By Rebecca Washenfelder

The Total Carbon Column Observing Network is a new network of ground-based solar observatories, dedicated to column measurements of greenhouse gases. We present CO₂ column abundances observed in Park Falls, Wisconsin and Lauder, New Zealand during May 2004 – June 2005. In Park Falls, Wisconsin, the peak-to-peak variation of column-average CO₂ is approximately 13 ppmv. In Lauder, New Zealand, the peak-to-peak variation of column-average CO₂ is approximately 4 ppmv. Assuming a secular trend of 2 ppmv yr^-1, we infer a peak-to-peak seasonal amplitude of 11 ppmv and 2 ppmv for Park Falls and Lauder respectively. These values are higher than model predictions by Olsen and Randerson [2003].