From late June through July, successive heat waves swept across large portions of the United States, breaking temperature records and placing more than 100 million people at a time under heat alerts. ABC, CBS, and NBC closely tracked the extreme heat as it moved across the country, repeatedly reporting threatened or broken records and warning viewers about dangerous conditions.What the networks did not explain was why these events kept arriving in rapid succession. Instead, viewers saw extensive reporting on dangerous and record-breaking heat without an explanation of how human-caused warming is making such extreme weather more frequent and severe.