Ethylene gas is the ripening agent that many fruits and veggies make themselves.  This gas makes them get ripe and then overripe.  If you put fruits and some vegetables in the fridge it can slow down the effects but it does not stop the gas from continuing to produce. 

The more the fruit ripens the more gas it makes. 

Farms pick fruits early to avoid them being on the vine where ethylene gas build up more sugars and acids to ripen quicker.  However, this is also how many fruits and veggies get their flavor so if picked too early did not get a chance to get all the ethylene to make them tasty.