Causes of Climate Change 
2.9. Conclusion
Both climate forcing mechanisms and the response of the climate system operate over a variety of different time scales. Response to forcing may be linear, quasi-linear or non-linear. Non-linearity in climatic change is the result of a complex interaction of feedback processes. It should be appreciated that different primary forcing mechanisms will initiate different feedback processes. Primary feedback processes will give rise to secondary feedback processes. Some may be positive, some negative, but generally, climatic feedback acts in a direction which augments the initial climatic response to forcing. How much it does so, and how quickly, depends upon the sensitivity of the global climate to radiative forcing.
External Forcing
-Galactic Variations
-Orbital Variations
·Obliquity
·Eccentricity
·Precession
·Milankovitch
-Solar Variations
Internal Forcing
-Orogeny
-Epeirogeny
-Volcanic Activity
-Ocean Circulation
-Atmosphere