"Astronomer Milutin Milankovitch developed the mathematical formulas upon which these orbital variations are based. He hypothesized that when some parts of the cyclic variations are combined and occur at the same time, they are responsible for major changes to the earth's climate (even ice ages). Milankovitch estimated climatic fluctuations over the last 450,000 years and described cold and warm periods. Though he did his work in the first half of the 20th century, Milankovich's results weren't proven until the 1970s.
A 1976 study, published in the journal Science examined deep-sea sediment cores and found that Milankovich's theory corresponded to periods of climate change. Indeed, ice ages had occurred when the earth was going through different stages of orbital variation."
Hays, J.D. John Imbrie, and N.J. Shackleton. "Variations in the Earth's Orbit: Pacemaker of the Ice Ages." Science. Volume 194, Number 4270 (1976). 1121-1132.
Lutgens, Frederick K. and Edward J. Tarbuck. The Atmosphere: An Introduction to Meteorology. From About.Com
Global warming and earth tilt are expected, not caused, it would seem by the inherit fact of the earth's rotation and wobble. Milutin Milankovitch discovered orbital eccentricity (see Wikipedia) cycles during the First World War. Way before global warming was even noticed. Those paying attention to science expected it, while others that knew it and also know the general public didn't, took advantage of that fact to receive funding to study a subject already well known, to some.
In the video below is a updated explanation from the
cassiopeiaproject on Apr 20, 2009