M. A. K. Khalil and R. A. Rasmussen, Oregon Graduate Institute of Science and Technology, Portland, Oregon 97291
CDIAC DB-1007The atmospheric-monitoring facility at Cape Meares, Oregon, is operated by the Oregon Graduate Institute of Science and Technology and was the first station in the world to carry out continuous automated measurements of atmospheric methane. The Cape Meares data represent some 119,000 atmospheric-methane measurements carried out from 1979 to 1992. Ambient air, collected 12 to 72 times daily, was analyzed with gas chromatography and flame-ionization detection by means of an automated sampling and measurement system. Despite the long course of the record and the large number of individual measurements, these data may all be linked to a single absolute calibration standard.
The data are contained in three files. The largest file (2.14 MB) contains all the individual atmospheric-methane measurements collected at Cape Meares from January 1979 to January 1992. A second file (189 kB) contains daily average concentrations of methane, sampling statistics, and interpolations for days when data were not taken. The last file (10 kB) contains monthly averages (derived from the individual and daily data) and statistics of dispersion, calculated by three different methods: the arithmetic mean (along with 90% confidence limits), the median (along with 5th and 95th percentile values), and a middle value (also with accompanying 90% confidence limits) based on a nonparametric statistical method. The data and accompanying descriptive material are available in digitized form only; hard-copy documentation is not available.
E. J. Dlugokencky, P. M. Lang, and K. A. Masarie, National Oceanic and Atmospheric Administration, Boulder, CO 80303
L. P. Steele, Commonwealth Scientific and Industrial Research Organisation, Aspendale, Victoria, Australia
CDIAC DB-1008This database presents atmospheric methane mixing ratios from flask air samples collected from 1983 to 1993 by the National Oceanic and Atmospheric Administration, Climate Monitoring and Diagnostics Laboratory's (NOAA/CMDL's) global cooperative air-sampling network. Air samples were collected approximately once per week at 44 fixed sites (37 of which were still active at the end of 1993). Samples were also collected at 5° -latitude intervals along shipboard cruise tracks in the Pacific Ocean between North America and New Zealand (or Australia) and at 3° -latitude intervals along cruise tracks in the South China Sea between Singapore and Hong Kong. The shipboard measurements were made approximately every three weeks per latitude zone by each of two ships in the Pacific Ocean and approximately once every week per latitude zone in the South China Sea. All samples were analyzed for methane at NOAA/CMDL by gas chromatography with flame-ionization detection, and each aliquot was referenced to the NOAA/CMDL methane standard scale.
In addition to providing the complete set of atmospheric methane measurements from flask air samples collected at the NOAA/CMDL network sites, this database also includes files that list monthly mean mixing ratios derived from the individual flask air measurements. These monthly summary data are available for 35 of the fixed sites and 21 of the shipboard sampling sites. (Shipboard sites are actually 3° or 5° latitudinal bands. In the Pacific Ocean, samples were collected at a minimum of two longitudes.)
The data for the complete set of individual measurements are contained in 85 files, ranging in size from 2.7 kB to 187 kB and totaling 2.7 MB. Two additional files contain the monthly summary data. One of these files (30.2 kB) contains all monthly mean methane values for NOAA/CMDL fixed monitoring sites. The second file (14.3 kB) contains all monthly mean methane values for NOAA/CMDL shipboard sites. An additional file (151.0 kB) contains a PostScript image showing the locations of all fixed sampling sites in the NOAA/CMDL cooperative air sampling network; also shown are the approximate sampling locations from ocean vessels participating in the shipboard sampling program. The data and accompanying descriptive material are available in digitized form only; hard-copy documentation is not available.
