Contrails are clouds caused by airplane exhausts, which geologists contend decrease daily temperature ranges on Earth. Following the 2001 World Trade Center attack, cancelled domestic flights triggered the first absence of contrails in decades. Resultant exceptional data capacitated causal inference analysis by propensity score matching. Estimated contrail effect was 6.8981°F.
This paper was originally published crediting a second author in addition to Dean Barron. At the request and agreement of both parties, this second author has been removed from the paper. - 9/2021, JNF