When the Intergovernmental Panel on Climate Change issued its last report in 2007, environmental tipping points were a footnote. A troubling footnote, to be sure, but the science was relatively new and unsettled. Straightforward global warming was enough to worry about. But when the IPCC meets in 2014, tipping points — or tipping elements, in academic vernacular — will get much more attention. Scientists still disagree about which planetary systems are extra-sensitive to climate shifts, but the possibility can’t be ignored.

As the world has talked for a dozen years about what to do next, new ship passages opened through the Arctic's once-frozen summer sea ice. In Greenland and Antarctica, ice sheets have lost trillions of tons. Mountain glaciers in Europe, South America, Asia and Africa are shrinking faster than before. By SETH BORENSTEIN, The Associated Press

Rome, Italy (CNN) -- Somewhere in the world, a child dies of hunger every five seconds -- even though the planet has more than enough food for all. U.N. Secretary-General Ban Ki-moon laid out this sobering statistic as he kicked off a three-day summit on world food security Monday in Rome. "Today, more than 1 billion people are hungry," he told the assembled leaders. Six million children die of hunger every year -- 17,000 every day, he said.

Earth’s atmosphere isn’t the only victim of burning fossil fuels. About a quarter of all carbon dioxide emissions are absorbed by the earth’s oceans, where they’re having an impact that’s just starting to be understood. Leading scientific experts believe that it’s possible to cut back on global warming pollution, improve the overall health and durability of our oceans, and prevent serious harm to our world—but only if action is taken quickly and decisively.

They say that everyone who finally gets it about climate change has an "Oh, shit" moment--an instant when the full scientific implications become clear and they suddenly realize what a horrifically dangerous situation humanity has created for itself. Listening to the speeches, groundbreaking in their way, that President Obama and Chinese President Hu Jintao delivered September 22 at the UN Summit on Climate Change, I was reminded of my most recent "Oh, shit" moment.