Simulated radiative forcing from contrails and contrail cirrus

A comprehensive general circulation model including ice supersaturation is used to estimate the climate impact of aviation induced contrails. The model uses a realistic aviation emissions inventory for 2006 to initiate contrails, and allows them to evolve consistently with the model hydrologic cycle. The radiative forcing from linear contrails is very sensitive to the diurnal cycle of flights. For linear contrails, including the diurnal cycle of flights reduces the estimated global radiative forcing by 55%, and for contrails cirrus estimates, the global radiative forcing is reduced by 25%. Estimated global radiative forcing from linear contrails is 0.0029±0.00125 W m−2. The instantaneous radiative forcing for contrails is found to exhibit a strong diurnal cycle. The integrated effect of contrail cirrus is much less sensitive to the diurnal cycle of flights. The estimated global radiative forcing from contrail cirrus is 0.012±0.01 W m−2. Over regions with the highest air traffic, the regional effect can be as large as 1 W m−2.