One difficulty with discussing the past history of the Earth is people’s habit of trying to get rid of the Medieval Warm Period or, if that task proves impossible, to keep it in its regional cage or demote it to a mere “anomaly”. In fact increasing evidence shows that it was global and major. But if you don’t want to get medieval on your temperature records, what about the Holocene Climatic Optimum? During which the Sahara was warm and wet and, it now seems, the Alps were ice-free. Which does, yes, take us back to Europe. But as part of an investigation of a worldwide phenomenon that cannot be denied and must be explained and for which CO2 is no explanation.
If your German is up to the job you can listen to Sebastian Lüning talk about the new Alpine findings here. Aber if not, the key point is that, if you believe in the “hockey stick” and think it extends backward until the last glaciation, which people like Al Gore seriously do seem to believe, then there can’t be a Holocene Climatic Optimum. Not that you’d be likely to call a warm period “Optimum” anyway because warming is bad. Whereas if there was one, well, you have to abandon the notion that any change in temperature is driven by humans or by CO2.
It remains theoretically possible that whatever natural warming was going on before 1950 stopped suddenly at that finish line, handing the torch to humans who then ran the next leg of the relay race. But it sure sounds like special pleading.
Lüning does in fact bring in poor Otzi, who apparently got buried in ice that wasn’t there when he died. So it advanced, then retreated again at least once. Then advanced again. Which means if it is now retreating again, it is not unprecedented and cannot without further discussion or support be pinned on CO2.
At least not if you believe in science.