Question: What did the Lord do to make the seasons, and hot and cold climates, when before the earth was apparently like a greenhouse (cf. Gen.2:4-6)?
Response: It doesn't say in the Bible exactly how God made the seasons, only that there are no seasons per se before Genesis 8:21-22, God's proclamation of the nature of the world to follow in the aftermath of the great flood. I am no expert in planetary mechanics (to say the least), but I believe that I am correct in saying that it is the angle of the tilt of the axis on which the earth rotates that provides the specifics of the seasonal differences (and the climate zones). Before the flood, we have no rainbows, long life-spans, no fermentation, and no seasons. One can certainly hypothesize that when the Lord judged the earth with the great flood, He also changed the tilt of its axis, an alteration which might explain all of the above (through differences in temperature, light and refraction angles, increases in penetration of cosmic radiation, etc.). The Lord had, of course, already cursed the ground in Genesis 3:17, but in Genesis 8:21, the phrase "curse the ground" has both a different verb and a different noun (although in NIV, for example, you would never know they are not both the same). Really, Genesis 8:21-22 is saying "I will never again diminish (i.e., worsen) the earth (i.e., its condition)". This is a "curse", alright, but the language indicates much more of a one time effect (like tilting the axis) than an active curse in the sense of what we understand to have happened to the ground in Genesis chapter three which subsequently must be cultivated to substantially produce. This interpretation (of finding a climate changing even in the language of Gen.8:21) is strengthened by the fact that v.22 really says "From this time forward ('odh - an adverb NIV conveniently leaves out), all the days of the earth there will be ... (the four seasons)". So that these two verses definitely link a new development, the seasons, with some diminution in the earth's former quality (i.e., the effects that a tilt in axis might have).
As I say, I am not even sure how to spell astrophysics or climatology, so you will have to take the above Bible interpretation (for which I can vouch) as one thing, and its applicability to the natural realm (which is hardly my area of expertise) as another. But, as I say, to me it is clear that God did something to the earth at the time of the flood, and that something resulted in the seasons. I am "tilted" to the tilt-hypothesis (which others espouse as well), but I would still believe what the Bible indicates about the origin of the seasons whatever the proximate physical cause might have been - nothing is impossible for a God who could even make the sun stand still in the heavens for an entire extra day with none of the physical consequences that science might imagine (Josh.10:13-14).
See also these links:
The Waters Above
Science and the Bible
Is the earth ever described as round in the Bible?
The problem of science and the Bible
The shape of the universe according to the Bible
Yours in Him who created all things and sustains them by the power of His Word of power, our Lord and Savior Jesus Christ.