Global warming my arse

the-smiling-buddha Seems to me that predicting a 20ft rise in sea levels is a pretty effective scare tactic

It may be, but more importantly it is a reflection of the science - against a predicted sea level rise of 1.4 ft, the collapse of one of the major ice sheets would result in a sea level rise of 20 ft.

Now regardless of whether you feel this is 'scary' or regardless of your dislike for Gore or his hypocrisy, this still remains scientifically sound.

the-smiling-buddha
But how credible is this claim if it is not supported by the IPCC

and if it were credible why doesn't the IPCC have ice sheet collapse as it's 'high' scenario

The IPCC make a single unambiguous prediction with regard to their research on sea level rises - an increase of between 28cm and 43cm.

This is likely to happen regardless of any other consequences of a rise in the worlds temperature.

The ice sheet collapse is a possible consequence of a rise in the worlds temperature and is not included in the IPCC remit.

the-smiling-buddha
The word you seek is not Ad hominem but hypocrisy

No it is correctly an ad hominem, you call Gore a hypocrite (he may be for all I know) - that is an ad hominem argument and has no bearing on the science.

the-smiling-buddha
"See, I don't even like to call it the environmental movement any more, because really it is a political activist movement, and they have become hugely influential at a global level." Patrick Moore founding member and former President of Greenpeace.

And long may it remain a political activist movement.