LAUSR

Meteorological data collected during the post‐9/11 flight grounding in the USA suggested that the removal of contrails increased diurnal temperature range (DTR), but subsequent research has contested this result. The 2010 Eyjafjallajokull eruption resulted in a 97% flight cancellation rate across the UK, offering another rare opportunity to compare DTR under contrail‐free skies against those with contrails. Temperature data from 199 UK meteorological stations indicate that a +3.4 °C DTR anomaly occurred during the grounding interval across the region previously affected by the highest flight densities, substantially larger than the +1.1 °C anomaly previously observed but smaller than other DTR anomalies (up to ~+6 °C) that were independent of the grounding. Although the observed DTR anomalies are largely attributable to weather system migration, a contribution of up to +1°C from contrail absence appears reconcilable with both the observed time evolution in DTR during the Eyjafjallajokull grounding period and previous results.