As atmospheric concentrations of carbon dioxide approach the milestone of 400 parts per million (ppm), a scientist at the Scripps Institution of Oceanography has launched a Website that will publish daily readings of CO2 concentrations, an online resource he hopes will drive home the urgent threat of rising greenhouse gas emissions. Ralph Keeling, director of the Scripps CO2 program and son of the first scientist to measure CO2 concentrations, hopes the daily tracker will attract more attention than weekly or monthly postings, providing a stark index of humanity’s effect on the global climate. “I hope that many people out there in decades to come will say, ‘Gosh, I will remember when it crossed 400,’” Keeling told ClimateWire. The measurements will come from the Mauna Loa observatory in Hawaii. Keeling’s father, Charles David Keeling, first started collecting CO2 concentrations in the 1950s from the same observatory, when few believed that carbon dioxide concentrations were in fact rising. His ongoing recording of CO2 concentrations came to be known as the “Keeling Curve.” As of April 22, CO2 concentrations had reached 398.36 ppm, according to the site, well above pre-industrial concentrations of about 280 ppm.