Andy Revkin today blogs about a 30km chunk of the Petrmann Glacier in Greenland breaking free. Yikes! We say! Run for the hills the see levels will rise!

Just hold on a minute! How much will this chunk of ice affect the global see levels? Well assume that this iceberg is only 20% submerged (still resting on some bedrock) and has a volume of 30km³.  With the oceans covering around 140 million square miles of ocean (363 million km2) this will raise ocean levels by about 16mm or 2/3 inch.

But in the Youtube video accompanying this piece, the problem is much more serious than that. It seems that the Greenland icecap is melting in the summer faster than the snow is replenishing it. If it all melted then see levels would rise by 20 feet or 7m (2min 50s), so Florida disappears beneath the sea. But hold on a minute, computer models show that all this cold water entering the Atlantic may cause a sudden Atlantic cooling in years to come. (1min 50s). I might be a little uneducated, but if the Atlantic cools around Greenland, then this will affect the air temperature. That means there will be cooler summer temperatures nearby. So the net melting process will be diminished, stop or even be reversed.

The message from this for the residents of Florida is not to run for the hills, but buy in a sweater or two, and be prepared for bigger beaches – the tide will go out, and never return.  However, for those a nervous disposition, I suggest take a shot of Whisky (Springbank 21 y.o. or Lagavulin 16 y.o. are my favourites), sit down and relax. The ice-melt will happen over decades, so see levels will not rise much in the next hundred years. Even with a 5 degree warming, most of Greenland will still be below freezing throughout the year. But this will not happen, as natural correction mechanisms will diminish the impact.