Climate change by 2060 was computed as the difference (air temperature) or ratio (
precipitation and solar radiation) of monthly mean climate between the GCM (unforced) control and 2xCO2 simulations at GCM grid boxes
coinciding with the crop modelling sites (Figure 13.1 b).
Rather, the observed doubling of the occurrence of 1 - SD drought years has
coincided with a doubling of the frequency
with which a negative
precipitation year produces a 1 - SD drought,
with 55 % of negative
precipitation years in 1995 — 2014 co-occurring
with a — 1.0 SD PMDI anomaly, compared
with 27 % in 1896 — 1994 (Fig. 1 A and B).