I’ll be better inclined to believe it when the people who say the sea levels are going to rise stop buying beachfront property and move toward the mountains.
I’ll also be less likely to discount them when they aren’t constantly talking about depopulating the planet by a final solution which will kill ~7.75 billion people.
Try this experiment: fill a glass to the top with ice, then fill it to the brim with water and set it on a saucer for a few hours. After the ice melts, let me know if the water level rises.