I should be happy with a slight warming, which BTW has manifested itself within my lifespan, mainly with peaking summer temps and short winters. My country in seeing increased crops and more possibilities in the flora.
However, if you go down to the warm-temperate climates, that is not the case.
And for the productive cooler seas, - yuppy. Hard to understand maybe (we are not fishes), - but as a fisherman I will verify this. The grounds on the northern seas are rich for instance. Heck, I spent the best part of a month fishing above the polar circle, and was amazed by the catch and it's variety. Still big codfish, and a very impressive catch at great depths (we went down to 900 fathoms).
As a sidenote for you WW2 geeks, there are many wrecks in our area, and HMS HOOD was on our charts. Normally the trawlers try not to go too nearm - lots of steel down there that will shred or destroy nets, as well as active explosives.
I lates went on another ship on the southern grounds. My skipper once fished a 500 lbs aircraft bomb, which was defused and later blown up on land. Standard routine. It was some 50-60 years old, and had rolled along with the nets and catch for enough time to look polished!