The global warming hiatus - a decade-plus slowdown in warming - could be chalked up to some buoys, a few extra years of data and a couple buckets of seawater.
That's the finding of a new study published on Thursday in Science, which uses updated information about how temperature is recorded, particularly at sea, to take a second look at the global average temperature. The findings show a slight but notable increase in that average temperature, putting a dent in the idea that global warming has slowed over the past 15 years, a trend highlighted in the most recent Intergovernmental Panel on Climate Change report.
The term " global warming hiatus" is a bit of a misnomer. It refers to a period of slower surface warming in the wake of the 1997-98 super El Niño compared to the previous decades. However, make no mistake, the globe's average temperature has still risen over that period (including record heat in 2014) and temperatures now are the hottest they've been since recordkeeping began in the 1880s. So let's call it what it really is: a slowdown, not a disappearance of global warming.
The new findings show that even the concept of the slowdown could be overstated.
"There is no slowdown in global warming," Russell Vose, the head of the climate science division at the National Centers for Environmental Information (NCEI), said. "Or stated differently, the trend over the past decade and half is in line with the trend since 1950."
Vose helped author the new study, which uses new information about how data is collected at sea to reanalyze surface temperature records. The new analysis essentially doubles the rate of temperature rise since 1998. That puts it more in line with warming trends since the 1950s, though some researchers said there were still some periods of faster warming on record since the 1950s.
Of course this discussion is all centered around changes in hundredths of degrees.
"The fact that such small changes to the analysis make the difference between a hiatus or not merely underlines how fragile a concept it was in the first place," Gavin Schmidt, the head of the NASA Goddard Institute for Space Studies, said.
Temperatures have warmed 1.6°F since the 1880s. Projections indicate the temperatures could rise as much as 11°F by century's end if greenhouse gas emissions aren't slowed and that the rate of warming could reach levels unseen in 1,000 years by 2030s.
The study was inspired by some new metadata, the data behind the data, that provided clues that scientists weren't properly accounting for certain types of measurements. Specifically, there have been a proliferation of buoys over the past 40 years and the survival of an antiquated measurement technique used by ships.
Buoys have increased global coverage of the oceans by up to 15 percent since the 1970s, but they have a known cold bias compared to measurements taken from ships.
Another more quirky feature of how global temperature is determined comes from ships. Prior to World War II, the most common way to measure ocean temperatures was dropping a bucket over the side of a ship and scooping up some seawater and dunking a thermometer in.