The small wiggles are seasonal variations caused by plants going dormant in the winter, and thus using no CO 2 . The Vostock ice cores have been analyzed for atmospheric CO 2 content over the last 1000 years. They show fairly steady CO 2 levels until the time of large-scale industrialization. The dashed portion of the curve is the Keeling curve from above. Deforestation, Rondonia district, Brazil.
Landsat images show healthy vegetation as red.
From USGS Earthshots page .