This is junk science because:
Science Daily reports:
Analysis has suggested that changes in the atmosphere will lead to more frequent conditions favorable for severe thunderstorms. According to recent studies there will be more damaging winds related to thunderstorms. The number of tornadoes and large hail is expected to remain at the same level as today.
Climate model simulations suggest that on average, as the surface temperature and moisture increases the conditions for thunderstorms becomes more frequent.
But as meteorologist Joe Bastardi pointed out yesterday, the atmosphere is not getting moister as it warms: