Re: If global warming melts all the glaciers, how long will it take them to ref

Hi Lisa,
If global warming is caused by the natural factors, and by manmade 
increases in greenhouse gasses, then it will take a very very long time 
for the glaciers to melt completely because many glaciers are so high up 
in the mountains that they are so cold that temperatures will have to 
increase by an amazing amount for the mountain tops to come to the 
melting point of water - 0 degrees Centigrade. How long? Thousands of 
years for all of the glaciers to melt - however, long before that we will 
all die of the boiling heat at the level where most of us live! We will 
have plenty warning as an increase of just 10 degrees C would be so 
catastrophic for other reasons that the melting of the glaciers would be 
our least problem! If you by 'glaciers' also mean the ice on Greenland 
and in Antarctica then the answer is 'much more than thousands of years' 
because those places are at 50 degrees below 0 C and warming the world by 
that much would be almost impossible to achieve by increases in 
greenhouse gases. We would have to burn so much oil and coal that there 
is no way we could dig it up fast enough. Do not worry about 
the 'complete melting of glaciers'! There would be PLENTY of time to move 
people (if we can afford it and to resettle them - rich countries would 
have no problems, while poor countries might be in serious trouble. A few 
rich countries are very flat - The Netherlands, and Denmark, for instance 
and would have to figure out how to build sea-walls or buy land somewhere 
else)- NO tidal wave would flood the coastal areas, as in the catastrophe movie 
that recently came out, showing huge tidal waves washing over New York 
city. Sea level rise is something that happens a few millimeters per 
decade, at most. In some places post-glacial rebound actually causes the 
coastline to receede - such as in Scandinavia where coastlines are rising 
at the rate of a centimeter per year in some places. Post-glacial rebound 
is the process of land, that was pressed down by ice-age glaciers, rising 
back up once the ice is gone. 

You can look at a map of the world that shows height above sea-level 
(usually a specific color in a typical school atlas) to see what areas 
would be affected by a rise in sea-level of a few meters (the likely rise 
in sea level within your, your childrens and grandchikldrens lifetime).

If ALL glaciers melted due to manmade greenhouse gases they would not 
start reforming until the temperarture was back down again, and that 
would happen when the gases had been absorbed in the oceans - this would 
take a few hundred yeras, once emissions stop. 

Now, the above answers mainly assumed that manmade gasses caused global 
warming. There are also natural warming and cooling factors - such as the 
Sun and volcanoes. We cannot predict what the Sun and the volcanoes will 
do in the future so all answers are under the assumption that nothing 
really strange will happen with the Sun or the volcanoes in the future. But 
if we double or triple the amount of greenhouse gas in the air during 
the next 100 years or so, then the warming from this is likely to be more 
than from any natural source.

You and your classmates may enjoy reading and discussing the book 'State 
of Fear' by Michael Crichton. It is a thriller about climate change and 
the politics of climate change. Most of the science in the book is all 
right - and the bit about the cannibals is really good!