What you've heard about is probably the "little ice age". Their is no agreed upon dates for start and stop but it's generally thought to have started around 1300-1500 and ended in the 18th or 19th century. It saw an increase in things like pack ice and a drop in average temperatures in Europe. Theirs a number of theories about what caused it including solar activity (solar flares), changes in ocean currents, human activity and volcanic activity. Probably a combination of many things.