Landmass especially. The increase in average temperature will concentrate over landmasses.
Depending on how fast the artic ice cap melt, we could see the average temperature over a year in western europe drop, while increasing over the summer months.
But climate is weird, that's why the less we perturb it, the better we get.
I'm not an expert, i merely did a lot of research during Covid (nothing better to do tbh), and since i've never asked myself the question, i never researched islands specifically.
I think you might be able to find NASA maps and compare the average temperature in 1991 and today, you'll have your response.
Depending on how fast the artic ice cap melt, we could see the average temperature over a year in western europe drop, while increasing over the summer months.
But climate is weird, that's why the less we perturb it, the better we get.