"Greenhouse warming of the Earth due to human activities is a possibility, moreover one for which mitigative/remedial actions of the types proposed here can be at once deliberate and effective. In contrast, Ice Age-severity cooling... that have occurred quasi-periodically many times during the last 1.2 million years, is a practical certainty. Moreover, a several-decade duration cold snap of Ice Age Maximum temperature-drop is known to have occurred in the Northern Hemisphere with essentially no warning during the last interglacial period, under precursor climatic conditions only slightly warmer than the present-day one."