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Global Patterns of Carbon Dioxide Emissions from Soils on a 0.5 Degree Grid Cell Basis (DB-1015)

DOI: 10.3334/CDIAC/lue.db1015

This data has been updated. Please see NDP-081.

Contributed by: James W. Raich 1 and Christopher S. Potter2

1Department of Botany
Iowa State University
Ames, IA 50011 USA
Email: jraich@iastate.edu

2NASA Ames Research Center
MS 242-2
Moffett Field, CA 94035 USA
Email: cpotter@gaia.arc.nasa.gov

Prepared by L.M. Olsen.
Carbon Dioxide Information Analysis Center
Date Published: March, 1996 (Revised for the web: 2002)

The Carbon Dioxide Information Analysis Center is a part of the Environmental Sciences Division of the OAK RIDGE NATIONAL LABORATORY (ORNL) and is located in Oak Ridge, Tennessee 37831-6290. The ORNL is managed by University of Tennessee-Battelle, LLC for the U.S. DEPARTMENT OF ENERGY under contract DE-AC05-00OR22725

Contents

Abbreviations

Abstract

1. Background Information

2. Data Checks Performed by CDIAC

3. References

4. How to Obtain the Data and Documentation

5. Listing of Files Provided

6. Description of the Documentation File

7. Description, Format, and Partial Listings of the Data Files

8. Fortran Codes to Access the Data



Abbreviations

CO2 = Carbon Dioxide CDIAC = Carbon Dioxide Information Analysis Center
FTP = file transfer protocol
QA = quality assurance
GIS = geographic information system
ARC/INFO is a registered trademark of the Environmental Systems Research Institute, Inc., Redlands, CA 92372.

Abstract

Raich, J. W. and C. S. Potter. 1995. Global Patterns of Carbon Dioxide Emissions from Soils. Global Biogeochemical Cycles 9(1)23-36. doi: 10.3334/CDIAC/lue.db1015

We use semi-mechanistic, empirically based statistical models to predict the spatial and temporal patterns of global carbon dioxide emissions from terrestrial soils. Emissions include the respiration of both soil organisms and plant roots. At the global scale, rates of soil CO2 efflux correlate significantly with temperature and precipitation; they do not correlate well with soil carbon pools, soil nitrogen pools, or soil C:N. Wetlands cover about 3% of the land area but diminish predicted CO2 emissions by only about 1%. The estimated annual flux of CO2 from soils to the atmosphere is estimated to be 76.5 Pg C yr-1, 1-9 Pg greater than previous global estimates, and 30-60% greater than terrestrial net primary productivity. Historic land cover changes are estimated to have reduced current annual soil CO2 emissions by 0.2-2.0 Pg C yr-1 in comparison with an undisturbed vegetation cover. Soil CO2 fluxes have a pronounced seasonal pattern in most locations, with maximum emissions coinciding with periods of active plant growth. Our models suggest that soils produce CO2 throughout the year and thereby contribute to the observed wintertime increases in atmospheric CO2 concentrations. Our derivation of statistically based estimates of soil CO2 emissions at a 0.5-degree latitude-by- longitude spatial and monthly temporal resolution represents the best-resolved estimate to date of global CO2 fluxes from soils and should facilitate investigations of net carbon exchanges between the atmosphere and terrestrial biosphere.

(Reproduced with permission of the American Geophysical Union.)

Keywords: Carbon release, climate change, soils, carbon dioxide emissions, global patterns.

DB-1015 includes the following data and documentation files: 1. Background Information

This database contains global, spatially explicit (0.5-degree grid cells) and temporally explicit (monthly and annual) model output of soil CO2 emissions. The calculated emissions include the respiration of both soil organisms and plant roots. Maps representing the soil emissions data are available for download and viewing as *.gif files.

The model (model B) used for these calculations is described in Raich and Potter (1995). The model is based on a stepwise linear multiple regression of 977 individual aggregated records of geographically referenced data on daily and/or monthly rates of CO2 flux rates from intact soils, temperature, precipitation, potential evapotranspiration, vegetation type, soil moisture status, and organic carbon and nitrogen contents of soil. These data points represent grid cells from every continent except Antarctica. Temperature and soil moisture status, as predicted by precipitation, were the only variables significantly correlated with soil CO2 efflux. Temperature and precipitation were, therefore, used as driving variables. The remaining model parameters for the mechanistic aspect of the model are (1) the soil CO2 efflux rate when temperature is zero and moisture not limiting, (2) the temperature coefficient and (3) the half-saturation coefficient of the precipitation function. These were obtained by Raich and Potter (1995) using least squares estimates with both Quasi-Newton and Simplex methods as described in Wilkinson (1990).

