The Pause in 2017 - Part 3 : Carter's Pause

Introduction

Another episode in my ongoing series looking at aspects of the claimed global warming pause, and what it looks like in 2017. In this post I start to look at a May 2017 post in Watts Up With That - NEW STUDY CONFIRMS: THE WARMING 'PAUSE' IS REAL AND REVEALING . (WUWT capitalization and quote marks).

The post is by Dr David Whitehouse, Science Editor for the GWPF, and refers to an article in Nature, Reconciling controversies about the 'global warming hiatus' . Dr Whitehouse says this paper confirms the pause was real, but it doesn't exactly say that. Rather, it says it depends on how the term is defined. For example, it starts

Between about 1998 and 2012, a time that coincided with political negotiations for preventing climate change, the surface of Earth seemed hardly to warm. This phenomenon, often termed the 'global warming hiatus', caused doubt in the public mind about how well anthropogenic climate change and natural variability are understood. Here we show that apparently contradictory conclusions stem from different definitions of 'hiatus' and from different datasets. A combination of changes in forcing, uptake of heat by the oceans, natural variability and incomplete observational coverage reconciles models and data. Combined with stronger recent warming trends in newer datasets, we are now more confident than ever that human influence is dominant in long-term warming.

The Pause Begins

There are a couple of points made by Dr Whitehouse I want to look at. Here I'll look at what he says about the origin of the pause claim. In the next article I'll look at Whitehouse's claim about a longer pause.

The Nature report says that the pause was first claimed by outsiders about 2006.

Some years after the record warm global-mean surface air temperatures (GMSTs) in 1998, claims were put forward by voices outside the scientific community that [global warming] stopped in 1998, arguing on the basis of the HadCRUT3 dataset that was available then that GMST had not increased over the period 1998–2005.

Dr Whitehouse objects, saying

The authors say the pause started with claims from outside the scientific community. Well, yes and no. It was tentatively suggested in 2006 and 2007 by climate sceptics many of whom were experienced scientists and quite capable of reading a graph and calculating statistics. A decade after it was raised, every time the 'pause' is debated it is a tribute to those who first noticed it and faced harsh criticism. It was the sceptics who noticed the 'pause,' and in doing so made a valuable contribution to science. For years it was only analysed and discussed on the blogosphere before journals took notice.

Whitehouse tries to paint those who first pointed to the pause as pioneers, putting forward a tentative hypothesis that global warming had stopped, who were ignored by climate scientists who couldn't accept challenges to their authority.

This claim is nonsense. These skeptics were doing what those trying to avoid measures to stop global warming have always done, looking for any vague argument to muddy the waters. They were not being tentative in their arguments, and were not saying anything new Scientists were right to ignore any argument that global warming had stopped when such arguments were based on a very brief period following a very strong El Niño.

One of the first claims that global warming had stopped (that is stopped, not paused), was Bob Carter. This was in a Daily Telegraph article from early 2006 - There IS a problem with global warming... it stopped in 1998 . There's nothing tentative in the headline, and the rest of the article is just as assertive.

Consider the simple fact, drawn from the official temperature records of the Climate Research Unit at the University of East Anglia, that for the years 1998-2005 global average temperature did not increase (there was actually a slight decrease, though not at a rate that differs significantly from zero).

Dr Bob Carter

Whitehouse objects to the harsh criticism directed at such claims, but the criticism was completely justified at this point - it's a meaningless claim. We are talking about just 8 years, starting with a very warm year caused by a strong El Niño. You can find many examples of 8 year declining trends, and quickly accelerating trends. It means little or nothing to the long term rise in temperatures.

Carter is using HadCRUT data, which at the time was at version 3. This shows less warming than the revised version 4. Here's what Carter's period of no warming, or slight cooling, looks like.

The Eight Years Bob Carter claims there was no global warming.

He starts the claimed pause on a very warm year, yet is still wrong to claim there has been no warming. The linear trend for the 8 years 1998-2005 was rising at the rate of 0.99 °C / century. This is almost identical to the trend of the preceding eight years, 1990-1997, of 1.09 °C / century.

