i think i foudn somthing that basically says only in the general vacinity of the fire and only minimally.
"The heat added to the atmosphere by forest fires dissipates quickly and has a primarily local effect on air temperature. Similarly, the waste heat given off by all of the world’s power plants, automobiles, and other equipment has only a small effect on global temperature."
i also have heard the theory of super volcanos being the cause of the mongols moving into eurrope do to massive climate change caused by the eurption. all over the place. (lots and lots of smoke)