Temperature Oscillations and Battery Life

That temp is from internal barometric sensor for temperature compenstaion of pressure sensor for accurate measurement of altitude. For measuring ambient temp is Garmin Tempe sensor.

It could be like that, but in previous versions this continuous variation down and up did not occur; and battery life has been drastically reduced.
The Manual states this: "Temperature Readings
The device may display temperature readings higher than the actual air temperature if exposed to
direct sunlight, held in hand or charged with an external battery pack. Furthermore, if the changes of
temperature are considerable, the device will take some time to reflect them."
And in the data fields, the following:
"Temperature Air temperature. Your body temperature affects the temperature of the
sensor.
Minimum temperature in 24
hours
The minimum temperature recorded in the last 24 hours with a temperature sensor
compatible temperature.
Maximum temperature in 24
hours
The maximum temperature recorded in the last 24 hours with a temperature sensor
compatible temperature."

For the Temperature field it does not indicate that a compatible external sensor is necessary

And as a reflection: what is the point of presenting this data in a field if it is something internal to the device and leads to user confusion.

@Bartek has described it correctly! The temperature display on the Edge is merely a by-product of the barometer chipset and delivers no meaningful values.

pedrosanch said:

And as a reflection: what is the point of presenting this data in a field if it is something internal to the device and leads to user confusion.

You have to ask Garmin!

Battery: turn off backlight and see what happens with remaining battery life!