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?