Image courtesy of NASA. You can track sunspot activity on a daily basis right here.

After a period of very high solar activity (high numbers of sunspots) in the 20th century, our sun has suddenly gone exceptionally quiet, according to astronomer Dr. David Whitehouse.

We are currently at the end of one cycle of activity and astronomers keep waiting for the sunspots to return and mark the start of the next cycle 24, but so far there has been no sign of that returning anytime soon.

Excerpts taken from Dr. Whitehouse's article, which was posted on the online version of The Independent...........

Sunspots - dark magnetic blotches on the Sun's surface - come and go in a roughly 11-year cycle of activity first noticed in 1843. It's related to the motion of super-hot, electrically charged gas inside the Sun - a kind of internal conveyor belt where vast sub-surface rivers of gas take 40 years to circulate from the equator to the poles and back. Somehow, in a way not very well understood, this circulation produces the sunspot cycle in which every 11 years there is a sunspot maximum followed by a minimum. But recently the Sun's internal circulation has been failing. In May 2006 this conveyor belt had slowed to a crawl – a record low. Nasa scientist David Hathaway said: "It's off the bottom of the charts... this has important repercussions for future solar activity." What's more, it's not the only indicator that the Sun is up to something.

During the 17th century Maunder Minimum, when sunspots were rare, it was also the period of time when the earth's northern hemisphere was sent into what scientists call the "Little Ice Age."

Studies show that by the end of the 20th century the Sun's activity may have been at its highest for more than 8,000 years. Other solar parameters have been changing as well, such as the magnetic field the Sun sheds, which has almost doubled in the past century. But then things turned. In only the past decade or so the Sun has started a decline in activity, and the lateness of cycle 24 is an indicator. The first stirrings of cycle 24 were supposed to arrive a year ago, then NOAA predicted it for March 2007, now they say March of 2008. The first indications that the Sun is emerging from its current sunspot minimum will be the appearance of small spots at high latitude. They usually occur some 12-20 months before the start of a new cycle. These spots haven't appeared yet so cycle 24 will probably not begin to take place until 2009 at the earliest, according to Whitehouse. The longer we have to wait for cycle 24, the weaker it is likely to be. Such behaviour is usually followed by cooler temperatures on Earth.

The tardiness of cycle 24 indicates that we might be entering a period of low solar activity that may counteract man-made greenhouse temperature increases. Some members of the Russian Academy of Sciences say we may be at the start of a period like that seen between 1790 and 1820, a minor decline in solar activity called the Dalton Minimum. They estimate that the Sun's reduced activity may cause a global temperature drop of 1.5C by 2020. This is larger than most sensible predictions of man-made global warming over this period.

Again, you can read the whole story here. Also at the end, Dr. Whitehouse has a list of the past seasons of the sun going back 1000 years.