The unpredictability of physical systems is not simply a result of the limitations of human knowledge. Physical systems are inherently unpredictable. No amount of research or computer power can overcome this unpredictability. Even if we knew everything there is to know about the present state of the universe and had an infinite computing capacity, we would still be unable to predict future weather and climate beyond narrow limits. The unpredictability is part of the universe itself.
Many variables affect weather and climate.
As a result, weather and climate are always changing. Even the rate of change varies. Change can be slow, or it can be exceedingly rapid, as in the case of asteroid impacts, volcanoes, or sudden variations of the output of the sun. The aim of science, it is often said, is to predict and control. Chaos theory demonstrates that prediction and control are necessarily quite limited, despite what advances we make in science and technology.