- The path of the earth around the galaxy is elliptical and its passage every 270 to 400 million years is near to center of the galaxy. In every 300 million years, Earth passes through the dust lane arm of the galaxy. The arm has accumulation of interstellar matter or the Nebulae. This nebula of galaxy interposes between sun and earth, because of which there is reduction in solar radiation reaching the earth’s surface which might bring in climate change.
- There is a regular fluctuation in the amount of energy irradiated from the outer surface of the sun or the photosphere, this alteration brings changes in the temperatures and precipitation.
- The changes in the net amount of solar energy received on earth may also change because of changes in relative distance between earth and sun.
- These are dark and cooler patches on the sun which increase and decrease in a cyclical manner.
- When the number of sunspots increases, cooler and wetter weather and greater storminess occur. A decrease in sunspot numbers is associated with warm and drier conditions.
- This Theory infers cycles in the variations in the earth’s orbital characteristics around the sun, the wobbling of the earth and the changes in the earth’s axial tilt. All these alter the amount of insolation received from the sun, which in turn, might have a bearing on the climate.
Orbital eccentricity of the earth: The eccentricity of the earth orbit is between 0.001 & 0.054. Earth takes 95,000 years to achieve its maximum eccentricity from the minimum. As eccentricity increases, days of summer increase both in northern and southern hemispheres.
- Obliquity or the axial tilt of Earth’s rotational axis: The axial tilt or obliquity of earth’s rotational axis is the angle between the axis of revolution and the axis of rotation of the Earth. The significance of obliquity is that it controls the latitudinal distribution of solar radiant energy and intensity and duration of different seasons.
The change in the obliquity is directly related to the temperature difference between summers and winters. Smaller is the obliquity; smaller is the change in temperature between summers and winters.
Axial precision or Precision of equinoxes: It is a slow and continuous change in the orientation of the rotational axis of the earth due to effects of gravity of the sun, the moon and of the nearby planets. Due to the effect of gravitational forces on earth the direction of axis of rotation changes and it forms a complete conical motion. This is also referred to as wobbling of the rotational axis of the earth. This cycle of axial precision is completed in every 26,000 years. The length and warmth of the season alter due to axial precision. It is seen that due to axial precision winters in northern hemisphere become much longer and warmer while summers in southern hemisphere become much longer and less warm.