To prevent extrapolation of the model beyond the range of observed temperatures,

  1. Soil CO2 fluxes were presumed to be zero at average monthly air temperatures less than -13.3 degrees Celsius
  2. For all temperatures greater than 33.5 degrees Celsius, soil CO2 fluxes were set equal to the rate predicted at 33.5 degrees Celsius.

Raich and Potter (1995) evaluated their model predictions against previously published annual soil respiration rates from specific locations and with published predictions by an annual model (Raich and Schlesinger, 1992) through linear regressions of predicted versus observed (or previously published predicted) soil emissions. Correlation coefficients were close to 0.5, intercepts not significantly different from zero and slopes not significantly different from one, indicating that the reliability of the predictions was not diminished by the monthly timescale and that the model provides quantitatively meaningful estimates of annual soil emissions.

2. Data Checks Performed bY CDIAC

One of the roles of the Carbon Dioxide Information Analysis Center (CDIAC) is quality assurance (QA) of data. The QA process is an important component of the value-added concept of assuring accurate, usable information for researchers, because data received by CDIAC are rarely in condition for immediate distribution, regardless of source. The following summarizes the QA checks performed on the Model B output presented in the data files:

  1. To get correct latitude/longitude locations for soil emissions, we plotted the predicted emissions over maps of vegetation types at the one degree grid cell level by Matthews (1985), and on the half degree grid cell level by Post et. al. (1996), and Olsen et al. (CDIAC, 1985). For the soil emission plots the 0.5 degree latitude band containing the Greenwich meridian and the 0.5 degree longitude band around the equator had to be skipped to achieve proper coastline alignment.
  2. When Model B output per grid cell (g C/m2/yr or /month) was multiplied by grid cell area (m2) (calculated according to the program from the Goddard Institute for Space Studies (see IV)), and these products summed, total global soil emission was found to be 80.4 Pg C/yr, while the published Model B value was 77.1 Pg C/yr (Table 1 & p 27 in Raich and Potter, 1995). Using the landmask information, provided by the authors, reduced the total global soil emission to 77.8 Pg C/yr.
  3. The contributors of the model output (authors of the paper) are in agreement with CDIAC analysts about the necessity of reporting the above mentioned two points.

    Note: 1 Pg C = 1.e15 g C

3. References

Matthews, E. 1985. Atlas of Archived Vegetation, Land-Use and Seasonal Albedo Data Sets. Goddard Space Flight Center Institute for Space Studies. N.Y, N.Y.

Olson, J. S., J. A. Watts and L. J. Allison. 1985. Major World Ecosystem Complexes Ranked by Carbon in Live Vegetation: A Database. NDP017. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory. Oak Ridge, Tennessee.

Post, W. M., A. W. King and S. D. Wullschleger, 1996. Soil Organic Matter Models and Global Estimates of Soil Organic Carbon. Nato ASI Series Vol 138: 201-222.

Raich, J. W. and C. S. Potter. 1995. Global Patterns of Carbon Dioxide Emissions from Soils. Global Biogeochemical Cycles 9(1)23-36.

Raich, J. W. and W. H. Schlesinger. 1992. The Global Carbon Dioxide Flux in Soil Respiration and its Relationship to Vegetation and Climate. Tellus. Ser. B 44:81-99.

Wilkinson, L. 1990. SYSTAT: The System for Statistics. version 5.0, SYSTAT: Evanston, Ill.


