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

## TL;DR

Aircraft contrails contribute to climate change, but adding special particles could reduce their warming impact without rerouting flights.

## Contribution

A novel method of reducing contrail climate effects by seeding ice-nucleating particles is proposed.

## Key findings

- Seeding ice-nucleating particles can reduce contrail ice particle formation by up to 1–2 orders of magnitude.
- This method could shorten contrail lifetimes and reduce their warming effect significantly.
- The approach may avoid the drawbacks of flight rerouting, such as increased CO2 emissions.

## Abstract

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.