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It’s amazing the confusion that accompanies climate change questions. That’s partly because it is a complex subject. So it’s not surprising that people can make glaring mistakes.

Here’s one, though, that’s easy to get your head around by a simple experiment you can do at home. It relates to the question of melting of the ice sheets in Greenland and Antarctica. David Attenborough covered this in the last episode of “The Frozen Planet” screened here recently. His point – that global warming could cause loss of this land ice into the sea leading to dramatic increases in sea level.

Of course, this gets denied by the climate change deniers.  I came across one recently who suggested an experiment to prove Attenborough wrong:

” I can only suggest that every one do the following experiment. Take one half glass of water. Add two or three ice cubes. On the outside of the glass mark the level of the water. Leave for a few hours until the ice has melted entirely. Note the water level compared with the mark.”

Well, yes. Think about it – look at the image. Melting those ice cubes is not going to make much difference to the water level is it? Most of their volume is already under water and there already contributing to the water level.

This is why melting of floating icebergs due to global warming will have a relatively small effect.

But that’s not what Attenborough was talking about.

His comments related to movement of ice from the ice sheets on Greenland and Antarctica into the sea. Partly from melting. But also from sliding of the ice sheet in Greenland as the water melt lubricates the ice/rock junction. And in Antarctica the fear is that warmer sea temperatures will diminish the effect of pack ice restraining glacier ice from moving into the sea. In both cases the problem arises from addition of land ice to the sea.

So here’s the proper experiment:

Take one half glass of water. On the outside of the glass mark the level of the water. Now add your three ice cubes. Leave for a few hours until the ice has melted entirely. Note the water level compared with the mark.”

Or even quicker.

Note the water level immediately after addition of the ice cubes!

Think about it! Try it at home.


Footnote: Much of the research on mechanisms of movement of these land ice sheets into the sea is relatively new. many of the current findings were jsut not available during preparation of the 1987 IPCC Fourth Assessment Report.  Consequently the concern is that the effects of climate warming may be greater than estimated by that review.