OK CLASS how many ice ages have we had and what caused the to end and warm up the earth?

Question

what was the reason for the end of past ice ages global warming? cant be no one to do this!

Answer 1

There have been quite a few ice ages in Earth's history.

Variations in Earths eccentricity, axial tilt, and precession (called the "Milankovitch Cycles") affect the seasonality of solar radiation reaching Earth's surface. These variations affect the accumulation of snowfall on the ground during Summer months, which changes the albedo of the planet's surface. This, along with several other feedback mechanisms, are believed to be the causes of Earth's ice ages.

However, these cycles have nothing to do with the current warming trend. In fact, were it not for the human influence on the climate, the climate would actually be in a slight cooling trend right now.

Answer 2

We know for certain that there have been four ice ages - we're currently in the fourth of them. There will almost certainly have been more but we can't prove their existence because the technique we use for calculating the coming and going of ice ages (oxygen isotope analysis) can only be extended back 542 million years to the time when the first multi-cellular organisms appeared on the planet.

Ice ages are the result of climatic changes brought about by the series of natural cycles that both the Earth and the Sun go through, they occur at approx 125 million year intervals and coincide with complex interactions between the different cycles.

There are times that are often (incorrectly) referred to as ice ages which occur at approx 100,000 year intervals. They're caused by the same cycles but aren't ice ages in the true sense of the word - more an advance or retreat of glacial ice.

Answer 3

The number of ice ages is unknown.

They ended because of the sun. There are cycles called Milankovic cycles which cause solar radiation to increase substantially.

How do we know that's not what's happening now?

Two independent and clear cut ways.

First the Milankovic cycles don't operate in some mysterious fashion. Solar radiation rises in an easily measurable way. Scientists have looked. Increased solar radiation ain't there.

Second, the last Milankovic peak was about 20,000 years ago, ending the last ice age. The peaks are fairly regular, spaced about 100,000 years apart. The next peak isn't due for another 80,000 years.

We were in a period of pretty stable climate, until we messed it up.

http://www.globalwarmingart.com/wiki/Image:Climate_Change_Attribution.png

Answer 4

I thought this area was for questions about Global Warming. Ice Ages have absolutely nothing to do with that.

Answer 5

more times then you count on fingers and toes.
these climatic fluctuations have various different reasons and we can only think of some good possibilities right now.
umm, orbital variations, solar output, volcanic upsets, asteroid and comets hits, flipping of magnetic poles, political discussions, and many more.
take your pick.

Answer 6

typically orbital cycles, but some warming periods in the past were caused by the greenhouse effect- by a natural increase
in [ghg]'s,but the only known source of increased [ghg] now is human activity.

http://en.wikipedia.org/wiki/Clathrate_Gun_Hypothesis

Answer 7

idk