Comment Re:really - the whole world's ? (Score 2) 57
To be fair, there have been times where Earth's temperature changed relatively rapidly.
On the other hand... those times tended not to work out very well for life :
Our current experiment with mass greenhouse gas emissions affecting the climate, Earth itself has kinda done it before, at the Paleocene-Eocene boundary. The associated Paleocene-Eocene Thermal Maximum (PETM) left the world such an altered place that we refer to it as a different era (the Eocene). The oceans took the brunt of the hit. Except the differences we have vs. the PETM are *not* to our favour:
* The arctic was ice-free going into the PETM; ours is not. The presence of ice creates an amplifying feedback process, where the more ice that melts, the more sunlight gets absorbed, creating more heat to melt more ice.
* We're releasing our carbon an order of magnitude faster (though our methane emissions are similar)
The PETM caused a 5-8C rise over 6000 years, but we're speed-running it, so it's really our best case. The worst case is the K-Pg extinction event
Only the worst excursions in history tend to result in large parts of the earth becoming relative sterile. But they all lead to mass disruptions in ecosystems and waves of global or at least local extinction (but new speciation of the survivors who take their place). Indeed, we probably owe our existence to the PETM - primates diversified and radiated after it. But that's little solace to species that didn't make it. Like, for example, dinoflagellates flourished during the PETM. But do you really want to replace reefs with red tide?