David Whitehouse

A new paper in a prestigious journal proves a 15-year hiatus in global warming. Why is it being ignored?

This article, in Nature magazine, ought to have been front page news – and might have been, had it suggested that global warming was worse than we had thought.  Instead, it underlines the sound science behind an inconvenient truth: that there has been a 15-year hiatus in global warming. To those of us who have been following the debate, this is no surprise.

In 2007 I pointed out that it was curious that in recent years the global annual average temperature had not increased at a time when greenhouse gasses were increasing rapidly and when the media was full of claims that the earth’s temperature was getting higher and higher. I proposed no explanation but said that it was a curious observation that would probably change in the near future. I was lambasted for being a denier and liar. Yet in the following years the global temperature did not increase.

Some vocal scientists spent more time saying it was wrong than actually looking at the data. While many in the media portrayed the phenomenon as a desperate weapon used by sceptics to undermine climate science, real scientists took notice and began to study the warming pause. It was not long before it was being discussed at conferences and in scientific journals. Something was clearly different about the nature of global temperature change since 1997 than it had been in the previous two decades. It was not only slower, but not increasing at all for many years. Indeed it was said in the prestigious scientific journal Nature that the “pause” or “hiatus” is the biggest problem in climate science.

The study of the warming hiatus is cutting-edge climate science not the “settled science” of the greenhouse effect and mankind’s input of greenhouse gasses into the atmosphere. It is not complicated. The three main global temperature datasets are freely available to anyone and there are many, not just professional climate scientists, who have the scientific and statistical skills to analyse what is after all not a great deal of data.

It is curious, and somewhat depressing, that the hiatus seemed to become an icon in the “battle” between those scientists who felt the need to defend science against sceptics who they fear are out to destroy it. Most of the media saw it that way and whenever a paper, or just a comment, came out saying the hiatus didn’t exist they were onto it. Environmental journalists seemed obsessed with bashing sceptics instead of reporting the science and, as for the many papers taking the hiatus seriously they seemed to be deliberately looking the other way. In doing so they were missing the biggest story in climate science.

A handful of scientists believe there is no hiatus. Analyse the data this way, they say, and you can argue it’s not there. Others reply that if you look at the data another way, it is obvious.

One problem the media have in reporting science is what I have called the “last paper effect.” How many times have you read or heard that this or that particular piece of research settles the debate or is the last word? The science on say bacon and cancer, on butter, on sugar, or the hiatus is settled by this latest paper. The problem is there is always another paper coming along later.

Last summer the US National Oceanic and Atmospheric Administration (NOAA) published a paper in the Journal Science that said the hiatus did not exist. They had “refreshed” some of the data and the hiatus had gone away. It was a very interesting paper, full of questions though many did not think it was the final word on the matter. However the media did. For a science story it got blanket coverage. Many who believed in the hiatus were asked if they would now admit they were wrong. The hiatus was over. It never existed. Official.

But as I said, it was inevitable that another paper would come along.

In the latest issue of the journal Nature Climate Science eleven distinguished scientists published new findings on surface temperature measurements and ocean heat content analysis. It is titled “making sense of the early-2000s warming slowdown.” The carefully constructed very first sentence summarizes the diversity of opinion.

“It has been claimed that the early-2000s global warming slowdown or hiatus, characterized by a reduced rate of global surface warming, has been overstated, lacks sound scientific basis, or is unsupported by observations. The evidence presented here contradicts these claims.”

The evidence they present – a straightforward analysis of the global temperature – is not new. It’s been done before in numerous peer-reviewed papers and over many years in climate sceptical blogs.

“In all three observational datasets the most recent 15-year trend (ending in 2014) is lower than both the latest 30-year and 50-year trends. This divergence occurs at a time of rapid increase in greenhouse gasses (GHGs). A warming slowdown is thus clear in observations; it is also clear that it has been a ‘slowdown’ and not a stop.”

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Whether the hiatus is a slowdown, a pause or a stop is debatable. It depends on how you analyse it. But it has clearly not gone away.

One would have thought that this would have been a great story for the world’s news media who were so enthusiastic to bury the hiatus. But no. They are looking the other way again. Almost none of the outlets who trumpeted the end of the hiatus has mentioned this latest research.

The hiatus is good for science. It tells us about natural climate variability of which our knowledge is still very limited. It holds valuable scientific information and in climate science, with it huge political and economic implications, we need all the information we can get. There are over 40 explanations for the warming hiatus proposed by scientists from small volcanoes, ocean movements, effects in the stratosphere, data gathering problems and many more. They can’t all be right they are all a valuable contribution to a scientific mystery. It shows us that the real science is not settled.

And another thing. About those sceptics who are seeking to deny and undermine climate science. It was the sceptics, not the scientists, who discovered the hiatus, this so-called biggest problem in climate science.

Dr David Whitehouse is the Science Editor of the Global Warming Policy Forum and a former BBC Science Correspondent.