global cooling

• India collided with Asia and formed the Himalayas. 
• Himalayan uplift started 40 ma, by 10 ma it had reached half the present height.  Upper atmosphere circulation was disrupted by high mountains - waves and ripples. At times ripples could draw cold air from the poles downwards encouraging ice sheet development. Then positive feedback mechanisms. 
• Rocky mountains and the Alps have a similar circulation pattern. 
• During mountain build up more weathering and erosion occurs. Sediments are removed from the mountain and end up buried in the ocean - removing CO2. 
• During the Paleogene and Neogene Alaska and Russia moved closer together, cutting off the warm pacific currents. 
• 30 ma the drake passage opened and the Antarctic circumpolar current flows around the edge of antarctica, isolating it from warmer tropical water. 
• 3 ma north and south America collided, the pacific and Atlantic oceans don’t mix and the gulf stream diverts towards NW Europe
• Milankovitch cycles aren't enough to produce an icehouse phase, they could produce an interglacial phase. 
• Icehouse timing depends on continental position, ocean and atmosphere, so is an interplay of factors.