They'll probably be extinct for other reasons, before climate change has a chance to wipe them out.
Remember, an increase in temperature will have a corresponding effect on the oxygen-carrying capacity of blood (and water) (reducing it). Cold-water species will not necessarily grow faster - they will more likely be forced into and restricted to areas of relictual cold water at extreme high latitudes.
Think also of the sperm whale - the bull migrating to high latitudes (very cold water) to dine on megasquid. If these cold waters vanish (due to global warming) then we'll lose a major component of the diet of these whales. If warm water was so condusive to growing 'large/mega' squid, why is it that these beasts are today limited to cold waters? There's more to this that simple temperature; if temperature was all it was about then we'd have the largest squid species in the tropics.
Many cephalopod species are unlikely to be able to tolerate increased temperature (high latitude or deep-sea); increased temperatures will only benefit those species tolerant of increased temperature; cold-water species will simply vanish.
I've also been reading that all the massive melting going on in polar climes will ultimately end up lowering salinity levels which would be devastating for a lot of ocean life. The reasoning behind the threatened extinction of polar bears is that their primary habitat is vanishing; these are creatures that are evolved to hunt on pack ice.
Incidentally, with that much polar ice melting and entering temperate seas, shouldn't this actually lower the water temperature by some degree? Like when you melt ice cubes in a room temperature liquid, it ends up lowering the total temperature. The influx of that much cooler water ought to have a detrimental effect on some of the major current systems. Also, as the cooler water temperatures meet more equatorial zones, won't this produce more - how should I say this - "dramatic" weather?
Global periods of warming and cooling have always been a natural, cyclical process. What has many of the planet's climatologists concerned is the fact that it appears to be happening at an accelerated rate. Mind you, in certain quarters this is still highly controversial. All I know is our weather here in S. California has definitely been getting wetter lately, and in the Southeast part of the country there have been more tropical storms and hurricanes per season recently. It may come to the point where the good citizens of New Orleans will have to tow Chef Paul Prudhomme out to block incoming storm surges with his body to save the Crescent City!
The most dramatic effect of melting ice sheets will be indeed the lowering salinity, hence water density in n.Atlantic for instance and as a consequence will most certainly stop the conveyor belt process (transporting salt out of the N.Atlantic and heat into it) known as the thermohaline circulation. This will have a detrimental effect on current weather patterns, marine, terrestrial organisms.
Quick bit of gene sequencing and we can cross breed the giant squid with the polar bear and make a furred, tentacled predator that is not bothered when the pack ice vanishes, capable of pursuing seals on both sea and land, and underwater. Also would make a tasty dish for bull sperm whales!
Seriously though, are there likely to be undiscovered, very large squid in the Arctic Ocean, or are they mainly an Antarctic thing?
Bully to your genetic monstrosity, Snafflehound! Bigger, better, more horrifying predators are the answer! Not sure about the question, but wow, the mythical Alaskan fur-bearing squid could finally become a reality!
As a lay person, I'm not fit to make any conclusive comment about areas where I've done little personal research, but the Arctic Ocean is the deepest body of water generally speaking (not counting fissures, trenches like the Challenger Deep, etc.) at about 12-15,000 feet deep. Post Cold War it's been revealed that one of the ways the Soviet Navy used to get rid of their old nuclear reactors was to dump them to the bottom, so I'm not sure how healthy an environment that might be for very sensitive creatures. Unless all those old Toho monster movies turn out to be correct, which I'm sad to say I doubt.
Warmer water usually but not always causes "cold blooded" animals like squid to grow faster but mature earlier at a smaller size. Colder water usually causes them to grow slower, live longer and mature at a larger size.
"A final potential upside to global warming is that with every degree Celsius warmer our planet gets, we could have up to 20 percent more calamari. Phillip Lee, director of the National Resource Center for Cephalopods, points out that squid are extremely sensitive to temperature, and individual cephalopods react to warmer weather by developing a larger body mass." - Dr. Phil Lee
Warmer water, even just a degree or two, will have a strong positive affect on squid growth rates. However, I disagree with Dr. Lee that it will make individual squid larger. In properly controlled experiments where individual animals were raised to maturity, the trend is typically for those raised at higher temperatures to mature sooner and at a smaller size.
Squid probably do benefit from the trend of “fishing down the food web” (Pauly). As we remove the tuna and other big predators they rapidly move in like weeds in a cleared patches of land. Anyone who seriously thinks this kind of messing with the environment is a “silver lining” is missing the point in my opinion. Other groups have also done better following human disturbance - roaches come quickly to mind.
Personally I think it isn’t surprising that the reporter chose a scientist from Texas (a big oil producer) for this report. For the other side of the story read the scientific paper above and do a Google scholar search on “acidification ocean corals” and make up your own mind.