Some regions and seasons will become wetter, others drier. Summer droughts are likely to intensify in the interiors of continents. Half the world's mountain glaciers could melt and Arctic ice would be reduced in both extent and thickness. Freshwater systems will experience changes in temperature, flows and levels, affecting biodiversity, water supplies and probably quality. Human conflict over access to water resources may increase.
Agricultural productivity is likely to vary across regions.
Although global productivity may stay about the same, there may be increased risk of famine in arid and semi-arid regions. Marine fisheries are likely to be affected in ways we cannot predict in any detail. Cold water species such as cod and haddock are likely to be reduced, but will probably be replaced by warmer water species such as mullets, soles and breams. Mass movements of people away from flooded or arid regions could cause conflicts and health problems. Human and animal diseases, such as malaria, and crop pests like Colorado beetle may spread to new areas.