As Fig. 29, but for March. Sulphate forcing is diagnosed explicitly in the model runs, whereas CO2 forcing is scaled from a calibrated diagnostic of forcing at the tropopause due to instantaneous doubling of CO2 computed during a 5 year period from the control run, adjusted to account for a reduction in downward longwave flux from stratospheric cooling. Contour 0.5K, negative values shaded. Observed values are as in Parker et al. Model anomalies are computed in a similar manner to the observed but using all data.
Anomalies are relative to the corresponding monthly average over the period.
Best fit linear regression lines are also shown.