The Accompanying Graph Shows the Number of Violent Tornados in the Last

The accompanying graph shows the number of violent tornados in the last 60 years. Based on when most global warming has occurred, one would conclude:

A) global warming has had a major impact on the number of tornados.
B) global warming has had a major impact on the number of tornados in the early part of the century.
C) global warming has had a major impact on the number of tornados since 2000.
D) global warming has not had an impact on the number of tornados.