Increases in the north-south gradient of atmospheric CO₂ at Northern Hemisphere measurement sites of the NOAA/CMDL Global Air Sampling Network reveal a shrinking carbon sink. 14 of 16 low altitude sites show differences with South Pole increasing at a faster rate than can be explained by fossil fuel emissions, resulting in an average north-south difference at remote marine sites nearly 1 ppm larger in 2003 than in 1992. Regardless of whether this trend will persist, it shows that large changes in the carbon cycle can occur rapidly and is a strong indication of the tenuous nature of terrestrial carbon sinks.