For time intervals below 24 hours, the trend displays a stronger persistence than the readings themselves. On the other hand, it is precisely the trend whose course reacts to weather changes of the synoptic scale. As apart from a very few exceptions the seasonal and the component remainder are relatively unaltered, a change in the emissions state must logically be primarily expressed in the trend component – where however times of 24 hours or more are characteristic. To be more succinct, the trend is expressed by two contradictory phenomena: persistence on the one hand and interaction with other atmospheric processes on the other. This is only possible at the level of different time scales.