Cod fisheries around the US, and especially in the Gulf of Maine have reached catastrophic levels - only 3% of sustainable levels. No doubt that overfishing played a major role in this, but even after extremely strict regulations were set in place, the numbers still didn't improve. Now, researchers have found that it's the oceans warming that actually destroyed the cod populations.
A major paper in Science today (free to read here) shows how that happened. They write in their abstract:
"Several studies have documented fish populations changing in response to long-term warming. Over the last decade, sea surface temperatures in the Gulf of Maine increased faster than 99% of the global ocean. The warming, which was related to a northward shift in the Gulf Stream and to changes in the Atlantic Multidecadal and Pacific Decadal Oscillations, led to reduced recruitment and increased mortality in the region’s Atlantic cod (Gadus morhua) stock. Failure to recognize the impact of warming on cod contributed to overfishing. Recovery of this fishery depends on sound management, but the size of the stock depends on future temperature conditions."
In other words - the oceans are warming up faster than the fish can take it.
Sure, the Gulf of Maine is warming way more than other areas, but this is not an isolated event. Look at the rate of warming for global oceans, from the same paper:
The entire deep red patch you see on the East Coast of the US is extremely worrying, but the Bering Sea in Europe and the South Pacific aren't doing much better. Of course, we don't have as many fisheries in the south Pacific so we don't know the environmental situation as good, but the odds are populations are collapsing there also.
As AGU also did, I feel the need to quote a classic paper by James Hansen from 1981:
“It is shown that the anthropogenic carbon dioxide warming should emerge from the noise level of natural climate variability by the end of the century, and there is a high probability of warming in the 1980’s.”
He anticipated that we'll start seeing the effects of global warming in the early 21st century... and he got that right!
