Plants have been shown to photosynthesize more with increased atmospheric levels of CO2, but the effect can be hard to determine. Lab researchers are reporting the first direct observational evidence of the impact CO2 has on increasing photosynthesis in natural environments. https://eesa.lbl.gov/eddy-fluxes-are-key-to-quantifying-how-much-more-plants-photosynthesize-with-increased-atmospheric-co2/