Blue summer skies finally reached Brussels this weekend, and with it came the fluffy aircraft contrails that crisscross Belgium’s busy skies. These white stripes are firmly in the EU’s sights due to their serious climate impact, distinct from and in addition to the warming from aircraft CO2 emissions. As a result EU law requires that from 2025, airlines’ ‘non-CO2 emissions’ must be monitored, reported, and verified, for all flights departing from the EU. As well as contrails, monitoring efforts will cover nitrous oxides, sulfur dioxide, and soot emissions. Airlines are pushing back against these requirements, saying the science is not yet strong enough to support an obligatory monitoring regime. This is not the only scientific point that airlines and governments disagree on. The EU’s position, backed by an extensive 2020 report, is that non-CO2 aircraft emissions have a climate impact at least or as great as the warming from aircraft’s CO2 emissions. The International Air Transport Association (IATA), which represents both European and international airlines, accepts that non-CO2 emissions have a warming impact overall, but says there is much less scientific consensus on the magnitude of warming. But monitoring these non-CO2 emissions is crucial, not only for policy making but also for day-to-day mitigation action. One point on which all agree is that contrails’ climate impact stems from a small number of flights, in certain regions and at certain times. Aircraft flying high in the atmosphere through cool and humid air have the greatest impact – particularly if the contrails persist at night. With strong data on when and where contrails are likely to form and persist, individual aircraft should be able to avoid in the future these zones, and seriously reduce their climate impact. |