People keep saying that, but I wouldn't be so sure. From an earlier comment of mine (edited for clarity/formatting):
Most recent study of methane flux/storage in the East Siberian Arctic Shelf: [1]
Arctic temperatures are estimated to rise 1.9x compared to global average: [2]
During Holocene Climate Optimum (the warmest period in human history) the arctic is estimated to have been 4-6C warmer than baseline (yearly average): [3]
That's not all that much. We're now already at 400ppm CO2, and recent unmitigated projections to 2100 (538ppm) simulate an arctic yearly average of ~ plus 8C [4].
And that most probably doesn't take a positive methane feedback loop into account. This is a significant gamble. The Paleocene–Eocene Thermal Maximum boundary showed a global average warming of 5C, mostly from arctic methane at a time where there wasn't even a large ice shelf, so with significantly lower capacity [5].
We can only guess what a global average temperature increase of 13C could do to the ecosystem that's currently feeding 7B people.
[1] http://rsta.royalsocietypublishing.org/content/373/2052/2014...
[2] http://onlinelibrary.wiley.com/doi/10.1029/2005GL025244/full
[3] https://epic.awi.de/38441/1/Beierlein_2015_Holocene_page1.pd...
[4] http://climatenewsnetwork.net/arctic-is-set-to-reach-13c-by-...
[5] https://en.wikipedia.org/wiki/Paleocene–Eocene_Thermal_Maxim...
Obviously that would be a terrible disaster the likes of which our race has never seen. 100 times the death toll of WW2 and would destroy pretty much all our infrastructure etc as supply chains fail etc. This is something we should strive to avoid at all costs but I do think the species would survive. We are quite a hardy bunch actually.