Figure 11: (a) Change in
CH4 abundance (mole fraction, in ppb = 10-9) determined
from ice cores, firn, and whole air samples plotted for the last 1000 years. Radiative
forcing, approximated by a linear scale since the pre-industrial era, is plotted
on the right axis.
(b) Globally averaged CH4 (monthly varying) and deseasonalised
CH4 (smooth line) abundance plotted for 1983 to 1999.
(c) Instantaneous annual growth rate (ppb/yr) in global atmospheric CH4
abundance from 1983 through 1999 calculated as the derivative of the deseasonalised
trend curve above. Uncertainties (dotted lines) are ±1 standard deviation.
[Based on Figure 4.1]