It's not really surprising that global temperatures have been falling back for the last 20 months, as they just couldn't keep up the rapid rises we saw in the second half of 2015 and the first half of 2016.
Depending on how you look at it, April 2018 was the seventh warmest since 1850, or the coldest since 2013 take your pick.
I suppose if we do see another blip in warming like that between 2012 and 2016 it could just about happen in an individual month, but 1.5°C over 12 months would be much harder to achieve.
I suppose the question is just how exceptional where those years, because putting on over 0.5°C is a lot of warming by the end of 2022.