New Ice Age Theory

amigoro writes "Most believe that the ice ages are the result of subtle changes in Earth's orbit, known as the Milankovitch cycles. According to one scientist, that is not the case. Robert Ehrlich of George Mason University in Fairfax, Virginia, has developed a model which hypothesizes a dimmer switch inside the sun that causes its brightness to rise and fall on timescales of around 100,000 or 41,000 years, exactly the same period as between ice ages on Earth. The main problem with Milankovitch cycles is that they can't explain how the ice ages go from 100,000 year cycle to 41,000 year cycle. The cycles predicted by Ehlrich's model line up with the observations."

Comments

Combination

[dohzer]

Could it not be a combination of both Milankovitch cycles and the dimming of the sun?

Re:Combination

[radtea]

While these solar fluctuations may exist (and I'm not an astronomer, just a meteorology/atmospheric science/climatology PhD student) I'd prefer to firm them up before they replace the classical orbital mechanisms that we know exist. Whether they cause the Ice Ages or not, they are present in the orbital path.

We do know the orbital fluxuations to exist, but we don't know that they cause terrestrial climate fluxuations. The problem is real: the dominant frequencies in the orbital fluxuations do not match well with the dominant frequencies in the climate fluxuations. Something more is going on, probably in our understanding of the global climate, which may impose frequencies of its own, like a resonant system excited by a non-resonant driving force.

Unfortunately, the kind of step-function we are giving the planet, and which it has had in the past from other natural occurences, is a pretty powerful excitation at all frequencies.

Real source

[edwardpickman]

It doesn't explain the cycles but the ice ages are generally believed to be caused by a shift in the jet stream that was caused by the Himalayan Mountains. The cycle's start parallels the rise of that mountain range cutting into the jet stream and causing the shift. The trigger is still up for debate but the cold air is being caused by the jet stream shifting south.

Re:Real source

[edwardpickman]

I went from a five to a troll? Some people need to read more. The jet stream is the likely source. Check maps of the Glaciers and you'll see they matched the position of the jet stream during the last ice age. The jet stream acts as a wall to the cold arctic air. Other factors keep the frost line in northern Canada but during an ice age the Jet Stream marks the limit the cold will shift. A study of glacerial sediments helped prove the process began around the time the Himalayan Mountains started to form. Maybe the theory is wrong but it's not my theory. I felt like I just got trolled because I made a pro evolution post on a Christian web site. Might help to do some reading before you troll. Another FYI the earth isn't flat and evolution isn't just an unlikely theory.

Re:Socrates would be disappointed

[theshowmecanuck]

"Whenever you eliminate the impossible, whatever remains, however improbable, must be the truth."
-- Sherlock Holmes

Duelling quotations. :-p

Ice Age Frequency

[Convector]

It's a neat idea. Are there any observations to support it? Peter Huybers from MIT just presented an alternative model which explains the 40 ky - 100 ky switch nicely without resorting to solar fluctuations. The basic idea is that you start out with ice ages every 40 ky, but at some point the ice accumulation retards heating, and one or even two thawing cycles get skipped. This gives you longer cold periods and a warm period every 80 ky or 120 ky. If you randomly distribute cycles with these two intervals, you can get a peak at 100 ky (but you can't just superimpose the sine curves with those two frequencies). He suggests that the 100 ky cycle isn't real, and just an effect we see from skipping some thaws. This is supposedly supported by oxygen isotope measurements, but I'm not enough of a geochemist to verify that.

What about Mars?

[tjl2015]

It seems that this theory should be fairly testable. If the orbital theory is correct, only Earth should display climate cycles of similar periods. If it's caused by the sun, then the whole inner solar system would be affected. Granted, it would be nearly impossible to see such evidence on Mercury and Venus, but perhaps evidence of some form would be left on Mars. I'm not quite up to speed on my astrogeology, does anyone know if we have any kind of reliable record of the ancient Martian climate?