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The Combination of Earth's Tilt and Eccentricity Cause Both Warming and Cooling

by Carl G. Looney
(Reno, NV, US)

Major forces affecting global climate

Major forces affecting global climate

The really cold period of the most recent ice age started about 75 kyrs 75,000 years ago when the Earth's eccentricity was approaching the maximum, which was about 62,500 kyrs ago. At that time the Earth's tilt was near minimum. So what did this do?

The near-minimum tilt meant that more of the solar radiation was more directly on the tropic regions to create warmer ocean surfaces, which would have moved via currents to the temperate zones. The near maximum eccentricity meant that Earth's perihelion added extra heat to the tropical oceans.

The warmer waters moved to temperate latitudes while the aphelion was colder. The warmer currents, say off Western Europe, and the colder air, put a lot more water vapor in the air, where it blocked the temperate zone irradiation and the colder air precipitated out the water vapor. Tremendous amounts of water vapor are the key.

Perhaps there was a lot of flooding at first, as the geological records show (huge rounded stones that were washed dozens and hundreds of miles rather being broken and carried by moving ice. But without solar irradiation, snow pack built up.

About 12,500 years ago, there was minimum eccentricity so the Earth was nearer the Sun a aphelion and about the same at perihelion. About 20,000 years ago, the Earth was approaching this minimum so that the Earth was relatively
warmer. Also the tilt was about in the middle between minimum and maximum and headed toward maximum, so there was more solar irradiation in the temperate zones to melt glaciers. At 20,000 years ago, the ice began melting sharply (the temperatures climbed sharply and the volume of ice declined sharply). At 9,000 years ago, there was maximum tilt.

In another thousand years, the tilt will be ready to slip past the midway to minimum tilt again, and in another 12,500 years we will be slipping to more max. than min. eccentricity. At that time, we will slide rapidly at first, then see-saw up and down with a downward trend in temperature and ice buildup. These slippages past the halfway points are nonlinear: the change is gradual, say from min. to max., at first but then speeds up and makes a big jump near the halfway mark.

So we have another 10,000 years of good times except for these little 80 year and 1500 year cycles that may be colder. Right now solar activity is slowing and the ll year solar cycles are lengthening, which correlates very highly with lowering temperatures on Earth.

Barry's Response - Yes, Carl, good introductory analysis and charts of our current position with respect to the two shortest Milankovitch Cycles forcing our climate. Thank you very much. See this page - https://www.stuffintheair.com/Blowin_in_the_Wind-milankovitch-cycles-climate.html - for more details

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100,000 year Milankovitch cycles
by: David Birch

If we take a look at the last 800,000 year Vostok ice core samples we can see the the Milankovitch cycles, however the last minimum eccentricity in these samples say 40,000 years BCE, with a maximum 8,000 years BCE? it also informs us that the last Obliquity maximum was around 8,000 years BCE Also maximum precession around 1,000 years BCE, this would suggest that we have passed the interglacial period that lasted 11/12,000 years.
CO2 lags behind rwmp by 800 years so have we seen the end of current warming? yes i believe we have, we are also entering into a very weak solar cycle as was cycle 24 this will also reduce TSI values globally, my belief is that we will soon see temperatures as low as the previous maunder minimum 1645-1715 during 2020-2050 as we head into a new ice age 50/60,000 years ahead.

Barry's Response - Thanks David. I Believe a minimum in sunspot activity over the next few decades will contribute to a period of lower temperatures as well.

Planetary orbits and temperature cycles
by: Doug Cotton

For more on cycles and reasons for possible links with planetary orbits see my site https://earth-climate.com and email me with any comments or questions.

Barry's Response - interesting. A lot of stuff. Update: The site is no longer available.

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