Did global warming 'pause'? Depends how you define 'pause'

The theory that global warming paused in the 2000s was largely put to rest last year when NOAA recalculated some of its data. However, a commentary published this month has called that recalculation into question.

Jonathan Hayward/The Canadian Press/AP/File
Ice floes in Baffin Bay above the Arctic Circle are seen from the Canadian Coast Guard icebreaker Louis S. St-Laurent, July 10, 2008.

After seemingly being put to rest last year, the controversy over a supposed “hiatus” has resurfaced, but this time with a key change in terminology that could temper the pitch of the discussion.

The idea that global warming took a hiatus in the 2000s has stoked political debate in the United States over the validity of climate models and scientists' near-universal consensus that global warming has been man-made. If a pause in global warming occurred even as global industries continued to rely on fossil fuels, then perhaps the changes seen in climate scientists could be attributed to natural variation after all, critics of climate change science have argued.

The debate would seem to have been put to rest last year, after scientists from the National Oceanic and Atmospheric Administration (NOAA) recalculated climate data to correct for known biases and found that global warming had not paused as proponents of the hiatus theory had suggested. Last November, the online science journal Scientific Reports published an article that affirmed the NOAA’s claim.

According to their research, the authors of the article stated that, “Even putting aside possible artifacts in the temperature record, there is no substantive evidence of a 'pause' or 'hiatus' in warming.”

Now, a commentary article penned by several climate scientists and published this month in the journal Nature Climate Change, takes issue with NOAA's conclusion.

“The interpretation [the NOAA group] made was not valid,” said John Fyfe, a climate scientist at Environment and Climate Change Canada. “The slowdown is there, even in this new updated data set.”

However, there is a significant difference in Dr. Fyfe's choice of language and in the language used by global warming skeptics, Nature commentator Jeff Tolferson says.

"Fyfe uses the term 'slowdown' rather than 'hiatus' and stresses that it does not in any way undermine global-warming theory."

Fyfe and his colleagues point out a "mismatch" between climate models predictions and actual observations, but stress that the data does not indicate that global warming reversed or even halted during that time, as has been suggested by the so-called hiatus theory. 

Fyfe said that he and his fellow authors believe that the Pacific Decadal Oscillation (PDO) was to blame for the slowdown since 2000. The PDO goes through positive, neutral, and negative cycles. When the PDO is negative, the Earth cools down, slowing global warming. The PDO was negative in the early 2000s.

Fyfe points out that the models are not perfect. The PDO may not be the best explanation for the slowdown they have identified. But, he says, after record warming years in 2014 and 2015, the slowdown is definitely over.

After climate change skeptics attempted to use the last round of “hiatus” evidence to claim that global warming had stopped, there may be fears that the new study will be seized upon by the same people. The climate change hiatus theory was the subject of congressional hearings led by Rep. Lamar Smith (R) of Texas last year. On Friday, NOAA reported receiving new requests from Representative Smith for all documents referring to "climate" and "temperature."

Penn State University climatologist and study co-author Michael Mann said that such concerns should not deter scientists from pursuing the truth.

“As scientists, we must go where the evidence takes us,” said Mann, “we can’t allow our worries about climate contrarians and how they might seek to misrepresent our work to dictate what we do and do not publish.”

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.