COLUMBIA - South Carolina Republicans and Democrats disagree on the primary cause of global warming, but majorities agree that it's time to take action, says a poll released Tuesday.

"I think the unity you see among legislators is reflected on the unity among voters," said David Beattie, the president of the Democratic polling firm Hamilton Beattie & Staff, which helped conduct the poll.

"Republicans and Democrats both agree that shifting to alternative energy sources will ultimately help, rather than hurt, our economy," said Q. Whitfield Ayres, the president of the Republican polling firm Ayres, McHenry & Associates Inc.

The two firms conducted the phone survey of 400 likely Democratic primary voters and 400 likely Republican primary voters in South Carolina.

According to the poll, taken April 14-19:

- 56 percent of Democrats said global warming is caused by human activity, while 57 percent of Republicans cited natural processes.

- 79 percent of Democrats think it's time to take action, while 56 percent of Republicans think now is the time to act.

- 64 percent of Democrats and 54 percent of Republicans think shifting to cleaner energy will help the economy.

- Democrats were three times more likely to think it's "very important" that the next president address global warming, 69 percent to 21 percent.

- Strong majorities in each party (87 percent of Democrats, 80 percent of Republicans) think the government should take steps to reduce the country's dependence on fossil fuels.

Conservation Voters of South Carolina and the Coastal Conservation League paid for the poll, which had a margin of error of 4.9 percent.

"We are unified in identifying, as many others have, the problems we have to face," said Rep. Ben Hagood, R-Sullivan's Island. "The solutions may not be as easy. There's a lot of hard work to do at the state and the national level in addressing the solutions to these problems."

Mr. Hagood is part of a bipartisan group of lawmakers who, with the environmentalists, presented the poll results Tuesday and announced that they're sending an "open letter" to presidential candidates encouraging them to present a comprehensive energy policy.

Ninety of the 124 House members and 21 of the 46 state senators signed the letter.

The letter comes two days before the eight Democrats vying for their party's nomination meet in Orangeburg for the first presidential debate of the 2008 election.

A Republican debate is scheduled for May 15 in Columbia.

In legislative action Tuesday, the following bills received key House approval:

- An extensive tax bill that, among other things, includes incentives for filmmakers and eliminates Sunday sales prohibitions not related to alcohol

- A study of the feasibility of offshore natural gas exploration

- A bill from Rep. Skipper Perry, R-Aiken, requiring additional study and information before a tax increment financing district can be approved

- Establishment of a group to study whether certain state agencies and departments should be modified, continue to exist in their current form or be eliminated