1. Overview
This file contains preliminary data published in WDCGG Data Summary No.51.

Species: Carbon Dioxide
Period: 1984-01 - 2025-12
Format: netCDF4

Dimensions:
------------
time = 504
year = 42
month = 12
bounds = 2
lat_30 = 6
lat_30_bounds = 6
lat_20 = 9
lat_20_bounds = 9
------------

Variables:
------------
mole_fraction_global (time)
    Global mean dry-air mole fraction
trend_global (time)
    Global trend in dry-air mole fraction
growth_rate_global (time)
    Global growth rate of dry-air mole fraction trend
mole_fraction_30deg (time, lat_30)
    Mean dry-air mole fraction in 30-degree latitude bands
trend_30deg (time, lat_30)
    Trend in dry-air mole fraction in 30-degree latitude bands
growth_rate_30deg (time, lat_30)
    Growth rate of dry-air mole fraction trend in 30-degree latitude bands
annual_observation_site_numbers_30deg (year, lat_30)
    Annual numbers of observation sites used for the global analysis in 30-degree latitude bands.
seasonal_cycle_30deg (month, lat_30)
    Mean seasonal cycle in 30-degree latitude bands (1984-01 to 2025-12)
seasonal_cycle_30deg_std (month, lat_30)
    Interannual standard deviation of seasonal cycle in 30-degree latitude bands
mole_fraction_20deg (time, lat_20)
    Mean dry-air mole fraction in 20-degree latitude bands
trend_20deg (time, lat_20)
    Trend in dry-air mole fraction in 20-degree latitude bands
growth_rate_20deg (time, lat_20)
    Growth rate of dry-air mole fraction trend in 20-degree latitude bands
------------

2. CSV Conversion Example
Data can be converted to CSV using Python3 and the xarray package. For example, 
In [1]: import xarray as xr
In [2]: data = xr.open_dataset('./xxxxx.nc')
In [3]: data['mole_fraction_global'].to_dataframe().reset_index().to_csv('output.csv', index=False)

