R help - Jul 2009 - how to calculate growth rate of CO2 (ppm) time series

Dear R Users,
I have CO2 mixing ratio(ppm) time series data during 1991-2000.
I would like to calculate CO2 growth rate /ppm.a-1
(is it derivative dt/dco2 ??)

Kindly can any one advise how to calculate above.

My data file looks like;

time, year, month, day, hour, min, sec, lat, long, height, CO2

1991.476722 1991 6 24 0 5 0 -38.93 145.15 4270 353.680

1991.476741 1991 6 24 0 15 0 -39.20 145.22 4270 353.950

1991.476747 1991 6 24 0 18 0 -39.43 145.28 4270 353.510

-----------------------------------------------

2000.740788 2000 9 28 3 5 0 -38.00 145.00 2280 366.750

2000.740794 2000 9 28 3 8 0 -38.00 145.00 1830 366.550

2000.740803 2000 9 28 3 13 0 -38.00 145.00 1220 370.550
Many great thanks,

Best Regards,
Yogesh

-- 
Yogesh K. Tiwari (Dr.rer.nat),
Scientist,
Indian Institute of Tropical Meteorology,
Homi Bhabha Road,
Pashan,
Pune-411008
INDIA

Phone: 0091-99 2273 9513 (Cell)
        : 0091-20-25904350 (O)
Fax    : 0091-20-258 93 825

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