While there are numerous factors involved with increased severity such as more impervious surfaces and loss of wetlands, selective reading of data to claim that storm severity will not be increased of such things as burning of fossil fuels is a dangerous error. See for example http://blog.ucsusa.org/astrid-caldas/hurricane-matthew-most-powerful-in-a-generation
Or http://nca2014.globalchange.gov/report/our-changing-climate/changes-storms