地球气候的地球“温室”之间的开关,在冰几乎是没有在世界范围内,和“冰室地球”,地球间歇性地远远从两极的冰。时候地球是在冰室地球阶段被称为冰河时代。最近的冰河时代始于大约260万年前,还没有结束。我们仍然在一个冰河时代,南极和格陵兰的事实仍被冰覆盖。冰河时代的最后几十到几百上千万年。冰河时代的特点是冰川时期,冰达到远离波兰人隔开的间冰期气候比较温和的地方。冰川期和间冰期在冰河时代最后的几万至几十万年。目前的间冰期始于大约12000年前。的米兰科维奇旋回负责短期内冰川期和间冰期冰河时代。这些周期时仍然存在地球是地球在一个温室的阶段。 The Earth was in the hothouse phase for about 250-260 million years before the current ice age. That's 2000 or so multiples of the very longest Milankovitch cycle. The Milankovitch cycles are not responsible for the hothouse Earth / icehouse Earth phases. It's plate tectonics that dictates whether Earth is in a hothouse Earth or icehouse Earth phase. So what aspects of plate tectonics govern whether the Earth is in a hothouse phase or icehouse phase? Below are a series of images depicting how the Earth looked over recent times.  35 million years ago, hardly any ice anywhere.  20 million years ago, just a tiny bit of ice in the very far north and very far south.  Current ice age, (~2.6 million years ago to present), with ice sometimes reaching as far as 45° latitude. Source: [Ron Blakey](http://cpgeosystems.com/paleomaps.html), via wikimedia.org. (Blakey's maps are 1200x600, which is a bit wide. I used the 640x320 previews at wikimedia.org.)
There are two key differences at the boundaries of the Pacific Ocean between the pre-ice age Earth and our current ice age Earth. One is the Indonesian seaway. That closed up 3 to 4 million years ago thanks to New Guinea, Indonesia, and the Malay Peninsula. The other is the Panama seaway. That closed up about 3 million years ago thanks to the formation of the Isthmus of Panama. The closing off of the Pacific near the equator drastically changed the global ocean conveyor belt, which in turn drastically changed the climate of the Earth. So which of these two seaway closures, if any, is the cause of the most recent switch from hothouse Earth to icehouse Earth? A number of researchers put the blame on the formation of the Isthmus of Panama (Bartoli 2005, Nie 2014). Others claim the closure of the Indonesian seaway was responsible (Cane and Molner 2001, Molner 2008). Yet others say "none of the above" (Lunt 2008). The jury is still out, but note that Smith and Pickering 2003 claim that plate tectonics are responsible for each of the four major icehouses in the last 620 million years.
[Bartoli, G., et al. (2005). "Final closure of Panama and the onset of northern hemisphere glaciation." *Earth and Planetary Science Letters*, 237.1: 33-44.](http://www.ldeo.columbia.edu/~polissar/teaching/F2012_G9600_Climate_Puzzles_of_the_Neogene/Bartoli_et_al_2005.pdf) [Blakey, Ron. cpgeosystems.com/paleomaps.html (website)](http://cpgeosystems.com/paleomaps.html) [Cane, Mark A., and Peter Molnar (2001). "Closing of the Indonesian seaway as a precursor to east African aridification around 3–4 million years ago." *Nature* 411.6834: 157-162.](http://water.columbia.edu/files/2011/11/Cane2001Closing.pdf) [Lunt, Daniel J., et al. (2008). "Late Pliocene Greenland glaciation controlled by a decline in atmospheric CO2 levels." *Nature* 454.7208: 1102-1105.](http://www.nature.com/nature/journal/v454/n7208/full/nature07223.html) [Molnar, Peter (2008). "Closing of the Central American Seaway and the Ice Age: A critical review." *Paleoceanography* 23.2.](http://onlinelibrary.wiley.com/doi/10.1029/2007PA001574/full) [Nie, Junsheng, et al. (2014). "Pacific freshening drives Pliocene cooling and Asian monsoon intensification." *Scientific Reports* 4.](http://www.nature.com/srep/2014/140627/srep05474/full/srep05474.html) [Smith, Alan G., and Kevin T. Pickering (2003). "Oceanic gateways as a critical factor to initiate icehouse Earth." *Journal of the Geological Society* 160.3: 337-340.](http://jgs.lyellcollection.org/content/160/3/337.short)