Even 'net zero' aviation could still cause significant global warming

Efforts to make flying greener mostly count carbon dioxide emissions only, but modelling shows this ignores 90 per cent of future flights’ contribution to climate change

Future flights will endanger the goals of the Paris climate agreement if efforts to achieve net-zero aviation fail to account for the warming effect of streaks of clouds created by planes, a study has found.

The research comes just days after the UK government announced its Jet Zero Strategy on 19 July, with a target of reducing carbon emissions from flights to net zero by 2050.

Nicoletta Brazzola  at ETH Zurich in Switzerland and her colleagues found that even if such efforts to reduce carbon emissions succeed, the aviation sector worldwide could increase global average temperatures by between 0.1°C and 0.4°C. Because the world has already warmed 1.1°C since the industrial revolution, Brazzola ’s team says the extra warming could compromise the Paris deal’s aim of holding temperature rises to 1.5°C.

The warming comes from the ways flights heat the atmosphere beyond the carbon dioxide emitted by burning jet fuel, which are the only emissions currently counted by international and most national efforts to decarbonise aviation. The main one of these non-CO2 effects is the contrails that form because of the soot, aerosols and water vapour released by aircraft engines.

“We found the mitigation efforts needed to get aviation to a place where it’s compatible with the Paris agreement are enormous,” says Brazzola.

Her team explored different future scenarios of demand for flights,