WASHINGTON (AFP) - US scientists say the familiar sunspot cycle seems to be entering a hibernation period unseen since the 17th century, a pattern that could have a slight cooling effect on global temperatures. For years, scientists have been predicting the Sun would by around 2012 move into solar maximum, a period of intense flares and sunspot activity, but lately a curious calm has suggested quite the opposite. The signs include a missing jet stream, fading spots and slower activity near the poles, said a trio of studies presented Tuesday at the annual meeting of the American Astronomical Societys Solar Physics Division in Las Cruces, New Mexico. This is highly unusual and unexpected, said Frank Hill, associate director of the National Solar Observatorys Solar Synoptic Network. But the fact that three completely different views of the Sun point in the same direction is a powerful indicator that the sunspot cycle may be going into hibernation. Solar activity tends to rise and fall every 11 years or so. The solar maximum and solar minimum each mark about half the interval of the magnetic pole reversal on the Sun, which happens every 22 years. Experts are now probing whether this period of inactivity could be a second Maunder Minimum, a 70-year period when hardly any sunspots were observed between 1645-1715 known as the Little Ice Age.