Keith wrote:ezz wrote:As i said there is absolutely no way of knowing for sure, but is it a risk worth taking?
I'm not saying it is, or it isn't. Simply questioning if the argument is fundamentally flawed? Is half of London really at risk?
Put some water in a glass, mark where I filled to.
Add some ice, water level obviously rises because there is more in the glass than before.
Having marked the 'sea level', let it melt
Ice gets less...
...water level remains the same.
Drink cold water, realise that the autofocus was aimed in between the glass and the paper
Not making light of the whole problem, just not convinced that the arguments aren't just a little exaggerated to scare the masses... as if...
Ooh, how scientific of you keith!
Although if you look closely at pic2, you will see some of the ice is above the surface level of the water , so your top level mark is inaccurate.
No one also seems to realise that ice and water have different densities.
Therefore you are wrong when you say when the ice melted the levels stay the same, if you had measured the volume off the water more accurately and your ice was all under the surface level when you had made your marks, you would have seen this.
( in experiments like this the ice is normally held under the water, under a metal plate for example to give as even a surface level as possible)
Ice is less dense than water, don't be confused about its solidity, the same amount of water when frozen takes up a larger volume, if you don't believe that, fill a glass bottle to the brim and fit a screw cap tightly then place in the freezer overnight, it the morning you can shout "eureka!" whilst cleaning up all the broken glass in your freezer.
So, to return to the arguement about sea levels, ice that is under the sea will take up a smaller volume when it melts, but that doesn't mean the sea levels will fall, if ice above the sea and on land melts and increases the volume of the sea (as Posh states).
There are also a few more things to take note of that flaw your experiment.
The density of sea water is different than that of pure water due to the salinity or dissolved salt content, the water now contains many different ions ( Sodium, Calcium, Gold , Chloride, Bromide, Carbonate etc), adding pure water (melting ice) to this would alter the salinity and density of the solution. This would probably balance out later as more salts from the land dissolve in the water, but now the volume of the land has decreased as the salts are leeched out.
Another major flaw in your experiment to replicate the sea in a pint glass was temperature.
Most things at higher temperatures increase in volume (metals expanding for example).
Water whilst decreasing in volume from ice to water, begins to increase slightly in volume as its temperature increases, then decreases again as more water becomes vapor and leaves the sea to become clouds that fall as rain on land washing more land (by solution and erosion) into the seas volume.
As you can see the arguments put forward by many scientists on the effects of climate change differ dramatically as with so many different factors to consider ( many more than I have stated) it is difficult to predict accurately the future levels of the sea.
I personally believe in the future that rainfall will be as much of a problem as rising sea levels.