Climate change would strongly affect agriculture, but scientists still don’t know exactly how. Most agricultural impacts studies are based on the results of general circulation models (GCMs). These climate models indicate that rising levels of greenhouse gases are likely to increase the global average surface temperature by 1.5-4.5 C over the next 100 years, raise sea-levels (thus inundating farmland and making coastal groundwater saltier), amplify extreme weather events such as storms and hot spells, shift climate zones poleward, and reduce soil moisture. Impacts studies consider how these general trends would affect agricultural production in specific regions. To date, most studies have assumed that agricultural technology and management will not improve and adapt. New studies are becoming increasingly sophisticated, however, and "adjustments experiments" now incorporate assumptions about the human response to climate change