I read a couple of articles today blaming the tornado outbreak on global warming. O’Reilly had an expert on that likened it to an outbreak in 1974 and blamed it on Pacific Ocean cooling or the La Nina effect.
The following references relate to 1974. The first talks about the tornado outbreak in 1974. The second shows that the fear had been global cooling with forecasts for warming in the future.
I would go with the sunspot theory rather than anything man made.
Read about the previous greatest tornado outbreak in 1974 here.
Read about global cooling in 1974, the mantra then of the environmental extremists, here.