There is publicity today (or nearly) about 2 new Port of Oakland railroad engine (OGRE). The publicity from the Port talks about the wonders of the new engines, but doesn't say what they are. Turns out they are Tier 4 diesels. I wondered what a Tier 4 diesel is, and found this link to YouTube. The link is dreadfully corny, but underneath the corn, there is basic information. My interpretation: It's diesel, with a whole lot of sensors and monitoring. It will have lower emissions of smoke (a very good thing). It will be quicker and cheaper to detect deterioration of parts -- the idea is to change out parts before they cause the whole engine's performance to deteriorate. Of course, part of performance is hauling the trains; but diesel smoke is also a big deal. If parts are fixed early, it will reduce smoke, even before pollutants become measurable in the engine's exhaust.

Smoke is one thing. Carbon dioxide is another -- I don't think Tier 4 will help very much about CO2, and therefore Tier 4 won't be a big help regarding the global climate.