4. How to Obtain the Data and Documentation

These data may be used with a vector or raster geographic information system (GIS) or non-GIS database systems. This database (DB-1015) is available free of charge from CDIAC. The files are available, via the Internet, from CDIAC's World-Wide-Web site (http://cdiac.ornl.gov), or from CDIAC's anonymous file transfer protocol (FTP) area (cdiac.ornl.gov) as follows:

  1. FTP to cdiac.ornl.gov (128.219.24.36).
  2. Enter "ftp" as the user id.
  3. Enter your electronic mail address as the password (e.g., fred@zulu.org).
  4. Change to the directory "pub/db1015" (i.e., use the command "cd pub/db1015").
  5. Set ftp to get ASCII files by using the ftp "ascii" command.
  6. Retrieve the ASCII database documentation file by using the ftp "get db1015.txt" command.
  7. Retrieve the ASCII data files by using the ftp "mget *.dat" command.
  8. Set ftp to get grpahics files by using the ftp "binary" command.
  9. Retrieve the graphics files (maps) files by using the ftp "mget *.gif" command.
  10. Exit the system by using the ftp "quit" command.
For non-Internet data acquisitions (e.g., floppy diskette or CD-ROM) or for additional information, contact:

Carbon Dioxide Information Analysis Center
Oak Ridge National Laboratory
P.O. Box 2008
Oak Ridge, Tennessee 37831-6290, U.S.A.

Telephone: 1-865-574-3645
Telefax: 1-865-574-2232
E-mail: cdiac@ornl.gov


5. Listing of Files Provided
This database consists of fourteen data files (*.dat), one text file (*.txt), and thirteen graphics files (*.gif).
Data files include:
  1. rp-modelb_ann.dat
  2. rp-modelb_jan.dat
  3. rp-modelb_feb.dat
  4. rp-modelb_mar.dat
  5. rp-modelb_apr.dat
  6. rp-modelb_may.dat
  7. rp-modelb_jun.dat
  8. rp-modelb_jul.dat
  9. rp-modelb_aug.dat
  10. rp-modelb_sep.dat
  11. rp-modelb_oct.dat
  12. rp-modelb_nov.dat
  13. rp-modelb_dec.dat
  14. landmask.dat
Text files include:
  1. db1015.txt
Graphics files include:
  1. ann.gif
  2. jan.gif
  3. feb.gif
  4. mar.gif
  5. apr.gif
  6. may.gif
  7. jun.gif
  8. jul.gif
  9. aug.gif
  10. sep.gif
  11. oct.gif
  12. nov.gif
  13. dec.gif

6. Description of the Documentation File

The db1015.txt (File 1) file is an ASCII text equivalent of this document.


7. Description, Format, and Partial Listings of the Data Files

Fourteen flat ASCII data files are provided with this data package.

The 'rp-modelb.*' files (13 files):

Thirteen global 0.5 degree lat/lon output files were produced by Model B as described in Raich and Potter (1995):

  • Twelve files representing the monthly CO2 flux from soil.
  • One file representing the annual CO2 flux from soil.

    Predicted CO2 flux from soil is expressed in units (integer format) of grams carbon (*100) per square meter of soil area.

    Note: (*100) conserves two decimal places for unit grams.


The 'landmask' file:

A 0.5 degree lat/lon file with grid cell area information on land/water designations. This file was used by the authors in the global summation of soil emissions.


File formats:

The data files are in ASCII GRID (text) format for ARC/INFO. Each file contains a single ASCII array with integer values. Coordinates listed below are in decimal degrees.

The ASCII file consists of header information containing a set of keywords, followed by cell values in row-major order. The file format is:

NCOLS xxx
NROWS xxx
XLLCORNER xxx
YLLCORNER xxx
CELLSIZE xxx
{NODATA_VALUE xxx}
row 1
row 2
.
.
.
row n

where xxx is a number, and the keyword NODATA_VALUE is optional and defaults to -9999. Row 1 of the data is at the top of the grid, row 2 is just under row 1 and so on. The end of each row of data from the grid is terminated with a carriage return in the file.

These six lines (header) appear in all of the data files, e.g.:
ncols 720
nrows 360
xllcorner -180
yllcorner -90
cellsize 0.5
NODATA_value -9999

To import this file into ArcInfo use the following command at an ARC prompt:
ASCIIGRID {INT | FLOAT}
Arguments
- the ASCII file to be converted.
- the name of the grid to be created.
{INT | FLOAT} - the data type of the output grid.
INT - an integer grid will be created.
FLOAT - a floating-point grid will be created.


8. FORTRAN CODES TO ACCESS THE DATA

A FORTRAN program designed to read and print the contents of these ASCII data is also included below.

