Climate change is now one of the greatest challenges facing humanity, but it seems that we have been here before; if we look at the world's climate over a much longer period than 150 years.

During the Paleocene-Eocene Thermal Maximum which occurred 50m years ago, the poles were ice-free tropical regions, with very high carbon levels, and temperature increases of as much as 5 degrees.

I am just wondering if what we are currently seeing was going to happen anyway? Has the discovery of oil, and the resultant human activity just accelerated an already inevitable outcome?

  • $\begingroup$ The question is if greenhouses effect would get us away from what it would be expected a long glaciar/integlaciar era. I passed a year studing were there was a good french team specialiced in that. They are studing how was the climate before pleistocene glaciations to prepare ourselves for what can come, yes, specialy Miocene's climate. Anyhow it is tricky. The question is how much time we have to react. $\endgroup$
    – user12525
    Jul 27, 2018 at 23:06
  • $\begingroup$ There is also geoengineering, that can come in some decads and if we have 200 years or so for reacting, who knows, maybe militars know more about this issue than scientifist does, a new glaciar period doesn't show nothing nice neither (so no for he question if this was going to be heated, naturaly we should enter in a new glaciar. that means 2/3 Eurasia and NorthAmerica covered by ice. scientifist wonder if we will 'return' to Miocene because CO2 levels have increased). $\endgroup$
    – user12525
    Jul 27, 2018 at 23:25

1 Answer 1


Earth's climate has changed in the past and will change in the future. It would have changed even if we didn't start spewing enormous amounts of CO2 to the atmosphere. The main difference here is the rate at which this is happening. Natural climate change unfolds over thousands or tens of thousands of years (btw - PETM was fairly rapid, but we don't know exactly how rapid). Current climate change happens much faster. You can see temperature records broken every single year.

Our modern civilisation developed in a fairly stable climate. We did not develop in a climate where we had ice-free poles, or higher sea levels. The geopolitical consequences of altering that too fast would be simply too much.

  • $\begingroup$ Note that Paleocene–Eocene Thermal Maximum(PETM) could have been developed 'quickly' as said. Things 'returning' to a past hotter climate could develop in a few decads, specialy talking about ice melting/sea level; whereas a new glaciar era would not be expected at least for the next 10.000 years acording to Pleistocene studies -leaving out of the study what humans have changed on the system-. $\endgroup$
    – user12525
    Jul 29, 2018 at 14:33

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