Issues and uncertainties affecting metrics for aviation impacts on climate

Metrics tools based on the concept of radiative forcing, are used for evaluating and guiding decision making associated with tradeoffs between environmental impacts, aircraft design, and operations to minimize the impacts of aviation on climate, once their limitations are assessed and resolved. Intergovernmental Panel on Climate Change (IPCC) reports use radiative forcing to compare different climate change mechanisms. The Kyoto Protocol has adopted the 100-yr global warming potential (GWP) to compare the climate impact from emissions for various greenhouse gases. The IPCC Special Report on Aviation proposed a radiative forcing index (RFI) to compare aviation effects and presented GWPs for aviation effects to counter the misuse of the RFI as an emission metric by policy makers and carbon-offsetting sites. It is required to continue the use, evaluation, and development of the GWP and GTP metrics, continue the development of global climate model, adapt common metrics, and continue development of socioeconomic metrics.