Why dont sea level rise estimates include the most accurate rate of glacial/ice sheet melting?

Question

I think this is occuring on a logarithmic scale rather than linear. The glaciers and Greenland/antartic ice are melting faster with time rather than melting in a uniform linear fashion.

Answer 1

The rate of melting is indeed increasing - most notably from the Arctic but as this is a floating ice mass and it's already displacing it's own mass of water and so can melt completely without affecting sea levels.

Other than the Arctic, the next largest net loss of ice and the largest consequent contributor to rising sea levels is Greenland, by comparison Antarctica is melting relatively quite slowly but the overall rate of melting from all sources is increasing.

Sea level rise estimates do allow for accelerated melting and if you look back at my previous answers you'll see that I often quote a figure of 3.1mm a year for current sea level rises, 6mm a year by 2050 and 12mm a year by 2100 with an average of 7.5mm a year over the course of this century.

Answer 2

There are two data points from satellites, taken one or two years apart. That data shows the melting rate in Greenland doubled, to One Cubic Mile of water per week (about, actually it was 56 cubic miles per year)..
If it doubled again in the next measure, next summer, your exponential or logarithmic plot would be right.
The place to watch is the deep parts in Antarctica, they hold far more ice than Greenland.
They are normally put together but I don't know why.
Maybe somebody can explain that.
The more likely mechanism for Antarctica is not melting.
Just the opposite, the evidence is that the ice accumulation is INCREASING!
The reason is that as incresingly humid air goes south, it gets colder and snows over Antarctica, the furtherst away from the shores and the height of the snow is INCREASING.
However, as the ice accumulates, all the many, many, glaciers that are moving to the shore are moving "faster" (no numbers).
Interesting point: The accumulation of ice puts greater pressure on the ice and some of it becomes "liquid" which can be detected from statellites, some 200 "lakes" have been counted deep under the surface. Remember, liquids act to "lubricate" glaciers moving down to the shores, therefore, I think, they glaciers will move faster and push old ice to the ocean water, in big chunks, bigger than Rhode Island.
[This is not as rare as it seems to most of us. The Matterhorn in Europe has glaciers and one of them had a deep lake that broke and flooded a town, killing many. This is now being constantly monitored by exploring under the glaciers, I saw it in PBS- TV]
The ice floes in the North Pole do not contribute anything to the ocean levels, whether they melt or not.
Water expansion, due to minute increases in the ocean temperature has some measurable effect, since the amount of water is so vast.
Next summer, see if the melting rate in Greenland doubles again, to TWO cubic miles per week.(or 112 cubic miles per year, or more).

Answer 3

You raise a good point. I'm not sure you can describe it as a log scale--but melting (and thus seal level rise) is increasingin rate.

The problem is that the rate is changing in an irregular fasion. And--making accurate projections requires data that is accurate. And that takes time to coolect and analyze.

So--its not that the predictions aren't accurate as far as tehy go--its that there's a lag time--and in a system which is changing at an unpredictable rate, that limits accuracy.

For example--we knew that the Artic pack ice was melting--and at an increasing rate through last year. Analysis and predictions were up to date using that data. But no one anticipated the jump of nearly an order of magnitude in pack ice melting tha toccured this year. So--any projections involving that data are virtually useless--and will be until the data and analysis can be updated.

Answer 4

Fill a glass with as many ice cubes as possible. Now fill the remaining space with water right up to the rim of the glass. Take a nap or read a book (I recommend "Basic Economics: A Citizen's Guide To the Economy" and "The Vision of the Anointed: Self-Congratulation As A Basis for Social Policy", both by Thomas Sowell). See what happens when the ice is fully melted. The water level in the glass has dropped! Seems when water freezes it expands (that means it gets bigger). It then displaces (that means it takes up more room) water until it melts. When ice melts it shrinks and lowers the water level.

Learn this: THERE ARE NO SOLUTIONS, ONLY TRADE-OFFS. If you want more of "A" you must be satisfied with less of "B".

Answer 5

Because the data is not solid enough yet to use the increasing rates. It would be called "alarmist".

So the more conservative linear rates are used. More explanation:

"The drafting of reports by the world’s pre-eminent group of climate scientists is an odd process. For many months scientists contributing to the Intergovernmental Panel on Climate Change tussle over the evidence. Nothing gets published unless it achieves consensus. This means that the panel’s reports are extremely conservative – even timid. It also means that they are as trustworthy as a scientific document can be."

George Monbiot

"Of course, being a consensus document, a lot of the material that I think is reasonably well-supported also gets weeded out through that process. If the IPCC says it you better believe it and then leave room to think it is actually a lot worse than they have said."

Tim Flannery

Answer 6

Current sea levels are 30cm lower today then durring the 1840's.