Why is the "Walkie Talkie" melting cars? Well, according to its architect, Rafael Viñoly, it's not because of the building's shape or material, but rather "the superabundance of consultants and subconsultants" that UK law requires.
As reported by BD Online, Viñoly admitted that the building's unusually hot solar reflection (or "death ray," as many headlines are calling it) had been predicted early in the design process; however, it was thought it would only reach a temperature of 36 degrees, "but in fact it’s 72."
Viñoly then went on, placing blame on the consultant-heavy nature of design in the UK: “One of the problems that happens in [...London] is the superabundance of consultants and sub consultants that dilute the responsibility of the designers until you don’t know where you are.”