explain how climatic shifts that are naturally occuring and not the result of some castrophic events like asteroid impact happen?

Climatic shift occur due to changes in climate systems caused by varying energy balances happening on earth. Asteroids can trigger increase in kinetic energy with global effect but can not really cause a change in climate systems

Explanation:

Climatic shift could be caused by increased levels of greenhouse gases in the atmosphere, changes in sun strength, shift of ocean currents, movement of tectonic plates and changes in levels of carbondioxide in the ocean. All these factors and others are natural occurring and should balance to create a specific climatic condition. Changes in one of these will led to addition on another resulting to climatic shift. However, for the asteroid, an impact on earth could result to dust and aerosols resulting to pollution, but not really a climatic shift.