More than 72,000 Americans are calling on ABC, CBS and NBC to reassess their priorities after a Media Matters analysis found that their nightly news programs devoted very little time to climate change in 2012 -- less than they covered the British royal family.

Even during the warmest year on record in the U.S., the nightly news programs combined devoted only 12 full segments to climate change. By contrast, these programs dedicated over seven times more coverage to the royals in 2012, as this graphic by the Climate Reality Project in collaboration with Media Matters illustrates:

The disparity was greatest on ABC World News, which dedicated 43 segments to the royal family and only one to climate change. NBC Nightly News wasn't much better, devoting 38 segments to the royals and only 4 to climate change. CBS Evening News covered climate change the most -- in 7 segments -- but still less than its 11 segments on the royal family.

This ongoing imbalance was illustrated just last week when scientists announced that the amount of carbon dioxide in the atmosphere is set to surpass 400 parts per million, likely for the first time in human history. ABC World News and NBC Nightly News ignored the story, even as NBC found time to cover Prince Harry's visit to the United States.

A previous Media Matters report found that the broadcast networks covered Donald Trump more than climate change in 2011.

When the broadcast networks did report on climate change, they often failed to connect the dots between climate change and particular extreme weather events like last year's record-breaking heat, massive wildfires in the West, and Hurricane Sandy. Continuing this trend, these networks have failed to report on recent near-record flooding in the Midwest in the context of climate change, which has increased the frequency of large rain storms and exacerbated flood risks.

A petition organized by Media Matters, the Sierra Club and the League of Conservation Voters urges the major broadcast networks to give climate change the attention it warrants, and to turn to scientists to explain when there is a connection between human activity, climate change, and extreme weather we are experiencing.