Toward Sustainable Aviation: Minimizing Aircraft Contrail Ice Particle Formation and Climate Effects by Controlled Seeding of Ice Nuclei Particles

Global aviation has contributed ∼3.5% to the anthropogenic climate forcing in 2018, of which around two-thirds (with substantial uncertainty) were due to non-CO₂ effects dominated by contrail cirrus. To be sustainable, the aviation industry faces a great challenge in reducing its climate footprint. There are ongoing efforts toward contrail avoidance via rerouting flights to avoid ice supersaturated regions, but serious reservations have been voiced against it because of extra fuel burning and resultant increased CO₂ emissions, among other issues. Based on simulations with a state-of-the-art aerosol and contrail microphysics model, we show that the aviation non-CO₂ climate effect associated with contrail cirrus may be significantly reduced via controlled seeding of a small amount of ice-nucleating particles (INPs). The optimized amount of INPs seeded will consume water vapor and minimize the peak relative humidity reached in the plume. In turn, this reduces the number of exhaust particles activating and forming contrail ice particles by up to 1-2 orders of magnitude, resulting in larger contrail ice particles that fall faster and shorter contrail lifetimes, which is expected to diminish the warming effect of contrail cirrus to a very small level. This novel approach may solve some of the issues associated with the proposed navigational contrail avoidance, but further research is needed to assess its feasibility and environmental impacts.