The Washington Post - For the first time since humans have been monitoring, atmospheric concentrations of carbon dioxide have exceeded 410 parts per million averaged across an entire month, a threshold that pushes the planet ever closer to warming beyond levels that scientists and the international community have deemed “safe.”
"It's another milestone in the upward increase in CO2 over time," Keeling said of the newest measurements. "It puts us closer to some targets we don't really want to get to, like getting over 450 or 500 ppm. That's pretty much dangerous territory.""As a scientist, what concerns me the most is not that we have passed yet another round-number threshold but what this continued rise actually means: that we are continuing full speed ahead with an unprecedented experiment with our planet, the only home we have," Katharine Hayhoe, a climate scientist at Texas Tech University, said in a statement on the milestone.
Planetary carbon dioxide levels have been this high or even higher in the planet's history — but it has been a long time. And scientists are concerned that the rate of change now is far faster than what Earth has previously been used to.