Observations of solar activity indicate sunspots are abnormally low. This could mean a new Maunder Minimum, a 70-year period with virtually no sunspots. The last occurred from 1645 to 1715. This period os also known as the "Little Ice Age."
The Sun normally follows an 11-year cycle of activity. The current cycle, Cycle 24, is now supposed to be ramping up towards maximum strength. Increased numbers of sunspots and other indications ought to be happening: but in fact results so far are most disappointing. Scientists at the NSO now suspect, based on data showing decades-long trends leading to this point, that Cycle 25 may not happen at all.
This could have major implications for the Earth's climate. According to a statement issued by the NSO, announcing the research:
An immediate question is whether this slowdown presages a second Maunder Minimum, a 70-year period with virtually no sunspots [which occurred] during 1645-1715.As NASA notes:
Early records of sunspots indicate that the Sun went through a period of inactivity in the late 17th century. Very few sunspots were seen on the Sun from about 1645 to 1715. Although the observations were not as extensive as in later years, the Sun was in fact well observed during this time and this lack of sunspots is well documented. This period of solar inactivity also corresponds to a climatic period called the "Little Ice Age" when rivers that are normally ice-free froze and snow fields remained year-round at lower altitudes. There is evidence that the Sun has had similar periods of inactivity in the more distant past.