My son visited the Mendenhall Glacier last year in Alaska, and he experienced it as shown above and in the first three photos below. The last photo was taken this year in the exact location the next to last photo was taken from last year. For many thousands of years this glacier has retreated at a rate of inches, and then more recently, feet. This past year, a quarter mile melted, as is shown in the last two photographs here. The whole area where their tents were last year is gone. This rate is continuing to astronomically accelerate! It was incredible for him to get to see this amazingly vast glacier, for in a few years it will be completely gone, after dominating the landscape for all of recorded history. This is a dramatic and indelibly memorable example of the current effects of global warming, which can be more subtle elsewhere.
(Note: Photo credits to Kevin and Kurt. Thanks for letting me use them!)