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Land cover change (LCC) and its impact on CO2 sequestration and radiative forcing (RF) could dramatically affect climate change, but there has been little effort to address this issue in South and Southeast Asia over a long period of time using actual land cover information. In this study, annual land cover data from 1992 to 2015 were used to assess the CO2 flux and corresponding RF due to LCC in South and Southeast Asia. The results showed that 553.2 x 10(3) km(2) of the region experienced LCC during this period, mostly due to land reclamation, urban expansion, and deforestation. These LCC caused a marked net decrease in net ecosystem productivity (NEP) as a composite of the various land cover categories during the whole study period, especially since 2001. The CO2 sequestration was 2160 TgCO(2) during the early 1990s however cumulative sequestration decreased by 414.95 TgCO(2) by 2015. Correspondingly, the cooling effect of NEP, i.e. the total actual RF, was -0.366 W m(-2) in South and Southeast Asia between 1992 and 2015. However, the potential RF of the cumulatively reduced NEP due to LCC relative to the 1990s resulted in a warming effect of 2.33 x 10(-3) W m(-2) in 2015. Our study provides an applicable framework to accurately assess the potential effect of large-scale LCC on climate.