A very small brick
And lately, it seems like more bricks have been coming out than have been going in.
Odds are good that this particular phenomenon is part of a natural cycle (except, of course, dead zones that are related to pollution runoff).
If you are a scientist and connect your work to support AGW, you will have access to billions in government funds. If you don't, you won't. A lot of what we see in this arena is that simple.