evidence: It’s the latest in a long list of broken records, and like the others, it promises to hold the title temporarily. Atmospheric CO2 is rising at accelerating rates—currently climbing at close to 3 ppm each year, and getting faster. Every year, the world sees new levels that were previously unrecorded in modern human history. The last time CO2 concentrations hit 415 ppm was likely close to 3 million years ago. [...] Not only are atmospheric concentrations still climbing, but the rate seems to be accelerating. Ralph Keeling, director of the Scripps Institute of Oceanography’s CO2 Program, which monitors CO2 concentrations at the Mauna Loa Observatory in Hawaii, noted that this year’s total increase will probably be around 3 ppm. The recent annual average has been hovering around 2.5 ppm. [...] It’s also important to note that today’s conditions aren’t perfectly comparable with those in the past. Even if today’s CO2 concentrations are similar to the levels seen millions of years ago, the rate at which they’re currently climbing probably "outstrips anything we’ve seen in the geological record for at least 65 million years," Foster said.