Yes, a Warming World Can Still Have "Cool" Spells

So says Bradford Plumer at the New Republic. That much is certainly true. But some other things Brad says in the article are not.

Despite what George Will might think, just because 1998 was the hottest year on record so far, and average temperatures have flat-lined since, that doesn't mean there's no long-term warming trend. There is.

Problem is, Brad, the 'fact' that 1998 was the hottest year on record was debunked almost two years ago

But McIntyre and McKitrick demonstrated it was based on incomplete and inaccurate data.
To NASA's credit, when McIntyre pointed out their temperature errors they quickly made corrections.
Still, the pro-warmers who dominate the Goddard Institute almost certainly recognized the impacts these changes would have on the global-warming debate, because they made no formal announcement of their recalculations.
In many cases, the changes are statistically minor, but their potential impact on the rhetoric surrounding global warming is huge.
The hottest year since 1880 becomes 1934 instead of 1998, which is now just second; 1921 is third.

And as for your upward-sloping trend with downward fluctuations. I can draw a graph too. The below graph "proves" that a cooling world can have warm spells.