The National Oceanic and Atmospheric Administration spends roughly $6 million per year to sample carbon dioxide, methane and nearly 20 other gases using a global network of ground stations, tall towers and aircraft.
But faced with shrinking budgets and an uncertain fiscal future, NOAA has stopped measuring greenhouse gas levels at a dozen ground stations, eliminated some aircraft monitoring and cut the frequency of remaining measurements in half. The agency scrapped plans to expand its network of tall towers and is now moving to shut down some of the seven existing sites.
It's interesting how NOAA collects data. In addition to monitoring stations and towers, the agency also collects samples submitted from volunteers and pays small plane operators for flasks that collect samples mid-flight.