This figure shows carbon dioxide measurements at Yasur volcano in Vanuatu on May 30, 2015. Yasur is a very active volcano and among the strongest sources of volcanic gas emissions on Earth. The OCO-2 data (left panel) show a small CO2 enhancement downwind (northwest) of the volcano. The middle panel shows the OCO-2 data rescaled to show the excess carbon dioxide concentration in the volcanic plume above the background concentration in the region. The figure shows that the volcanic signal is very small - only 1 percent above the background atmospheric carbon. This demonstrates why extremely sensitive satellite sensors like OCO-2 are needed to detect localized CO2 sources. The right panel shows the actual carbon dioxide concentrations highlighting the measurement pixels considered part of the volcanic plume.