observation Fourier-Transform Spectrometer (TANSO-FTS) onboard the greenhouse gases observing satellite (GOSAT). Overall functions and performances including signal to noise ratio and spectral resolution are discussed.

The article focuses on a study which examines the combined aerosol and greenhouse gas retrieval using multiple satellite viewing angles simultaneously. It offers information on the Greenhouse Gases Observing Satellite (GOSAT) and the Orbiting Carbon Observatory (OCO). The degree of freedom analysis for aerosol parameters using diverse spectrometer specifications is discussed.

Peatland restoration may provide a potential after-use option to mitigate the negative climate impact of abandoned peat extraction areas; currently, however, knowledge about restoration effects on the annual balances of carbon (C) and greenhouse gas (GHG) exchanges is still limited. The aim of this study was to investigate the impact of contrasting water table levels (WTL) on the annual C and GHG balances of restoration treatments with high (Res-H) and low (Res-L) WTL relative to an unrestored bare peat (BP) site. Measurements of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes were conducted over a full year using the closed chamber method and complemented by measurements of abiotic controls and vegetation cover. Three years following restoration, the difference in the mean WTL resulted in higher bryophyte and lower vascular plant cover in Res-H relative to Res-L. Consequently, greater gross primary production and autotrophic respiration associated with greater vascular plant cover were observed in Res-L compared to Res-H. However, the means of the measured net ecosystem CO2 exchanges (NEE) were not significantly different between Res-H and Res-L. Similarly, no significant differences were observed in the respective means of CH4 and N2O exchanges in Res-H and Res-L, respectively. In comparison to the two restored sites, greater net CO2, similar CH4 and greater N2O emissions occurred in BP. On the annual scale, Res-H, Res-L and BP were C sources of 111, 103 and 268 g C m-2 yr-1 and had positive GHG balances of 4.1, 3.8 and 10.2 t CO2 eq ha-1 yr-1, respectively. Thus, the different WTLs had a limited impact on the C and GHG balances in the two restored treatments three years following restoration. However, the C and GHG balances in Res-H and Res-L were considerably lower than in BP owing to the large reduction in CO2 emissions. This study therefore suggests that restoration may serve as an effective method to mitigate the negative climate impacts of abandoned peat extraction areas. [ABSTRACT FROM AUTHOR]

Drained peatlands are significant hotspots of carbon dioxide (CCO2) emissions and may also be more vulnerable to fire with its associated gaseous emissions. Under the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol, greenhouse gas (GHG) emissions from peatlands managed for extraction are reported on an annual basis. However, the Tier 1 (default) emission factors (EFs) provided in the IPCC 2013 Wetlands Supplement for this land use category may not be representative in all cases and countries are encouraged to move to higher Tier reporting levels with reduced uncertainty levels based on country or regional specific data. In this study, we quantified (1) CCO2-C emissions from 9 peat extraction sites in the Republic of Ireland and the United Kingdom, which were initially disaggregated by land use type (industrial vs. domestic peat extraction), and (2) a range of GHGs that are released to the atmosphere with the burning of peat. CCO2-C emissions were strongly controlled by soil temperature at the industrial sites (bare peat), and by soil temperature and leaf area index at the vegetated domestic sites. Our derived EFs of 1.70 (±0.47) and 1.64 (±0.44) t CCO2-C ha-1 yr-1 for the industrial and domestic sites respectively, are considerably lower than the Tier 1 EF (2.8 ± 1.7 t CCO2-C ha-1 yr-1) provided in the Wetlands Supplement. We propose that the difference between our derived values and the Wetlands Supplement value is due to differences in peat quality and, consequently, decomposition rates. Emissions from burning of the peat (g kg-1 dry fuel burned) were estimated to be approximately 1346 (CCO2), 8.35 (methane, CH4), 218 (carbon monoxide, CO), 1.53 (ethane, C2H6), 1.74 (ethylene, C2H4), 0.60 (methanol, CH3OH), 2.21 (hydrogen cyanide, HCN) and 0.73 (ammonia, NH3) and emphasises the importance of understanding the full suite of trace gas emissions from biomass burning, rather than focussing solely on CCO2 and CH4 emissions. Our results highlight the importance of generating reliable Tier 2 values for different regions and land-use categories. Furthermore, given that the IPCC Tier 1 EF was only based on 20 sites (all from Canada/Fenno-Scandia) we suggest that data from another 9 sites significantly expands the global dataset, as well as adding a new region. [ABSTRACT FROM AUTHOR]

