Sujet : Re: "Washington Post Accidentally Admits Earth at Coolest Point in the Last 485 Million Years"
De : wthyde1953 (at) *nospam* gmail.com (William Hyde)
Groupes : rec.arts.sf.writtenDate : 28. Sep 2024, 01:37:04
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <vd7j3g$u4fv$1@dont-email.me>
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D wrote:
I watched a documentary the other day about the fall of the akkadian empire, and apparently they suspect it was due to the 4.2 kiloyear event. It turns out that within 230:ish years, nature, (without any CO2) changed dramatically which led to less rain, which led to food shortage. Estimates say that the temperature in the region dropped 1-2 degrees C, naturally in such a short time.
Did it say the global temperature dropped that much? Or was this a regional event? Regional events of this kind are common. IIRC it is believed that the Mayans also ran into unfavourable climate change, though this is not settled. But it's doubtless settled enough for a TV show.
Who would have thought that nature could change so much, without CO2?
I would. And so would literally anybody else who spent some time reading on the subject.
The global temperature can be changed rapidly by vulcanism. An eruption like Pinatubo can cool the world for a short time (half a degree C for the norther hemisphere in this case) but the tail of the cooling lasts a long time, so with a series of closely spaced eruptions the cooling can last for decades. One study implies that about 50% of the little ice age cooling was due to vulcanism.
In the historical records, eras which are very low in tropical volcano eruption tend to be warm.
Changes in ocean circulation can have a strong impact on regional climates and can occur quite rapidly, as we may discover later this century. Ice age climates are even more variable, with the younger Dryas cooling setting in over less than five years in the Northern Hemisphere, cooling winters several degrees C, while leaving summers unaltered. There is some reason to believe that this event was set off by volcanic cooling. But at the moment that's just an idea.
Solar. While this doesn't seem to ever amount to much, it does exist, and if it adds to the above, which it may have done in the little ice age, it can be significant.
But none of these processes is active now.
I
thought that was close to impossible, and that without man, nature only changes on 10000 year spans. ;)
Thus you begin to learn. Keep it up.
William Hyde