Long-term Variability, Extremes, and Changes in Temperature and Hydro Meteorology

The Science Panel for the Amazon is an unprecedented initiative convened under the auspices of the United Nations Sustainable Development Solutions Network (SDSN). The SPA is composed of over 200 preeminent scientists and researchers from the eight Amazonian countries, French Guiana, and global partners. These experts came together to debate, analyze, and assemble the accumulated knowledge of the scientific community, Indigenous peoples, and other stakeholders that live and work in the Amazon. The Panel is inspired by the Leticia Pact for the Amazon. This is a first-of-its-kind Report which provides a comprehensive, objective, open, transparent, systematic, and rigorous scienti fic assessment of the state of the Amazon’s ecosystems, current trends, and their implications for the long-term well-being of the region, as well as opportunities and policy relevant options for conservation and sustainable development. Abstract Observed and projected changes in the Amazon show that current climate and hydrology tendencies can be differen-tiated both spatially and temporally, exhibiting two seesaw spatial patterns, one north-south and the other west-east, and an intensification of the wet and dry seasons. In the present, the northwestern Amazon shows an increase in rainfall and runoff, while in the southern part it is the opposite. The region, including the central and eastern Amazon, does not show a significant rainfall trend as a whole. How-ever, observations suggest an increase in rainfall extremes and intensification of droughts and floods, with little overall change in mean annual river discharges. Temperature records show an overall warming of the Amazon in recent decades, especially from the year 2000 to the present over the eastern Amazon. Evapotranspiration (ET) is reduced in the southern Amazon, probably as a result of land-use change, but uncertainties are still high due to the lack of systematic observations across the basin. This analysis is based on a literature review of findings based on different observational, reanalysis, and satellite datasets of rainfall, temperature, and river discharge records, and different methodologies (parametric and non-parametric tech-niques), leading to different levels of confidence, consistency, and magnitude of trends. show a drier and warmer climate in the eastern leading to an evapotranspiration. experience conditions, but rainfall Abstract This chapter discusses observed hydroclimatic trends and also projections of future climate in the Amazon. Warming over this region is a fact, but the magnitude of the warming Amazon. Changes in floods and droughts largely due to natural climate variability and land use change are also assessed. For instance, in the first half of the 20th century extreme flood events occurred every 20 years. Since 2000, there has been 1 severe flood every 4 years. During the last four decades, the northern Amazon has experienced enhanced convective activity and rainfall, in contrast to decreases in convection and rainfall in the southern Amazon. Climate change in the Amazon will have impacts at regional and global scales. Significant reductions in rainfall are projected for the eastern Amazon. This will have consequences for regional hydrology, and consequently, increasing vulnerability of ecosystem services for the local and regional population in and outside the Amazon.