Climatic scenarios The scenarios used in the estimates of global warming effects

Climatic scenarios The scenarios used in the estimates of global warming effects on agriculture and forestry were based on both General Circulation Model (GCM) simulations at 2 x C0 2 climate and palaeoclimatic reconstructions. The GC M scenarios are described in detail in Working Group I Report. The analog scenarios used in Soviet studies at mid-latitude Northern Hemisphere agriculture impacts are based on climate reconstructions of three past warm epochs as discussed in Chapter 1. Where reference is made to an equivalent doubling of atmospheric C0 2 , this is taken to be 460 ppm in about the year 2030 (which is the current best estimate, Working Group I). This represents a ca 60% increase over pre-industrial levels because C0 2 comprises about 60% of estimated greenhouse gas