I'm not sure why you've chosen glacier forecasts to pick on. At least in aggregate they're one of the most predictable effects of climate change--look at this mass balance graph [0]. If public communicators said glaciers would be gone by 2020 (which I've never seen someone say) they were wrong, but the science behind it is clear and glaciers are on the way out.

[0] https://www.climate.gov/news-features/understanding-climate/...