Accurate solubility estimates are fundamental for (i) Earth-System models forecasting the climate change taking into consideration the atmosphere-ocean balances and trades of greenhouse gases, and (ii) using field data to calibrate and validate the algorithms simulating those trades. We found important differences between the formulation generally accepted and a recently proposed alternative relying on a different chemistry background. First, we tested with field data from the Baltic Sea, which also enabled finding differences between using water temperatures measured at 0.5 or 4 m depths. Then, we used data simulated by atmospheric (Meteodata application of WRF) and oceanographic (WW3-NEMO) models of the European Coastal Ocean and Mediterranean to compare the use of the two solubility algorithms in Earth-System modelling. The mismatches between both formulations lead to a difference of millions of tons of CO2, and hundreds of tons of CH4 and N2O, dissolved in the first meter below the sea surface of the whole modelled region. [ABSTRACT FROM AUTHOR]

Stream networks were recently discovered as major but poorly constrained natural greenhouse gas (GHG) sources. A fundamental problem is that several measurement approaches have been used without cross comparisons. Flux chambers represent a potentially powerful methodological approach if robust and reliable ways 5 to use chambers on running water can be defined. Here we compare the use of anchored and freely drifting chambers on various streams having different flow velocities. The study clearly shows that (1) drifting chambers have a very small impact on the water turbulence under the chamber and thus generate more reliable fluxes, (2) anchored chambers enhance turbulence under the chambers and thus elevate fluxes, (3) the bias of the anchored chambers greatly depends on chamber design and sampling conditions, and (4) there is a promising method to reduce the bias from anchored chambers by using a flexible plastic foil seal to the water surface rather than having rigid chamber walls penetrating into the water. Altogether, these results provide novel guidance on how to apply flux chambers in running water, which will have important consequences for measurements to constrain the global GHG balances. [ABSTRACT FROM AUTHOR]

Methane is the second-most important greenhouse gas after carbon dioxide and accounts for around 10 % of total European Union greenhouse gas emissions. Given that the atmospheric methane budget over a region depends on its terrestrial and aquatic methane sources, inverse modelling techniques appear as powerful tools for identifying critical areas that can later be submitted to emission mitigation strategies. In this regard, an inverse modelling system of methane emissions for Europe is being implemented based on the Weather Research and Forecasting (WRF) model: the Aarhus University Methane Inversion Algorithm (AUMIA) v1.0. The forward modelling component of AUMIA consists of the WRF model coupled to a multipurpose global database of methane anthropogenic emissions. To assure transport consistency during the inversion process, the backward modelling component will be based on the WRF model coupled to a Lagrangian particle dispersion module. A description of the modelling tools, input data sets, and 1-year forward modelling evaluation from 1 April 2018 to 31 March 2019 is provided in this paper. The a posteriori methane emission estimates, including a more focused inverse modelling for Denmark, will be provided in a second paper. A good general agreement is found between the modelling results and observations based on the TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor satellite. Model–observation discrepancies for the summer peak season are in line with previous studies conducted over urban areas in central Europe, with relative differences between simulated concentrations and observational data in this study ranging from 1 % to 2 %. Domain-wide correlation coefficients and root-mean-square errors for summer months ranged from 0.4 to 0.5 and from 27 to 30 ppb, respectively. On the other hand, model–observation discrepancies for winter months show a significant overestimation of anthropogenic emissions over the study region, with relative differences ranging from 2 % to 3 %. Domain-wide correlation coefficients and root-mean-square errors in this case ranged from 0.1 to 0.4 and from 33 to 50 ppb, respectively, indicating that a more refined inverse analysis assessment will be required for this season. According to modelling results, the methane enhancement above the background concentrations came almost entirely from anthropogenic sources; however, these sources contributed with only up to 2 % to the methane total-column concentration. Contributions from natural sources (wetlands and termites) and biomass burning were not relevant during the study period. The results found in this study contribute with a new model evaluation of methane concentrations over Europe and demonstrate a huge potential for methane inverse modelling using improved TROPOMI products in large-scale applications. [ABSTRACT FROM AUTHOR]

