According to Genesis the Rainbow is a sign or promise to us that the earth will never again be flooded.
The good news of God's kingdom (Daniel 7:13,14; 2:44) that is now proclaimed on a global scale (Matthew 24:14; 28:19,20) is not doom and gloom for the humble meek ones of the earth. At Matthew (5:5) Jesus referred to Psalm (37:11,29,38). There it says not only will the meek (upright) inherit the earth they will reside forever upon it. Psalm (92:7) points out divine intervention will happen when the wicked cover the earth just as grass or vegetation does. Proverbs (2:21,22) also informs that the wicked will be removed from earth but the upright remain.
Isaiah (11:4) and Revelation (19:11,15) both say the wicked will be removed (not by water) but by the words from Christ's mouth. Jesus words will be as sharp as an executioner's sword to slay the wicked. Jeremiah the prophet (25:31-33) also says the wicked will be destroyed from one end of the earth to the other.
When Jesus takes action it will be doomsday for the wicked, but eternal life for the upright, righteous meek of the earth. Jesus will usher in peace on earth and peace to men of goodwill.