Global Monitoring Division (original) (raw)

The graph shows recent monthly mean carbon dioxide measured at Mauna Loa Observatory, Hawaii. The last four complete years of the Mauna Loa CO2 record plus the current yearare shown. Data are reported as a dry mole fraction defined as the number of molecules of carbon dioxide divided by the number of molecules of dry air multiplied by one million (ppm). Click for a graph of the full Mauna Loa record. The last year ofdata is still preliminary, pending recalibrations of reference gases and otherquality control checks. The dashed red line with diamond symbols representsthe monthly mean values, centered on the middle of each month. The black linewith the square symbols represents the same, after correction for the averageseasonal cycle. The latter is determined as a moving average of ten adjacentseasonal cycles centered on the month to be corrected, except for the firstand last five years of the record, where the seasonal cycle has been averagedover the first and last ten years, respectively. The Mauna Loa data are beingobtained at an altitude of 3400 m in the northern subtropics, and may not bethe same as the globally averaged CO2 concentration at the surface.

The table shows annual mean carbon dioxide growth rates for Mauna Loa. The annual mean rate of growth of CO2 in a given year is the difference inconcentration between the end of December and the start of January of thatyear. If used as an average for the globe, it would represent the sum of allCO2 added to, and removed from, the atmosphere during the year by humanactivities and by natural processes. There is a small amount ofmonth-to-month variability in the CO2 concentration that may be caused byanomalies of the winds or weather systems arriving at Mauna Loa. Thisvariability would not be representative of the underlying trend for thenorthern hemisphere which Mauna Loa is intended to represent. Therefore, wefinalize our estimate for the annual mean growth rate of the previous year inMarch, by using the average of the most recent November-February months,corrected for the average seasonal cycle, as the trend value for January 1.Our estimate for the annual mean growth rate (based on the Mauna Loa data) isobtained by subtracting the same four-month average centered on the previousJanuary 1. Preliminary values for the previous year are calculated in Januaryand in February. The values in this table are subject to change depending onquality control checks of the measured data, but any revisions are expected tobe small. The estimated annual growth rates for Mauna Loa are close, but notidentical, to the global growth rates. The standard deviation of thedifferences is 0.26 ppm.

Click here for the Mauna Loa CO2 monthly mean data.

Contact: Pieter Tans, ESRL/GMD, ph. 303 497 6678, Pieter.Tans@noaa.gov

References:

C.D. Keeling, R.B. Bacastow, A.E. Bainbridge, C.A. Ekdahl, P.R. Guenther, and L.S. Waterman, Atmospheric carbon dioxide variations at Mauna Loa Observatory, Hawaii, Tellus, vol. 28, 538-551, 1976.

K.W. Thoning, P.P. Tans, and W.D. Komhyr, Atmospheric carbon dioxide at Mauna Loa Observatory 2. Analysis of the NOAA GMCC data, 1974-1985, J. Geophys. Research, vol. 94, 8549-8565, 1989.

The graph shows recent monthly mean carbon dioxide globally averaged over marine surface sites. The Global Monitoring Division of NOAA/Earth System Research Laboratory hasmeasured carbon dioxide and other greenhouse gases for several decades at aglobally distributed network of air sampling sites (Conway, 1994). A globalaverage is constructed by first fitting a smoothed curve as a function of timeto each site, and then the smoothed value for each site is plotted as afunction of latitude for 48 equal time steps per year. A global average iscalculated from the latitude plot at each time step (Masarie, 1995). Thelast four complete years plus the current year are shown here. The last yearof data is still preliminary, pending recalibrations of reference gases andother quality control checks. Data are reported as a dry mole fraction defined as the number ofmolecules of carbon dioxide divided by the number of molecules of dry airmultiplied by one million (ppm). The dashed redline with diamond symbolsrepresents the monthly mean values, centered on the middle of each month. Theblack line with the square symbols represents the same, after correction forthe average seasonal cycle. The latter is determined as a moving average often adjacent seasonal cycles centered on the month to be corrected, except forthe first and last five years of the record, where the seasonal cycle has beenaveraged over the first and last ten years, respectively. Click for acomparison with recent trends in carbon dioxide at Mauna Loa, Hawaii, which has the longest continuous record of direct atmospheric CO2 measurements.

The table shows annual mean carbon dioxide growth rates based on globally averaged marine surface data. The annual mean rate of growth of CO2 in a given year is the difference inconcentration between the end of December and the start of January of thatyear. It represents the sum of all CO2 added to, and removed from, theatmosphere during the year by human activities and by natural processes. Theannual mean growth during the previous year is determined by taking theaverage of the most recent December and January months, corrected for theaverage seasonal cycle, as the trend value for January 1, and then subtractingthe same December-January average measured one year earlier. Our first estimate for the annual growth rate of the previous year is producedin January of the following year, using data through November of the previousyear. That estimate will then be updated in February using data thoughDecember, and again in March using data through January.We finalize ourestimate for the growth rate of the previous year in the fall of the followingyear because a few of the air samples on which the global estimate is basedare received late in the following year. The values in this table are subjectto change depending on quality control checks of the measured data, but anyrevisions are expected to be small. The estimates of the global mean CO2concentration, and thus the annual growth rate, are updated every month as newdata come in. The statistics are as follows. If we estimate during a givenmonth ("m") the global average CO2 during the previous month ("m-1"), the result differs from theestimate made (up to almost a year later) when all the data are in, with astandard deviation of 0.57 ppm. For month m-2, the standard deviation is 0.17ppm, and for month m-3 it is 0.10 ppm. We decided to provide the global meanestimateswith a lag of two months. Thus, a December average is first calculatedduring the following February.

Click here for the globally averaged marine surface data.

Contact: Thomas Conway, ESRL/GMD, ph. 303 497 6681, Thomas.J.Conway@noaa.gov or Pieter Tans, ESRL/GMD, ph. 303 497 6678, Pieter.Tans@noaa.gov

References:

T.J. Conway, P.P. Tans, L.S. Waterman, K.W. Thoning, D.R. Kitzis, K.A. Masarie, and N. Zhang, Evidence of interannual variability of the carbon cycle from the NOAA/CMDL global air sampling network, J. Geophys. Research, vol. 99, 22831-22855, 1994.

K.A. Masarie, P.P. Tans, Extension and integration of atmospheric carbon dioxide data into a globally consistent measurement record, J. Geopys. Research, vol. 100, 11593-11610, 1995.