A broad coalition of civic leaders, elected officials, and labor, environmental and social activists launched a campaign Wednesday aimed at convincing U.S. politicians that they should curb greenhouse gas emissions for moral and ethical reasons.

The Climate Ethics Campaign — which kicked off with a Capitol Hill news conference headlining Senate Environment and Public Works Committee Chairman Barbara Boxer (D-Calif.) — comes as negotiators are struggling to make progress at U.N. climate talks in Durban, South Africa.

“We believe it’s time to talk about our moral obligation to prevent the human suffering ­created by climate change, to safeguard the poor and most vulnerable communities from harm they did not create, and to protect the natural environment that is the source of all life,” said campaign coordinator Bob Doppelt, executive director of the Resource Innovation Group, a nonprofit association affiliated with Willam­ette University.

But the call also comes at a moment when Congress has shown little appetite for tackling the issue of global warming. There is no serious drive to pass a cap on greenhouse gas emissions or a more-modest federal renewable energy standard.

The climate talks are the first in years with not a single member of Congress attending. Only a handful of congressional aides are making the trip.

The 2009 U.N. negotiations in Copenhagen represented the high-water mark in terms of congressional attendance, with then-House Speaker Nancy Pelosi (D-Calif.) leading a delegation of more than 20 members to the talks. Senate Foreign Relations Committee Chairman John F. Kerry (D-Mass.) and Sen. James M. Inhofe (Okla.), the top Republican on the Environment and Public Works Committee, attended separately.

Michael Levi, senior fellow for energy and the environment at the Council on Foreign Relations, noted that in 2009 the House had passed a bill that would have imposed nationwide limits on greenhouse gases, and there was an expectation at the time that the Senate might pass a similar bill in 2010. “U.S. lawmakers aren’t attending this year because there isn’t much for them to contribute absent U.S. domestic action,” Levi said.

In a statement, Inhofe noted that two years ago in Copen­hagen he announced that climate legislation was dead even as Democrats assured U.N. delegates it would become law: “My friends on the other side of the aisle clearly don’t want to face world leaders now that they’ve failed to deliver and as the Kyoto process is all but dead.”

Kerry has attended six U.N. climate conferences, but his spokeswoman said he did not plan to go this year because his work on the deficit reduction committee was expected to continue through December.

House Energy and Commerce Committee ranking member Henry Waxman (D-Calif.) said he could not make the trip because Congress was in session.

At the news conference, Boxer said it would take increased public pressure to ensure action on climate change. “Right now, we do not have the votes to do what we need to do,” she said. “To take it to the next step, we need a grass-roots movement that is huge.”

Some environmentalists have questioned the Obama administration’s negotiating strategy in Durban; 16 environmental leaders sent a letter Tuesday to Secretary of State Hillary Rodham Clinton suggesting that her deputies commit to negotiating a binding climate pact by 2020.

U.S. special climate envoy Todd Stern said in statement that the administration was focused on solidifying the progress made in last year’s talks. Those talks, he said, saw “commitments for the first time from all major economies, developed and developing alike” for cutting greenhouse gas emissions by 2020, “and principles for a system of transparency so that all countries can see whether others are meeting their commitments.”