The affect of global warming on GPS

A story in today’s Arizona Daily Star gets it wrong, and right, when they talk about the impacts of global warming on GPS. Quoting from a commentary in the journal Science, they say:

"Temperature directly affects atmospheric density," wrote lead
author Jan Lastovicka, of the Institute of Atmospheric Physics in
Prague.

"At altitudes between 200 and 800 kilometers, atmospheric drag
causes measurable decay of the orbits of satellites and space debris."

…Changes in the ionosphere, where satellites orbit, can affect how
radio waves travel, making GPS systems less effective, the commentary
said.

The place the credited Bloomberg News service went wrong (other than the headline) is in the lead-in, where the article says…

As global warming and greenhouse gases raise temperatures near the Earth’s surface, they cool the outer atmosphere and may change the orbits of global-positioning satellites, a group of scientists said.

So let’s be clear here. GPS satellites orbit the earth at an altitude of 11,000 nautical miles. This is too high to be affected by the changes in the outer atmosphere mentioned in Science. What the scientists are saying though, is that temperature changes can affect how radio waves travel. Unfortunately, they give no indication of the degree of error we might see.