The most reputable sources say it means globe. We don't care about atheist sources since they are rudely bias and full of corruptions.
Bible Commentaries for Isaiah 40:22,
Jamieson, Fausset & Brown: Commentary on the Whole Bible,
“It is he--rather, connected to the last verse, Have ye not known?--have ye not understood Him that sitteth...? (vs.26) [MAUDER]. Circle--applicable to the globular form of the earth, above which, and the vault of the sky around it, above it, He sits. For “upon” translate “above.” as grasshoppers--or locusts in His sight (Num.13:33), as He looks down from on high (Ps.33:13, 14; 113:4-6).”
Matthew Henry's Commentary,
"Now that which is here said of God is (1.) That he has command of all creatures. The heaven and the earth themselves are under his management: He sits upon the circle, or globe, of the earth, v. 22. He that has the special residence of his glory in the upper world maintains a dominion over the lower world, gives law to it, and directs all the motions of it to his own glory. He sits undisturbed upon the earth, and establishes it. He is still stretching out the heavens, his power and providence keep them still stretched out, and will do so till the comes that they shall be rolled together like a scroll. He spreads them out as easily as we draw a curtain to and fro, opening these curtains in the morning and drawing them close again at night. And the heaven is to this earth as a tent to dwell in; it is a canopy drawn over our heads, et quod tegit omnia coelum --- and it encircles all. --Ovid. See Ps.104:2 (2.) That the children of men, even the greatest and mightiest, are as nothing before him. The numerous inhabitants of this earth are in his eye as grasshoppers in ours, so little and inconsiderable, of such small value, of such little use, and so easily crushed. Proud men's lifting up themselves is but like the grasshopper's leap; in an instant they must stoop down to the earth again. If the spies thought themselves as grasshoppers before the sons of Anak (Num.13:33), what are we before the great God? Grasshoppers live but awhile, and live carelessly, not like the ant; so do the most men. (3.) That those who appear and act against him, how formidable soever they may be to their fellow-creatures, will certainly be humble and brought down by the mighty hand of God."
The Bible Knowledge Commentary (1985 Edition)
“God’s sovereign control over the world (40:21-26). 40:21-22. From His sovereign position in heaven God watches over His created universe. You (used four times in v.21) refers to people in general. The force of the first question, for example, is “Doesn’t everyone know this?” (cf. v. 28) The Lord is like a king sitting enthroned above the circle (hug, “horizon,” which is circular; cf. Job 26:10: Prov.8:27) of the earth and over His people who by comparison seem like mere grasshoppers. The heavens (the sky) are pictured as spread out like a tent for Him to live in (cf.Ps.104:2). Isaiah was not presenting a detailed idea of God’s abode. He was merely using imagery that his readers would easily understand.”
Henry Morris Study Bible,
“40:22 circle of the earth. Hebrew khug, translated “compassed” in Job 26:10 and “compass” in Proverbs 8:27. All three, in context, clearly refer to the spherical shape of the earth.
40:22 stretcheth out the heavens. This phrase is possibly a reference to the expanding universe, as envisioned by modern astronomers. There are numerous references in Scripture to the “stretching-out” or “spreading-out” of the heavens (space) when God created the universe. See, for example, Job 9:8; Psalm 104:2; Isaiah 42:5; 44:24; 51:13; Jeremiah 10:12. Alternatively, the “heavens” referred to here may refer simply to the atmospheric heavens, spread out like a curtain or “tent to dwell in” around a circle of the earth. This atmospheric “tent”, refracting and spreading light over the hemisphere, is sharply distinct from the darkness outside.”
Matthew Poole's Commentary,
"That sitteth, as a judge or governor upon his throne,
upon the circle of the earth; or, above the circle &c.; far above this round earth, even in the highest heavens; from whence he looketh down upon the earth, where men appear to him like grasshoppers. He alludes to one that looks down upon the earth below him from some high place. As here we have the circle of the earth, so elsewhere we read of the circle of heaven,
Job 22:14, and of the circle of the deep, or sea,
Proverbs 8:27, because the form of the heaven, and earth, and sea is circular and round, as is evident both from sense, and from the principles of philosophy.
As grasshoppers; small and contemptible in his sight. Compare
Numbers 13:33.
Stretcheth out the heavens as a curtain, and spreadeth them out as a tent to dwell in, for the benefit of the earth and of mankind, that all parts might partake of its comfortable influences. See Poole "
Job 9:8"; See Poole "
Psalm 104:2". "
4th century St.Ambrose,
"Scripture points out what is impossible for men, for God declares: 'Who hath measured the waters in the hollow of his hand and weighed the heavens with his palm and the bulk of the earth in his hand? Who hath weighed the mountains in scales and the rocks and the groves in a balance?' And further on: 'Who sitteth upon the
globe of the earth, and the inhabitants thereof are as locusts, who stretcheth out the heavens as an arch?' Who, then, ventures to put his knowledge in the same plane with that of God?” (St.Ambrose, "Hexameron" The Fathers Of The Church series translated by John J. Savage, p.231).