Environmental Quality, Climate Change, and Society in the 21st Century

As the trends of the 20^th century demonstrate, the variation and degradation in the quality of the environment have been intertwined with human influences on atmospheric composition. Asia has been seriously exposed to vulnerabilities arising due to extremes occurring in air quality and climate. Changes in atmospheric composition, notably the emissions of anthropogenic greenhouse gases and aerosols, have influenced the climate of all the inhabited continents and in particular Asia. In this presentation, we investigate the manner in which natural and anthropogenic factors have altered atmospheric composition and forced changes on temperature and precipitation in Asia. Using observations and global climate model simulations to construct a causal understanding of the trends in Asia evidenced over the past several decades, it becomes clear that anthropogenic aerosols have counteracted greenhouse gas effects to a significant extent with regards to climate forcing, temperature and precipitation. This understanding, along with a characterization of the scientific uncertainties, is followed by model-based projections of atmospheric composition, air quality, and climate for Asia over the 21^st century in response to emissions scenarios of greenhouse gases and aerosols. We will discuss the changes anticipated in the 21^st century for key variables, which is information input for Asia society planning and decision-making.