If your Altimeter profile is on for an extended period of time with the device in a fixed location while the local weather changes, the device will give incorrect altitude readings.
If your Altimeter profile is on and the weather changes frequently while you climb in altitude or go down in altitude, the device will give you incorrect readings.
If the Barometer profile is on for an extended period of time as you climb in altitude or go down in altitude, the device assumes that you are standing still and interprets your changes in altitude as changes in sea level air pressure. It will therefore give you incorrect sea level air pressure readings.
You’re on the second day of your two-day hike. You realize that you forgot to switch from the Barometer profile to the Altimeter profile when you started moving in the morning.You know that the current altitude readings given by your Suunto Ambit2 are wrong. So, you hike to the nearest location shown on your topographic map for which an altitude reference value is provided. You correct your Suunto Ambit2 altitude reference value accordingly and switch from Barometer to Altimeter profile. Your altitude readings are correct again.