Could Vanishing Sunspots Signal a Little Ice Age?

Sunspots1 Sunspot formation is triggered by the Sun's magnetic field, which scientists at the National Solar Observatory say is steadily declining, predicting that by 2015 there may be no remaining sunspots. The sun may stay spotless for several decades. The last time the sunspots disappeared altogether, historical records show, was in the 17th and 18th century, and coincided with a lengthy cool period known as the Little Ice Age.

According to an analysis of recent solar trends by William Livingston and Matthew Penn of the National Solar Observatory in Tucson:

"We have observed spectroscopic changes in temperature sensitive molecular lines, in the magnetic splitting of an Fe I line, and in the continuum brightness of over 1000 sunspot umbrae from 1990-2005. All three measurements show consistent trends in which the darkest parts of the sunspot umbra have become warmer and their magnetic field strengths have decreased, independently of the normal 11-year sunspot cycle. A linear extrapolation of these trends suggests that few sunspots will be visible after 2015."

Sunspots are vast regions of electrically charged, superheated gas (plasma) on the surface of the sun, formed when upwellings of the magnetic field trap the ionized plasma. The magnetic field prevents the gas from releasing the heat and sinking back below the sun’s surface. These areas are somewhat cooler than the surrounding sun surface and appear when viewed from Earth as dark spots.

During the period from 1645 to 1715, a time known as the Maunder Minimum, there were almost no sunspots. This period coincided with the Little Ice Age, which produced lower than average temperatures in Europe. According to William Livingston, their results should be treated with caution as their techniques are relatively new and it is not yet known if the decline in magnetic field strength will continue, and that “only the passage of time will tell whether the solar cycle will pick up.”

David Hathaway, a solar physicist with the Marshall Space Flight Center in Huntsville, Alabama, also cautioned the calculations do not take into account that many small sunspots with relatively weak magnetic fields appeared during the last solar maximum, and if these are not included in the calculations the average magnetic field strength would seem higher than it actually was..

Casey Kazan via


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