The Fourier-transform spectrometer on board the Japanese GOSAT satellite offers an excellent opportunity to study the impact of instrument resolution on retrieval accuracy of CO2 and CH4. This is relevant to further improve retrieval accuracy and to optimize the cost-benefit ratio of future satellite missions for the remote sensing of greenhouse gases. To address this question, we degrade GOSAT measurements with a spectral resolution of ≈ 0.24 cm-1 step-by-step to a resolution of 1.5cm-1. We examine the results by comparing relative differences at various resolutions, by referring the results to reference values from the Total Carbon Column Observing Network (TCCON), and by calculating and inverting synthetic spectra for which the true CO2 and CH4 columns are known. The main impacts of degrading the spectral resolution turn out to be consistent for the first two approaches; pure forward model errors identified with simulated measurements are much smaller. For GOSAT spectra, the most notable effect on CO2 retrieval accuracy is the increase of the standard deviation of retrieval errors from 0.7% to 1.0% when the spectral resolution is reduced by a factor of six. The retrieval biases against atmospheric water abundance and airmass become stronger with decreasing resolution. The error scatter increase for CH4 columns is less pronounced. The selective degradation of single spectral windows demonstrates that the retrieval accuracy of CO2 and CH4 is dom inated by the spectral range where the absorption lines of the target molecule are located. For both GOSAT and synthetic measurements, retrieval accuracy decreases with lower spectral resolution, suggesting increasing interference errors. [ABSTRACT FROM AUTHOR]

Global warming has accelerated the formation of permafrost thaw ponds in several subarctic and arctic regions. These ponds are net heterotrophic as evidenced by their greenhouse gas (GHG) supersaturation levels (CO2 and CH4), and generally receive large terrestrial carbon inputs from the thawing and eroding permafrost. We measured seasonal and vertical variations in the concentration and type of dissolved organic matter (DOM) in five subarctic thaw (thermokarst) ponds in northern Quebec, and explored how environmental gradients influenced heterotrophic and phototrophic biomass and productivity. Late winter DOM had low aromaticity indicating reduced inputs of terres trial carbon, while the high concentration of dissolved organic carbon (DOC) suggests that some production of non-chromophoric dissolved compounds by the microbial food web took place under the ice cover. Summer DOM had a strong terrestrial signature, but was also characterized with significant inputs of algal-derived carbon, especially at the pond surface. During late winter, bacterial production was low (maximum of 0.8mgCm-3 d-1) and was largely based on free-living bacterioplankton (58%). Bacterial production in summer was high (up to 58mgCm3 d1), dominated by particleattached bacteria (67%), and strongly correlated to the amount of terrestrial carbon. Primary production was restricted to summer surface waters due to strong light limitation deeper in the water column or in winter. The phototrophic biomass was equal to the heterotrophic biomass, but as the algae were mostly composed of mixotrophic species, most probably they used bacteria rather than solar energy in such shaded ponds. According to the δ13C analyses, non-algal carbon supported 51% of winter and 37% of summer biomass of the phantom midge larvae, Chaoborus sp., that are at the top of the trophic chain. Our results point to a strong heterotrophic energy pathway 25 in these thaw pond ecosystems, where bacterioplankton dominates the production of new carbon in both summer and winter. [ABSTRACT FROM AUTHOR]

The Geostationary Emission Explorer for Europe (G3E) is a concept for a geostationary satellite sounder that targets at constraining the sources and sinks of the greenhouse gases carbon dioxide (CO2) and methane (CH4) for continental-scale regions. Thereby, its primary focus is on Central Europe. G3E carries a spectrometer system that collects sunlight backscattered from the Earth's surface and atmosphere in the near-infrared (NIR) and shortwave-infrared (SWIR) spectral range. Solar absorption spectra allow for spatiotemporally dense observations of the column-average concentrations of carbon dioxide (XCO2), methane (XCH4), and carbon monoxide (XCO) including sampling of the diurnal variation with several measurements per day during summer. Here, we present the mission concept and carry out an initial performance assessment of the retrieval capabilities. The radiometric performance of the 4 grating spectrometers is tuned to reconcile small ground-pixel sizes (~ 2 km × 3 km at 50° latitude) with short single-shot exposures (~ 2.9 s) that allow for sampling continental regions such as Central Europe within 2 h while providing sufficient signal-to-noise. The noise errors to be expected for XCO2, XCH4, and XCO are assessed through retrieval simulations for a European trial ensemble. Generally, single-shot precision for the targeted XCO2 and XCH4 is better than 0.5% with some exception for scenes with low infrared surface albedo observed under low sun conditions in winter. For XCO, precision is generally better than 10%. Performance for aerosol and cirrus loaded atmospheres is assessed by mimicking G3E's slant view on Europe for an ensemble of atmospheric scattering properties used previously for evaluating nadir-viewing low-Earth-orbit (LEO) satellites. While retrieval concepts developed for LEO configurations generally succeed in mitigating aerosol and cirrus induced retrieval errors for G3E's setup, residual errors are somewhat greater in geostationary orbit (GEO) than in LEO. G3E's deployment in the vicinity of the Meteosat Third Generation (MTG) satellites suggests making synergistic use of MTG's sounding capabilities e.g. with respect to characterization of aerosol and cloud properties or with respect to enhancing carbon monoxide retrievals by combining G3E's solar and MTG's thermal infrared spectra. [ABSTRACT FROM AUTHOR]

