Coal and renewable energy weren't absent from the presidential debate last night, but environmental groups are bemoaning the fact that climate change wasn't brought up.The Hill's E2 Wire notes that a petition was delivered to debate moderator Jim Lehrer with more than 160,000 signatures, asking the PBS host to ask the candidates about climate change. But he didn’t. And while Obama and Romney traded punches on energy policy, neither mentioned climate change or carbon emissions.“Millions of Americans felt the impacts from climate change this year, so it's disappointing it wasn't discussed. Sadly, warming is a global issue too, so hopefully it will come up in the next debate focused on international policy,” said Jamie Henn, co-founder of the climate advocacy group 350.org.Both candidates voluntarily waded into a discussion about renewable energy and fossil fuels during discussions about increasing American energy independence and reducing the federal deficit. But while President Obama and Mitt Romney have both proclaimed their love of coal (the direct quote from Romney last night was "I like coal."), analysts have noted that both have good reasons to stay away from climate change.David Baker of the San Francisco Chroniclelooked at the issue this morning. He notes that Romney is worried about alienating the GOP's base, which has increasingly rejected climate change over the past few years. A poll conducted last month by Bloomberg found that only 26 percent of Republicans believe human activity is warming the planet. Contrast that with 78 percent of Democrats and 56 percent of independents. "The GOP is as stony a ground for that issue as you can find today," said Jerry Taylor, a senior fellow at the Cato Institute libertarian think tank and a frequent critic of federal environmental policy.Obama, on the other hand, is worried about alienating independents. And he's hoping to win coal mining battleground states like Pennsylvania and Ohio, where Cato fellow Jerry Taylor adds: "Amongst those voters, swing voters in swing states, there's very little appetite for doing anything on climate change."