Between the start of 1997 and the end of 2014, average global surface temperature stalled. This 18-year period is known as the global warming pause, also sometimes referred to as the global warming hiatus. The rise in global temperatures that alarmed climate campaigners in the 1990s had slowed so much that the trend was no longer statistically significant. It has been the subject of much research and debate in peer-reviewed scientific journals.
Then, in the spring of 2015, El Niño, a warm ocean phase in the equatorial Pacific developed. It rapidly drove up global temperatures by 0.5°C in less than a year. In fact, the 2015/16 El Niño turned out to be the strongest such event in recorded history and helped to make 2015 and 2016 the warmest years in the modern warm period.
This El Niño spike encouraged a number of climate activists and campaigners to claim that the warming pause was now over for good. Some said we were on the verge of runaway global warming. Others even denied that a hiatus ever existed.
One of these scientists is Dr Phil Williamson from the University of East Anglia. Writing in the Spectator, he rather confusingly claims that the non-existent pause 'ended' when there was a sudden rise in global temperatures in 2015 and 2016. Climate activists make much of the recent run of these record-breaking warm years, but they are quite wrong to blame climate change. These records are primarily a product of El Niño, a short-term and entirely natural ocean phase that habitually drives up global temperatures for a short period of time.
It is obvious that the sudden rise in temperatures during the most recent El Niño was far too fast to be the result of long-term global warming. After all, global temperatures have risen very gradually by 1°C in the last 150 years or so. Williamson is also wrong in claiming that global temperatures have not dropped since the end of the El Niño spike. Since it peaked last year, they have declined by 0.4°C. They are now almost back to where they were before the start of the El Niño:
I noted in an earlier article that the world's media were ignoring research papers in mainstream scientific journals that showed that global temperatures had slowed or stalled.
This attitude is noteworthy and seems to be the new norm. Last week, a group of climate scientists who have analysed temperature data from the lower atmosphere concluded that since around 2000 there had been a hiatus in temperature increases, stressing that this was inconsistent with what is known about natural climatic change. What is more, computer climate simulations, so central to the case for climate alarm, did not predict this might happen and cannot explain why it did. This is another important paper confirming the existence of the hiatus, and another case of the mainstream media’s lack of interest.
Still, many climate activists claim that the 'missing heat' must have gone into the oceans. In reality, the evidence is not as clear as they maintain. The best data we have to throw some light on ocean temperatures comes from the ‘Argo’ system of monitoring buoys which are now giving us unprecedented levels of high-quality observational data. Yet a recently published analysis shows that for the past decade or so, although average global ocean temperatures have slightly increased, the oceans of the northern hemisphere and indeed most of the southern hemisphere have not warmed at all. Warming, the Argo buoys show, is coming from just one region of the South Pacific.
The lesson of the pause is not that the greenhouse effect doesn’t exist, but rather that the computer models, which predicted an acceleration in global warming, and on which current policy is based, have proved to be inaccurate. Nevertheless, the pause is an important event that enriches our understanding of a highly complex climate system. In the future, a long-term rise in global temperatures may resume. There is a good chance, however, that the recent super El Niño only interrupted the 1997-2014 pause. No-one knows. But if the pause were to resume or warming keeps slowing down, many of the fundamental assumptions of climate science would have to be re-assessed.
Dr David Whitehouse is the science editor of the Global Warming Policy Forum (GWPF)