The original calc uses an incorrect method that was actually debunked in the Harry Potter revisions (here).
Instead we should do a simple temperature changing calc.
Assuming 1200 degrees Celsius, 1.103 bar pressure and 287.05 J/kg-k specific gas constant, density of air at that temperature is 0.2608380778284 kg/m^3.
Volume was calculated 461 356 818 000 m^3 in the former calc.
461356818000*0.2608380778284 = 1.2033942560014697e11 kg
Assuming the original temperature is 16 degrees Celsius, change of temperature is 1184.
E=mcdeltat
1.2033942560014697e11*919*1184 = 1.3094084763781752e17 Joules, City level