Storms are a very important area of questions because they can cause great damage to lives and property in a short amount of time. So, when it comes to predicting storms or more important blaming humankind for those storms there are many questions.

First, the IPCC makes it clear it is impossible to discover the cause of any one extreme weather event, including from greenhouse gases for two reasons:

1) “extreme events are usually caused by a combination of factors”.

2) “a wide range of extreme events are a normal occurrence in an unchanging climate”. (AR4 FAQ 9.1 Page 696) 

However, the IPCC goes on to state that it does not matter if climate change is natural or man-made as either “can lead to changes in the likelihood of the occurrence or strength of extreme weather events and climate events or both”. They note more models today are examining extreme events. (AR5 Executive Summary Page 121)

Overall, the IPCC notes since AR4 the models are better at tracking “general characteristics” of storms and cyclones. However, they admit models today are “too zonal and underestimate cyclone intensity.” (AR5 Chapter 9 Executive Summary Page 743)

The IPCC notes they have seen “increases in the frequency and intensity of heat waves and heavy precipitation events”. They go on to say these can occur even with small climate changes. (AR4 FAQ 10.1 Page 783)

This is an interesting statement as the IPCC acknowledges models have varied greatly for water cycles, with regional scales leading the way. However, the IPCC points out this despite this “the mechanisms of change are revealed, increasing confidence in projections”.  This is a common theme that the IPCC is always learning even in failure, as illustrated here. (AR5 Section 12.4.5 Page 1076)