Thxs for the info.

Trying to figure the global environmental cost of carbon, then trying to figure how to make the consumer pay for it will be an impossible task-- too many unpredictable variables in nature.

For example, consider this info taken from Wikipedia:

http://en.wikipedia.org/wiki/Ice

"When ice melts, it absorbs as much heat energy (the heat of fusion) as it would take to heat an equivalent mass of water by 80 °C, while its temperature remains a constant 0 °C."

Now I am no scientist, but this suggests to me that the global ice is a tremendous global warming buffer--can absorb unbelievable amounts of heat without exhibiting any visible change.  The melting and shrinking we see now is just the proverbial 'tip of the iceberg'.

Just imagine if Antartica's gigatons of ice have absorbed the equivalent of 75 degrees of global warming over the last two hundred years resulting in the net effect of the one degree rise in global temperature increase we have seen so far.  Once the ice's heat absorbsion reaches 80 degrees, then a tipping point is reached where any more global warming starts to vastly accelerate the water phase transition [ice to water] releasing huge icebergs, glacial flows, and monstrous jokulaups.

Bob Shaw in Phx,AZ  Are Humans Smarter than Yeast?

I'm not a physicist, but I believe the energy is absorbed when the ice goes from solid to liquid form.  So I don't think your "we're almost at the tipping point" argument works.
Hello Biologyfool,

Respectfully disagree. The absorbed energy is unseen, increased atomic vibration.  Only when the ice has absorbed the required total energy is when it melts. Unmelted ice has a thermal conductivity coefficient too, as linked here:

http://tinyurl.com/lkwrg

The colder the ice: the faster it absorbs heat.  It is all very complex, way above my limited understanding.  Ongoing research is trying to get a better handle on this:

http://www.usap.gov/scienceSupport/sciencePlanningSummaries/2003_2004/indiv_projs/O253.htm

I assume supercomputer modeling is required to adjust for all the inter-related physical effects of solar radiation, albedo reflectivity, air & water thermal currents, snow insulation, glacial flow rates, etc.... on & on & on.

Bob Shaw in Phx,AZ  Are Humans Smarter than Yeast?

You are talking about heat of fusion. For example if you place a pot full of ice on the stove and turn it on high a constant amount of energy is being applied. The ice begins to melt but the water stays at zero, once all the ice has melted then the water temp climbs.  The energy is absorbed when the melting occurs. Now the bad part is all earths ice reflect a great deal of energy beacause it is white. How much more will we retain after our reflective blanket is gone?
totneila -

You are more or less correct, but perhaps misunderstanding the process a bit.   True, water does have a comparatively high heat of fusion and therefore quite a bit of heat must be absorbed before ice will melt.

However, once the ice is melted, the heat that has been absorbed doesn't really go anywhere, as it just resides as the free energy of water's liquid phase. In other words, liquid water has greater free energy than solid water (just as steam has a higher free energy than liquid water).  When the liquid water freezes again, that phase free energy (or heat of fusion) must then be removed. So, the freeze/thaw process is fully reversible, with energy being added in on one case, and removed in the other.

But you are generally correct if what you are driving at is that the earth's huge inventory of ice is a vast  heat sink. The smaller that heat sink becomes, the less damping effect it will have on atmospheric and oceanic temperature changes. The trick is figuring out how important this factor is in the whole global warming picture.

Hello Joule,

Your last paragraph is a better and more concise wording of what I was trying to express--Thxs

I have been trying to google more info on this phenomenon, to get a better handle on just how close we are to an ever-increasing number of cascading inflection points, but it is frustrating because many technical reports are behind paywalls.  Makes one wonder if the critical data is top secret-- that would explain why the milgov is trying to muzzle James Hansen and other scientists.  Who knows?

Bob Shaw in Phx,AZ  Are Humans Smarter than Yeast?

You might be better off putting your question to the folks at RealClimate.org. They're pretty hospitable, and some of them seem to be on the climate science cutting edge.
totoneila -

Addendum re ice melting:

One thing I perhaps wasn't too clear on is that as you start adding heat to ice, it will gradually and very linearly starting increasing in temperature all the way up the melting point of 32 degrees F.

But then something odd happens: the temperature stops climbing and becomes sort of stuck at 32 degrees for a period of time. The reason is that this is the phase change point, where the solid water absorbs heat to become liquid water.

However, when the ice does finally melt, it does not suddenly release energy and steeply rise in temperature. No, the water from the freshly melted ice  is but a fraction of a degree over 32 degrees. Thus, you can have both water and ice at 32 degrees: it just depends on which direction you're coming from.

Of course once the ice has melted, if heat is still being applied, the liquid water will continue aborbing heat and gaining in temperature in a very linear fashion, until you reach the boiling point, at which time the same sort of pause in temperature rise occurs, as the liquid water absorbs enough heat to cause vaporization (i.e., the 'heat of vaporization').

The technical term I was taught was "phase change". I got nailed on this one when me [and much more intelligent buddy] attempted to dry lab a very basic lab experiment plotting temperature against time on a substance going through a phase change. We guessed a linear plot. Oh well, two lesssons for the price of one. Substances can be at the same temperature and have significantly different heat content at their melting point ... and the freebee lesson: a fully delveloped form of the scientific method is dependent on experimentation [testing of a hypotheses.]
RE: monstrous jokulaups:

I am certainly not one to let the chance for a monstrous joke elapse without making it!