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107 comments on Senate Foreign Relations Cmte: "The Hidden Cost of Oil"

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joule on March 30, 2006 - 4:36pm Permalink | Subthread | Parent | Comments top
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.

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totoneila on March 30, 2006 - 4:51pm Permalink | Subthread | Parent | Comments top
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?

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SqueakyRat on March 30, 2006 - 6:12pm Permalink | Subthread | Parent | Comments top
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.
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joule on March 30, 2006 - 5:01pm Permalink | Subthread | Parent | Comments top
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').

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R W Reactionairy on March 31, 2006 - 3:11am Permalink | Subthread | Parent | Comments top
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.]
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107 comments on Senate Foreign Relations Cmte: "The Hidden Cost of Oil"

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