alt Hacker NewsHaving followed every bit of info, data, and discussion(that I can find) on climate, geology, etc, since I was a child in the 1970's, I can point to the fact that earth climate science is ferociously complex, but that almost all of the variables are pushing towards a much warmer planet, and that there is NO big offset. Like it or lump it, we have whatever passes for a global civilisation, where we are so intertwined that we cut special "deals" with the people we are bombing and bieng bombed by, for certain trade items, ie: gasses for chip production, "humantarian exemptions", etfuckingcetera, and so the real threat to All That™, is ocean rise, as it can wipe out shipping fast under some realistic scenarios , which if fact, are playing out there preliminary set points.
https://www.ospo.noaa.gov/products/ocean/sst/contour/
Short term (low single-digit decades): rapid sealevel rise. When (not "if") the Thwaites Glacier goes and the West Antartic Ice Sheet floats (not melts, just gets seawater underneath it) then we're looking at circa 5 metres, stabilising globally in about 12 days.
Goodbye every single coastal city, air or sea port, industrial area, power plant, transport infrastructure in the world.
Medium term (high single-digit decades): rapid global warming pushing the habitable zones to the poles and sub-polar regions. Note, critically, that means agriculture, as there are no established ecosystems to hunt/gather from at the poles.
We are heading for ~7º C by the end of the 21st century. Never mind 4º, double it.
Long term (millennia): another mass extinction event, much as the previous ones. We're 75-80% of the way through already, though.
Geological terms...
Hundreds of thousands of years: if humans go extinct, the planet will recover in 100K years or so, with plentiful but severely species-impoverished ecosystems.
Tens of millions of years: lots of new species, new rich ecosystems form.
Hundreds: if another sentient species evolves, it will have a hard time bootstrapping an technological civilisation, as we've extracted most of the the easy-to-access resources.