without getting into a huge debate but putting the record straight. Is it not the case the sun has been warming all of its life even through the colder periods, and also hasn't volcanic activity decreased over time. I think the iceage now people have a rather dangerous view they are putting forward and are driven by some worrying hidden agenda. "Theoretical models of the sun's development suggest that 3.8 to 2.5 billion years ago, during the Archean period, the Sun was only about 75% as bright as it is today. Such a weak star would not have been able to sustain liquid water on the Earth's surface, and thus life should not have been able to develop. However, the geological record demonstrates that the Earth has remained at a fairly constant temperature throughout its history, and in fact that the young Earth was somewhat warmer than it is today. The general consensus among scientists is that the young Earth's atmosphere contained much larger quantities of greenhouse gases (such as carbon dioxide and/or ammonia) than are present today, which trapped enough heat to compensate for the lesser amount of solar energy reaching the planet" from -- Kasting, J.F., Ackerman, T.P. (1986). "Climatic Consequences of Very High Carbon Dioxide Levels in the Earth’s Early Atmosphere". Science 234: 1383-1385. And fr volcanic activity see http://www.volcano.si.edu/faq/index.cfm?faq=06 However if you hold with Gaia hypothosis then maybe the earth will restabalise. But the cost may be a world with out human dominance!