Some scientists believe that Southeast Asia is the primary place where new air is transported into the stratosphere. SEAC4RS will investigate that hypothesis and provide new insights into exactly what the effects are of the pollution vapors and tiny particles called aerosols that reach the stratosphere. Do the particles reflect incoming solar energy and produce a net cooling of our planet? Do the gases alter the chemical balance of the upper atmosphere and features like our protective ozone layer? SEAC4RS will address these issues of global concern.