As the graph shows on the right side, the warming which occurs between ice ages has nearly reached its peak, and a cool-down should begin within the next few centuries. The precipitation level has probably not increased enough yet to start the reversal in less than a century.

Evidence indicates that the cause of global warming is heat within the earth's core. It could be solar energy, but it cannot be carbon dioxide for three major reasons: The quantities are too miniscule and the mechanism is nonexistent, as indicated on the global warming page, and environmental factors such as carbon dioxide would be way too erratic for the precise cycling of global climate change through the ice ages.

I find that the evidence for the cause of global warming is most likely heat in the earth's core rather than solar energy, because the oceans are heating much more significantly than the air, and because I would expect solar energy to be subject to more erratic effects when combined with complexities of climate, while cyclic heat variations in the earth's core could be very precise.

However, I also recognize that there is a correlation with the earth's orbit which cannot be ignored. A likely explanation is that when the earth tilts in the right direction, the core of the earth could shift in a southerly direction, where oceans are more exposed for heating. The core of the earth would be much hotter and denser than the rest of the molten material causing it to shift with gravity effects. This explanation can also account for the increasing severity of each ice age. There is a continuous increase in the differential temperature between the earth's core and the material around it, as the planet cools.

Observations are in line with this logic. Warm ocean currents are melting ice at the poles and damaging coral reefs. It's primarily ocean temperatures that are increasing, and secondarily air temperatures.

Rainfall is greatly increasing in the upper plains (of USA). That moisture originates with evaporation of the Pacific Ocean, which must be heating up.

Atmospheric temperature is over-played in the hype on global warming.

Change in air temperature is not of much significance at even moderate levels, let alone the minute levels being questioned. The reason is because air has very low heat capacity. The oceans are said to have more than 1000 times as much heat capacity as the atmosphere.

Increases in temperatures below the ground surface have recently been detected. This includes unusual melting of ice on lakes in Minnesota.

Increases in CO2 in the atmosphere have been occurring for about a century. But only about 3% of the CO2 has human origins. A likely source of the increase is heating of oceans, which causes CO2 to be released.

Heating of oceans appears to be the cause of ice ages. Increased evaporation would create more cloud cover and reduce radiant heating. The cool-down would cause snow to accumulate in northern areas faster than it melts resulting in more of the suns radiant energy being reflected away.

Evidence for cloud cover causing ice ages is in the albedo effect, which means reflection of radiation. Ocean levels drop 300-400 feet during ice ages. They expose more land than is covered by ice. And much of it is in tropical zones which have intense radiation.

Therefore, if the sun's radiation were getting to the earth's surface during an ice age, it would create more atmospheric heat than usual, not less. This indicates that radiation is blocked out during ice ages. Since cool-down occurs for about 80 thousand years, only cloud cover would block radiation that long, not dust or gases from asteroids or geological events.

The most likely cause of oceans being heated is hot spots cycling in the earth's core. A very significant point of evidence is that recent ice ages have been cycling at 100 thousand year intervals. Environmental causes would not be so consistent. But convection in the earth's core could produce very precise repetitious cycles.

A lot of heat from the earth's core gets to the surface, as indicated by deep wells which produce warm water. Oceans are deeper than deep water wells. So the oceans are picking up a lot of heat from the earth's core. Any increase, and an ice age would surely be the result.

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Model of Ice Age: As oceans are heated due to hot spots rotating in the earth's core, precipitation increases, air temperatures increase slightly, and atmospheric carbon dioxide increases. This state continues for a few centuries, until a trigger mechanism reverses the temperatures. The trigger is probably a large volcanoe, which cools the earth's surface. This results in much winter snow, which does not melt during the summer. The snow reflects much radiation during the summer creating a precipitous decline in temperatures. The cold temperatures and snow then continue for eighty thousand years, until the oceans get so low that they expose a large amount of land mass, which causes heat-up to occur.

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The Precipitation Problem: Conditions would have gotten very dry during an ice age, because ocean levels drop about 400 feet (150 meters), while the mysterious factor which heats the oceans probably disappears. But the front edge of the ice sheet should have been quite humid, because the ice would be pushing into a warmer environment. Also, there would be streams of water running off the front edge of the ice sheet.

This means the front edge of the ice sheet may have been the only place suitable for human habitation. These conditions could have been the reason why Africans migrated into Europe during the previous ice age. Conditions would have been quite inhospitable in Africa and much more attractive in front of the ice sheet.
Human Migration (external link)

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News Article - The last weather ship in the world lies anchored in a severe and lonely place in the Norwegian Sea. Since 1948, its crews have taken water temperatures to produce the longest continuous set of deep-ocean data available. After about 4 decades, those data revealed a dramatic, persistent rise in the temperature 2,000 meters deep. Is it a sign of a fundamental change in deep-ocean circulation? Of global climate change? Uwe Send, an oceanographer at the University of Kiel in Germany, says no one knows. "The problem is, we don't have this information but in a very few places in the ocean," he says.

Theory
Global Warming Main Page