Planet increase of temperature?

Question

I believe I have read somewhere that throughout earth history there was almost none ice on the poles, so the planets temperature must have been high. This was interrupted by catastrophes such as meteor impacts that, for small periods of time, changed the climate into ice-ages.

Now here’s the question. Could the climate changes be a natural thing and the pollution only act to speed it?

Answer 1

The climate changes ARE a natural thing, but they have never been this dramatic, even in the times of the ice ages.  If you've seen "An Inconvienient Truth", it explains more on this theory.

Answer 2

The planet has indeed been free of ice.  We have climate records dating back a little over half a billion years and during that time there have been 4 ice ages and 4 periods when the world was ice free.  During each ice free period temperatures were considerably higher than they are now - up to 20 degrees C higher (36 F).

These natural cycles occur over very long periods of time and the changes in temperature are very small on a year by year basis.  The reasons for these cycles are complicated but the keywords, should you wish to look them up for more info, are Solar Variation, Milankovitch Cycles and Feedback Effect.

The concern at the moment is the speed at which the earth is warming up.  In the last 100 years it's warmed as much as it did in the preceding 10,000 years.  We have accurate climate records strecthing back over half a million years and it's fair to say that natural temp rises have never come close to those we're experiencing at present.  Despite intensive studies there's nothing that can attribute the current rapid rises to natural effects alone.