Astronomy/Climate Change


Earth's orbit around the sun has eccentricity of 0.017 which is close to circle. So if we consider the earth's axis of rotation(about 23.5 degrees), anyway I think that is the thing that affect the climate in a large scale. Right? Which is playing a major role? Earth's orbit or axis of rotation?

You are correct. The tilt of our axis is much more important than the change in our distance from the Sun. It is the cause of the seasons, and is so much more important than the eccentricity that the Northern hemisphere has its summer in July, when we are furthest from the Sun, and its winter in January, when we are closest to the Sun.

The eccentricity does have a theoretical effect, but it is swamped by the effects of the tilt, which are 20 times larger at most latitudes, and even the differences in geography at different places are more important than the eccentricity. If we had a much larger eccentricity, like Mars, its effects would be more noticeable; but since our orbit is more nearly a circle than not, you can almost completely ignore the eccentricity in figuring out what the weather is like. (Of course climatologists do take it into effect, because it is very easy to factor it in; but it makes very little difference.)

For examples of how different things affect the weather, you might check out the following pages on my website:

Planetary Temperature Factors (at )
Seasons on the Other Planets (at )
Climatic Zones (at )
and Orbital Effects on Planetary Temperatures (at ) *Note: This is partially a finished page, and partially three sets of notes typed out in class in different semesters; each of the three sets of notes takes a slightly different approach to the subject, and I think the third one is most relevant to your question, as it includes a discussion of how even the fact that the Southern Hemisphere has more oceans than the Northern Hemisphere is more important than our eccentricity*

One final note: The eccentricity of our orbit (and other numbers associated with our orbit) change(s) over very long periods of time, so there are times when eccentricity is more important than now. But those were either a very long time ago, or a very long time from now. I don't have a discussion of that on my website, but there is an example of how that works for Mars at the end of the page about Oppositions of Mars (at ). I forget the exact numbers for the Earth, but know that our eccentricity can be as low as zero, and almost as much as 10%, at various times during a period of about two million years.


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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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