Changes in the long-term temperature and precipitation patterns that can either be natural or linked to human activities.

Variations in energy from the sun - The more sunspots there are, the more heat is given off by the sun.

Axial tilt - When the angle of the tilt is greater, there is a higher average temperature.

Eccentricity - Colder periods occur when the Earth's orbit is more circular and warmer periods when it is more elliptical.

Volcanic activity - Reduced temperatures are often experiences elsewhere in the world as volcanic aerosols reflect sunlight away which reduces the global temperatures.

Has increased the volume of greenhouse gases that exits naturally