[duozerk]

You can't grow food for a large population when average planetary temps are at +5C. It doesn't mean it's locally always +5C warmer than it used to be; it means you're seeing insane temperature swings in a matter of days, constantly - in both directions, it just so happens that the average is +5C.

Not to mention, at +5C it is all but certain shallow methane hydrate deposits (those stabilized by temperature, not pressure) all over the world are now outgassing CH4; not to mention several other similar tripwires, and likely not all of which we've even identified.

Edit: I can't seem to be able to reply to your comment below, not sure why. You're absolutely wrong about those Siberia figures, and they're not supported by current scientific consensus.

[trashtester]

If you farm a siberia that's 5 degrees warmer and more humid (also in ipcc data), you can maybe feed 10 billion just from there.