In 1974, CO2 levels were 330 ppm, well below Hansen’s safe maximum of 350 ppm.
The Super Outbreak is the largest tornado outbreak on record for a single 24-hour period. From April 3 to April 4, 1974, there were 148 tornadoes confirmed in 13 US states, including Illinois, Indiana, Michigan, Ohio, Kentucky, Tennessee, Alabama, Mississippi, Georgia, North Carolina, Virginia, West Virginia, and New York; and the Canadian province of Ontario. It extensively damaged approximately 900 square miles (1,440 square kilometers) along a total combined path length of 2,600 miles (4,160 km).
The Super Outbreak of tornadoes of 3–4 April 1974 remains the most outstanding severe convective weather episode of record in the continental United States. The outbreak far surpassed previous and succeeding events in severity, longevity and extent.