Severe Thunderstorms and Tornadoes in the United States
"...Congress attempted to clarify the federal role in mitigating damages from windstorms (including tornadoes and thunderstorms) by passing the National Windstorm Impact Reduction Act of 2004 (P.L. 108-360). It is not evident whether the program made progress toward its objective:achievement of major measurable reductions in the losses of life and property from windstorms. Authorization for the program expired at the end of FY2008. In the 112th Congress, legislation introduced in the Senate (S. 646) and in the House (H.R. 1379) would reauthorize the wind hazards program (Title II) through FY2015. Similar legislation was passed by the House in the
111th Congress, but no action was taken by the Senate.

It is not clear whether changes to climate over the past half-century have increased the frequency or intensity of thunderstorms and tornadoes, or were responsible for the intense and destructive tornado activity in April and May of 2011. An issue for Congress is whether future climate change linked to increases in greenhouse gas emissions will lead to more frequent and more intense thunderstorms and tornadoes, and whether efforts by Congress to mitigate long-term climate change will reduce potential future losses from thunderstorms and tornadoes..."