The newspapers reported today that G-8 leaders had reached an agreement of sorts on cutting global warming emissions by half by mid-century. But it wasn’t a real agreement, they said—more of a way to put off the argument. Which is a least a little bit of good news—because that level of reductions is so feeble that it will allow the planet to slide right over the brink of disaster. It’s not just us—our friends at AVAAZ called it “mush,” Greenpeace said it was “nothing but flower words,” and Oxfam said it “did nothing to lower the risk faced by the world’s poor.” The World Wildlife Federation termed it downright pathetic.

How, you might ask, could the world’s leaders agree on so misguided a set of targets? One answer, of course, is the power of special interests over politics. But another is that they seem to be working off of very old information. According to the Financial Times, which ran a special section on the G-8 meeting Monday, “the goal was arrived at” by reasoning that “keeping the concentration of carbon dioxide in the atmosphere below 550 parts per million” would be enough to ward off disaster. But that number is two decades old—and if anyone still believed in it, their faith was shaken last fall when the Arctic melted. We’re at 387 ppm now and the Arctic is melting. What does that tell you?

It tells us that we need badly to get to work—and that if we manage to spread a new, more acccurate number it could have real effects on the international negotiations. We’ve seen what happens when old science and political convenience rule the day; it’s time to bring our leaders up to date.