" The Earth’s climate abruptly warmed by 5–8 C during the Palaeocene–Eocene thermal maximum (PETM), about 55.5 million years ago..." Thus begins a new paper by Bowen et al. in Nature Geoscience DOI: 10.1038/NGEO2316 The PETM is rather well known, and this new work constrains how much and how fast and from what sources the C may have been added to the atmosphere. None of that is my point here. It got hot and stayed hot until chemical reactions with rocks reduced CO2 concentrations again, thousands (or tens of thousands) of years later. Point is that no large scale extinctions have been linked to PETM. Plants and animals (fish, corals,etc.) kinda slid on through. it was actually the beginning time of primates, more or less. There was a large increase in sea level, so one would not want to ignore that. Regarding current or projected global catastrophes this time around, studies on PETM do not (so far) support a great deal of concern. I think it is fair to bear that in mind, and to stay tuned for evidence of PETM badness that may arise later. The thing that is different this time around is us. Humans by the billions running the planet (about half of it, depending on which metric you prefer). Wholly dependent on agriculture, itself wholly dependent on water, temperature and soils being all three right in the same places. With those same water resources strongly competed for by thermal power generation. With a large part of population living (and cropping) very near sea level. With all international marine commerce facilities located right at current sea level. That is what is different, this time around. It is where our attention should be focused this time around. Not on planetary meltdown - on maintaining the human enterprise. Same planet. Same heat-up. Very different in terms of one group of primates.
