At first these NetCDF files with extensions like .nc and .cdf were a bit of a mystery to me. These files won't open in everyday programs I'm used to like Excel or text editors. But I'm making progress manipulating them in Matlab.
A website I often refer to for OLR graphs is Ole Humlum's
Climate4You.com's temperature page
here (excerpt with just the OLR graphs
here).
But I guess that page needs to be manually updated and was last updated 2011; the data stops around 2010. Here's the first OLR graph from that page with global coverage using NOAA satellites that started measuring in June 1974: