You would sacrifice the largest source of freshwater on earth for the climate?

EDIT: The Great Lakes are not land-locked either. They flow out to the Atlantic Ocean via the St. Lawrence River.

Isn't Baikal much larger?

It depends on how you measure. By surface area, no. By volume, yes.

Those are the largest [above ground] freshwater bodies on the planet. That is not a good idea.

We're going to need them.

Millions of people depend on the Great Lakes for their supply of fresh water. Water scarcity is already a problem, that would make it worse.