Led by Clinton, the U.S. delegation will include Environmental Protection Agency Administrator Lisa Jackson, White House Council on Environmental Quality Chairwoman Nancy Sutley, Assistant Secretary of State Kerri-Ann Jones, and Todd Stern, special envoy on climate change, among others. While German Chancellor Angela Merkel and British Prime Minister David Cameron are not expected to attend, the conference will feature more than 100 other heads of state.
"It would send a very poor signal if the United States did not send the highest level of delegation possible," said Jake Schmidt, international climate policy director for the Natural Resources Defense Council, noting that any agreements made at the conference won't carry as much weight otherwise.
Waxman agrees that the conference is significant. "There should be no less interest in trying to deal with the problem of climate change, which is becoming a bigger issue every single year as our planet gets hotter and hotter and we see more aberrant weather conditions causing enormous damage," he said.
But many lawmakers — and even some U.S. experts on global sustainability issues — see the summit as a chaotic conglomeration dealing with a wide variety of issues with little chance of reaching meaningful agreements.
Part of the problem is the collapse of public confidence in the U.N. process and the inability of recent global conferences to produce measurable results. Divisions between developed and developing countries, as well as tensions between those with big goals and those with small appetites, have caused previous climate talks and similar conferences to unravel, with no results to show for the effort.
"I just don't see this thing working," said Andrew Light, a senior fellow at the Center for American Progress specializing in international climate and science policy. Light, who is not attending this year, described Rio+20 as "a unique sort of mess."
The Rio+20 website, however, says the summit will set the global sustainability agenda for the next decade, with discussions to be held on topics ranging from sustainable energy and oceans management to food security and urban transportation.
Many members of Congress have other priorities at home next week.
Senate Foreign Relations Committee Chairman John Kerry, D-Mass., who until recently had been rumored to be organizing a delegation of lawmakers to attend the summit, is still unsure whether he will make it. "The senator is eager to attend, but the Senate schedule is uncertain so we're still trying to figure out his plans," said Kerry spokeswoman Jodi Seth on Wednesday.
Another climate champion in Congress, Rep. Edward Markey, D-Mass., who chaired a select committee on global warming in the last Congress, has confirmed that he will not be going to Rio.
Even Senate Environment and Public Works ranking member James Inhofe, R-Okla., who has famously done fly-ins to environmental and climate conferences merely to mock them, is not likely to attend, he said. "No, but I thought about it," Inhofe said this week. He lamented that Rio is further away than Copenhagen, Denmark, where he flew in to spend a mere two hours at the 2009 U.N. climate talks.
Amy Harder contributed contributed to this article