Re: The Climate, Environment and Energy Thread
Reply #51 –
I suppose the first thing you have to define when discussing the idea of glacial or inter-glacial periods is defining what either period is, some will refer to the Maunder Minimum as an Ice Age but others suggest hardly! For example what is the "period" interval, 11kyr, 19, 23, 40, 100kyr?
If it's 11kyr, and the Maunder Minimum was perhaps a sign of solar dynamics that triggered the Little Ice Age, the next seems overdue.
Fwiw, a lot of commentary denies the Maunder Minimum was an effect because it only lasted a short time in relation to the claimed period of the Little Ice Age, but of course that ignores that the possibility that the solar dynamic effect causing the Maunder Minimum were only present when low solar sunspot activity was actually being observed and detectable by the best people of the time. If the solar dynamics had no effect was it orbital dynamics, if so what changed in this regard on such a short cycle, certainly not orbital dynamics?
The problem is the best data available only goes back about 450kyr, from ice cores, and that the evidence for influences from orbital dynamics in those cores is only weak if not merely just a correlation. The Earth has precessed many times over that period, like a clock that ticks out 26kyr cycles. So much so that some even question the validity of Milankovitch cycles, if they are real, there are climate effects but it seems they are not explained by orbital dynamics. Further if they are real they most likely don't happen(that is the polite don't) in 11kyr cycles, or 23kyr, or 40kyr but closer to 500kyr cycles. Actually, a huge flaw is that if followed explicitly a modelling of the Milankovich cycle predicts asymmetric freezing and thawing of Earth's opposing poles, and that is not what happened as the record shows the whole Earth cooling or warming. I won't get into the arbitrary choices made when analysing or modelling data, it's a rabbit warren.
The take home is that orbital effects have an influence, but they are not likely to be the explanation of climate dynamics, think of them as a small contributing factor not a outright cause. It's the largess of humans to explain these things, and claim to have the answer, it's much smarter to admit there is no answer and talk about only what we know.
Humans are pattern matching machines, and we are powerless in taming this evolved ability.
Opinion.
Many will post commentaries declaring what the weather will do next century like it's a certainty!
Reality.
We have magnetic field records in rocks 4Gyr old, we have thousands of years of detailed human records about Earth's magnetic fields and fluctuations, we can measure these things with instruments more sensitive and accurate than any thermometer. Yet we can't predict where the magnetic north pole will be next year beyond a general trend in direction and speed, it's behaviour tomorrow is a mystery! It's finely detailed movement is chaotic!