Defining success and limits of field experiments to test geoengineering by marine cloud brightening

Marine cloud brightening (MCB) has been suggested as a possible solar radiation management approach to geoengineering the Earth’s climate in order to offset anthropogenic global warming. We discuss the utility of field experiments to test MCB. These experiments, if appropriately designed, would provide an unprecedented controlled environment to not only test MCB, but to understand aerosol impacts on climate. We discuss the science of MCB and review a set of field experiments that has been proposed as de minimis first steps to field test the concept. Our focus is upon issues of success determination, international oversight and/or governance, and outcomes if initial tests are deemed successful.