Astronomy/sun spots


do sun spots effect temperatures here on Earth?

Individual spots rarely if ever affect surface temperatures. But flares and coronal mass ejections can occasionally increase temperatures in the upper atmosphere, and there are relatively minor 'cumulative' effects due to large numbers of spots changing the brightness of the Sun. Though directly blocking some of the light of the Sun, sunspots actually slightly increase its brightness, so when the Sun has very few spots it is a little fainter, and when it has a lot of spots it is a little brighter. The effects involved on solar brightness are very minor, generally being no more than a tenth of one percent of the overall solar brightness, but they continue for a few years at a time, and if there are a lot of spots for decade after decade it can noticeably increase the temperature of the Earth (in fact a small portion of the current increase in global temperatures is due to the larger than normal number of sunspots during the last half century), and if there are very few spots for decade after decade it can noticeably decrease the temperature (such as the 'little ice age' caused by the so-called Maunder Minimum in the mid to late 1600's and early 1700's).

For a moderately detailed discussion of the mechanism behind the small changes in solar brightness caused by spots, an image showing the brighter than normal regions surrounding sunspots, diagrams of the fluctuations in sunspot numbers, and a diagram comparing the number of sunspots in recent decades to changes in average solar brightness, see The Sunspot Cycle, at (keep in mind that most of the pages on my website represent images and notes that I cobbled together for use in my lectures, and are not as polished or complete as a textbook discussion would be, and although correcting that flaw is one of my goals, it is a relatively long-term goal).


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Courtney Seligman


I can answer almost any question about astronomy and related sciences, such as physics and geology. I will not answer questions about astrology and similar pseudo-scientific rubbish.


I have been a professor of astronomy for over 40 years, and am working on an online text/encyclopedia of astronomy, and an online catalog of NGC/IC objects.

Astronomical Journal, Publications of the Astronomical Society of the Pacific (too long ago to be really relevant, but you could search for Courtney Seligman on Google Scholar)

I received a BA in astronomy and physics and a MA in astronomy, both from UCLA. I was working on my doctoral dissertation when I started teaching, and discovered that I preferred teaching to research.

Awards and Honors
(too long ago to be relevant, but Phi Beta Kappa and Sigma Xi still keep trying to get me to become a paying member)

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