Earth’s oceans are steadily warming

Robinson Meyer writes: It’s sometimes said that modern science spends too much time on the documentation of a new trend and too little time on the replication of old ones. A new paper published Wednesday in the open-access journal Science Advances is important just because it does the latter. In fact, it sheds light on the scientific process in action—and also reveals how climate-change denialists can muddy that process.

Here’s the big takeaway from the new study: Across the planet, the ocean surface has been warming at a relatively steady clip over the past 50 years.

This warming trend shows up whether the ocean is measured by buoy, by satellite, or by autonomous floating drone. It also shows up in the global temperature dataset created and maintained by the National Oceanic and Atmospheric Administration (NOAA).

In fact, the warming shows up in both datasets in essentially the same way. This is important because it confirms the integrity of the NOAA dataset — and adds further evidence to the argument that ocean temperatures have steadily warmed this century without a significant slowdown.

“Our results essentially confirm that NOAA got it right,” says Zeke Hausfather, a researcher and economist at the University of California Berkeley. “They weren’t cooking the books. They weren’t bowing to any political pressure to find results that show extra warming. They were a bunch of scientists trying their hardest to work with messy data.”

Here’s why the finding matters: In June 2015, NOAA published an update to its long-running dataset of historical global temperatures. Thomas Karl, the director of the National Centers for Environmental Information, and his colleagues at NOAA explained in a paper in Science that the old database had a critical flaw. In trying to merge temperature readings taken by ships and buoys, NOAA had been allowing “cooling bias” to seep into its numbers.

In other words, NOAA’s global temperature estimates had been too low, and its measurement of climate change was too conservative. With this newly updated data in hand, Karl and his colleagues found there had been no slowdown in global warming during the 2000s.

NOAA’s new findings disagreed with those of the U.K. Met Office, whose widely used global temperature dataset does show a slowdown in the 2000s.

So: Was there a slowdown? This is an interesting problem of some scientific interest. Researchers have pointed to El Niño, to multiyear oceanic cycles, and to the post-Soviet reforestation of Russia as possible explanations for the change.

But here’s the thing: The slowdown, or lack thereof, never threw the larger phenomenon of human-caused climate change into question. In fact, even among the most conservative estimates, the globe kept warming right through the slowdown. The overwhelming consensus of Earth scientists is that the planet is harmfully warming due to human industrial activity. What’s more, if a slowdown did occur in the 2000s, it seems to have abated now. The previous three years — 2014, 2015, and 2016 — have all broken the record as the hottest year ever in the modern temperature record.

But this hasn’t seemed to matter in public debate, as climate-change denialists have found enormous success casting doubt on global warming by glomming onto this “slowdown” debate. [Continue reading…]

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