Cross Post from Scroggles!: The Flood and Global Warming

I'm reading through Genesis right now and have been noticing some interesting details about creation that I haven't noticed before. For example, during the flood account in Genesis chapter 7 the Bible states that:

¹⁸And the water prevailed and increased greatly upon the earth; and the ark floated on the surface of the water. ¹⁹And the water prevailed more and more upon the earth, so that all the high mountains everywhere under the heavens were covered.

I understand that some people argue that Noah's flood could have been a localized flood instead of a world wide flood, but this passage seems to rule out the possibility of this flood not being world wide. When it says that all the mountains under the heavens were covered with water, that doesn't seem to leave any mountains on the earth remaining uncovered.

Also in Genesis chapter 9 after the flood has receded, God makes His "Rainbow Covenant" with Noah and all creation stating:

¹¹"And I establish My covenant with you; and all flesh shall never again be cut off by the water of the flood, neither shall there again be a flood to destroy the earth"

To me, this promising from God seems to negate the possibility of God allowing global warming to cause world wide flooding that would turn the earth into a "water world". This doesn't mean that there can't be localized flooding, but there cannot be another world wide flood to wipe out all creation.