Introduction
I'm going to try to update some temperatures as they come in (No promises).
Dr Roy Spencer has announced the value for his UAH 6, and it's a rise, up to 0.41 °C, compared with the 1981 - 2010 base period. This makes it the 3rd warmest August in the UAH 6 data set, only slightly cooler than August last year, and 0.11 °C cooler than August in 1997.
To put this into some context this graph compares temperatures around the two major El Niños of 1997 and 2016.
What this shows is that whilst the El Niño spikes were very similar in terms of absolute temperature, the years preceding the 2016 El Niño were warmer than the years preceding that of 1998, and so far the year following 2016 has been warmer.
The Forecast
The increase in temperature has pushed the average temperature for 2017 to 0.32 °C, up from 0.30 °C in July. The forecast reflects this with a rise from 0.30 ± 0.08 in July to 0.32 ± 0.06 °C.
| Rank | Year | Anomaly | Probability | Change |
|---|---|---|---|---|
| 1st | 2016 | 0.51 °C | 0.0% | +0.0% |
| 2nd | 1998 | 0.48 °C | 0.0% | +0.0% |
| 3rd | 2010 | 0.33 °C | 30.4% | +11.0% |
| 4th | 2015 | 0.26 °C | 63.8% | -1.4% |
| 5th | 2002 | 0.22 °C | 5.6% | -8.7% |
| 6th | 2005 | 0.20 °C | 0.2% | -0.6% |
| 7th | 2003 | 0.19 °C | 0.0% | -0.2% |
| 8th | 2014 | 0.18 °C | 0.0% | +0.0% |
This slight rise in the forecast has edged UAH 6 close to the third place set in 2010. As a result, whilst it's still most likely that 2017 will be 4th warmest, the chances of finishing 3rd have increased somewhat.
Analysis of UAH 6
I'm going to look in some detail at the trend of UAH 6 and what it means for Christopher Monckton's Great Pause. I'm using UAH 6 for this, as it is the closest current data set to Monckton's preferred RSS 3.3 set. This is still being published but has now been superseded by version 4, which shows rather more warming. To be clear, the only reason I am using UAH 6 is that it shows by far the least warming of any data set.
First of all lets look at UAH 6 over its lifetime.
Blue - linear trend.
Red - 12 month moving average.
The peak in 2016 is very similar to that of 1998, but as mentioned above the years before and after have been much warmer. This can be more clearly seen by looking at a 2 year rolling average.
Blue - linear trend.
Red - 24 month moving average.
UAH 6 continues to set new records averaged over the last 24 months, and is currently 0.15°C warmer than the high point in 1998. For a clearer picture of the climate, here's the same graph using 20 year averages.
Blue - linear trend.
Red - 20 year moving average.
Whatever the truth behind the Pause, it has had very little impact on the long term trend. The trend over the entire life of UAH 6 is currently 1.25°C / Century (a lot less than in other data sets). The trend up to 1997 was just 0.93 °C / Century. A year later it had risen to 1.64 °C / Century. None of these trends are significantly different from each other.
Blue - trend to August 2017.
Green - trend to 1998.
Red - trend to 1999.
Christopher Monckton's Great Pause
A reminder that Christopher Monckton's Great Pause, which he used to annotate every month in Watt's Up With That, was a ludicrous example of cherry-picking, in which he would take one data set (RSS 3.3), work out the trend starting at each month up to the current month, and then choose the earliest starting month yielding a negative trend. He would then claim that this represented the start of the Great Pause (his capitalization), and tell his readers exactly how many months it had lasted. It didn't matter that the actual start would move backwards and forwards each month.
Using Monckton's definition there is currently no Pause. Or at least not one lasting more than 5 years - taking the strictest definition there has been a pause since May 2015, but I would hope even Monckton has more sense than to talk about a 2 year pause.
Limiting ourselves to trends of at least 5 years, the closes to Monckton's pause is to cherry pick the starting month that gives the slowest rate of warming. This is December 1997, with a trend of 0.58 °C / Century.
But we can just as easily cherry-pick starting dates that will give extremely fast rates of warming. For example, since April 2005, UAH 6 has been warming at over 2 °C / Century. Since September 2006, it has been warming at over 3 °C / Century, and since August 2007, the rate of warming has been more than 4 °C / Century. Of course all of these steep rises rely on the warm El Niño last year, just as the pause relies on starting with a very warm El Ni˜o. And none of these Great Warmings are statistically significant, any more than Monckton's Great Pause was. And, as with the Pause the lines don't meet up.
When Will the Pause Return?
Curiously, Christopher Monckton asked the same question back in January, but neglected to even attempt an answer. Whilst it might have been possible for a brief return in a year or so, if there had been a strong La Niña this year, the fact that temperatures have continued to be so high throughout this year makes any return in the next couple of years highly unlikely, and unless something very dramatic happens I doubt we will ever see a return to a pause stretching back to before 1998.
To simplify things lets use annual averages, rather than monthly. Now, assume 2017 does finish up within my prediction interval, but at the low end, i.e. around 0.26 °C, what would it take for the Great Pause to return by the end of 2018? For this to happen, 2018 would have to average -0.22°C. That would be a pretty phenomenal drop in temperature in a single year. It would require 2018 to be the coldest year since 1992.
Alternatively, if 2018 was to drop to -0.1 °C, equal to the coldest single year during the Great Pause, and then stay at that level for the next few years, we still wouldn't see the return of the Pause until 2020.
In other words, for there to be a return of Monckton's Pause anytime in the next few years would require a period of cold unlike anything seen during the last 25 years.
Citations
Analysis for this blog post used R.
R Core Team (2015). R: A language and environment for statistical computing.R Foundation for Statistical Computing, Vienna, Austria. URL
https://www.R-project.org/.
Graphics produced with the GGPlot package
H. Wickham. ggplot2: Elegant Graphics for Data Analysis. Springer-Verlag New York, 2009.
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