Abstract The atmospheric CO 2 growth rate (CGR) variability is largely controlled by tropical temperature fluctuations. The sensitivity of CGR to tropical temperature $$\left({{{{\rm{\gamma }}}}}_{{{{\rm{CGR}}}}}^{{{{\rm{T}}}}}\right)$$ γ CGR T has strongly increased since 1960, but here we show that this trend has ceased. Here, we use the long-term CO 2 records from Mauna Loa and the South Pole to compute CGR, and show that $${{{{\rm{\gamma }}}}}_{{{{\rm{CGR}}}}}^{{{{\rm{T}}}}}$$ γ CGR T increased by 200% from 1960–1979 to 1979–2000 but then decreased by 117% from 1980–2001 to 2001–2020, almost returning back to the level of the 1960s. Variations in $${{{{\rm{\gamma }}}}}_{{{{\rm{CGR}}}}}^{{{{\rm{T}}}}}$$ γ CGR T are significantly correlated with changes in precipitation at a bi-decadal scale. These findings are further corroborated by results from a dynamic vegetation model, collectively suggesting that increases in precipitation control the decreased $${{{{\rm{\gamma }}}}}_{{{{\rm{CGR}}}}}^{{{{\rm{T}}}}}$$ γ CGR T during recent decades. Our results indicate that wetter conditions have led to a decoupling of the impact of the tropical temperature variation on the carbon cycle.