According to the 57th Japan Antarctic Research Expedition (JARE)/National Institute of Polar Research (NIPR), a daily mean atmospheric CO2 concentration value of 400.06 ppm was observed at Syowa Station, Antarctica, on May 14, 2016. This is the first time that the CO2 concentration at Syowa Station has exceeded 400 ppm since NIPR and the Tohoku University in Japan initiated observations in 1984. In addition, the monthly mean CO2 concentration value for June 2016 reached 400.51 ppm. CO2 is a greenhouse gas, and its atmospheric concentration is increasing owing to human activities since the Industrial Revolution. Global warming associated with the increase in atmospheric CO2 and other greenhouse gases has become a serious problem worldwide. "The fact that an atmospheric CO2 concentration over 400 ppm was observed at Syowa implies that anthropogenic activities are definitely affecting the Antarctic region, even though Antarctica is far from the northern hemisphere where the population is concentrated," said Daisuke Goto, an assistant professor at NIPR. CO2 has exceeded 400 ppm at many locations on Earth; however, the Antarctic was the only region where CO2 had not yet reached 400 ppm. "It is important to continue monitoring the atmospheric CO2 concentration," Goto emphasized.