If someone is prepared to believe the current global average temperature is about -28C (top of the Greenland ice sheet), they'll believe anything. (including perhaps "6 impossible things before breakfast"?)
Josh's ridiculous WUWT cartoon has a huge "off the charts cold" swing during the Younger Dryas event representing the
global average temperature. Temperatures reached about -50C
locally at the top of the Greenland icesheet according to Alley's
GISP2 ice-core data. (remember Josh apparently just arbitrarily divided the GISP2 temperatures by 4 in his efforts to try to 'scale' the data (aka completely fudge it and misuse it) to within a ~4C global average temperature change from the end of the Last Glacial Maximum to pre-industrial times.
But, Globally it was only about a
0.6C net cooling swing.
"Plotting Younger Dryas temperature and climate anomalies
against latitude shows that climate anomalies increased in
magnitude toward the poles with opposite signs in the
Northern and Southern Hemispheres (Figure 7) (Shakun and
Carlson, 2010), reflecting the bipolar seesaw response (Blunier
and Brook, 2001). Nevertheless, greater cooling at high northern
latitudes than warming at high southern latitudes results in
a net global cooling of 0.6 C likely caused by more extensive
snow and sea-ice cover increasing Northern Hemisphere
albedo during the Younger Dryas (Shakun and Carlson, 2010)."
Reference:
“The Younger Dryas Climate Event.” In Elias, S.A. (ed.) The Encyclopedia of Quaternary Science vol. 3 (pp. 126-134). Amsterdam : Elsevier.
http://people.oregonstate.edu/~carlsand/carlson_encyclopedia_Quat_2013_YD.pdf