C FORTRAN 77 CODE TO (1) READ GRIDDED (0.5 degrees) GLOBAL SOIL EMISSIONS AND
C LAND-MASK INFORMATION AND (2) LABEL GRID-CELLS WITH  LATITUDE/LONGITUDE
C LOCATIONS
C CDIAC - AB - 3/96
C====
      REAL LAT,LONG,LAND
C
C ARRAY SF CONTAINS THE RAICH AND POTTER MODELED ANNUAL SOIL
C CO2 EMISSIONS.
C ARRAY TSF CONTAINS THE RAICH AND POTTER MODELED MONTHLY SOIL
C CO2 EMISSIONS.
C ARRAY SSF CONTAINS THE ANNUAL SUM OF THE RAICH AND POTTER
C MODELED MONTHLY SOIL CO2 EMISSIONS.
C
      DIMENSION LAND(360,720),SF(360,720)
      DIMENSION SSF(360,720),TSF(12,360,720)
C====
C CALCULATE GRID CELL AREAS WITH THE PROGRAM FROM THE GODDARD INSTITUTE
C FOR SPACE STUDIES
      PARAMETER (IM=720,JM=360)
      REAL DXYP(JM),DXV(JM),COSP(JM)
      TWOPI=6.283185
      RADIUS=6375000.
      DLON=TWOPI/IM
      DLAT=.5*TWOPI/(JM-1)
      FJEQ=.5*(JM+1)
      COSP(1)=0.
      COSP(JM)=0.
      DO 10 J=2,JM-1
   10 COSP(J)=COS(DLAT*(J-FJEQ))
      DO 20 J=2,JM
   20 DXV(J)=.5*RADIUS*DLON*(COSP(J-1)+COSP(J))
      DXYP(1)=.25*DXV(2)*RADIUS*DLAT
      DXYP(JM)=.25*DXV(JM)*RADIUS*DLAT
      DO 30 I=1,IM
      DO 30 J=2,JM-1
        DXYP(J)=.5*(DXV(J)+DXV(J+1))*RADIUS*DLAT
30    CONTINUE
C====
C FOR LAND/WATER DISTINCTION:
      OPEN(8,FILE='landmask.dat',STATUS='OLD')
C FOR YEARLY INPUT:
      OPEN(10,FILE='rp-modelb_ann.dat',STATUS='OLD')
C FOR MONTHLY INPUT:
      OPEN(12,FILE='rp-modelb_jan.dat',STATUS='OLD')
      OPEN(14,FILE='rp-modelb_feb.dat',STATUS='OLD')
      OPEN(16,FILE='rp-modelb_mar.dat',STATUS='OLD')
      OPEN(18,FILE='rp-modelb_apr.dat',STATUS='OLD')
      OPEN(20,FILE='rp-modelb_may.dat',STATUS='OLD')
      OPEN(22,FILE='rp-modelb_jun.dat',STATUS='OLD')
      OPEN(24,FILE='rp-modelb_jul.dat',STATUS='OLD')
      OPEN(26,FILE='rp-modelb_aug.dat',STATUS='OLD')
      OPEN(28,FILE='rp-modelb_sep.dat',STATUS='OLD')
      OPEN(30,FILE='rp-modelb_oct.dat',STATUS='OLD')
      OPEN(32,FILE='rp-modelb_nov.dat',STATUS='OLD')
      OPEN(34,FILE='rp-modelb_dec.dat',STATUS='OLD')
C FOR OUTPUT:
      OPEN(36,FILE='RP_ANN.SE',STATUS='UNKNOWN')
      OPEN(38,FILE='RP_ANN.ALL',STATUS='UNKNOWN')
C====
C INITIALIZE ARRAYS:
      DO 40 I=1,360
       DO 40 JJ=1,720
        LAND(I,JJ)=0.D0
        SF(I,JJ)=0.D0
        SSF(I,JJ)=0.D0
        DO 40 II=1,12
         TSF(II,I,JJ)=0.D0
40    CONTINUE
C====
C FILL LAND/WATER ARRAY OF 0.5*0.5 DEGREE GRID-CELLS BY READING VALUES
C READ FIRST 6 LINES
      DO 50 I=1,6
50     READ(8,*)
      DO 60 I=1,360
C VALUES ARE ZEROS OR ONES
60     READ(8,*)(LAND(I,JJ),JJ=1,720)
