A study published in Geophysical Research Letters and co-authored by LASP scientist Tom Woods has found that total solar irradiance (TSI)—a measure of the Sun’s energy output—may not be as low during the Little Ice Age as previously understood. Low total solar irradiance has been thought to be a cause of the Little Ice Age, a time in the 17th Century coinciding with a period of unusually low sunspot activity known as the Maunder Minimum.
The authors analyzed direct measurements of solar magnetic activity during the recent 2008-2009 period of low sunspot activity, which they argue was similar to the activity level during the Maunder Minimum. They found that even when there were no sunspots, the Sun had a baseline level of magnetic activity. Previous estimates of TSI during the Maunder Minimum assumed a much lower baseline of magnetic activity; thus the authors have suggested that earlier estimates of the TSI during the Maunder Minimum are possibly too low. The researchers argue that the Maunder Minimum probably had levels of magnetic activity and TSI similar to 2008-2009 values, which are lower by 140 to 360 ppm than the previous solar cycle minimum in 1996. This paper does not dispute that low solar activity during Maunder Minimum contributed to colder temperature in the 1700s, but instead suggests that there are additional non-solar drivers for the cold temperatures during the Little Ice Age.
The study relied on data from the Solar Influences Data Center, National Solar Observatory, Geostationary Operational Environmental Satellites (GOES), and Solar and Heliospheric Observatory (SOHO).
Schrijver, C. J., W. C. Livingston, T. N. Woods, and R. A. Mewaldt (2011), The minimal solar activity in 2008–2009 and its implications for long-term climate modeling, Geophys. Res. Lett., 38, L06701, doi:10.1029/2011GL046658.
Tom Woods, co-author: 303-492-4224 or Tom.Woods@lasp.colorado.edu
Stephanie Renfrow, LASP press office: 303-735-5814 or Stephanie.firstname.lastname@example.org