Ask Ethan #42: Is the Sun brighter in the Summer? (Synopsis)

“The brighter you are, the more you have to learn.” -Don Herold

There's a big difference between the Summer Sun and the Winter Sun, and I'm not talking about anything to do with the Sun itself.

Image credit: SOHO-EIT Consortium, ESA, NASA. Image credit: SOHO-EIT Consortium, ESA, NASA.

No, I'm talking about what you feel here on Earth due to the Sun's rays! There's no doubt that the Sun warms the Earth, and that it warms your portion of the Earth very differently during the Summer months as opposed to the Winter months. But did you ever stop to consider why? Is it the Sun's fault? Our orbit's fault? Something else?

Image credit: Larry McNish / RASC Calgary Centre. Image credit: Larry McNish / RASC Calgary Centre.

It turns out that all of the factors can be measured and quantified, and only two truly matter. What are they? Go read the whole thing and find out!


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If you go beyond the level of casual observations of apparent strength/heat, the variation of distance is important to the climate. A six percent variation translates into approximately 80watts/ per meters squared, the "forcing" due to human added greenhouse gases is roughly one and a half watts per square meter! You can divide the solar forcing by four (area of circle divided by area of sphere), and maybe another 1.5 because some of the suns energy is reflected not absorbed, but that still leaves the variation in distance as a order of magnitude greater than the (so far) human contribution.

So interestingly the rate of angular progress around an orbit also varies as the inverse square law, so the total amount of radiation received in a season is conserved as the phase of the elliptical orbit changes, but the strength of the seasons is changed by the precession of the axis over its roughly 23000 cycle. Currently the northern hemisphere has long mild summers, eleven thousand years from now summer would be shorter, but more intense.

By Omega Centauri (not verified) on 21 Jun 2014 #permalink