Depending upon weight they may not be able to take off, and depending on weight, may not be able to maintain flight.
Global Warming is a fraud so this article is chicken-little nonsense.
“Higher altitude airports”
My turf; ASEL. Denver, Leadville, Aspen, Grand, Eagle, etc. It is sad the Luddites claim warming will result up to 2.5° warming, but it really would take much, much more than that to ground airplanes.