MANCHESTER, New Hampshire (Reuters) -- Presidential hopeful Mitt Romney broke with Republican orthodoxy on Friday by saying he believes that humans are responsible, at least to some extent, for climate change.

"I believe the world is getting warmer, and I believe that humans have contributed to that," he told a crowd of about 200 at a town hall meeting in Manchester, New Hampshire.

"It's important for us to reduce our emissions of pollutants and greenhouse gases that may be significant contributors."

The former Massachusetts governor fielded questions on topics ranging from the debt ceiling to abortion on his first full day of campaigning for 2012 Republican primary nomination.

Romney leads opinion polls in New Hampshire by a wide margin, and is among the top contenders nationally to win the Republican primary.

But the candidate lost the publicity battle on Thursday when his campaign launch in New Hampshire was overshadowed by Republican star Sarah Palin, who swooped in as part of her East Coast bus tour to dominate local media coverage.

In addressing climate change and energy policy, Romney called on the United States to break its dependence on foreign oil, and expand alternative energies including solar, wind, nuclear and clean coal.

"I love solar and wind (power) but they don't drive cars. And we're not all going to drive Chevy Volts," he said referring to electric cars.

The United States can not go it alone in attempting to trim emissions levels and give a free pass to countries such as China and Brazil, Romney said. "It's not called American warming, it's called global warming," he said.

Software developer Michael Hillinger, 60, of Hanover, New Hampshire, posed the climate change question.

Romney's answer provided plenty of wiggle-room, Hillinger said, but "he is taking a more forthright stand than any of the other candidates."

At an event in Manchester last week, former House Speaker Newt Gingrich, also running for president, said that climate change is "the newest excuse to take control of lives" by "left-wing intellectuals."

Asked to lay out a specific plan for the economy, Romney outlined seven points but referred to his 2010 book "No Apology" as containing his policy ideas in details.

"It's a good book. I'll give you a discount," he quipped.

Romney skirted a question about whether doctors who perform abortions, or women who have abortions, should face criminal sanctions if Roe v. Wade, the 1973 U.S. law that protects abortion rights, were overturned.

"I am pro-life," he said, adding that decisions on abortion law should be returned to state jurisdiction.

Abortion is one of several issues on which Romney's critics accuse him of flip-flopping over the years. In the past, including during his race in 2002 to be Massachusetts governor, he has said he supports the substance of Roe v. Wade.

(Editing by Greg McCune)

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