The reports of a plateau in we saw were due to a change in instrumentation and methodology.
Specifically, in the mid 1990s, ocean water temperature reporting moved from ships cooling water intake data to dedicated free-standing buoys.
It turns out that there is significant heating present in the ships that is not present in the newer methods:
Nope, climate change didn’t pause for about 15 years, scientists say – again. But just how did that misunderstanding happen?
From around 1998 to 2012, the rise in global temperatures seemed to plateau, according to NOAA’s Extended Reconstruction Sea Surface Temperature (ERSST) dataset.
To most climate scientists, this so-called hiatus was another puzzle of our complex climate system for them to work out. But to people who were already skeptical of global warming, this data was evidence for the idea that human-induced climate change is a hoax.
But the data itself was unsound, scientists now say. There is no evidence of a hiatus.
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For decades, sea surface temperatures were measured on ships, using water sucked into a ship’s engine room. But in the mid-1990s, scientists began deploying a new strategy across the world’s oceans: thermometers on buoys. By the late 1990s, this method had taken off, Hausfather says.
But here’s the catch: the buoys bobbing on the surface of the sea take colder measurements than those taken within the warm engine room of a ship. And, in the ERSST version 3b, scientists had just tacked on the buoy data without adjusting for that difference.
When NOAA scientists realized the problem, they calculated that difference and weighted the data differently, resulting in ERSST version 4. And, according to their calculations, version 4 showed more than twice as much warming, on the global scale, as version 3b.
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Instead of looking at all the data mashed together, Hausfather and his colleagues studied the trends in the data from different sources separately, including data from ships, buoys, satellites, and drifting robots called Argo floats.
“The authors did a great job of inter-comparing independent and semi-independent SST data sets,” Thomas Karl, the lead author on the 2015 NOAA paper and former director of NOAA’s National Centers for Environmental Information, writes in an email to the Monitor. “Their results show the importance of independent measurements to clarify observational uncertainties.”
“This paper further allays any qualms that there may have been scientific errors or any non-scientific agendas,” Kevin Trenberth, senior scientist in the Climate Analysis Section at the National Center for Atmospheric Research, who was not part of either paper, writes to the Monitor. “Lamar Smith owes Tom Karl an apology.”
So from the late ’90s to the early teens, there was a transformation in the sources of the data, and if you view the data filtered by source, you see the ΔT, but if you view it in aggregate, it shows a moderation.
Good science, but bad news. We are in for a world of hurt.