In the grander picture the galaxy rotates at a roughly constant velocity and relative to this the Sun and its planetary system move around the galactic centre in an elliptical orbit estimated to take around 240 million years – see http://robertkernodle.hubpages.com/hub/The-Cosmology-Climate-Connection-…. The Sun and the solar system have a round and round motion around the galactic centre and an up and down motion across the galactic plane – simultaneously. It may also be said it has an in and out motion too as a result of the elliptical orbit and at the same time the Milky Way moves around the centre of a super cluster of neighbouring galaxies.
However, when looking at the Earth's motions within the solar system, it is thought that every 100,000 years the eccentricity of its orbit around the Sun oscillates between 0 and 5 per cent (and there follows a clever little animation of the Milankovitch cycles). The Moon, Sun and the planets exert gravitational forces (known as tidal forces). Tidal forces, it is also thought, influence sun spot cycles – but that might be old physics. The Moon exerts tidal force on the Earth, as it is closest and its orbit is configured into that of the Earth closely. It particularly affects the oceans, and therefore global climate. The tides mix ocean bottom water with warmer surface water, and vice versa. The Sun creates huge convection cells, the Moon's influence on the tides affects the atmosphere by producing small regular changes in pressure and winds. In addition, over the course of 18/19 years the inclination of the Moon in the sky causes the tidal bulge in Earth to move to a more or a less northerly position. The Moon influences storms and rainfall levels. The Sun, on the other hand, is more obvious. Solar radiation levels = variable heat input to the lower atmosphere. Solar ultraviolet radiation interacts with the ozone in the stratosphere. Changes in the solar modulated cosmic ray flux affect cloud processes, thunderstorm electrification, and thermodynamics. I always get worried when the latter is mentioned as it is bandied around rather loosely on the blogosphere but the web author appears to be quoting from reliable sources and provides a list of articles and authors in the bibliography. Cosmic rays emitted by the Sun and by the galaxy influence climate on Earth (quoting Usoskin and Koraltsov, 2008) and at this point the blog author adds the Fairbridge and Richard Mackey element (see post from yesterday). The implication is that the Moon and the Earth also have an orbit that has a barycentre – but read the piece yourself to get a more detailed idea of what is being suggested. It does seem to be a factor in Piers Corbyn's weather forecasting at www.weatheraction.com who freely admits he uses solar and lunar data to predict the weather – well enough for people to pay good money for those forecasts. Corbyn has of course been ridiculed endlesslay by the CAGW fraternity – even suggesting his predictions are not as secure as he makes out. Unfortunately for them, Corbyn is running a commercial enterprise and if he was quoting nonsense people would not shell out the dosh. That is quite unlike the average climate scientist who is funded by taxpayers – and they have no choice in the matter, unlike the punters Corbyn attracts.