Why has rainfall increased 30% in the last several decades?

This is a very interesting topic for me. It seems there are cycles of long and short duration in all details about the weather everywhere. Here in California it was very wet when La Nina effects were high and very dry when La Nina effects were low. About 150 years ago more rain fell in one season than in any year since. In 1846 it snowed more than in any year since. There are better records for some places than others and most of our global weather is never recorded. so, all in all you might not have enough data to make any sense of why the weather is like it is.