Not seeing the thermodynamic models, it is hard to speculate. However, after talking with some of my colleagues yesterday, the jury is still out with me on this one. If there was this world wide thermal event, there should be evidence in the KT layer suggesting such. Is the carbon ratio in the KT layer synonymous with this type of thermal event? I just don't know. However, there is at least some recent data (albeit scaled down by a very large factor) from the Tunguska event of 1908. The best evidence to date is that a meteor exploded during entry into the Earth’s atmosphere. Trees were flattened as far away as 30 kilometers due to this explosion prior to surface impact. And interesting side note: There is an increase of Iridium in the local area, not unlike the Iridium found in the KT layer.
Why did the meteor “explode” prior to impact? It has been proposed that the aerodynamic pressure build up of the atmosphere was greater that the ability of the meteor to remain in one piece. This caused it to explode roughly 10 kilometers above the Earth’s surface with an estimated energy release similar to a 15 Megaton thermonuclear device. This in effect turned the kinetic energy into heat energy. The forest directly under this fireball was immediately ignited.
The 64-dollar question is would it be possible for a meteor with the mass required for the KT event also create enough of a pressure wave to have a similar breakup? Since there is evidence of a crater (Tunguska has none), this suggests the meteor did not succumb to a total atmospheric breakup (kinetic energy to heat energy). With this in mind, would there be enough ejecta during the reentry releasing kinetic energy to heat coupled with the actual impact to create this worldwide heat pulse?
There was a recent Scientific American article about the near global scale fires started by the ejecta.