Any historical examples of destructive climate warming?
To answer the question 


  Are there any known or suspected historical i.e. Holocene climatic warming associated with negative impacts on human populations?


One recent (actual) example that come to mind is the sea level rising. Here we see that since the early satellite measurements in 1993, sea level rise was about 8 cm. On the same page, less reliable gauges indicated a coastal sea level rise of 20 cm between 1870 and the late 1990.

Some Islands are particularly vulnerable to sea level changes, in regard with fresh water supplies, soils and shore degradation following storms and strong high tides, etc. Marshall Island (~2 m), Maldives (~1 m) are examples of emplacements with very low mean ground level. It is really a question of time before these places become unlivable.

While these are small islands, other populous places are quite vulnerable to similar situations such as Bangladesh.