TABLE 2-1 Well-Mixed Greenhouse Gases

 

CO2

CH4

N2O

CFC-11

HFC-23

CF4

Preindustrial concentration

~280 ppm

~700 ppb

~270 ppb

0

0

40 ppt

Concentration in 1998

365 ppm

1745 ppb

314 ppb

268 ppt

14 ppt

80 ppt

Rate of concentration changea

1.5 ppm/yrb

7.0 ppb/yrb

0.8 ppb/yr

−1.4 ppt/yr

0.55 ppt/yr

1 ppt/yr

Atmospheric lifetime

5 to 200 yrc

12 yrd

114 yrd

45 yr

260 yr

>50,000 yr

NOTE: CF4 = perfluoromethane; CFC-11 = chlorofluorocarbon-11; HFC-23 = hydrofluorocarbon-23; ppm = parts per million; ppb = parts per billion; ppt = parts per trillion.

a Rate is calculated over the period 1990 to 1999.

b Rate fluctuated between 0.9 and 2.8 ppm yr-1 for CO2 and between 0 and 13 ppb yr-1 for CH4 over the period 1990 to 1999.

c No single lifetime can be defined for CO2 because of coupling with surface reservoirs.

d This lifetime has been defined as an “adjustment time” that takes into account the indirect effect of the gas on its own residence time.

SOURCE: IPCC (2001).



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