Expectations were extremely modest for the Rio+20 Earth Summit that ended last week—and the best thing that might be said about the conference is that it managed to clear that very low bar. Despite the presence of more than 50,000 people and about 100 heads of state and government—though not, notably, U.S. President Barack Obama—the summit produced very little of note. The final statement that was negotiated at Rio—titled "The Future We Want"—was 253 paragraphs of affirmations and entreaties that added up to little more than a plea for something better. The Chinese diplomat Sha Zukang, who headed Rio+20 for the U.N., called the statement "an outcome that makes nobody happy," while environmental NGOs were blunter: "A failure of epic proportions" said Kumi Naidoo, the executive director of Greenpeace International, adding that the statement itself was "the longest suicide note in history."

(LIST: Rio Climate Summit: Top 10 Priorities for a Planet in Peril)

It's tempting to use the failure of the Rio+20 conference as evidence that international environmental summits and accords are simply unworkable. But it's hardly only environmental issues that are gridlocked at the global level. Just a few days before Rio, the leaders of the world's most powerful countries failed to make much progress on either the European financial crisis or the violence in Syria—two problems that are more immediately pressing than climate change, water shortages, endangered species or just about any other big-picture issue that was kicked around in Rio. If the leaders of the world can't come together to avert what could be the next great global recession or a growing Syrian bloodbath, fixing the infinitely more complex problem of climate change seems all but hopeless.

So how worried should we be? There's no shortage of frightening studies that tell us we're headed for a climate tipping point—we've covered them here at Going Green. But we've heard warnings about imminent environmental collapse before, and they haven't yet been right, as the Danish economist and environmental contrarian Bjorn Lomborg points out in an essay in the latest edition of Foreign Affairs.

Lomborg looks back to an influential 1972 report called The Limits to Growth, by the Club of Rome—a blue-ribbon collection of business leaders, scholars and government officials convened at the time by the Italian tycoon Aurielo Peccei. Based on forecasts drawn from computer models developed by the Massachusetts Institute of Technology, the Club of Rome predicted that the world was about to hit a wall on vital natural resources like food and energy, even as it was choked by pollution.