Carbon Dioxide Levels Pass 'Depressing' Milestone

In a development climate scientists are calling "depressing" and "troubling"—but not the least bit surprising—the level of the main global warming pollutant has passed a new milestone. Monitoring stations all over the Arctic are measuring more than 400 parts per million of carbon dioxide in the atmosphere, a level the world hasn't seen for at least 800,000 years, reports AP. Before the burning of fossil fuels began in the Industrial Age, levels were close to 275 parts per million, and have been rising steadily ever since. The 350 mark considered the highest safe level was passed years ago.

Only the Arctic has reached the 400 level so far, but the rest of the world will soon follow. Global carbon emissions hit a record high of 34.8 billion tons last year, according to the International Energy Agency. Climate scientists describe the 400 milestone as more of a psychological one than a scientific one. "It's just a reminder to everybody that we haven't fixed this, and we're still in trouble," says the global monitoring director at the National Oceanic and Atmospheric Administration's Earth System Research Lab. (More carbon dioxide stories.)