To generalize and simplify, your scientists have evidence in sea floor core samples and in various glacial ice core samples of 17 ice ages "small" and "large" over the last 1.8 million years. They have evidence (Milankovitch cycle) that "something" caused and still will cause the Earth to go temporarily out of circular orbit approximately every 1OO,OOO years. This temporary periodic eccentricity of the Earth's orbit explains the 17 ice ages the Earth has had in the last 1.8 million years.
      See the movie in RealVideo  "STOPPING THE COMING ICE AGE"
     Your scientists add other evidence to this already complex physical dimension:
        1. Numerous Earthly pole reversals, magnetic or physical, or both.
        2. 9O degree Earth axis shifts, as the Egyptian priests told Herodotus, namely, that the Sun has not always risen where it rises now and that in former times the ecliptic had cut the equator at right angles!
        3. The differing periodicity of cataclysms blamed on various large planet sized bodies orbiting "physically" by your Earth, or smaller meteors actually impacting during the epochal past causing upheaval and devastation on major and minor scales.
     Your scientists evidence shows that the ice ages, or "cool periods" have lingered for up to 1OO,OOO years and in between each "ice age" there are warm "interglacial periods". The shortest interglacial period was approximately 8OOO years, and the longest interglacial lasted approximately 12,OOO years. The interglacial warm period you are in now started about 11,8OO years ago, causing all these scientists, archaeologists, and historians to think that you are the first "civilization" on Earth, absolutely ludicrous.

    Civilizations dwindle at onset of cold weather, and continue to "devolve" into primitive existence until the "ice age" ends and they can then "evolve" from "hunter gatherers" into yet another agrarian "civilization".

    When your current infrastructure breaks down, and soon it will my human friends, and the next ice age begins, only about 12,000 years will pass before you will start making your tools of stone and your clothes from animal hide again!

    Previous "cultures" sprang up in previous interglacial periods in the "recent" 1.8 million years past. Never, of course, with this many people breeding and breathing. When the weather changes, the "culture" has gone back to "cave-man" "hunter gatherer" orientation except for the ones who have been, for "time" immemorial, prepared with underground habitation, stores of food and forms of "aerial" transportation to get them around to the various "garden spots" still on the Earth, appearing as "angels from heaven" to the primitive survivors of apocalypse.

         The term "global warming" is an OUTRIGHT LIE. The warming is not global in nature. As the weather changes and we proceed into the next ice age, the cold spots get colder and the warm spots get warmer, there are less places lending themselves to the growing of food. Two years ago, Antarctic registered the coldest temperature in recorded history, and at the equator the recorded temperatures are rising. The carbon dioxide in the atmosphere quadrupled by 1996 from levels measured in ice cores dated from 1800.

    The differential between the low pressure zones and the high pressure zones caused by the accelerating differences in temperature give rise to many more hurricanes, more tornadoes, excessive flooding, extended drought, frequent freezing in temperate zones, etc. In 1987 the United States ATE MORE THAN IT GREW FOR THE FIRST TIME IN HISTORY.