The guys who have been studying the phenomenon for decades say it's real
Very true.
In Austria we gather weather data since 1760. We have the oldest meteorological service in the world (since 1851). They see a rise of nearly 2 degree Celsius in the Alps over the last 100 years. Thats locally gathered data and therefore no need for a NASA conspiracy theory.
You can download their data from here:
http://www.zamg.ac.at/cms/de/klima/informationsportal-klimawandel/daten-download
http://zamg.ac.at/histalp/
Daily data goes back to 1948, monthly data goes back to 1760.