<P> Although these are the primary three factors in shaping Earths climate, there are other, external, factors that can help shape Earth's climate . These external factors usually affect Earth climate on a very different time scale than the other three, and include factors such as meteors striking Earth and geomagnetic storms . These external forces usually contribute to climate change on a time scale, as meteorites strike the earth, on average, every 50 to 100 million years, where as geomagnetic storms occur periodically through the sun's eleven - year activity cycle . With all of these factors affecting climate in their own way, it becomes easy to see that Earth's climate is in fact, largely dependent on various solar effects / circumstances . </P> <P> Perhaps one of the most apparent factors contributing to Earth climate change is the angle at which the earth is tilted . This is the angle at which Earth's axis of rotation is from the vertical, also known as Earth's obliquity . Earth's current tilt angle is approximately 23.5 degrees . The axial tilt angle affects climate largely by determining which parts of the earth get more sunlight during different stages of the year . This is the primary cause for the different seasons Earth experiences throughout the year, as well as the intensity of the seasons for higher latitudes . For example, in the Northern Hemisphere, if there were no axial tilt, i.e. Earth's obliquity would be zero degrees, then there would be no change in the seasons from year to year . This would be because there would be no difference in the amount of solar irradiation received, year - round, anywhere on Earth . On the other hand, if Earth's axial tilt angle was great (45 + degrees), the seasonality of each hemisphere, individually, would be highly exaggerated . Summers would be extremely hot, with substantially more hours of daylight than night each day . Winters would be extremely cold, with substantially more hours of night than daylight each day . This is because, during summer for the northern hemisphere, if the earth is tilted more (pointed towards the sun more), there would be more available hours in which the suns rays can strike any certain place, thereby increasing the number of daylight hours at any given place, with more and more daylight hours at higher latitudes . Also, because the northern hemisphere would be tilted much more towards the sun, it would be physically closer to the sun, thereby increasing the intensity of the sun's rays hitting the northern hemisphere, thereby causing the northern hemisphere to become hotter . Likewise, during winter for the northern hemisphere, there would be fewer hours of daylight because the northern hemisphere would essentially be pointed away from the sun . Fewer daylight hours means less solar radiation hitting the northern hemisphere, especially at higher latitudes, and therefore causing the northern hemisphere to become colder . The same things can also be said about the southern hemisphere, particularly at high latitudes . In either case, the climate around the equator is not affected nearly as much as the higher latitudes, thereby creating a sizable difference in how obliquity affects different latitudes . This is all, of course, dependent on what the actual tilt angle is at any given point in time . The thing is, though, that Earth does in fact change obliquity over time in a cyclic pattern . Earth's obliquity does not change much, though, as obliquity has been determined to cycle between the small range of 22.2 degrees to 24.5 degrees, in a cycle that lasts approximately 41,000 years . Therefore with the small tilt variation over time, the Earth has always been thought to have had a seasonal climate, at least in the high latitudes due to the solar affect of changing Earth obliquity . </P> <P> Earth's eccentricity can also play a large role in Earth climate change . The role is perhaps not as large of an impact as Earth's Obliquity, but still large nonetheless . Eccentricity is defined as the difference in shape between an ellipse and a perfect circle . It is also known by a simpler definition as simply being a measurement of how elliptical something is . In the case of climate, eccentricity is applied to the shape of Earth's orbit . In a similar fashion to Earth's obliquity, the more uniform Earth's orbit is (more like a perfect circle), the less difference there is in climate change throughout the year . Unlike obliquity, eccentricity affects the entire planet approximately the same, instead of primarily changing polar climate . The base idea with eccentricity is this: "How far away is the earth as a whole from the sun?" If there is no eccentricity to Earth's orbit, then Earth will remain at the same distance from the sun throughout the year, therefore producing no climate change, seeing as how the Earth's orbit would be perfectly circular around the sun . On the other hand, if Earth's orbit has a very high eccentricity, Earth would be very close to the sun (compared to a perfectly circular orbit) during two opposite seasons, and very far away from the sun during the other two opposite seasons . This effect can be seen by analyzing any ellipse, and observing how flat or how skinny the ellipse becomes as its eccentricity increases . </P> <P> Mathematically, the eccentricity of an ellipse is given by the following equation: </P>

How would seasons on earth be different if earth's orbit were less elliptical