Impacts of greenhouse gases and deforestation in Amazon Basin climate extreme indices

Abstract

To evaluate the individual and combined impacts of increasing greenhouse gases and deforestation on extreme precipitation events in the Amazon Basin, we carried out 4 numerical experiments with the regional Eta model forced from the initial and boundary conditions of the global HadGEM2-ES model: (1) control experiment (CTRL); (2) RCP8.5 scenario; (3) DEFOREST scenario; and (4) RCP8.5+DEFOREST scenario. To analyze changes in extreme rainy events associated with the increase in greenhouse gases, deforestation, and their combined effect, anomalies were calculated from the sensitivity and control experiments. In the RCP8.5 scenario, there was an increase in the maximum number of consecutive dry days (CDD), a reduction in the maximum number of consecutive wet days (CWD), a reduction in total annual precipitation (PRCPTOT), and an increase in the maximum precipitation accumulated in 5 consecutive days (RX5Day). The DEFOREST scenario evidenced an increased CDD, and a reduction in the other indices (CWD, PRCPTOT, and RX5Day). Furthermore, the RCP8.5+DEFOREST scenario exhibited an increased CDD, and a reduction in the other indices (CWD, PRCPTOT, and RX5Day), but with more intense increases and reductions than observed in the DEFOREST scenario. In general, towards the end of the 21st century, the 3 scenarios are projected to increase the drought period, mainly on the boundary between the Brazilian states of Amazonas and Pará.