This is generally regarded as the period 1300 – 1850AD. Several forcings appeared to have contributed, including the 1257 eruption of Samalas volcano. The AMOC (Atlantic oceanic current) also seems to have slowed due to a sudden influx of freshwater following the ‘Medieval Warm Period’ 950-1250AD. A part of this current, called the Gulf Stream, is crucial for keeping Europe warm. Slight changes have global impacts, which is why it’s a concern today, as the current is slowing down.
A very small contribution to the cooling may have been from a slight decline solar radiation. However, the Maunder Minimum didn’t begin until 1645AD (Fig. 1) three hundred years after cooling began in the Northern Hemisphere.
Actual ice ages: we’re currently living in the Quaternary Period, which itself is an Ice Age. Confused? Don’t be. This page explains the difference between ice ages (Periods) and glacials (epochs).