Climate scientists are concerned about the increase in carbon dioxide (CO2) levels in the atmosphere because CO2 is a greenhouse gas, trapping heat from sunlight. One of the best time series measuring CO2 levels is recorded monthly on the top of Mauna Loa in Hawaii. Because it is in the middle of the Pacific, the measurements are not contaminated with emissions from local traffic or industry.
CO2 levels are in parts per million (ppm)
time is fractional years with the month fraction added.