cycles

keepitmoving

at the end of these 100,000 year cycles of temperature, what causes the peak temperature to fall?

DrClapeyron

Precession, obliquity or eccentricity.

Xnn

Changes in earths orbit normally drive long term climate changes (warming and cooling) and are amplified by changes in greenhouse gases (CO2 and CH4) along with changes in snow and ice coverage (albedo).

http://stephenschneider.stanford.edu...ddiman2003.pdf

BTW, it wasn't always a 100,000 year cycle. For a significant period of time, the temperature cycle was 41,000 years. It's not entirely clear what caused that shift or if there really is a 100,000 year cycle as opposed to a series of 82,000 and 123,000 year cycles that happen to average out at 100,000 years.

keepitmoving

thanks.

Andre

Not done yet,

Another problem is that the 413,000 years eccentricity cycle clearly shows up in the insolation cycles as amplitude modulation here, but it does not show up in the oceanic benthic foraminifera isotope proxies as well as the ice cores.



The graph shows that the total resulting solar forcing at 65 degrees north in the summer does not resemble the stages of glaciation a lot. Note especially that 400,000 years ago we see one of the biggest spikes in the glaciation together with the one of the least variation in summer forcing compared to 200,000 years ago when one of the strangest variation in summer forcing is seen together with only a small spike.

Apparantly there is some more to it, although this wasn't even the reason why Karner and Muller challenged the Milankovitch idea here.

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