The scientists at NASA have plotted average global temperatures since 1880, both the annual averages plus five-year averages to smooth out any short term fluctuations in any given year due to things like El Nino. They plot the temperatures as the deviation from the 30-year average taken over the period 1951-1980. As they point out, “Sixteen of the 17 warmest years in the 136-year record all have occurred since 2001, with the exception of 1998.”
You may recall how global warming denialists right up until 2015 claimed that there was no warming at all and showed this graph of average temperatures to make their case.
There was something odd about their choice of start and end points for their graph. Why 1997 as the starting point? Why end at 2011? The reason is simple. 1997 was an unusually warm year and 2011 was an unusually cold year. By taking those two as the end points and using linear regression, you could get a flat line and Presto! No global warming. That strategy fell apart when a rapid succession of very hot years since 2012 made their claims ludicrous because the rapid rise was undeniable.
2016 was the hottest year on record. But the first half of 2017 is the second hottest on record, just below 2016. Given that 2016 was so hot, it may well be that in the next few years the average temperatures will not exceed it. If so, I would not be at all surprised to see another round of the misleading use of statistics, with denialists coming out with a new graph that starts at 2016.