Pliocene as climate analog

[trm1958]

How good is the Pliocene as an analog for 2100? Almost every specis, and even many genera, had not evolved yet. The continents were in slightly different places…did the Panama isthmus even exist? If not no Gulf Stream. The Himalayan mountains were lower, probably affecting wind patterns. Earth was a different planet then. Can we extrapolate?

[be cause]

I like the timing .. 6.42.42 ..

[mitch]

The Pliocene was studied because it most closely matches modern conditions.  The Isthmus of Panama was uplifted by 3 million years ago, and was an effective barrier for ocean communication since about 6 million years ago.  While the continents have moved, it is relatively small--for example the Atlantic is about 90 km wider now--not enough to matter from a climate modeling perspective. the gateways to the Arctic were narrower but still adequate to let water flow in from both the Pacific and Atlantic. 

The main use of modeling paleoenvironments is not to find a perfect analogy but to explore how a variety of parameters affect the global climate.

[trm1958]

Could the PETM be a climate analog for 2200 or 2300? Is such AGW plausible?

[kassy]

There are a number of problems.

If we go really basic then for an analogue you would need a situation which approaches our current  problem. The Pliocene does not qualify, temperatures might be close but the pushes are not.

There is a big difference between Milankovitch forcing which changes which part of Earth is warmer and thus changes things via albedo and huge carbon excursions which have an effect everywhere.

The latter tend to lead to extinction events. They all happened a long time ago and overa long time frame. So translating anything to rather short time frames like where will we be 77 years is problematic. We don´t know.

One thing we did forget was work out what 10 years around 1,5C would do. Or 1,2C or some value in between.

There is no real true analogue because well we were not there at the time and now we are here and the question is how long it keeps working. Neither the Pliocene, nor the PETM are going to help with that on a time scale relevant to us.

[sidd]

As I like to say, we have blasted thru Eemian and will be lucky to stop in the Wisconsinian.

sidd

[El Cid]

The Wisconsinian was a glaciation period. How could we stop there on the way to a warmer world???

Did you mean the Miocene maybe?

[sidd]

I misspoke ... is should have been Holsteinian or MIS11

sidd