      CLOSE(UNIT=8)
C====
C FILL EMISSION ARRAY OF 0.5*0.5 DEGREE GRIDCELLS/MONTH BY READING VALUES
C READ MONTHLY FILES
      DO 70 II=1,12
       IF(II.EQ.1)INFILE=12
       IF(II.EQ.2)INFILE=14
       IF(II.EQ.3)INFILE=16
       IF(II.EQ.4)INFILE=18
       IF(II.EQ.5)INFILE=20
       IF(II.EQ.6)INFILE=22
       IF(II.EQ.7)INFILE=24
       IF(II.EQ.8)INFILE=26
       IF(II.EQ.9)INFILE=28
       IF(II.EQ.10)INFILE=30
       IF(II.EQ.11)INFILE=32
       IF(II.EQ.12)INFILE=34
C READ FIRST 6 LINES
      DO 65 I=1,6
65     READ(INFILE,*)
       DO 70 I=1,360
C VALUES ARE IN UNITS OF '100 * G C/M2' == 100 TIMES GRAMS C
        READ(INFILE,*)(TSF(II,I,JJ),JJ=1,720)
        DO 70 JJ=1,720
C CHECK WITH LAND/WATER VALUES IF EMISSION VALUE SHOULD BE KEPT
         IF(LAND(I,JJ).LE.0.D0) TSF(II,I,JJ)=0.D0
C SUM MONTHLY VALUES TO YEARLY VALUES
         SSF(I,JJ)=SSF(I,JJ)+TSF(II,I,JJ)
70    CONTINUE
      CLOSE(UNIT=12)
      CLOSE(UNIT=14)
      CLOSE(UNIT=16)
      CLOSE(UNIT=18)
      CLOSE(UNIT=20)
      CLOSE(UNIT=22)
      CLOSE(UNIT=24)
      CLOSE(UNIT=26)
      CLOSE(UNIT=28)
      CLOSE(UNIT=30)
      CLOSE(UNIT=32)
      CLOSE(UNIT=34)
C====
C READ YEARLY VALUES
C READ FIRST 6 LINES
      DO 75 I=1,6
75     READ(10,*)
      LONG=-179.75D0
      LAT=89.75D0
      II=0
      SUMA=0.D0
      SUMM=0.D0
      DO 90 I=1,359
       II=II+1
C VALUES ARE IN UNITS OF '100 * G C/M2' == 100 TIMES GRAMS C
       READ(10,*)(SF(I,JJ),JJ=1,720)
C SKIP AROUND THE EQUATOR
       IF(LAT.EQ.0.25D0) THEN
         LAT=-0.25D0
C LINE UP CALCULATED CELL AREA (DXYP) WITH LATITUDE
         II=II+1
       ENDIF
       DO 80 JJ=1,719
C CHECK WITH LAND/WATER VALUES IF EMISSION VALUE SHOULD BE KEPT
        IF(LAND(I,JJ).LE.0.D0) SF(I,JJ)=0.D0
C SUM TO GLOBAL EMISSIONS:
        SUMA=SUMA+SF(I,JJ)*DXYP(II)
        SUMM=SUMM+SSF(I,JJ)*DXYP(II)
C WRITE OUT > RP_ANN.SE:
        IF(SF(I,JJ).GT.0.D0) WRITE(36,'(7(2X,G12.6))')
     & LAT,LONG,SF(I,JJ),SSF(I,JJ),LAND(I,JJ),DXYP(II)
C WRITE OUT ALL:
         WRITE(38,'(7(2X,G12.6))') LAT,LONG,SF(I,JJ)
        LONG=LONG+0.5D0
        TLONG=TLONG+0.5D0
C SKIP AROUND THE GREENWICH TIMELINE
        IF(LONG.EQ.-0.25D0) THEN
          LONG=0.25D0
        ENDIF
80     CONTINUE
       LAT=LAT-0.5D0
       LONG=-179.75D0
90    CONTINUE
      CLOSE(UNIT=10)
      CLOSE(UNIT=36)
c WRITE OUT SUMS AS OVERALL CHECK (executed on a DEC-ALPHA)
      WRITE (6,*) SUMA,SUMM
C SUMA=  7.7761701E+18  SUMM=  7.7761701E+18 >> 77.8 P gC/yr
      STOP
      END