Note that none of the ACCRI models estimated RF for contrails, contrails-cirrus, and indirect RF for the 2050-S2 scenario.
As not all ACCRI models simulated the temperature change, the applicability of the Lund et al.
ACCRI program has made some important contributions to advance the scientific understanding of climate impacts of aviation emissions.
Despite the complexities of the climate system, ACCRI helped constrain some uncertainties; however, large uncertainties have emerged in some areas (e.g., indirect effects of aerosols on clouds) that need to be further constrained.
ACCRI has contributed to the estimation of aviation-induced cirrus cloud climate forcing based on global observation datasets and increased the level of scientific understanding from "very low" to "low." The largest contribution of aviation emissions to climate change results from the presence of contrails and associated cirrus clouds and also from enhanced ozone concentrations in the upper troposphere and lower stratosphere.
METRICS FOR AVIATION EFFECTS ON CLIMATE: ACCRI CONTRIBUTIONS
A key part of ACCRI's focus has been the refinement of analytical tools and metrics that simplify the complex understanding of the science as an aid in decision-making.
Prior to the new findings from ACCRI, the summary analyses for RF in LEE2009 have been held as the standard reference for the understanding of aviation effects on climate.
Aviation-related RF values are quite inhomogeneous in space and time and varying degrees of coupling are used by the ACCRI models.
In ACCRI, there has been a focus on understanding the linkages between, and interpretations of, different emission metrics, whose key findings are highlighted in D.
IMPLEMENTATION OF ACCRI RESULTS IN A SIMPLE CLIMATE MODEL
New short-lived climate forcer (SLCF) pathway, such as the impact of nitrates and the indirect sulfate response identified in ACCRI studies, climate modules are not currently included in the APMT-I and will be added upon their further refinement.