The impact of rising greenhouse gases and deforestation on temperature extremes in the Amazon basin

O impacto do aumento dos gases de efeito estufa e do desmatamento nos extremos de temperatura na bacia amazônica

Understanding the impacts of climate change and land-use change is crucial for anticipating environmental risks in the Amazon, a region that plays a key role in global climate regulation. This study aimed to investigate the individual and combined impacts of increased greenhouse gas (GHG) concentrations and deforestation on temperature extremes in the Amazon region. Numerical experiments were conducted using the regional climate model Eta, driven by initial and boundary conditions from the global model HadGEM2-ES. The GHG increase scenario followed projections from the Intergovernmental Panel on Climate Change (IPCC) under the Representative Concentration Pathway (RCP8.5). The impact of deforestation was evaluated through an experiment in which the entire Amazon rainforest was removed. The combined scenario represents the integration of RCP8.5 and total deforestation. All experiments revealed anomalous increases in the annual maximum temperature (TXx), annual minimum temperature (TNx), the percentage of days when the maximum temperature (TX) exceeded the 90th percentile (TX90p), and days when the minimum temperature (TN) exceeded the 90th percentile (TN90p). Notably, deforestation caused more significant changes in temperature-related climate indices than the RCP8.5 scenario, with extreme increases of approximately 6 °C to 7 °C observed in up to 60% of the year. In contrast, the combined scenario showed the most intense anomalous impacts, with temperature increases reaching up to 9 °C occurring in as much as 90% of the year. In summary, both GHG increases and deforestation intensify the magnitude and frequency of temperature extremes in the Amazon.

Keywords:
Climate extremes; temperature indices; Eta model; global model HadGEM2-ES