So far, only James E Hansen seems to think that we have already passed the tipping point, in April 2008 at 385ppm.
This page was last edited three years ago and doesn't mention the exceeding of 400ppm which was this year.
https://en.m.wikipedia.org/wiki/Tipping_point_(climatology)
Has anyone mentioned methane clathrate yet? Anyone mentioned melting permafrost yeilding methane?
Funny word, 'permafrost'. You'd be forgiven for thinking it meant permanent.
Patronisation aside, the fact that it is usually frozen *peat bog* at high latitude is, serpently, evidence of the very warm periods (Eocene?) of the prehistoric past.
The trouble there is that all that fossil carbon was safely tucked underground at the time; had been for about 300 million years, in some cases. (For a laugh, try getting cap rock age data from an oil company).
Small tap or not, this carbon is ancient and the next upswing of the "natural cycle" is going to be a real scorcher. The habitable latitude range is going to be narrow, however far north it may shift.
See also "Earth Story" with Aubrey Manning. Specifically the bit with the wing cases of a mediterranean species of beetle in excavation in northern England.