What a great event! It should definitely happen more often.

Police raided the Black Panther's headquarters in Illinois. It was found that there was only one bullet fired by the Panthers vs the multiple that the police fired.

When the return-interval describes the expected recurrence frequency for a single site/region, we must expect many more occurrences over a wider area. This is explained by maths and mathematics (the Binomial distribution and probabilities). Then a small change in the probabilities (probability density function) can lead to a large increase in the number of observed events. Furthermore, the definition of climate change is indeed a changing probability density function (climate is weather statistics), which means that a past 500-year event is no longer a 500-year event, but perhaps a 100-year event. In other words, this is not surprising and is in accordance with mathematical reasoning. Actually, it is to be expected, especially since a warming leads to a higher evaporation rate and more moisture in the atmosphere. The fact that the return intervals are estimated for single sites/regions means that we can expect a dramatic increase in similar extreme weather events in the future. We can gauge this development by studying the number of record-breaking events: see http://onlinelibrary.wiley.com/doi/10.1029/2008EO410002/pdf