a positive trendP < 0.01
In accordance with trends in seasonal ΔCO 2 , annual ΔCO 2 exhibits a positive trend over the past 40 years (+0.132 ± 0.064 ppm/year, P < 0.01; Fig. 1C ).
In accordance with trends in seasonal ΔCO 2 , annual ΔCO 2 exhibits a positive trend over the past 40 years (+0.132 ± 0.064 ppm/year, P < 0.01; Fig. 1C ).