I. G. Enting, Commonwealth Scientific and Industrial Research Organisation, Aspendale, Victoria, Australia
T. M. L. Wigley, University Corporation for Atmospheric Research, Boulder, CO 80307
M. Heimann, Max Planck Institut fr Meteorologie, Hamburg, Germany
CDIAC DB-1009
This database contains the results of various projections of the relation between future CO2 concentrations and future industrial emissions. These projections were contributed by groups from a number of countries as part of the scientific assessment for the report, Radiative Forcing of Climate Change, issued by Working Group 1 of the Intergovernmental Panel on Climate Change in 1994. Three types of calculations are included: (1) forward projections, calculating the atmospheric CO2 concentrations resulting from specified emission scenarios; (2) inverse calculations, determining the emission rates that would be required to achieve stabilization of CO2 concentrations via specified pathways; (3) impulse-response-function calculations, required for determining Global Warming Potentials. The projections were extrapolations of global-carbon-cycle models from pre-industrial times (starting at 1765) to A.D. 2100 or 2200. The assessment focused on uncertainties about the current carbon budget and on those arising from differences between models. To separate these effects, a set of standard conditions was used to explore intermodel differences, and a series of sensitivity studies was used to explore the consequences of current uncertainties in the carbon cycle.
The contents of this data base are divided into three subsets: inputs, results, and report. The inputs subset (11 files totaling 130 kB) contains the empirical time-series data that were used as the basis of the modelling projections. These data include historical and modern measurements of atmospheric CO2 concentrations, CO2 emissions from industry and land-use changes, and carbon-14 activities for atmospheric CO2.
The results subset (46 files totaling 1.02 MB) contains the projections (as time series) contributed by ten groups of carbon-cycle modelers. The categories of data in this subset include projected CO2 concentrations for specified emission scenarios, ocean CO2 fluxes for specified regimes of emissions or atmospheric concentrations, and industrial emissions (from inverse calculations) for specified concentration time series (i.e., stabilization pathways).
The report subset (8 files totaling 4.45 MB) contains a set of PostScript files that constitute the report, Future Emissions and Concentrations of Carbon Dioxide: Key Ocean/Atmosphere/Land Analyses (CSIRO Division of Atmospheric Research Technical Paper No. 31). This report details the specifications for the modelling projections, the models that were used, and the results that were obtained. The data and accompanying descriptive material are available in digitized form only; hard-copy documentation is not available.
M. A. K. Khalil and R. A. Rasmussen, Oregon Graduate Institute of Science and Technology, Portland, Oregon
CDIAC DB-1010
This data set presents globally averaged atmospheric concentrations of CFC-11 (trichlorofluoromethane, CCl3F). The monthly global average data are derived from flask air samples collected at eight sites in six locations from 8/80 to 7/92. The sites are Barrow (Alaska), Cape Meares (Oregon), Cape Kumukahi and Mauna Loa (Hawaii), Cape Matatula (American Samoa), Cape Grim (Tasmania), and Palmer Station and the South Pole (Antarctica). CFC-11 was determined with a dual electron-capture gas chromatograph referenced to a primary calibration standard. The absolute accuracy of the measurements was estimated at ± 5%. At each collection site, monthly averages were obtained from flask samples collected every week in triplicate. The monthly global averages were obtained by calculating an area-weighted average of the CFC-11 concentrations.
The data set also contains annual global average data for 1975 to 1985, obtained from sampling only at the South Pole and in the U.S. Pacific Northwest. To obtain the annual values, large numbers of samples collected in Januaries were analyzed and averaged. The averaged data from the South Pole and the Pacific Northwest were then corrected to reflect global means by comparison of the January data with the six-location measurements made during the overlap period (1980 to 1985). The corrected two-location January global averages were then used to obtain middle-of-the-year (annual average) concentrations, calculated as the average of each sequential pair of January values.
