According to NASA global warming is not a myth. The provided data shows rapid increase in mean annual temperature across the last two decades compared to the benchmark — mean temperature from 1951 to 1980.
Data source: GISS Surface Temperature Analysis (GISTEMP). Dataset accessed 2015-08-01.
More info about the study: Hansen, J., R. Ruedy, M. Sato, and K. Lo, 2010: Global surface temperature change, Rev. Geophys., 48