ce ages as tcions increasingly fell out of favor. o prove t . By time, e Joo find a geologist or meteorologist y.” Not until t of a potassium-argon meting ancient seafloor sediments were ed.

    tc enougo explain cycles of ice ages. Many otors are involved—not least tion of tinents, in particular t tly understood. It ed,  if you  t and inescapable ice ages. e are very lucky, itappears, to get any good  all. Even less ood are tive balminess erglacials. It is mildly unnerving toreflect t tory—t of farming, tionof toics and ing and science and all t—aken placeypical patcerglacials ed as little as eigs ten th anniversary.

    t is, ill very muc’s just a some of t period of glaciation, aroundty t 30 percent of tenpercent still is—and a furt is in a state of permafrost. ters of all ter on Eart botuation t may be unique in Eartory. t ters t glaciers even in temperate places suce natural, but in fact it is a most unusual situation for t.

    For most of its ory until fairly recent times ttern for Earto be  ice anyed about fortymillion years ago, and o not bad at all. Ice ages tend to evidence of earlier ice ages, so tcuregro it appears t  seventeen severe glacial episodes in t 2.5million years or so—t coincides us in Africafolloed culprits for t epocion of t disrupting air flos. India, once an island, ers into t forty-five million years, raising not only t alsot tibetan plateau be tonly cooler, but diverted  made to more susceptible to long-term c five millionyears ago, Pana