Prescribed burning is a forest management practice that is widely used in Australia to reduce the risk of damaging wildfires. It can affect both carbon (C) and nitrogen (N) cycling in the forest and thereby influence the soil-atmosphere exchange of major greenhouse gases, i.e. carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). To quantify the impact of a prescribed burning (conducted on 27 May 2014) on greenhouse gas exchange and the potential controlling mechanisms, we carried out a series of field measurements before (August 2013) and after (August 2014 and November 2014) the fire. Gas exchange rates were determined at 4 replicate sites which were burned during the combustion and another 4 adjacent unburned sites located in green islands, using a set of static chambers. Surface soil properties including temperature, pH, moisture, soil C and N pools were also determined either by in situ measurement or by analysing surface 10 cm soil samples. All of the chamber measurements indicated a net sink of atmospheric CH4, with mean CH4 uptake ranging from 1.15 to 1.99 mg m-2day-1. The burning significantly enhanced CH4 uptake as indicated by the significant higher CH4 uptake rates at the burned sites measured in August 2014. While within the next 3 months the CH4 uptake rate was recovered to pre-burning levels. Mean CO2 emission from forest soils ranged from 2721.76 to 7113.49 mg-2 day-1. The effect of prescribed burning on CO2 emission was limited within the first 3 months, as no significant difference was observed between the burned and the adjacent unburned sites in both August and November 2014. The temporal dynamics of the CO2 emission presented more seasonal variations, rather than burning effects. The N2O emission at the studied sites was quite low, and no significant impact of burning was observed. The changes in understory plants and litter layers, surface soil temperature, C and N substrate availability and microbial activities, resulting from the burning, were the factors that controlled the greenhouse gas exchanges. Our results suggested that the low intensity prescribed burning would decrease soil CO2 emission and increase CH4 uptake, however, this effect would be present within a relative short period. Only slight changes in the surface soil during the combustion and very limited damages in the mineral soils supported the quick recovery of the greenhouse gas exchange rates. [ABSTRACT FROM AUTHOR]

Even if greenhouse gas emissions were stopped today sea level would continue to rise for centuries with the long-term sea-level commitment of a two-degree-warmer world significantly exceeding 2 m. In view of the potential implications for coastal populations and ecosystems worldwide we investigate, from an ice-dynamic perspective, the possibility to delay sea-level rise by pumping ocean water onto the surface of the Antarctic Ice Sheet. We find that due to wave propagation ice is discharged much faster back into the ocean than would be expected from a pure advection with surface velocities. The delay time depends strongly on the distance from the coastline at which the additional mass is placed and less strongly on the rate of sea-level rise that is mitigated. A millennium-scale storage of at least 80 % of the additional ice requires placing it at a distance of at least 700 km from the coast line. The pumping energy required to elevate the potential energy of ocean water to mitigate the currently observed 3 mm yr-1 will exceed 7 % of the current global primary energy supply. At the same time the approach may be the only way to protect entire coastlines or specific regions that cannot be protected by dikes. [ABSTRACT FROM AUTHOR]

Thermokarst lakes are important emitters of methane, a potent greenhouse gas. However, accurate estimation of methane flux from thermokarst lakes is difficult due to their remoteness and observational challenges associated with the heterogeneous nature of ebullition (bubbling). We used multi-temporal high-resolution (9-11 cm) aerial images of an interior Alaskan thermokarst lake, Goldstream Lake, acquired 2 and 4 days following freeze-up in 2011 and 2012, respectively, to characterize methane ebullition seeps and to estimate whole-lake ebullition. Bubbles impeded by the lake ice sheet form distinct white patches as a function of bubbling rate vs. time as ice thickens. Our aerial imagery thus captured in a single snapshot the ebullition events that occurred before the image acquisition. Image analysis showed that low-flux A- and B-type seeps are associated with low brightness patches and are statistically distinct from high-flux C-type and Hotspot seeps associated with high brightness patches. Mean whole-lake ebullition based on optical image analysis in combination with bubble-trap flux measure15 ments was estimated to be 174 ± 28 and 216 ± 33mLgas m-2 d-1 for the years 2011 and 2012, respectively. A large number of seeps demonstrated spatio-temporal stability over our two-year study period. A strong inverse exponential relationship (R² ≤ 0.79) was found between percent surface area of lake ice covered with bubble patches and distance from the active thermokarst lake margin. Our study shows that optical remote sensing is a powerful tool to map ebullition seeps on lake ice, to identify their relative strength of ebullition and to assess their spatio-temporal variability. [ABSTRACT FROM AUTHOR]

