Guest essay by Sheldon Walker
A quick recap for anybody who missed my first article.
My first article can be found here.
I have developed a new technique for analysing global warming (and other things). It is called Multi Trend Analysis, or MTA. It analyses the data in a time interval, by calculating the trend between every possible pair of points in the interval. The trend includes all of the data points between each pair of points as well. This can involve a lot of trends. To analyse the interval [January 1975 to December 1999] involves 16,920 trends. A trend is basically a linear regression.
I have developed methods that allow large numbers of trends to be analysed quickly, and the results displayed either graphically or in a table. A trend has 4 main attributes, a start date, an end date, a length, and a slope (with global warming, the slope is the warming rate). In my first article, I displayed graphs of warming rate versus trend length, but any of the 4 main attributes can be graphed against any of the others.
Most people think that the graphs look good, but I am still investigating whether the graphs are actually useful for analysing global warming. They may end up just being eye candy, but I am hoping that they will prove to be useful for something.
After my first article, I decided to use MTA to try and prove that the Pause exists. I wanted to compare a graph of the interval where the Pause existed, against a graph of an interval where “The Pause” did not exist (a reference interval). If there was a significant difference, and it was the right kind of difference (e.g. a lower warming rate), then I would have good evidence that the Pause existed.
Picking the right intervals was important. From my previous investigations into the Pause, I knew that the core years were from 2002 to 2013. This is a 12 year interval with a very low warming rate. Moving the start date to 2001 increased the warming rate slightly, but gave a longer slightly weaker Pause. Moving the start date to 2000 increased the warming rate even more, but gave an even longer weaker Pause. Moving the finish date to 2014 also increased the warming rate, and moving the finish date to 2015 weakened “The Pause” considerably, because of the 2015 El Nino.
So I had a limited range of years for the Pause. I knew that there had been consistent warming since 1975, so my Pauseless interval had to start in or after 1975. From 1975 to 2015 there are 41 years. The first 25 years or so have definite warming, and the Pause started after that. It would be best if my Pauseless reference interval was the same size as my Pause interval, because I wanted to compare apples with apples. In the end, I decided to divide the 41 years into 3 * 13 + 2. This gave me two 13 year Pauseless reference intervals, one from [January 1975 to December 1987], and one from [January 1988 to December 2000], and one 13 year Pause interval from [January 2001 to December 2013]. This fitted nicely with my beliefs about the Pause, and gave me 2 reference periods to compare with. It would also be nice to compare the 2 reference intervals to each other, to see if they were consistent. I didn’t mind not using 2014, and 2015, because I knew that they weakened the Pause. I could worry about those 2 years later if I found evidence that the Pause did exist.
I did the MTA analysis, and graphed the results. Normally I don’t look at trends less than 10 years, because they are less stable. However, working with 13 years intervals only gave me trends from 10 years to 13 years. The graphs showed what I wanted to see, but they were a bit “thin”. I did the analysis again using a minimum trend length of 8 years, and got graphs that were much more robust.
I should mention quickly that all of the data comes from the NOAA global combined land and ocean temperature series. I will repeat my analysis with the other temperature series when I get time, but I thought that using NOAA first was appropriate, given that they have a reputation as “Pause Busters”.
I will first show the 3 full scatter graphs individually, one for each interval. These are good for examining the shape, checking the warming rates for different trend lengths, and getting a good idea about the overall warming rate. The rightmost point on each graph corresponds to a linear regression for the whole interval.
I will then show a single graph which contains the same 3 intervals, but plotted as outlines on a single graph. This is much better for comparing the different intervals with each other. The colour of an outline graph will be the same colour as the full scatter graph for the interval
Here is the MTA graph for the first Pauseless reference interval, [January 1975 to December 1987].
Here is the MTA graph for the second Pauseless reference interval, [January 1988 to December 2000].
Here is the MTA graph for the third interval, the one showing the Pause, [January 2001 to December 2013].
Here is the outline MTA graph which shows all 3 intervals, each with the same color as the previous graph for the interval.
I think that the results can be seen clearly from the graphs, but I will mention a few points from the outline graph.
Note that the 2 reference intervals are in quite good agreement. The first, the orange one, has an overall warming rate of just over 2 degC/century. The warming rate appears to be increasing slightly near the right end.
The second green reference interval has an overall warming rate of about 1.29 degC/century. The warming rate appears to be decreasing slightly near the right end (as it approaches the Pause).
The blue Pause interval has much less variability that the 2 reference intervals. The warming rate is mostly between 0 and 1 degC/century. it has an overall warming rate of about 0.54 degC/century, and appears to be increasing slightly at the end. Perhaps the end of 2013 showed a small increase in temperature, which then became larger in 2014 and 2015.
If we average the overall warming rates for the 2 reference intervals, we get about 1.65 degC/century. The Pause has an overall warming rate of less than 33% of the average of the 2 reference intervals.
To be more specific, the Pause has an overall warming rate of about 27% of reference interval 1, and less than 42% of reference interval 2. These percentages represent a large reduction in the warming rate, and justify the name “Slowdown”, or “Hiatus”, or “Pause”.
Could anybody deny the Pause, after seeing that evidence? I expect that there will be many “Pause deniers” who will stubbonly refuse to accept the proof that I have presented here. Of course, anybody can overturn my proof if they can find a significant error in it. That is the way that science works.
A final word about the future. The Pause has been weakened by the 2015 El Nino. That does not mean that it never existed. Anybody gloating over the Pause becoming weaker, should bear in mind that El Nino’s do not last forever. Once the El Nino’s temperature increase has gone, the Pause will probably strengthen. A La Nina may also give the Pause a boost. Do not underestimate the Pause, it may surprise you yet.