A growing shadowy fleet of tankers carrying sanctioned Iranian, Venezuelan, and Russian oil is filling up with the cheapest fuel available, hampering efforts to reduce emissions from shipping, according to Reuters. Hundreds of tankers carrying sanctioned oil are a problem because they are difficult to track due to their opaque ownership and use of non-Western insurance and other maritime services, and they have little incentive to comply with cleaner shipping standards. “You’re seeing greater numbers of ships that have found ways to circumvent sanctions by operating outside Western jurisdictio…