Not a question that could have a specific answer as it would all depend on what metric you were evaluating. For example, hydrological variation could change ice dynamics at altitude and in the Antarctic interior but atmospheric temperature fluctuations won’t. So, the ice here could change significantly whilst temperatures were constant, or, somewhat paradoxically, it would increase during periods of warming.
Similarly, Antarctic sea-ice extent is increasing as warmer temperatures melt fresh-water ice, this has a higher freezing point than the seas and oceans and again, we have a situation where the ice is growing in response to warmer temperatures.
If one was to focus on global temperatures then it would be wisest to take a global perspective and consider ice in all it’s forms. This helps to eliminate regional variations such as ocean and atmospheric currents.
Generalisations…
? Total land ice mass (glaciers and Antarctica). The land mass of Antarctic ice is probably increasing as a consequence of an accelerated hydrological cycle bringing enhanced levels of precipitation. The Antarctic interior is always below freezing so no ice-melt will occur, for this reason it’s not a very good metric.
Glacial ice outside the Polar regions is far more susceptible to temperature change because it generally exists within more moderate climate zones. In these regions some 50% of the glaciers have melted, 95% of those that remain are melting. There should be a state of equilibrium between accumulation and ablation with a relatively static firn line, this is no longer the case anywhere in the world. Consequently, the sensitivity of non-Polar glacial ice makes it an unreliable metric.
? Total ice mass. This is perhaps the best option as it focuses on mass as opposed to area, extent, volume, density etc. It’s the one measurement that truly tells us how much ice there is.
? Arctic sea ice mass. Short-term there are too many variables, for example, in the coming days it’s likely there will be a significant breaking up of the Arctic ice. Ice that forms part of the central body will be lost and the mass will decline sharply, out of context it could appear that global warming has caused the rapid loss when in reality it’s going to be caused by cyclonic conditions. Averaged over many years this is a good indicator.
? Arctic sea ice extent. Good for telling us that something is happening, bad for telling is what. Many factors affect the extent and it’s quite possible for extent to increase whilst all other metrics decrease, and visa versa – it all depends on compaction and depth of the ice
? Antarctic sea ice extent. This increases as temperature rise due to upwelling of cold water columns bringing fresh melt-water to the surface where it quickly freezes. Local dynamics and the Antarctic Oscillation affect sea-ice extent here, again it’s not a very good indicator unless taken in context and over the long term.
? Antarctic sea ice mass. As per Antarctic sea-ice extent.
? Antarctic total ice mass (land and sea). As per Antarctic sea-ice extent plus Antarctic land ice-mass.
? Antarctic land ice mass. Increases as temperatures rise due to enhanced precipitation, peripheral ablation is less than interior accumulation. Variations in mass are indicative of change but don’t identify what that change is.
Whilst Antarctic sea-ice extent is increasing, the mass is decreasing. Interior Antarctic glacial ice mass balance is increasing, peripherally it’s decreasing. Every metric for the Arctic and non-Polar regions are decreasing. Total annual global mass loss is approaching a trillion tonnes, roughly half from Greenland and half from Antarctica.
EDIT: TO FLOSSIE
At it’s winter peak the Arctic ice is about the same size as Antarctica but during the summer month’s it’s considerably smaller. New Arctic ice is typically less then 2m thick, multiyear ice is up to 10 metres whereas in Antarctica most of the continent is covered by very deep of ice (4,700m at the deepest, 2,500 metres average). There’s about 27,000 trillion tonnes of ice in Antarctica, 2,500 trillion in Greenland and roughly 30 to 60 trillion tonnes in the Arctic (it varies seasonally).
Ice around the edges is going to be the most sensitive to temperature changes. I consider glaciers outside of Antarctica and Greenland, along with Arctic sea ice mass and extent, to be the best indicators. The Antarctic and Greenland ice sheets, at least at present, have too much thermal inertia. The action of the frostline on the cabin windows is a far more sensitive indicator of temperature trends than the melt rate of a block of ice in the cabin.
Before doing any work that measures temperature , global enthalpy needs to be determined. We could could spend a trillion dollars trying to see if global warming counts, or we could control our populations starting now, while moderating specs of release of pollutants to the environment. There never will be sufficient proof for one to 'prove it' any more that there will be proof of God. Responsible people don't need proof---they do what is right rain or shine.
