The Geofish Hypothesis
We have gone through big and little thermal cycles since the beginning of the Earth. Abundant water regulates the temperature so life can exist. The only atmospheric insulator of importance is water vapour and condensate.
Plate tectonic cycles are on the order of 600 million years. We are now in a very cold period, as opposed to the tropical dinosaurs. Two million years ago, plate tectonics and ocean currents were set up to allow continental (continuous) glaciation.
The Northern Hemisphere is set up to have two regular thermal cycles controlled by ocean currents. One is a 40 year full cycle, that gives us twenty years of warmth followed by 1972 (twenty years of cold). This cycle is probably controlled by El Nino cycles (frequent or rare).
As well, there is the 600 year cycle with 300 years of bitter cold (Thames freezes over), followed by 300 years of warmth. This cycle is caused by a complete flip of ocean currents, making either the north or south full of warm water. When we hit the depth of this cycle, hurricanes will only hit Brazil.
The southern hemisphere is in continuous glaciation. The northern ice advance comes in a 20 to 40,000 year full cycle. 10-20,000 years of ice with continents at full height (and sinking fast), and 10-20,000 years of low land springing up.
Currently, we are peaked with a warm cycle and going down fast. This last warm period may have been a peak of two cycles.
This hypothesis can be blown up by doing lots of new physics. We can find out where we are exactly with the cycles if they do a full heat energy calculation of the oceans. We need lots of physics at the water-air interface.
ps - legal crap -- I am not a 'climate denier' as they have shortened the term. If we don't do any more physics, then we can all run around like headless chickens as it gets colder. Since we are in an 'Age of Philosophy', this hypothesis can be yelled at, and ignored. :)