In the span of a single lifetime, none.

Over the course of human history, one theory holds that the slowly-changing variation in the direction of Earth's axis may be responsible for some long-term climate changes. This is a tough one to prove or disprove, as other factors (including the varying eccentricity [ovalness] of Earth's orbit around the sun) may also be responsible.

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 2 words with the pattern O-AL-E--. That is, eight letter words with 1st letter O and 3rd letter A and 4th letter L and 6th letter E. In alphabetical order, they are:

odallers

ovalness

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 7 words with the pattern O---NE-S. That is, eight letter words with 1st letter O and 5th letter N and 6th letter E and 8th letter S. In alphabetical order, they are:

oiliness

onliners

ooziness

openness

ordinees

ovalness

overnets

The Earth's orbital path around the Sun isn't a circle; it is an ellipse, a sort of oval shape. Some orbits are ALMOST circular, like the Earth's; some are more oval, like Pluto's. A comet has an elliptical orbit which is VERY stretched out.

An ellipse doesn't have a center, exactly; it has a "focus". Actually, it has TWO "foci", which define the ovalness of the ellipse. The Sun is at one focus of the Earth's elliptical orbit. (There is no physical object at the other focus of the ellipse.)

The Moon's orbit is elliptical, too, with the Earth at one focus of the ellipse.

Octobers, Oversees, Overseas, Octagons _______________

oarlocks, oatcakes, oatmeals, obelises, obelisks, obelisms, obelizes, obligees, obligers, obligors, obliques, obscures, observes, obsesses, obtrudes, obverses, obviates, ocarinas, occiputs, occludes, occupies, ocherous, ochreous, octagons, octanols, octettes, octopods, octuples, oculists, odalisks, oddballs, oddities, oddments, odonates, odorants, odorizes, odorless, odysseys, oenomels, oersteds, oestrins, oestrous, oestrums, offbeats, offcasts, offences, offenses, offerers, offerors, officers, offloads, offramps, offsides, ofttimes, ogreisms, ogresses, oilbirds, oilcamps, oilholes, oiliness, oilseeds, oilskins, oinomels, oldsters, oldwives, olefines, olestras, olicooks, olivines, ologists, olorosos, omentums, omicrons, omikrons, omitters, omphalos, onanisms, onanists, onrushes, oogamies, oogamous, oogenies, oologies, oomiacks, oophytes, oosperms, oospores, ooziness, opalines, openings, openness, operands, operants, operates, opinions, opossums, oppidans, opposers, opsonins, optimums, opuntias, oquassas, oralisms, oralists, orations, oratress, orbitals, orbiters, orchards, orchises, orchitis, orcinols, orderers, ordinals, ordurous, oreganos, organics, organons, organums, organzas, orgiasts, orgulous, orifices, origamis, ornithes, orphisms, orphreys, orreries, ortolans, osmundas, ossetras, ossicles, ossifies, osteitis, osteoids, osteomas, osteoses, osteosis, ostioles, ostmarks, ostomies, otalgias, otalgies, otitides, otitises, otocysts, otoliths, ottomans, ouabains, ouguiyas, outbacks, outbakes, outbarks, outbawls, outbeams, outbless, outboxes, outbrags, outbulks, outburns, outcalls, outcasts, outclass, outcomes, outcooks, outcries, outcrops, outcross, outcrows, outdares, outdates, outdoers, outdoors, outdrags, outdraws, outdress, outdrops, outduels, outearns, outfaces, outfalls, outfasts, outfawns, outfeels, outfinds, outfires, outflies, outflows, outfools, outfoots, outfoxes, outgains, outgazes, outgives, outglows, outgnaws, outgrins, outgross, outgrows, outguess, outhauls, outhears, outhowls, outhunts, outjumps, outkeeps, outkicks, outkills, outlands, outlasts, outleads, outleaps, outliers, outlines, outlives, outlooks, outloves, outmodes, outmoves, outpaces, outplans, outplays, outplods, outplots, outpolls, outports, outposts, outpours, outprays, outpress, outpulls, outraces, outrages, outranks, outrates, outraves, outreads, outrides, outrings, outroars, outrocks, outrolls, outroots, outsails, outsells, outserts, outsides, outsings, outsizes, outsoars, outsoles, outspans, outstays, outsulks, outswims, outtakes, outtalks, outtasks, outtells, outtrots, outturns, outvotes, outwaits, outwalks, outwards, outwears, outweeps, outwiles, outwills, outwinds, outworks, outyells, outyelps, ovalness, ovaritis, ovations, overacts, overages, overalls, overarms, overawes, overbets, overbids, overbuys, overdoes, overdubs, overdyes, overeats, overjoys, overlaps, overlays, overlets, overlies, overmans, overpass, overpays, overplus, overruns, overseas, oversees, oversets, oversews, oversuds, oversups, overtips, overtops, overuses, overwets, ovicides, oviducts, ovoidals, ovulates, oxalates, oxalises, oxazines, oxbloods, oxhearts, oxidants, oxidases, oxidates, oxidises, oxidizes, oxyacids, oxyphils, oxysalts, oxysomes, oxytones, ozonides, ozonises, ozonizes