Arctic sea ice mass would be the greatest mass of ice on earth. Note that in a bath of stirred ice and water, when ice starts to melt, the mix is 0 degrees C. If ice continues to melt to repletion, at this point only can the water temp increase from 0 degrees C . A trillion m^3 or 1 pound of ice unmelted renders the same temperature. Further, if one looked at ocean volumes, ice swells when it freezes, so levels would pretty much stay similar.
None of the above, global temperatures have been flat for over a decade and Arctic Sea ice is trending down and Antarctic Sea Ice is trending up. There is insufficient data to use glacial mass as a proxy.
Assuming you want indicators of LONG TERM GLOBAL temperature TRENDS, and not some (cherry-picked or representative) snapshot only:
Mass captures all three dimensions, extent only two.
Arctic and Antarctic capture only part of the globe.
Antarctic is bigger than Arctic which is (I think) bigger or at least not much smaller than glaciers.
THUS
The most complete indicator would be "Total Ice Mass"
The weakest indicator would be "Arctic sea ice extent"
Interpolate the rest.
Edit: Anti-science liar-deniers will try to gobbledy-gewk such basic logic to twist and distort truth in conformance with their handlers' pseudo-science croc of the week, which this may or may not be a reflection of: http://answers.yahoo.com/question/index;...
Total land ice, is a reasonable indicator, but glaciers are affected by local conditions such as deforestation (Himalaya's Kilimanjaro)
Arctic ice, is not good a good indicator, as there are so many variables,AO & AMO ocean currents cyclones etc,
Antarctic ice extent is my number 1 reference ( although it is spooky whats happening there now) and I definitely don't believe this B.S. about warmer water causing more ice or less salinity, Antarctica is colder now, sea and atmosphere.
Antarctic ice mass, I do not believe we can measure it (especially by GRACE) I cannot see how when extent is increasing mass is decreasing (by what means? it's too cold too melt, glacial action slows down with increasing ice extent, that only leaves sublimation)
Arctic sea ice mass would be the greatest mass of ice on earth???????????
Greater than Antarctica?
I would say that ice melt, rather than temperature is the bottom line. Some people calim that temperature data shows that climate sensitivity is low, Personally, I beleive that declining solar activity and the Asian brown cloud are holding back the warming.
http://www.worldwidewords.org/turnsofphr...
http://www.woodfortrees.org/plot/sidc-ss...
And if climate sensitivity is low, where are all the clouds?
http://www.climate4you.com/ClimateAndClo...
http://www.climate4you.com/images/CloudC...
Climate models have a dismal record in predicting ice melt. They underestimate ice melt.
http://www.skepticalscience.com/climate-... Note Figure 5.
Back to the question The best indication of how much of a problem we have would be Antarctic land ice mass, as recent findings indicate that Antarctic ice melt may contribute more to sea level rise than Greenland ice melt.
If we are talking about global temperature changes then the only reliable indicator is global ice mass. Other choices in your list deal with regions. There are, however, indicators that area regional that can be held as more reliable than other regions regarding global temperatures. I mean if you have one part of the globe that has it's temperatures bottles up while another part of the globe has many global weather patterns passing through it there would be a difference in meaning of one temperature change to the other.
There is a lot of information on sea ice all in one place at a popular sceptic web site ...
Please rank the following, as to how meaningful or accurate of an indicator they are of average temperature conditions, from most to least meaningful
Total land ice mass (glaciers and Antarctica)
Total ice mass
Arctic sea ice mass
Arctic sea ice extent
Antarctic sea ice extent
Antarctic sea ice mass
Antarctic total ice mass (land and sea)
Antarctic land ice mass
Also, if you wish to provide references, and/or briefly explain your rankings, feel free.
As a bonus, if you have any good sources of the behavior of any or all over the past couple of decades, that would be nice.
?During the last ice age (when glaciers covered more land area than today) the sea level was about 400 feet (122 meters) lower than it is today. At that time, glaciers covered almost one-third of the land.
?During the last warm spell, 125,000 years ago, the seas were about 18 feet (5.5 meters) higher than they are today. About three million years ago the seas could have been up to 165 feet (50.3 meters) higher.
History says nothing about higher CO2 levels causing any of it.
Bonus?
Non, I prefer thermometers.
