**********************************************************************
*** Atmospheric CO concentrations (ppbv)  derived from flask       ***
*** samples collected at Estevan Point, Canada                     ***
*** Source: L.P. Steele                                            ***
***              P.B. Krummel                                      ***  
***              R.L. Langenfelds                                  ***
***              Commonwealth Scientific,                          ***
***              and Industrial Research Organisation,             ***
***              Aspendale, Victoria,                              *** 
***              Australia  3195                                   ***                   
***                                                                ***   
*** February 2003                                                  ***
***                                                                ***
**********************************************************************

Year	Jan.	Feb.	Mar.	Apr.	May	Jun.	Jul.	Aug.	Sep.	Oct.	Nov.	Dec.	Ann. Ave.

1993							85.68	95.47	106.57	114.78	125.73	139.98	
1994	151.04	161.88	172.51	167.1	146.81	114.68	94.79	107.62	124.52	125.79	115.65	108.99	132.62
1995	127.54	157.64	177.3	171.18	139.05	109.49	92.72	90.08	95.57	104.8	118.96	129.17	126.13
1996	136	145.89	149.16	142.57	134.88	114.11	98.03	103.79	105.46	105.65	117.8	132.02	123.78
1997	142.38	150.66	153.98	155.05	141.31	116.47	101.56	88.27	87.36	102.07	120.23	133.78	124.43
1998	145.02	159.98	172.4	173.05	151.78	121.62	108.03	125.7	151.19	154.64	152.15	154.72	147.52
1999	161.09	165.28	162.11	154.7	138.19	109.59	91.35	89.31	90.4	103.32	122.16	124.47	126.00
2000	123.63	136.13	148.22	146.83	129.47	102.44	83.91	78.84	83.32	102.83	119.85	125.07	115.05
2001	134.73	145.11	147.58	143.19	129.48	106.8	84.2	77.47	88.6	103.49	113.19	119.64	116.12


Monthly values, expressed in parts per billion by volume (ppbv), are linked to the gravimetrically derived 
scale of NOAA/CMDL using a single high-pressure cylinder standard with a CO mole fraction of 196 ppbv.  
Stability of the CSIRO scale and variations in instrument response are monitored with about 20 high 
pressure cylinder standards, with lifetimes of 4 to 10 or more years, spanning a CO range of 20 to 
400 ppbv.  Monthly values are calculated as the mean of the daily values from a smooth curve fit to 
the data using curve-fitting routines described by Thoning et al. 1989.  Annual values are the arithmetic 
means of the 12 monthly values.