Over the last century, atmospheric CO2 levels have increased by over 20%. The increase in atmospheric CO2 drives climate changes such as varied precipitation and extreme temperatures that could impact the CO2 uptake of trees and tree growth. While both climate changes and atmospheric CO2 may impact tree growth and CO2 uptake, the net effects of increased atmospheric CO2 on tree growth is still unknown. To further investigate this, we studied how the growth-climate relationships and carbon isotope ratios in trees from Western Minnesota vary over three time periods: 1930s, 1950s, and 2000s. Tree cores from Bonanza Prairie were collected, annual tree growth crossdated, measured, and δ13C isotopic ratio were quantified using EA IRMS. The detrended growth data was then analyzed with the Palmer Drought Severity Index (PDSI) data from the National Climate Data Center and with atmospheric CO2 levels collected from Mauna Loa Station over the selected time periods. The detrended growth data was also analyzed with δ13C isotope values to determine the correlation between growth and uptake in CO2. δ13C becomes more related to the atmospheric CO2 over time. In the 1950s, δ13C is only marginally related to CO2 concentration (R2 = 0.131, p=0.6188) but in the 2000s it is strongly related to atmospheric CO2 (R2 =0.7808, p=0.0055). Surprisingly, there was no significant correlation between PDSI and carbon isotope levels in the 1950s (R2= 0.0601, p=0.6039) and in the 2000s (R2=0.0057, p=0.8353). However, there was a significant correlation between average growth and PDSI (R2= 0.2455, p=7.5645E-09). These results suggest that as atmospheric CO2 increases, the carbon isotope levels also increase leading to trees that are less sensitive to drought because the trees require less water for the same carbon intake.