The article says the following: "It took less than a year to discharge," a much more believable number.
To assume that these scientists understand all there is to know about modeling worldwide flow for how a glacial lake would drain under breakout conditions the like of which no modern human has EVER witnessed, requires more credulity than is warranted by the data. It is not unusual for all sorts of wild claims to be made in the executive summary of a paper in order for the grantor to be happy. The principal information here is that there is solid evidence there was a lake, a good estimate of its volume, and they may have evidence that it did break out. It MIGHT have taken two weeks for the lake to drain, but I seriously doubt that our knowledge of how fresh water distributes displacement from under a massive ice age cap is so sophisticated. IMHO, they're claiming a whole lot more certainty about events 8,500 years ago than I think our archaeological knowledge can justify.
I would assume a breakout like this might start a chain reaction, lifting vast amounts of sheet ice that would then flow into the oceans to melt. That is a much more likely scenario given the posited impact on global climate.
Let's do a little arithmetic. Lets divide the released volume of the lake, according to the article, by the current surface area of the world's oceans to see how far they would rise as a result of the released water (I know that the ocean surface area was smaller then, but it works for a crude reality check):
(163,000 km3/361,800,000 km2)(1,000 m/km) = 0.45 meters.
Try it yourself.
Think about it. The authors say that this lake is twice the size of the Caspian Sea. Now spread that water over 70% of the Earth's surface and ask yourself if that volume would be large enough to add 100 feet of water. You might also ask if the lake represents sufficient thermal mass to cool the atmosphere by itself. I doubt it. However, the ICE that might have been released into the oceans with the breakout might have sufficient heat of transformation to have such an effect, particularly because the melting fresh water might develop a thermal inversion layer at the surface.
Glacial collapse raised sea levels over 100 feet, not some damned lake. It didn't happen over a matter of days.