The climate change and hardness of seasons have strong logic. Earth's axis is tilted 23.4 degrees, which causes seasons but due to lot of factors it getting closer towards 23.5.

Scientific research base interesting article by Dutton institution
https://www.e-education.psu.edu/eme811/node/642
making it more simple to understand. I was shocking that this slightness will go bigger by time and reach 23.5 in 2060.