Well, it’s not the Horsemen of the Apocalypse, but it’s a start.

A coalition of U.S. environmental and social justice groups has asked President Obama to step up and attend the Earth Summit, a gathering of international bigwigs next month in Rio. It’ll be an important opportunity to meet influential people from other countries, attend critical meetings, and lead high-level negotiations. Oh, and figure out how to build a green economy, Van Jones-style, around the globe.

Twenty years ago, when George Bush Sr. was hedging about attending the first Rio Earth Summit, a pack of green groups tried to convince him with a spooky video featuring a horse charging through a burning wasteland and James Earl Jones warning ominously of the planet’s imminent demise. He did attend, and had some fascinating conversations, while Barbara enjoyed her stay as well.

This year, many of the major U.S. green groups were weirdly silent about the Earth Summit — until this week, when they sent Obama a letter:

We are writing on behalf of civil society organizations that represent more than 5 million Americans to urge you to commit as soon as possible to lead the United States delegation to the Rio+20 Earth Summit in Brazil in June.

Your presence at this Summit would signal its critical importance to all Americans, demonstrate our country’s deep concern over urgent global issues that will inevitably affect our security and well-being, and highlight our nation’s determination to be a contender in the race to a low-carbon green economy.

The letter [PDF] also asks Obama to roll out a list of commitments from the U.S. to promote the green economy here and abroad. The groups want Obama to push for elimination of fossil-fuel subsidies, sign onto the U.N.’s Sustainable Energy for All Initiative, which aims to bring clean power to developing countries, and crack down on ocean pollution and overfishing.

Twenty-two groups signed onto the letter, including four of the seven groups behind the Horsemen of the Apocalypse video in 1992 (the National Audubon Society, The Wilderness Society, and the Rainforest Action Network are still MIA), and some notable additions, among them the National Tribal Environmental Council, Physicians for Social Responsibility, and the Union of Concerned Scientists.

No word yet from the prez on whether he’s accepting the invitation. German Chancellor Angela Merkel is reportedly out. So is British Prime Minister David Cameron — never mind that Cameron once pledged to lead the “greenest government ever,” and the U.N. postponed the Earth Summit so it wouldn’t conflict with the other huge event of mind-blowing global importance next month: the British Queen’s Diamond Jubilee. (Seriously, Brits, why do you even still have a queen? You tell me that and I’ll try to explain why we have the Electoral College. Deal?) Also bailing are members of the European parliament, who say they can’t afford the hotels, which have jacked up their rates for the occasion.

The good news is that the presidents and prime ministers of more than 130 other nations have RSVPed for the event. And if Obama does decide to attend, I happen to know that there are still bunks available at one of the beachside hostels at Copacabana, cheap. I’m sure he’d find something worthwhile to do.