I just don't understand how people can believe in climate change and also believe that "ROI for me and my shareholders" is still a good way to make decisions. Buffett certainly isn't going to be an activist investor, because pushing oil companies to change will provide worse ROI than just staying the course. We need to be doing more to combat climate change, including a carbon tax. If that happens, oil companies will be much less profitable, so it seems like Buffett is betting that won't happen, which seems like a very cynical and coldhearted move.
Also, let's not forget that us humans have to live in the environment, so "a terrible cost for the environment" is a terrible cost for humans. Unfortunately, that cost is externalized so it doesn't affect Buffetts precious ROI.