Before God does something the people are warned first. Noah warned the world of coming destruction before the flood, the Bible says he was a preacher of righteousness.
2 Peter 2:5
(5) And spared not the old world, but saved Noah the eighth person, a preacher of righteousness, bringing in the flood upon the world of the ungodly;
Jeremiah warned of the Babylonian captivity and the destruction of Jerusalem
Jeremiah 4:4
(4) Circumcise yourselves to the LORD, and take away the foreskins of your heart, ye men of Judah and inhabitants of Jerusalem: lest my fury come forth like fire, and burn that none can quench it, because of the evil of your doings.
God always warns first so today the world is being warned of coming destruction to the world and only those in Christ will be safe. Look at these verses at what will happen when Jesus returns
Revelation 6:14-17
(14) And the heaven departed as a scroll when it is rolled together; and every mountain and island were moved out of their places.
(15) And the kings of the earth, and the great men, and the rich men, and the chief captains, and the mighty men, and every bondman, and every free man, hid themselves in the dens and in the rocks of the mountains;
(16) And said to the mountains and rocks, Fall on us, and hide us from the face of him that sitteth on the throne, and from the wrath of the Lamb:
(17) For the great day of his wrath is come; and who shall be able to stand?
Revelation 16:19-21
(19) And the great city was divided into three parts, and the cities of the nations fell: and great Babylon came in remembrance before God, to give unto her the cup of the wine of the fierceness of his wrath.
(20) And every island fled away, and the mountains were not found.
(21) And there fell upon men a great hail out of heaven, every stone about the weight of a talent: and men blasphemed God because of the plague of the hail; for the plague thereof was exceeding great.
Jeremiah 4:23-27
(23) I beheld the earth, and, lo, it was without form, and void; and the heavens, and they had no light.
(24) I beheld the mountains, and, lo, they trembled, and all the hills moved lightly.
(25) I beheld, and, lo, there was no man, and all the birds of the heavens were fled.
(26) I beheld, and, lo, the fruitful place was a wilderness, and all the cities thereof were broken down at the presence of the LORD, and by his fierce anger.
(27) For thus hath the LORD said, The whole land shall be desolate; yet will I not make a full end.
God is giving us an invitation
Ezekiel 18:32
(32) For I have no pleasure in the death of him that dieth, saith the Lord GOD: wherefore turn yourselves, and live ye.