Sunspots may be going into hibernation, a phenomenon unseen since the 17th century that could lead to cooler global temperatures, scientists said Tuesday. It’s not clear how rising temperatures from greenhouse gas emissions may offset global cooling, and scientists are still not totally sure how our star affects Earth’s climate, however. But a forthcoming period of solar quiet will help settle the questions.

Activity in the sun is building toward an expected peak sometime in 2013. Yet, despite a few notable solar flares, things are strangely calm. There are fewer sunspots in this cycle than expected, and they’re fainter than usual, for instance. The east-west plasma jet stream inside the sun is apparently missing, and the magnetic field’s pace of migration toward the poles is slowing down.

Based on these sets of findings, which were presented Tuesday at the annual meeting of the American Astronomical Society's Solar Physics Division in Las Cruces, N.M., heliophysicists believe the current solar cycle, Cycle 24, could be the last one for a while. The sun might be entering a period of hibernation.

This was previously observed from 1645 to 1715, a period known as the Maunder Minimum in which there were practically no sunspots. The period coincided with part of the “Little Ice Age,” in which average temperatures in the northern hemisphere dropped by 2 to 4 degrees F.