There is so much water in the ocean. Incomprehensible amounts of water. That again, is very, very well circulated. Circulation is key. To think we could fuck it up beyond repair is just human ego talking. Has pollution occurred? Yup, no doubt. Enough to make fish into poisonous mutants unfit for consumption? Sorry, not buying it. Show me some data please.
Here's a couple things about global warming that no one likes to talk about. We are still technically in an ice age, albeit on the tail end of one, so yeah Earth is warming up, no surprises there. You also know that the average temperature across Earth history is a few degrees warmer than what we see in the present day right? Again, no surprises that we see Earth heating up. Another beef I have with global warming reporting (though not really related to anything you said), like the study NASA recently published about melting of the ice sheet on Greenland. It stated, "some melting has occurred the past few days." What the fuck does that even mean? Some melting? That is about as vague and scientifically null as anything I have ever read. And what happened a few days later? Did melting continue, or did it freeze back up?
Who cares about how far the fish swam. It's the water around the fish that is being circulated and moved around. It's not like that water just sits there stagnating. I could very well be wrong, but like I said, I need to see some data before I buy these things. Because in my mind things just don't add up.
