See, here's the deal: Earth's atmosphere--which is what we're worried about getting too hot--doesn't exist by itself in a vacuum. (It can't, for one thing.) It's bound to a blob of rock and water about 7,500 miles across. It's an envelope of mixed gases about 100 miles thick, laying atop this enormous mass of solid and liquid.
Earth is really a water world. 78% of its surface is covered with water, and if things were actually a few degrees warmer, enough ice would melt that the percentage would be even higher.
The problem is, there isn't enough heat.
The atmosphere is a tiny fraction of the biosphere's total mass--and by "biosphere" I mean anything on the Earth's surface that is not rock. And by definition, the atmosphere is made of air, which does not have a very large specific heat capacity.
Unlike, say, water.
So the issue we're faced with, according to this study, is that the ocean temperatures are cooling--or at least remaining steady--while the atmosphere is warming.
The atmosphere can't do any meaningful, long-term warming as long as the water temperature remains steady. The water will exert a cooling influence on the air and it can store a lot more heat than the air can. If "runaway global warming" were taking place, the ocean temperatures would be rising, on average...and they aren't.
This means one of several things. Most likely, it means we don't know what the hell the global climate is doing, nor do we really understand why. It may mean that "global warming" is not happening; it may mean that air temperature can fluctuate wildly without affecting the global climate, so that while short-term temperature anomalies can be large, the long-term effect they have on the climate may be minimal. It may mean that the oceans--working as an enormous thermal "flywheel", if you will--are one of the major feedback elements maintaining a climate which is stable in the long term.
There is no real evidence to suggest that Earth's climate can warm catastrophically over the course of, say, a century. There is plenty of evidence which demonstrates that Earth has taken about a hundred years to go from "temperate" to "ice age". Which should we worry about?