Global carmakers, stung by emissions scandals, are racing to hunt down every gram of harmful CO2 spewed out on the roads as tougher pollution rules kick in. Auto manufacturers gearing up for Europe's biggest annual car show in Geneva are celebrating the end of the sector's crisis.

European sales have returned to the levels last seen in 2008 before a global financial meltdown inflicted deep dents on their business. But a dark cloud has gathered over the outlook because of emissions scandals, especially involving European market leader Volkswagen, and the road to recovery will be paved with unprecedented efforts to fight auto pollution, involving equally unprecedented costs.

"Solutions are more and more expensive," said Marc Charlet, at Mov'eo, an automotive and mobility research network. "There is much at stake here, and the competition is fierce." European rules for combustion engines were always going to become more stringent, but Volkswagen's emissions cheating, the industry's biggest pollution scandal to date, has turbo-charged regulators' eagerness to crack down on pollution.