Quote:
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Originally Posted by aurora
We've already been long past where we should have been based on the last few interglacials.
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This statement made me wonder about just how this interglacial compares with the past few interglacials. To check it out, I downloaded the Vostok ice core temperature data, based on duterium, from this NOAA
website and plotted it up. The resulting 420,000 year temperature
graph shows the current interglacial and 4 previous ones. The data show that 91% of the time over the past 420,000 years the temperature was colder than it is now. Glacials periods last considerably longer than interglacials.
To compare interglacials, I plotted up the current and 3 previous interglacial temperatures vs time on the same graph, by shifting the time scale of the previous interglacials by 120,000, 228,000 and 315,000 years. This is shown
here. These data indicate that the warmup time for the previous 3 interglacials was similar to the current one, and they reached temperatures 2 to 3 degrees C higher than the current temperature. One of the interglacials (228,000 ybp) had a very short duration at elevated temperature, but the other two peaked a bit higher than the current one, and slowly drifted through the present temperature before descending again into a glacial period.
This chart suggests that we may be about due for a slide into another glaciation over the next few thousand years. This, of course assumes that the past mechanisms for glaciation are not overridden by current human activity.
It also suggests that 2 or 3 degrees C rise from here would not be unprecidented during an interglacial, although these have in the recent past occurred at the beginning than the end of the interglacial period.
In any case, on this time scale, AGW may be just a blip, because at the current rate we will probably use up all the earth's fossil fuel in a couple of hundred years, possibly staving off another glaciation by a few hundred years.
Seems to me that we better learn to adapt, because continued temperature stability appears to be unlikely based on the Vostok record. Any climate change will cause dislocations, but warming is probably preferable to cooling, from the standpoint of being able to feed the earth's billions.