Two cheers for carbon tariffs Paul Krugman Share The Democratic carbon proposal says, in general terms, that we should levy tariffs on imports from countries that don’t take sufficient steps to limit greenhouse gas emissions. European nations plan to use a carbon border adjustment mechanism as a response to the threat of climate change. Photo: AP So how should we think about carbon tariffs? From past experience, I know we’ll hear a number of voices denouncing them as a new form of protectionism and/or asserting they’re illegal under international trade law. These voices should be ignored.