[CyLith]

As far as CO2 alone is concerned, that is true. The issue is that if you burn a fire cleanly, you (ideally) produce only CO2. If you burn the fire poorly, you produce less CO2 per se, and a _lot_ more particulates, which is bad for air quality. On burn days, the sky is noticeably smoggier all throughout the mountains, and the sunsets are tinted red. I imagine this would have the effect of trapping in daytime heat similarly to how cloudy nights after sunny days are warmer. And since pile burning generally happens during the day, we get an amplified greenhouse effect up here.

[plasticchris]

Smoke particles reduce overall solar radiation absorbed by the earth-atmosphere at local and/or regional scales during individual fire events or burning seasons.

Source: https://doi.org/10.1016/j.foreco.2013.02.020