There's no doubt that sea levels have been rising, and most scientists expect the trend to accelerate due to climate change.

On Thursday, a coalition of environmental groups sought to focus attention on the threat, and to promote alternative energy, by illustrating the potentially disastrous consequences of rising sea levels in Charleston and other coastal communities in the Lowcountry.

The Southern Alliance for Clean Energy released a video and a series of images illustrating that, if sea levels were to rise by 5 feet, about half the Charleston peninsula, most property near the marsh in Mount Pleasant, much of Sullivan's Island and nearly all of Folly Beach would be under water.

And that's on a clear day with no rain.

An international group of climate scientists predicted last fall that sea levels will rise by 23 inches this century as the oceans warm, which would be roughly double the rise documented during the last century.

That prediction from the Intergovernmental Panel on Climate Change did not account for the record-setting pace of melting polar ice, however.

"The potential is so astounding, if it continues," Duke University Professor Orrin Pilkey said at a panel discussion in Charleston addressing the issue. "I think that 3 to 5 feet is a conservative estimate for coastal management here."

Pilkey and others assembled by the environmental groups discussed climate change and rising sea levels for more than two hours before a crowd of about 100 people at the downtown branch of Charleston County Public Library. The thrust of the message was that individuals and governments must act, and act quickly, to reduce the emissions that are causing climate change. Those emissions are particularly produced by burning fossil fuels for power and transportation.

Downtown resident Richard Saunders attended the presentation but said he had trouble accepting what was said because politics are so tied up in the issue of climate change.

"I'm suspicious of political zealotry," he said.

Diane Anderson of Mount Pleasant was also in the audience. She didn't perceive any political motives behind the presentation, and said the images of local communities being swamped by rising seas was about what she expected.

"I'm glad to see that someone is addressing this," Anderson said.

Even with current sea levels, Charleston is facing hugely expensive projects to address flooding and drainage problems.

The price tag for the largest drainage improvement project, on the West Side of the peninsula, is estimated to cost $130 million, and the city doesn't know where it will get the money.

The Southern Alliance for Clean Energy hopes the rising seas issue will bring more public urgency to energy conservation and the development of alternative energy sources.

The Alliance is a consortium of groups including the Charleston-based Coastal Conservation League.

The group's "Rising Seas" video was produced by Architecture 2030, a group that advocates a moratorium on coal-fired power plants. The Southern Alliance for Clean Energy opposes an expansion of nuclear power as well, saying that conservation and alternative energy sources such as offshore wind farms make more sense.

"Don't let anybody back you into a corner, that it's a nuclear plant or nothing, because it's simply not true," said Steve Smith, executive director of the Alliance.