It appears that whether or not it is occurring depends upon your start and end dates. At least so far, the GISS repairs to their data suggest that the 1930s were very slightly warmer than either the 1990s or 2000s; that the warming trend throm the 1910s to the 1930s was about twice as steep as for the time from the 80s to 2000s; that the 1930s were consistantly warm; and that the annual variation dwarfs the centries worth of warming one year, and completely bleeds off a centuries worth of warming the next.
So...from 1630 to now, it has warmed. from 1901 to now it has warmed. from 1930s to now it has cooled. from 1953 to 2003 it has cooled. from 1970 to now it has warmed. from 1998 to now it has cooled. From 1900 to 2000 it has remained the same (miniscule cooling of -.05C).
The point is, once the data is corrected, any trend that would correspond to any anthropogenic cause is lost. Of course the temperature goes up and down. That’s what planets do.