And yet, as so often happens, splitting trends into smaller sections gives a very misleading picture. The 8 years leading up to 1998 and the 8 years following 1998 were both warming at a slow rate, but joining the two together gives a 16 year trend of 2.39 °C / century. More than double the rate of warming of either 8 year period looked at in isolation. Here are the two trends in context, which shows where the problem is.

Bob Carter's 8 year pause, compared with the previous 8 years.

Pause Comparisons

By the third paragraph Carter makes a curious argument:

In response to these facts, a global warming devotee will chuckle and say "how silly to judge climate change over such a short period". Yet in the next breath, the same person will assure you that the 28-year-long period of warming which occurred between 1970 and 1998 constitutes a dangerous (and man-made) warming. Tosh.

Dr Bob Carter

It's a false equivalence to compare a 28 year period with an 8 year one. The warming since 1970 is statistically significant - it's very unlikely to have occurred by chance The trend over the much shorter pause period has very little significance at all.

But in comparing the two periods he seems to be accepting that his claim that global warming has stopped for the past 8 years is tosh. He's implying his 8 years is as meaningful as the alarmist's 28 years, and so both are meaningless - the pause that so many skeptics have been clinging onto was originally just a parody.

But lets look at the warming since 1970 in more detail. It's interesting he starts in 1970 as the first 8 years (1970-1977) really did show a slight negative trend. By Carter's argument global warming had stopped before it started.

But by 1998 the trend over Carter's 28-year-long warming period was upwards, at a rate of 1.42°C / century. So if global warming stopped in 1988, how much does adding the 8 years of no warming reduce the warming since 1998? In fact the warming rate over the 36 years from 1970-2005 increased to 1.74°C / century. The effect of Carter's eight problem years was to add almost a third of a degree warming per century.

In this case there are two problems with the skeptics claim - the trend over the 8 year period did not stop as claimed, but was rising at a slightly slower rate, but, more importantly, it ignores the big increase in temperatures required for their cherry-picked period. This graph illustrates the problems.

Bob Carter's pause in relation to the previous 28 years of warming.

As a final aside, if you think it is fine to take an eight year period as evidence of temperature trends, and if you think it's OK for such a period to begin or end on an unusually warm year, you would presumably be interested in what's been happening recently. Take, for example, the nine years 2008-2016. According to HadCRUT4, temperatures have been rising at the rate of 4.02°C / century. Needless to say this is much faster than the long term trend - and is as meaningless as the pause.

In the 11 years since Bob Carter announced global warming had stopped, temperatures have been rising at 2.63 °C / century - more than a degree per century faster than they were before the pause. If Carter was still around, he could now be writing articles saying There IS a problem with the global warming pause... it ended in 2007.

Conclusion

Contrary to Whitehouse's suggestion, there was absolutely no reason in 2006 for scientists to take seriously, claims that global warming had stopped. These claims were for meaninglessly short periods, they were not based on any statistical foundation, and they required starting at the record breaking El Ni&ntile;o year of 1998. It should have been obvious to anyone with a degree of skepticism that claims of a pause were unsustainable, and were probably being raised to distract from the evidence that warming had if anything accelerated in the early part of the 21st century.

Moreover, there wasn't anything especially original in the pause argument. Skeptics had long argued that global warming had stopped, or never existed. For example, in 2001 Alan Caruba was stating that there had been no warming since the 50s:

Listen closely. The earth warmed about one degree Fahrenheit between 1850 and 1950. Since then, not one single piece of scientific data, largely collected from meteorological satellites, as well as radiosonde balloons, has supported the lies that the earth is warning. A half-century has passed since the last, brief warming and the only thing the current data points to is a slight cooling. Indeed, back in the 1970's, the Greens were writing books predicting a new Ice Age.

Alan Caruba - The biggest liars on Earth: The UN's Global Warming Panel

In 2000 Dr Fred Singer was saying the balance of the evidence showed no warming since about 1940, and there was overwhelming evidence that there was no warming trend since 1980. (He made the claim again in Watts Up With That recently.)

The only reason the idea that there had been some sort of hiatus in global warming started to be given any credence were some cooler the years after 2006, which allowed the appearance of a pause to be extended for longer, possibly more significant periods.