Take a look at Hansen 1993, scaling from radiation changes in last glacial epoch (plain
orbital mechanics affecting irradiation), 3 ± 1 °C, Chylek 2007, differences
between the Holocene and the last glacial maximum, 1.3 °C to 2.3 °C, and Bender et al 2010, looking at the response from Mount Pinatubo and the volcanic aerosols, with current temperature ranges, 1.7 to 4.1 °C.