Mr. Marchionne is a firm believer that the most realistic and available solution to reduce car pollution is reducing engine size. This agrees with Fiat's new policy on smaller turbo-charged engines, called T-Jet, and also the latest iteration of the common-rail JTD diesels. Speaking about other green car technologies, he acknowledges the benefit possible from hybrid powertrains, but believes that they're complex and expensive, and therefore more suitable for expensive cars. Regarding hydrogen, he stated that it isn't expected to be ready until 2020, but he finds it will be a real revolution once the technology is viable.
[Source: L'Hebdo (thanks to Jeroen for the tip)]