The IPCC 4th assessment report states that greater than 40% of species are likely to be extinct given a temperature increase of ~3.8C, with 30% of species at increasing risk of extinction given a temperature increase of only ~1.5C.

A rise of 1.5C is certain to happen by 2100, even in the best case scenario where emissions peak soon; and a rise of 4.0C is depressingly likely given the current continuous rise in emissions.

See pages 22, 23 and 29 of the synthesis report: http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr.pdf

I would recommend everyone reads this report; it's not too long, and I found it very readable and succinct.

Given that we're all going to be affected, isn't it worth knowing the facts about this stuff?

Also readable online at http://www.ipcc.ch/publications_and_data/ar4/syr/en/main.htm...

I would assume this is where the 70% came from: "[...] As global average temperature increase exceeds about 3.5°C, model projections suggest significant extinctions (40 to 70% of species assessed) around the globe." http://www.ipcc.ch/publications_and_data/ar4/syr/en/mains3-4...

> 40 to 70%

That's one heck of a margin of error.

Are you an ecologist or other relevant professional?

Are you?

The point of my comment was that the parent is no more qualified to make this statement than James Cameron was to make the original. It's like doing statistics by eyeball: you possibly say something's "pure nonsense" except for effect without understanding what you're talking about, and I'm sure James Cameron has some context for making these statements.