Drained organic soils are considered as hotspots for greenhouse gas (GHG) emissions. Particularly arable lands and intensively used grasslands have been regarded as the main producers of carbon dioxide (CO2) and nitrous oxide (N2O). However, GHG balances of former peatlands and associated organic soils not considered as peatland according to the definition of the Intergovernmental Panel on Climate Change (IPCC) have not been investigated so far. Therefore, our study addressed the question to what extent the soil organic carbon (SOC) content affects the GHG release of drained organic soils under two different land-use types (arable land and intensively used grassland). Both land-use types were established on a mollic Gleysol (named Cmedium ) as well as on a sapric Histosol (named Chigh). The two soil types significantly differed in their SOC contents in the topsoil (Cmedium: 9.4-10.9%SOC; Chigh: 16.1-17.2% SOC). We determined GHG fluxes (CO2, N2O and methane (CH4)) over a period of 2 years. The daily and annual net ecosystem exchange (NEE) of CO2 was determined with the closed dynamic chamber technique and by modeling the ecosystem respiration (RECO) and the gross primary production (GPP). N2O and CH4 were determined by the close chamber technique. Estimated NEE of CO2 significantly differed between the two land-use types with lower NEE values (-6 to 1707 gCO2-Cm-2 yr-1) at the arable sites and higher values (1354 to 1823 gCO2-Cm-2 yr-1) at the grassland sites. No effect on NEE was found regarding the SOC content. Significantly higher annual N2O exchange rates were observed at the arable sites (0.23-0.86 g N m-2 yr-1) compared to the grassland sites (0.12-0.31 g N m-2 yr-1). Furthermore, N2O fluxes from the Chigh sites significantly exceeded those of the Cmedium sites. CH4 fluxes were found to be close to zero at all plots. Estimated global warming potential, calculated for a time horizon of 100 years (GWP100) revealed a very high release of GHGs from all plots ranging from 1837 to 7095 gCO2 eq. m-2 yr-1. Calculated global warming potential (GWP) values did not differ between soil types and partly exceeded the IPCC default emission factors of the Tier 1 approach by far. However, despite being subject to high uncertainties, the results clearly highlight the importance to adjust the IPCC guidelines for organic soils not falling under the definition, to avoid a significant underestimation of GHG emissions in the corresponding sectors of the national climate reporting. Furthermore, the present results revealed that mainly the land-use including the management and not the SOC content is responsible for the height of GHG exchange from intensive farming on drained organic soils. [ABSTRACT FROM AUTHOR]

Many factors are known to influence greenhouse gas emissions from coastal wetlands, but it is still unclear which factors are most important under field conditions when they are all acting simultaneously. The objective of this study was to assess the effects of water table, salinity, soil temperature and vegetation on CH4 emissions and ecosystem respiration (Reco) from five coastal wetlands in the Liaohe Delta, northeast China: two Phragmites australis (common reed) wetlands, two Suaeda salsa (sea blite) marshes and a rice (Oryza sativa) paddy. Throughout the growing season, the Suaeda wetlands were net CH4 sinks whereas the Phragmites wetlands and the rice paddy were net CH4 sources emitting 1.2-6.1 gCH4m-2 y-1. The Phragmites wetlands emitted the most CH4 per unit area and the most CH4 relative to CO2 . The main controlling factors for the CH4 emissions were water table, temperature and salinity. The CH4 emission was accelerated at high and constant (or managed) water tables and decreased at water tables below the soil surface. High temperatures enhanced CH4 emissions, and emission rates were consistently low (< 1mgCH4 m-2 h) at soil temperatures < 18 °C. At salinity levels> 18 ppt, the CH4 emission rates were always low (< 1mgCH4 m-2 h-1) probably because methanogens were outcompeted by sulphate reducing bacteria. Saline Phragmites wetlands can, however, emit significant amounts of CH4 as CH4 produced in deep soil layers are transported through the air-space tissue of the plants to the atmosphere. The CH4 emission from coastal wetlands can be reduced by creating fluctuating water tables, including water tables below the soil surface, as well as by occasional flooding by high-salinity water. The effects of water management schemes on the biological communities in the wetlands must, however, be carefully studied prior to the management in order to avoid undesirable effects on the wetland communities. [ABSTRACT FROM AUTHOR]