Bill: It is the opposite. The tornadoes in Oklahoma are evidence the climate has not changed. This map shows the most likely location of a tornado this week based on the locations of past tornadoes.
Where is the most likely location of tornadoes? Oklahoma. Where did the EF-4 tornado occur earlier this week? Oklahoma.
If an EF-4 tornado were to occur in mid-May in San Francisco, Mexico City or Montreal that would be evidence of a changed climate. Tornadoes in Oklahoma are not.