A quote from The Guardian:
Last year, a paper in Nature co-authored by Sir David King, the UK
government's former chief scientific adviser and currently the
government's climate change envoy, concluded that a "tipping point" in
the global oil supply had been reached since 2005, with global
conventional production hitting a ceiling of around 75 million barrels
per day (mbd) despite price increases of 15% a year.
Is that proper grammatical usage of tense? "Had been reached" seems to stand for Past Perfect; yet since, to my taste, implies an ongoing process and hence seems to call for Present Perfect Continuous (as in "The reactor has been in operation since 2005" or "I've been trying to understand English grammar since God knows when").
Best Answer
As emrys says, it is the since which is awkward here.
I think what the Guardian author means is that the tipping point was reached not in 2005 or at some specific point since 2005, but in the years since 2005. This would reflect what Murray and King said in the 2012 Nature paper: "In 2005, global production of regular crude oil reached about 72 million barrels per day. From then on, production capacity seems to have hit a ceiling at 75 million barrels per day."
But the past perfect is correct here; the author is referring to what was said a year ago by Murray and King, who were referring to the years between 2005 and 2012. The title of the Murray/King paper at that time was in the present perfect: "Climate policy: Oil's tipping point has passed".