France's air pollution crisis became yet more dramatic Monday, as Paris banned half of its region's cars from the roads.

After highly polluted air became trapped close to the ground across France last week by unseasonably warm weather, authorities introduced free public transport over the weekend in Paris, Bordeaux, Caen, and Rouen. Now Paris has announced that only cars with odd numbered registration plates will be allowed to drive as of 5:30 this morning. To enforce the ban, police patrols will monitor traffic and dole out 22 fines to transgressors. Should poor air quality continue—and it's highly likely it will—on Tuesday cars with even numbered registration plates will take to the roads alone. Many are already asking whether the temporary ban will really work, and whether such short-term measures will be enough.

Early reports suggest it's working okay. France's National Centre for Road Information reported that congestion is down by 60 percent. This should help to ease, if not eradicate, high levels of toxic particulates entering the atmosphere, where warm air above is trapping them close to the ground.

In the future, however, Paris will need to do a lot more. Driving bans like the current one only seem to work as an emergency stopgap, and with climate change progressing, the sort of unseasonal weather France is experiencing is only likely to increase. As long-term measures, similar bans have failed before in other cities, including Lagos, Nigeria, and Milan, Italy, where drivers with the money simply bought a second car to circumvent the ban. Traffic levels remained similar. 

What France really needs to do, according to a number of environmentalists, is slash its dependency on diesel-powered engines. An estimated 60 percent of French vehicles currently run on diesel. This higher than average level dates from the 1960s, when French governments promoted diesel in the mistaken belief that it was cleaner than gasoline. In fact, diesel has both higher carbon emissions and carcinogenic fine particles, the form of invisible pollution from which France is currently suffering a major spike. The noxiousness of diesel has led to a paradoxical debate where far-from-benign gasoline emissions have gained the perverse position of being perceived as the lesser of two evils.

France's heavy investment in diesel vehicles means that, to date, there's been little effective pressure to reduce the country's diesel dependency —even this year, Paris introduced 320 new diesel-powered public buses

Exactly who is responsible for this environmental misstep has become a key city issue in recent days. As Paris mayoral candidates and Greens in France's ruling coalition trade accusations in what is becoming an increasingly ugly fight, France's currently noxious air might just be the watershed beyond which advocating for diesel becomes a political liability. No politician now wants to be associated with Paris's new buses and Anne Hidalgo, current mayoral frontrunner, has vowed to eliminate diesel entirely from the area of Paris under her jurisdiction. This crisis could well be the beginning of the end of France's love affair with diesel.