Observations of atmospheric chemistry are important. Scientist record data about the chemical composition of air over time to watch for any changes. One example of this is the Keeling Curve - a series of measurements from 1958 to today which show a steady rise in of the concentration of carbon dioxide. Observations of atmospheric chemistry are made in observatories such as that on Mauna Loa and on mobile platforms such as aircraft, ships and balloons. Observations of atmospheric composition are increasingly made by satellites giving a global picture of air pollution and chemistry. Surface observations have the advantage that they provide long term records at high time resolution but provide data from a limited vertical and horizontal space. Some surface based instruments such as LIDAR can provide concentration profiles of chemical compounds and aerosol but are still restricted in the horizontal region they cover. Many observations are shared on-line.