So went Googling around this morning as this same exact thing happened to my wife's car this morning. Started it up and about 30 seconds later the rear glass sounded like it buckled under pressure and a huge fracture appeared at the bottom just slightly higher than the wiper and then caved in on itself a few seconds later. Temperature has been pretty steady in the last few days and this morning was only about high 40s/low 50s(F). I verified and the rear defroster WAS NOT on at the time of the incident. I saw the previous user said this was covered under manufacturer warranty. I thought glass was not covered and if it is unto how many years/miles? We are going through our insurance for the replacement but I need to verify if there is going to be a charge or not.