A note on how to avoid contrail cirrus

Aircraft induced cirrus clouds have a major effect on climate. Here we use operational radiosonde data with high vertical resolution to estimate the effect of a small change in flight altitudes on the contrail and cirrus formation. It is shown that a substantial fraction of contrails and contrail induced cirrus can be avoided by relatively small changes in flight level, due to the shallowness of ice-super-saturation layers.