Increased incidences of respiratory infections, malaria, and other diseases.
Changing growing seasons lead to bad harvests and widespread food shortages
Increased droughts cause regional water shortages
Sea levels rise more than expected (>1m), displacing millions of people
More frequent flooding leads to coastal destruction in developing nations, increasing the spread of diseases locally.
Due to the reduction of the high atmosphere braking effect on low orbital bodies, the use of low orbit for satellites due to the general general increase in the time for the natural degradation leading to burn out will create a higher right to space missions.
Release of methane clathrate from ocean bottom releases enormous amounts of methane to atmosphere, leading to runaway greenhouse effect
Thawing tundra releases methane trapped in permanently frozen organic matter, leading to enhanced warming
Increases in precipitation over Greenland, combined with other warming effects there, leads to pools of liquid water that melt into the ice sheet as moulins. Liquid water gets deep into the ice sheet, lubricating and destabilizing it, and huge discharges of ice spill into the north Atlantic.
Huge discharges of ice spill into the north Atlantic, chilling and freshening the surface water, stabilizing the upper ocean. This shuts down deep convection, and we experience a rapid climate change (not quite so fast as The Day After Tomorrow).