The end of the first half of the Holocene — between about 5 and 4 ka — was punctuated by
rapid events at various latitudes, such as an abrupt increase in NH sea ice cover (Jennings et al., 2001); a decrease in Greenland deuterium excess, reflecting a change in the
hydrological cycle (Masson - Delmotte et al., 2005b); abrupt cooling events in European climate (Seppa and Birks, 2001; Lauritzen, 2003); widespread North American drought for centuries (Booth et al., 2005); and changes in South American climate (Marchant and Hooghiemstra, 2004).
In any event those changes in the temperature of the Earth as a whole are tiny as a result of the
rapid modulating effect of changes in the speed of the
hydrological cycle and the speed of the flow of radiated energy to space that always seeks to match the energy value of the whole spectrum of energy coming in from the sun.