As someone - and I regret to say I've forgotten who - commented, the ETS (European Trading System) CO2 permit price (aka EU carbon allowances, or European Allowances (EUAs), apparently) seems to have spiked recently. Why?
Of course, I don't know, so I asked Google. The answer looks to be mostly the EU fiddling with the supply. See the FT, or the EU's own ETS Market Stability Reserve will start by reducing auction volume by almost 265 million allowances over the first 8 months of 2019. This, of course, is one of the problems with any such scheme: people fiddle with it when it delivers the "wrong" answer. In this case, the low price was a "yes" answer to the question "did you pols bung too many permits at heavy industry in order to buy them off and make yourself popular?".