Which is one of the most widely used climate classification systems?

It's a well known fact that the Planet goes through phases of hot and cold cycles. In the human lifetime we cannot even begin to understand how our planet works.

Globular Martian, our understanding has progressed by great leaps and bounds, starting with Fourier over 200 years back, then Arrhenius over 100 years back & then over the last 50 years it has transformed out of all recognition.