I don’t think this is the only possibility. I think it demonstrates what we are all subject to. If he goes there regularly, the changes he sees are gradual. It can be hard for us to see just how much things changed without a good reference point to contrast against. If our reference point is last week, then we are somewhat more unlikely to notice the changes that have occurred over decades (especially if they aren't incredibly stark).
It's kind of like where I live. We've got two seasons. We have the season of baking cookies in your car (one of the weekly's actually did this a few years back with butter cookies in a car), and the season of leave your door open to cool things off at night. It's hard to truly notice a few degrees difference when it's almost always mind-numbingly hot. I don't notice the difference in the summer. To me, despite obvious data to the contrary, there hasn't been a change in summer temperatures.
Similarly, if I went out to the lake right now, after not having been there in probably 7-8 years, it would blow my mind how low it is. If I was going out there every single week, I might have a kind of awareness that is lower, but it won’t be as apparent because it was a gradual change from my perspective.
The changes from Mike's perspective are likely indistinguishable because of the perspective of the nearness of his data points.
