tusenfem writes "So, as far as I can see, there is no "unusual low.""

This article discusses the low and also contains a graph (1991-2008) of the Ap index.
http://wattsupwiththat.wordpress.com...sunspots-gone/

There is also some discussion here about solar cycle 24 & 25.
http://science.nasa.gov/headlines/y2..._longrange.htm

"AA Index" is not the most precise indicator but it has the advantage of a monthly data timeline going back to 1868. Global Sea Surface Temperature (SST) data timeline goes back to 1880. Therefore "AA Index" permits a long term analysis against ocean temperature. "Ap Index" is a better parameter but has a shorter data history. Other parameters such as solar wind speed and density may be even a better parameter but are only a recent data series. Therefore when looking at a link between long-term temperature trends and the intensity of the magnetic field within the solar winds, the "AA Index" is a rough order approximation.