Defining "properly" when related to taxes is too difficult for a HN comment. Also, I'm neither a climate scientist nor do I consider myself an expert in economy. I'm rather concerned about climate change, so my numbers would likely be much higher than necessary.

But I'd suggest putting a bunch of scientists in a room for a while to figure out the environmental impact and define some acceptable limit of yearly pollution. Then raise taxes until we're under the limit. Or something similar.