Despite the impression some conservatives have that network news is obsessed with global warming, conservationists and liberal media critics Tuesday charged that TV is ignoring the climate change issue, making it worse because lawmakers don't feel pressure to react.

"It's time the nation's top evening newscasts give climate change the coverage it deserves. If we want to see action to address this issue, the media needs to connect the dots between climate change and the extreme weather we're seeing right outside our windows," said Vanessa Kritzer of the League of Conservation Voters.

The league has joined with the Sierra Club and Media Matters to petition networks for more climate change news. "It's disheartening that in a year that saw record-breaking heat, massive wildfires and Hurricane Sandy, the networks failed to help their viewers understand the connections to climate change," said Emilee Pierce of Media Matters.

It would be easy to shrug off such complaints in light of the sweeping coverage of Hurricane Sandy and the melting of the global ice cap, both big stories on TV recently.

But several groups, including Media Matters, have conducted studies of the media's coverage of the environment and global warming and find that with the exception of the Hurricane Sandy blip, there are fewer stories about the issue.

Media Matters, for example, found that the networks ran between 17 and 22 minutes of global warming coverage all year. A nonprofit journalism website called The Daily Climate found that the worldwide media, including TV, magazines and newspapers, cut coverage of the subject by 2.4 percent last year.

Critics say coverage matters. "National broadcasters have the power to influence decision makers and shape public discourse -- with that power comes the responsibility to report on the issues that matter most to Americans," said Sierra Club's Maggie Kao.