Monthly Graph - This shows hourly averaged CO₂ data collected on the Space Needle and from a buoy off the Washington coast (west of Aberdeen, WA) over the last 30 days. The CO₂ values over Seattle are higher and much more variable because many of our daily activities such as cooking with gas or driving to work release CO₂ into the atmosphere.

Seasonal Graph - This shows daily averaged data collected on the Space Needle and from a buoy off the Washington coast (west of Aberdeen, WA) over the last few years. The Space Needle instrument was installed in February 2010 so the data record is still short, but the offshore buoy has been recording atmospheric CO₂ since June of 2006. We measure the CO₂ offshore because that usually gives us a good clean record of CO₂ concentrations in the air entering the United States before local CO₂ sources increase the CO₂ levels. The seasonal CO₂ cycle reflects natural variations in the growth of land plants in the Northern Hemisphere. In the spring and summer plants pull CO₂ out of the atmosphere as they start to grow and put on leaves. This growth makes a noticeable drop in the northern hemisphere atmospheric CO₂ concentrations. In the fall and winter when plants begin to die back and trees drop their leaves, the atmospheric CO₂ increases.