Environment

TORNADO_1094

Residents begin digging through the rubble of their home after it was destroyed by a tornado that hit Joplin, Mo., on Sunday evening, May 22, 2011. The tornado tore a path a mile wide and four miles long, destroying homes and businesses. (AP Photo/Mike Gullett)

TORNADO_1093

Storm clouds dwarf a farm near Lamar, Mo., as the sun sets on Sunday, May 22, 2011. A storm earlier produced a large tornado that moved through much of Joplin, Mo., damaging a hospital and hundreds of homes and businesses. (AP Photo/Charlie Riedel)

TORNADO_1092

Emergency personnel assess the damage to the Academy Sports building in Joplin, Mo., following the tornado that struck the city on Sunday evening, May 22, 2011. (AP Photo/The Joplin Globe, Roger Nomer)

TORNADO_1091

An emergency worker searches a Walmart store that was severely damaged by a tornado in Joplin, Mo., on Sunday, May 22, 2011. (AP Photo/Charlie Riedel)

TORNADO_1089

Don Atteberry, 89, surveys damage at his home in Joplin, Mo., on Monday, May 23, 2011, after it was severely damaged by a tornado on Sunday. The twister killed at least 89 people. (AP Photo/Charlie Riedel)

TORNADO_1088

On Monday, May 23, 2011, Anita Stokes salvages items from her Joplin, Mo., home, which was destroyed Sunday by a tornado. The large twister moved through much of the city, damaging a hospital and hundreds of homes and businesses and killing at least 89 people. (AP Photo/Charlie Riedel)

TORNADO_1087

A rescue worker walks past debris at Joplin High School in Joplin, Mo., on Monday, May 23, 2011. A large tornado moved through much of the city Sunday, severely damaging the school, a hospital, and hundreds of homes and businesses. The twister killed at least 89 people. (AP Photo/Charlie Riedel)

TORNADO_1085

A body is seen in a tornado-ravaged car while emergency workers wait for a medical team to arrive in Joplin, Mo., on Monday, May 23, 2011. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Charlie Riedel)

TORNADO_1084

Emergency workers wait for a medical team after finding a body in a tornado-ravaged car in Joplin, Mo., on Monday, May 23, 2011. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Charlie Riedel)

TORNADO_1083

** FILE ** An emergency worker searches a tornado-damaged Walmart store in Joplin, Mo., on Monday, May 23, 2011. A large tornado moved through much of the city Sunday, damaging a hospital and hundreds of homes and businesses. (AP Photo/Charlie Riedel)

TORNADO_1082

On Monday, May 23, 2011, an emergency worker searches a Walmart store that was severely damaged by a tornado in Joplin, Mo., on Sunday. (AP Photo/Charlie Riedel)

TORNADO_1081

Emergency workers wait for a medical team after finding a body in a tornado-ravaged car in Joplin, Mo., on Monday, May 23, 2011. A large tornado moved through much of the city Sunday, damaging hundreds of homes and businesses. (AP Photo/Charlie Riedel)

TORNADO_1079

A destroyed helicopter lies on its side in the parking lot of the Joplin Regional Medical Center in Joplin, Mo., on Sunday, May 22, 2011. A large tornado moved through much of the city, damaging the hospital and hundreds of homes and businesses. (AP Photo/Mark Schiefelbein)

TORNADO_1077

The damaged St. John's Regional Medical Center is seen in the distance through tornado debris in Joplin, Mo., on Monday, May 23, 2011. A large tornado moved through much of the city Sunday, damaging the hospital and hundreds of homes and businesses and killing at least 89 people. (AP Photo/Charlie Riedel)

TORNADO_1075

A shelf cloud containing a thunderstorm approaches a tornado-ravaged neighborhood of Joplin, Mo., on Monday, May 23, 2011. A large tornado moved through much of the city Sunday, damaging a hospital, hundreds of homes and businesses and killing at least 89 people. (AP Photo/Charlie Riedel)

TORNADO_1073

A man carries a young girl who was rescued after being trapped with her mother in their home after a tornado hit Joplin, Mo., on Sunday evening, May 22, 2011. The tornado tore a path a mile wide and four miles long, destroying homes and businesses. (AP Photo/Mike Gullett)