When is the next Ice Age due ?

According to Emily Shuckburgh and Prof. Erik Wolf in a letter to the Times , the next Ice Age is not expected for another 50,000 years. Their claim seems to be based on a 2016 paper in Nature by Andrey Ganopolski, R. Winkelmann & H. J. Schellnhuber, Nature 529, 200–203 (14 January 2016).

“Even without man-made climate change we would expect the beginning of a new ice age no earlier than in 50.000 years from now”

The paper also claims that the Earth narrowly avoided the inception of a new ice age just before the Industrial Revolution, because CO2 levels were 40ppm above some hypothetical threshold of 240ppm. Of course humans were responsible for this (luckily this time) due to deforestation and land use change.

The leading hypothesis currently is that Ice Ages initiate when summer insolation reduces sufficiently so that it fails to melt back the previous winter snow. Ice then slowly accumulates leading to an increase in albedo as the northern ice sheets slowly grow. There are two causes for this effect, both of which interplay one with the other. Changes in the obliquity of the earth modulate summer insolation at both poles. Precession of the seasons, due to the precession of the earth’s axis, change the timing of the summer equinox. Combined together they then modulates the distance ‘R’ to the sun during summer months, simply because the earth has an elliptical orbit . The strength of this precession ‘forcing’ is amplified by \frac{1}{R^2} at high eccentricity.


Read the rest here: http://clivebest.com/blog/?p=8187

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