3. Contact
wdcgg@met.kishou.go.jp

4. netCDF HEADER
netcdf dataset_co2 {
dimensions:
	time = 504 ;
	year = 42 ;
	month = 12 ;
	bounds = 2 ;
	lat_30 = 6 ;
	lat_30_bounds = 6 ;
	lat_20 = 9 ;
	lat_20_bounds = 9 ;
variables:
	int64 time(time) ;
		time:units = "days since 1984-01-01 00:00:00" ;
		time:calendar = "standard" ;
	int year(year) ;
		year:long_name = "Calendar year" ;
	int month(month) ;
		month:long_name = "Calendar month" ;
	int bounds(bounds) ;
		bounds:long_name = "Vertices of cell boundaries" ;
	int lat_30(lat_30) ;
		lat_30:bounds = "lat_30_bounds" ;
		lat_30:units = "degrees_north" ;
		lat_30:long_name = "Latitude band center in 30-degree latitude" ;
	int lat_30_bounds(lat_30, bounds) ;
		lat_30_bounds:long_name = "Latitude band boundaries" ;
		lat_30_bounds:units = "degrees_north" ;
	int lat_20(lat_20) ;
		lat_20:bounds = "lat_20_bounds" ;
		lat_20:units = "degrees_north" ;
		lat_20:long_name = "Latitude band center in 20-degree latitude" ;
	int lat_20_bounds(lat_20, bounds) ;
		lat_20_bounds:long_name = "Latitude band boundaries" ;
		lat_20_bounds:units = "degrees_north" ;
	double mole_fraction_global(time) ;
		mole_fraction_global:_FillValue = 9.96920996838687e+36 ;
		mole_fraction_global:long_name = "Global mean dry-air mole fraction" ;
		mole_fraction_global:units = "ppm" ;
	double trend_global(time) ;
		trend_global:_FillValue = 9.96920996838687e+36 ;
		trend_global:long_name = "Global trend in dry-air mole fraction" ;
		trend_global:units = "ppm" ;
	double growth_rate_global(time) ;
		growth_rate_global:_FillValue = 9.96920996838687e+36 ;
		growth_rate_global:long_name = "Global growth rate of dry-air mole fraction trend" ;
		growth_rate_global:units = "ppm yr-1" ;
		growth_rate_global:comment = "growth_rate(t) = [trend(t+1) - trend(t-1)] * 6. Growth rates are not provided for the first and last 12 months of the record because trend estimates near the endpoints are less reliable." ;
	double mole_fraction_30deg(time, lat_30) ;
		mole_fraction_30deg:_FillValue = 9.96920996838687e+36 ;
		mole_fraction_30deg:long_name = "Mean dry-air mole fraction in 30-degree latitude bands" ;
		mole_fraction_30deg:units = "ppm" ;
	double trend_30deg(time, lat_30) ;
		trend_30deg:_FillValue = 9.96920996838687e+36 ;
		trend_30deg:long_name = "Trend in dry-air mole fraction in 30-degree latitude bands" ;
		trend_30deg:units = "ppm" ;
	double growth_rate_30deg(time, lat_30) ;
		growth_rate_30deg:_FillValue = 9.96920996838687e+36 ;
		growth_rate_30deg:long_name = "Growth rate of dry-air mole fraction trend in 30-degree latitude bands" ;
		growth_rate_30deg:units = "ppm yr-1" ;
		growth_rate_30deg:comment = "growth_rate(t, X) = [trend(t+1, X) - trend(t-1, X)] * 6. Growth rates are not provided for the first and last 12 months of the record because trend estimates near the endpoints are less reliable." ;
	int annual_observation_site_numbers_30deg(year, lat_30) ;
		annual_observation_site_numbers_30deg:_FillValue = -2147483647 ;
		annual_observation_site_numbers_30deg:long_name = "Annual numbers of observation sites used for the global analysis in 30-degree latitude bands." ;
	double seasonal_cycle_30deg(month, lat_30) ;
		seasonal_cycle_30deg:_FillValue = 9.96920996838687e+36 ;
		seasonal_cycle_30deg:long_name = "Mean seasonal cycle in 30-degree latitude bands (1984-01 to 2025-12)" ;
		seasonal_cycle_30deg:units = "ppm" ;
		seasonal_cycle_30deg:comment = "Mean over years of [mole_fraction(t, X) - trend(t, X)] for each calendar month" ;
	double seasonal_cycle_30deg_std(month, lat_30) ;
		seasonal_cycle_30deg_std:_FillValue = 9.96920996838687e+36 ;
		seasonal_cycle_30deg_std:long_name = "Interannual standard deviation of seasonal cycle in 30-degree latitude bands" ;
		seasonal_cycle_30deg_std:units = "ppm" ;
		seasonal_cycle_30deg_std:comment = "Standard deviation over year of [mole_fraction(t, X) - trend(t, X)] for each calendar month" ;
	double mole_fraction_20deg(time, lat_20) ;
		mole_fraction_20deg:_FillValue = 9.96920996838687e+36 ;
		mole_fraction_20deg:long_name = "Mean dry-air mole fraction in 20-degree latitude bands" ;
		mole_fraction_20deg:units = "ppm" ;
	double trend_20deg(time, lat_20) ;
		trend_20deg:_FillValue = 9.96920996838687e+36 ;
		trend_20deg:long_name = "Trend in dry-air mole fraction in 20-degree latitude bands" ;
		trend_20deg:units = "ppm" ;
	double growth_rate_20deg(time, lat_20) ;
		growth_rate_20deg:_FillValue = 9.96920996838687e+36 ;
		growth_rate_20deg:long_name = "Growth rate of dry-air mole fraction trend in 20-degree latitude bands" ;
		growth_rate_20deg:units = "ppm yr-1" ;
		growth_rate_20deg:comment = "growth_rate(t, X) = [trend(t+1, X) - trend(t-1, X)] * 6. Growth rates are not provided for the first and last 12 months of the record because trend estimates near the endpoints are less reliable." ;

// global attributes:
		:title = "WDCGG Data Summary No.51: Preliminary Dataset" ;
		:institution = "WDCGG" ;
		:species = "co2" ;
		:species_long_name = "Carbon Dioxide" ;
		:references = "See Data Summary for detailed methodology" ;
		:creation_date = "2026-10-21 11:46:01 (UTC)" ;
		:creator_script = "create_release_netcdf.py" ;
}