P. C. Novelli and K. A. Masarie, National Oceanic and Atmospheric Administration, Climate Monitoring and Diagnostics Laboratory, Boulder, Colorado, and Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, Colorado
CDIAC DB-1011
Beginning in 1988, individual-site files provide CO mixing ratios measured in parts per billion on samples from the NOAA/CMDL Cooperative Air Sampling Network. Data are provided through June 1993 for stations at which the first sample was collected before July 1991. The air-sampling network uses more than 30 land-based sites for CO measurements. Shipboard sampling has also been carried out every 5° of latitude for two cruise tracks [the Wellington Star (PAW) and the California Star (OPC)] between North America and Australia or New Zealand and every 3° of latitude for cruise tracks between Hong Kong and Singapore [Carla A. Hills and Great Promise (SCS)]. Sampling frequencies are approximately weekly for the fixed sites, average one sample every 3 weeks per latitude zone for PAW and OPC, and average about one sample every week per latitude for SCS.
At each sampling, two flasks were filled with the sampled air. All samples were analyzed for CO by gas chromatography at the NOAA/CMDL laboratory in Boulder, and all measurements were referenced to the CMDL CO scale. From 1988 to 1991, the contents of one flask was analyzed one or more times. The difference in CO mixing ratio between (or among) the aliquots was used as an indication of the precision of the measurement. Beginning in October 1991, a single aliquot from each flask was analyzed to simplify flask-handling procedures and to have flask-pair agreement as an additional diagnostic in evaluating the quality of the data.
Philippe Amiotte Suchet and Jean-Lue Probst, Centre National de la Recherche Scientifique, Center de Geochimie de la Surface, Strasbourg Cedex, France
CDIAC DB-1012
The net flux of atmospheric-soil CO2 (FCO2) and the bicarbonate flux from rivers to the oceans (FHCO3), both in moles per square kilometer per year (mol km-2 year-1), were estimated with GEM-CO2, a global model for present-day atmospheric-soil CO2 consumption by the chemical erosion of continental rocks. These data are referenced to a 1° by 1° world grid. This database contains 64,800 records and is available as a flat ASCII file and as an exported ARC/INFO Version 7.0 coverage.
GEM-CO2 is based on a set of empirical relationships between the flux of atmospheric-soil CO2 consumed by rock weathering (FCO2) and the drainage (runoff) on the major rock types outcropping on the continents. The model assumes that the consumption of atmospheric CO2 by continental weathering is primarily influenced by drainage, air temperature, and the proportion of carbonate rocks outcropping the continents.
The relationships between FCO2 and drainage were calculated with drainage data and the concentrations of the major dissolved elements for 232 French monolithological drainage basins. For each watershed, the bicarbonate river flux was calculated with drainage and HCO3- concentration measurements. The atmospheric-soil CO2 consumed by weathering was considered equal to the total HCO3- flux for streams draining silicate rocks and equal to half the HCO3- flux for streams draining carbonate rocks. Weathering increases when drainage increases and varies by rock type. Under this assumption, the empirical relationship between FCO2 and drainage was then determined for each rock type as follows and listed according by FCO2 consumption from smallest to largest: (1) plutonic and metamorphic rocks, (2) sands and sandstones, (3) acid volcanic rocks, (4) evaporitic rocks, (5) basalts, (6) shales, and (7) carbonate rocks. The proportion of carbonate materials in rocks is highly variable and difficult to estimate. This model assumes that only carbonate and evaporitic rocks contain any carbonate materials; therefore, the relationship between FCO2 and the drainage intensity for shale rocks may be subject to caution.
The estimates produced from GEM-CO2 have been verified with three large river basins, the Garonne (France) in temperate climate; and the Congo and Amazon basins in tropical equatorial climates. The simulated results were found to be of the same magnitude as estimates obtained from field measurements.
Globally, for each grid cell, a mean lithology was determined with FAO-UNESCO lithological and soil maps. Drainage intensity for each grid cell was estimated from values for continental mean monthly precipitation and evapotranspiration supplied by the National Center for Atmospheric Research in Boulder, Colorado. The results show that the consumption of CO2 is mainly localized in the northern hemisphere (because of its large continental area with a high proportion of carbonate rocks) and in equatorial regions (which are very humid).
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kng 02/15/96