Pears ripen quicker when placed in a paper bag by themselves or with other ripening fruit such as bananas or apples. Cold temperatures prevent pears from ripening, so they shouldn't be placed in the refrigerator until after they have ripened.
Pears release ethylene gas as they ripen. Placing several pears together in a paper bag helps them ripen quicker by keeping the gas contained and in contact with the fruit. As one pear begins to ripen, the gas it gives off speeds up the ripening of the other pears. Bananas, apples and avocados also release ethylene gas as they ripen, and storing them next to the pears on the counter or in a fruit basket can help the pears ripen quicker. Placing a piece of ripe fruit in a paper bag with the pears causes even faster ripening.
Color is not an accurate way to determine ripeness, as most pears do not change color. Determining if a pear is ripe involves pressing its flesh near the stem; If it yields even slightly, it is ripe. Pears can quickly become overripe, so they must be checked daily. Once the pears have ripened, placing them in the refrigerator slows down, but does not stop, the ripening process, and they should be eaten within a couple of days.